[PATCH v7 00/11] LSM: Three basic syscalls

[PATCH v7 00/11] LSM: Three basic syscalls

[Casey Schaufler]

Add three system calls for the Linux Security Module ABI.

lsm_get_self_attr() provides the security module specific attributes
that have previously been visible in the /proc/self/attr directory.
For each security module that uses the specified attribute on the
current process the system call will return an LSM identifier and
the value of the attribute. The LSM and attribute identifier values
are defined in include/uapi/linux/lsm.h

LSM identifiers are simple integers and reflect the order in which
the LSM was added to the mainline kernel. This is a convention, not
a promise of the API. LSM identifiers below the value of 100 are
reserved for unspecified future uses. That could include information
about the security infrastructure itself, or about how multiple LSMs
might interact with each other.

A new LSM hook security_getselfattr() is introduced to get the
required information from the security modules. This is similar
to the existing security_getprocattr() hook, but specifies the
format in which string data is returned and requires the module
to put the information into a userspace destination.

lsm_set_self_attr() changes the specified LSM attribute. Only one
attribute can be changed at a time, and then only if the specified
security module allows the change.

A new LSM hook security_setselfattr() is introduced to set the
required information in the security modules. This is similar
to the existing security_setprocattr() hook, but specifies the
format in which string data is presented and requires the module
to get the information from a userspace destination.

lsm_list_modules() provides the LSM identifiers, in order, of the
security modules that are active on the system. This has been
available in the securityfs file /sys/kernel/security/lsm.

Patch 0001 changes the LSM registration from passing the name
of the module to passing a lsm_id structure that contains the
name of the module, an LSM identifier number and an attribute
identifier.
Patch 0002 adds the registered lsm_ids to a table.
Patch 0003 changes security_[gs]etprocattr() to use LSM IDs instead
of LSM names.
Patch 0004 implements lsm_get_self_attr() and lsm_set_self_attr().
New LSM hooks security_getselfattr() and security_setselfattr() are
defined.
Patch 0005 implements lsm_list_modules().
Patch 0006 wires up the syscalls.
Patch 0007 implements helper functions to make it easier for
security modules to use lsm_ctx structures.
Patch 0008 provides the Smack implementation for [gs]etselfattr().
Patch 0009 provides the AppArmor implementation for [gs]etselfattr().
Patch 0010 provides the SELinux implementation for [gs]etselfattr().
Patch 0011 implements selftests for the three new syscalls.

https://github.com/cschaufler/lsm-stacking.git#lsm-syscalls-6.3-rc2-a

v7: Pass the attribute desired to lsm_[gs]et_self_attr in its own
    parameter rather than encoding it in the flags.
    Change the flags parameters to u32.
    Don't shortcut out of calling LSM specific code in the
    infrastructure, let the LSM report that doesn't support an
    attribute instead. With that it is not necessary to maintain
    a set of supported attributes in the lsm_id structure.
    Fix a typing error.
v6: Switch from reusing security_[gs]procattr() to using new
    security_[gs]selfattr() hooks. Use explicit sized data types
    in the lsm_ctx structure.

v5: Correct syscall parameter data types.

v4: Restore "reserved" LSM ID values. Add explaination.
    Squash patches that introduce fields in lsm_id.
    Correct a wireup error.

v3: Add lsm_set_self_attr().
    Rename lsm_self_attr() to lsm_get_self_attr().
    Provide the values only for a specifed attribute in
    lsm_get_self_attr().
    Add selftests for the three new syscalls.
    Correct some parameter checking.

v2: Use user-interface safe data types.
    Remove "reserved" LSM ID values.
    Improve kerneldoc comments
    Include copyright dates
    Use more descriptive name for LSM counter
    Add documentation
    Correct wireup errors

Casey Schaufler (11):
  LSM: Identify modules by more than name
  LSM: Maintain a table of LSM attribute data
  proc: Use lsmids instead of lsm names for attrs
  LSM: syscalls for current process attributes
  LSM: Create lsm_list_modules system call
  LSM: wireup Linux Security Module syscalls
  LSM: Helpers for attribute names and filling an lsm_ctx
  Smack: implement setselfattr and getselfattr hooks
  AppArmor: Add selfattr hooks
  SELinux: Add selfattr hooks
  LSM: selftests for Linux Security Module syscalls

 Documentation/userspace-api/index.rst         |   1 +
 Documentation/userspace-api/lsm.rst           |  73 +++++
 MAINTAINERS                                   |   1 +
 arch/alpha/kernel/syscalls/syscall.tbl        |   3 +
 arch/arm/tools/syscall.tbl                    |   3 +
 arch/arm64/include/asm/unistd.h               |   2 +-
 arch/arm64/include/asm/unistd32.h             |   6 +
 arch/ia64/kernel/syscalls/syscall.tbl         |   3 +
 arch/m68k/kernel/syscalls/syscall.tbl         |   3 +
 arch/microblaze/kernel/syscalls/syscall.tbl   |   3 +
 arch/mips/kernel/syscalls/syscall_n32.tbl     |   3 +
 arch/mips/kernel/syscalls/syscall_n64.tbl     |   3 +
 arch/mips/kernel/syscalls/syscall_o32.tbl     |   3 +
 arch/parisc/kernel/syscalls/syscall.tbl       |   3 +
 arch/powerpc/kernel/syscalls/syscall.tbl      |   3 +
 arch/s390/kernel/syscalls/syscall.tbl         |   3 +
 arch/sh/kernel/syscalls/syscall.tbl           |   3 +
 arch/sparc/kernel/syscalls/syscall.tbl        |   3 +
 arch/x86/entry/syscalls/syscall_32.tbl        |   3 +
 arch/x86/entry/syscalls/syscall_64.tbl        |   3 +
 arch/xtensa/kernel/syscalls/syscall.tbl       |   3 +
 fs/proc/base.c                                |  29 +-
 fs/proc/internal.h                            |   2 +-
 include/linux/lsm_hook_defs.h                 |   4 +
 include/linux/lsm_hooks.h                     |  27 +-
 include/linux/security.h                      |  45 ++-
 include/linux/syscalls.h                      |   6 +
 include/uapi/asm-generic/unistd.h             |  11 +-
 include/uapi/linux/lsm.h                      |  86 ++++++
 kernel/sys_ni.c                               |   5 +
 security/Makefile                             |   1 +
 security/apparmor/include/procattr.h          |   2 +-
 security/apparmor/lsm.c                       | 104 ++++++-
 security/apparmor/procattr.c                  |  11 +-
 security/bpf/hooks.c                          |   9 +-
 security/commoncap.c                          |   8 +-
 security/landlock/cred.c                      |   2 +-
 security/landlock/fs.c                        |   2 +-
 security/landlock/ptrace.c                    |   2 +-
 security/landlock/setup.c                     |   6 +
 security/landlock/setup.h                     |   1 +
 security/loadpin/loadpin.c                    |   9 +-
 security/lockdown/lockdown.c                  |   8 +-
 security/lsm_syscalls.c                       | 145 ++++++++++
 security/safesetid/lsm.c                      |   9 +-
 security/security.c                           | 191 +++++++++++--
 security/selinux/hooks.c                      | 156 ++++++++--
 security/smack/smack_lsm.c                    | 113 +++++++-
 security/tomoyo/tomoyo.c                      |   9 +-
 security/yama/yama_lsm.c                      |   8 +-
 .../arch/mips/entry/syscalls/syscall_n64.tbl  |   3 +
 .../arch/powerpc/entry/syscalls/syscall.tbl   |   3 +
 .../perf/arch/s390/entry/syscalls/syscall.tbl |   3 +
 .../arch/x86/entry/syscalls/syscall_64.tbl    |   3 +
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/lsm/Makefile          |  12 +
 tools/testing/selftests/lsm/config            |   2 +
 .../selftests/lsm/lsm_get_self_attr_test.c    | 268 ++++++++++++++++++
 .../selftests/lsm/lsm_list_modules_test.c     | 149 ++++++++++
 .../selftests/lsm/lsm_set_self_attr_test.c    |  70 +++++
 60 files changed, 1555 insertions(+), 101 deletions(-)
 create mode 100644 Documentation/userspace-api/lsm.rst
 create mode 100644 include/uapi/linux/lsm.h
 create mode 100644 security/lsm_syscalls.c
 create mode 100644 tools/testing/selftests/lsm/Makefile
 create mode 100644 tools/testing/selftests/lsm/config
 create mode 100644 tools/testing/selftests/lsm/lsm_get_self_attr_test.c
 create mode 100644 tools/testing/selftests/lsm/lsm_list_modules_test.c
 create mode 100644 tools/testing/selftests/lsm/lsm_set_self_attr_test.c

-- 
2.39.2

[PATCH v7 01/11] LSM: Identify modules by more than name

[Casey Schaufler]

Create a struct lsm_id to contain identifying information
about Linux Security Modules (LSMs). At inception this contains
the name of the module, an identifier associated with the security
module and an integer member "attrs" which identifies the API
related data associated with each security module. The initial set
of features maps to information that has traditionaly been available
in /proc/self/attr. They are documented in a new userspace-api file.
Change the security_add_hooks() interface to use this structure.
Change the individual modules to maintain their own struct lsm_id
and pass it to security_add_hooks().

The values are for LSM identifiers are defined in a new UAPI
header file linux/lsm.h. Each existing LSM has been updated to
include it's LSMID in the lsm_id.

The LSM ID values are sequential, with the oldest module
LSM_ID_CAPABILITY being the lowest value and the existing modules
numbered in the order they were included in the main line kernel.
This is an arbitrary convention for assigning the values, but
none better presents itself. The value 0 is defined as being invalid.
The values 1-99 are reserved for any special case uses which may
arise in the future. This may include attributes of the LSM
infrastructure itself, possibly related to namespacing or network
attribute management. A special range is identified for such attributes
to help reduce confusion for developers unfamiliar with LSMs.

LSM attribute values are defined for the attributes presented by
modules that are available today. As with the LSM IDs, The value 0
is defined as being invalid. The values 1-99 are reserved for any
special case uses which may arise in the future.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-security-module <linux-security-module@vger.kernel.org>
---
 Documentation/userspace-api/index.rst |  1 +
 Documentation/userspace-api/lsm.rst   | 55 +++++++++++++++++++++++++++
 MAINTAINERS                           |  1 +
 include/linux/lsm_hooks.h             | 18 ++++++++-
 include/uapi/linux/lsm.h              | 53 ++++++++++++++++++++++++++
 security/apparmor/lsm.c               |  8 +++-
 security/bpf/hooks.c                  |  9 ++++-
 security/commoncap.c                  |  8 +++-
 security/landlock/cred.c              |  2 +-
 security/landlock/fs.c                |  2 +-
 security/landlock/ptrace.c            |  2 +-
 security/landlock/setup.c             |  6 +++
 security/landlock/setup.h             |  1 +
 security/loadpin/loadpin.c            |  9 ++++-
 security/lockdown/lockdown.c          |  8 +++-
 security/safesetid/lsm.c              |  9 ++++-
 security/security.c                   | 12 +++---
 security/selinux/hooks.c              |  9 ++++-
 security/smack/smack_lsm.c            |  8 +++-
 security/tomoyo/tomoyo.c              |  9 ++++-
 security/yama/yama_lsm.c              |  8 +++-
 21 files changed, 217 insertions(+), 21 deletions(-)
 create mode 100644 Documentation/userspace-api/lsm.rst
 create mode 100644 include/uapi/linux/lsm.h

diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
index f16337bdb852..54c0f54cde89 100644
--- a/Documentation/userspace-api/index.rst
+++ b/Documentation/userspace-api/index.rst
@@ -31,6 +31,7 @@ place where this information is gathered.
    sysfs-platform_profile
    vduse
    futex2
+   lsm
 
 .. only::  subproject and html
 
diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
new file mode 100644
index 000000000000..6ddf5506110b
--- /dev/null
+++ b/Documentation/userspace-api/lsm.rst
@@ -0,0 +1,55 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
+.. Copyright (C) 2022 Intel Corporation
+
+=====================================
+Linux Security Modules
+=====================================
+
+:Author: Casey Schaufler
+:Date: November 2022
+
+Linux security modules (LSM) provide a mechanism to implement
+additional access controls to the Linux security policies.
+
+The various security modules may support any of these attributes:
+
+``LSM_ATTR_CURRENT`` is the current, active security context of the
+process.
+The proc filesystem provides this value in ``/proc/self/attr/current``.
+This is supported by the SELinux, Smack and AppArmor security modules.
+Smack also provides this value in ``/proc/self/attr/smack/current``.
+AppArmor also provides this value in ``/proc/self/attr/apparmor/current``.
+
+``LSM_ATTR_EXEC`` is the security context of the process at the time the
+current image was executed.
+The proc filesystem provides this value in ``/proc/self/attr/exec``.
+This is supported by the SELinux and AppArmor security modules.
+AppArmor also provides this value in ``/proc/self/attr/apparmor/exec``.
+
+``LSM_ATTR_FSCREATE`` is the security context of the process used when
+creating file system objects.
+The proc filesystem provides this value in ``/proc/self/attr/fscreate``.
+This is supported by the SELinux security module.
+
+``LSM_ATTR_KEYCREATE`` is the security context of the process used when
+creating key objects.
+The proc filesystem provides this value in ``/proc/self/attr/keycreate``.
+This is supported by the SELinux security module.
+
+``LSM_ATTR_PREV`` is the security context of the process at the time the
+current security context was set.
+The proc filesystem provides this value in ``/proc/self/attr/prev``.
+This is supported by the SELinux and AppArmor security modules.
+AppArmor also provides this value in ``/proc/self/attr/apparmor/prev``.
+
+``LSM_ATTR_SOCKCREATE`` is the security context of the process used when
+creating socket objects.
+The proc filesystem provides this value in ``/proc/self/attr/sockcreate``.
+This is supported by the SELinux security module.
+
+Additional documentation
+========================
+
+* Documentation/security/lsm.rst
+* Documentation/security/lsm-development.rst
diff --git a/MAINTAINERS b/MAINTAINERS
index ec57c42ed544..9700ea3ff3da 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18813,6 +18813,7 @@ S:	Supported
 W:	http://kernsec.org/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git
 F:	security/
+F:	include/uapi/linux/lsm.h
 X:	security/selinux/
 
 SELINUX SECURITY MODULE
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 6e156d2acffc..32285ce65419 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1665,6 +1665,20 @@ struct security_hook_heads {
 	#undef LSM_HOOK
 } __randomize_layout;
 
+/**
+ * struct lsm_id - Identify a Linux Security Module.
+ * @lsm: name of the LSM, must be approved by the LSM maintainers
+ * @id: LSM ID number from uapi/linux/lsm.h
+ * @attrs: which attributes this LSM supports
+ *
+ * Contains the information that identifies the LSM.
+ */
+struct lsm_id {
+	const u8	*lsm;
+	u64		id;
+	u64		attrs;
+};
+
 /*
  * Security module hook list structure.
  * For use with generic list macros for common operations.
@@ -1673,7 +1687,7 @@ struct security_hook_list {
 	struct hlist_node		list;
 	struct hlist_head		*head;
 	union security_list_options	hook;
-	const char			*lsm;
+	struct lsm_id			*lsmid;
 } __randomize_layout;
 
 /*
@@ -1708,7 +1722,7 @@ extern struct security_hook_heads security_hook_heads;
 extern char *lsm_names;
 
 extern void security_add_hooks(struct security_hook_list *hooks, int count,
-				const char *lsm);
+			       struct lsm_id *lsmid);
 
 #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
 #define LSM_FLAG_EXCLUSIVE	BIT(1)
diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
new file mode 100644
index 000000000000..aa3e01867739
--- /dev/null
+++ b/include/uapi/linux/lsm.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Linux Security Modules (LSM) - User space API
+ *
+ * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#ifndef _UAPI_LINUX_LSM_H
+#define _UAPI_LINUX_LSM_H
+
+/*
+ * ID tokens to identify Linux Security Modules (LSMs)
+ *
+ * These token values are used to uniquely identify specific LSMs
+ * in the kernel as well as in the kernel's LSM userspace API.
+ *
+ * A value of zero/0 is considered undefined and should not be used
+ * outside the kernel. Values 1-99 are reserved for potential
+ * future use.
+ */
+#define LSM_ID_UNDEF		0
+#define LSM_ID_CAPABILITY	100
+#define LSM_ID_SELINUX		101
+#define LSM_ID_SMACK		102
+#define LSM_ID_TOMOYO		103
+#define LSM_ID_IMA		104
+#define LSM_ID_APPARMOR		105
+#define LSM_ID_YAMA		106
+#define LSM_ID_LOADPIN		107
+#define LSM_ID_SAFESETID	108
+#define LSM_ID_LOCKDOWN		109
+#define LSM_ID_BPF		110
+#define LSM_ID_LANDLOCK		111
+
+/*
+ * LSM_ATTR_XXX definitions identify different LSM attributes
+ * which are used in the kernel's LSM userspace API. Support
+ * for these attributes vary across the different LSMs. None
+ * are required.
+ *
+ * A value of zero/0 is considered undefined and should not be used
+ * outside the kernel. Values 1-99 are reserved for potential
+ * future use.
+ */
+#define LSM_ATTR_CURRENT	100
+#define LSM_ATTR_EXEC		101
+#define LSM_ATTR_FSCREATE	102
+#define LSM_ATTR_KEYCREATE	103
+#define LSM_ATTR_PREV		104
+#define LSM_ATTR_SOCKCREATE	105
+
+#endif /* _UAPI_LINUX_LSM_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index d6cc4812ca53..ce6ccb7e06ec 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -24,6 +24,7 @@
 #include <linux/zstd.h>
 #include <net/sock.h>
 #include <uapi/linux/mount.h>
+#include <uapi/linux/lsm.h>
 
 #include "include/apparmor.h"
 #include "include/apparmorfs.h"
@@ -1215,6 +1216,11 @@ struct lsm_blob_sizes apparmor_blob_sizes __lsm_ro_after_init = {
 	.lbs_task = sizeof(struct aa_task_ctx),
 };
 
+static struct lsm_id apparmor_lsmid __lsm_ro_after_init = {
+	.lsm = "apparmor",
+	.id = LSM_ID_APPARMOR,
+};
+
 static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
 	LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
@@ -1910,7 +1916,7 @@ static int __init apparmor_init(void)
 		goto buffers_out;
 	}
 	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
-				"apparmor");
+				&apparmor_lsmid);
 
 	/* Report that AppArmor successfully initialized */
 	apparmor_initialized = 1;
diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c
index e5971fa74fd7..5232c80be5b3 100644
--- a/security/bpf/hooks.c
+++ b/security/bpf/hooks.c
@@ -5,6 +5,7 @@
  */
 #include <linux/lsm_hooks.h>
 #include <linux/bpf_lsm.h>
+#include <uapi/linux/lsm.h>
 
 static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
 	#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
@@ -15,9 +16,15 @@ static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(task_free, bpf_task_storage_free),
 };
 
+static struct lsm_id bpf_lsmid __lsm_ro_after_init = {
+	.lsm = "bpf",
+	.id = LSM_ID_BPF,
+};
+
 static int __init bpf_lsm_init(void)
 {
-	security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), "bpf");
+	security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks),
+			   &bpf_lsmid);
 	pr_info("LSM support for eBPF active\n");
 	return 0;
 }
diff --git a/security/commoncap.c b/security/commoncap.c
index 5bb7d1e96277..bbc0a210506a 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -25,6 +25,7 @@
 #include <linux/binfmts.h>
 #include <linux/personality.h>
 #include <linux/mnt_idmapping.h>
+#include <uapi/linux/lsm.h>
 
 /*
  * If a non-root user executes a setuid-root binary in
@@ -1440,6 +1441,11 @@ int cap_mmap_file(struct file *file, unsigned long reqprot,
 
 #ifdef CONFIG_SECURITY
 
+static struct lsm_id capability_lsmid __lsm_ro_after_init = {
+	.lsm = "capability",
+	.id = LSM_ID_CAPABILITY,
+};
+
 static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(capable, cap_capable),
 	LSM_HOOK_INIT(settime, cap_settime),
@@ -1464,7 +1470,7 @@ static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
 static int __init capability_init(void)
 {
 	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
-				"capability");
+			   &capability_lsmid);
 	return 0;
 }
 
diff --git a/security/landlock/cred.c b/security/landlock/cred.c
index ec6c37f04a19..2eb1d65f10d6 100644
--- a/security/landlock/cred.c
+++ b/security/landlock/cred.c
@@ -42,5 +42,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_cred_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			   LANDLOCK_NAME);
+			   &landlock_lsmid);
 }
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index adcea0fe7e68..fa0e6e76991c 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1307,5 +1307,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_fs_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			   LANDLOCK_NAME);
+			   &landlock_lsmid);
 }
diff --git a/security/landlock/ptrace.c b/security/landlock/ptrace.c
index 4c5b9cd71286..eab35808f395 100644
--- a/security/landlock/ptrace.c
+++ b/security/landlock/ptrace.c
@@ -116,5 +116,5 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
 __init void landlock_add_ptrace_hooks(void)
 {
 	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
-			   LANDLOCK_NAME);
+			   &landlock_lsmid);
 }
diff --git a/security/landlock/setup.c b/security/landlock/setup.c
index 3f196d2ce4f9..9104133d04ca 100644
--- a/security/landlock/setup.c
+++ b/security/landlock/setup.c
@@ -8,6 +8,7 @@
 
 #include <linux/init.h>
 #include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
 
 #include "common.h"
 #include "cred.h"
@@ -24,6 +25,11 @@ struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = {
 	.lbs_superblock = sizeof(struct landlock_superblock_security),
 };
 
+struct lsm_id landlock_lsmid __lsm_ro_after_init = {
+	.lsm = LANDLOCK_NAME,
+	.id = LSM_ID_LANDLOCK,
+};
+
 static int __init landlock_init(void)
 {
 	landlock_add_cred_hooks();
diff --git a/security/landlock/setup.h b/security/landlock/setup.h
index 1daffab1ab4b..38bce5b172dc 100644
--- a/security/landlock/setup.h
+++ b/security/landlock/setup.h
@@ -14,5 +14,6 @@
 extern bool landlock_initialized;
 
 extern struct lsm_blob_sizes landlock_blob_sizes;
+extern struct lsm_id landlock_lsmid;
 
 #endif /* _SECURITY_LANDLOCK_SETUP_H */
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index d73a281adf86..556d43e37177 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -20,6 +20,7 @@
 #include <linux/string_helpers.h>
 #include <linux/dm-verity-loadpin.h>
 #include <uapi/linux/loadpin.h>
+#include <uapi/linux/lsm.h>
 
 #define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS"
 
@@ -214,6 +215,11 @@ static int loadpin_load_data(enum kernel_load_data_id id, bool contents)
 	return loadpin_check(NULL, (enum kernel_read_file_id) id);
 }
 
+static struct lsm_id loadpin_lsmid __lsm_ro_after_init = {
+	.lsm = "loadpin",
+	.id = LSM_ID_LOADPIN,
+};
+
 static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
 	LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
@@ -265,7 +271,8 @@ static int __init loadpin_init(void)
 	if (!register_sysctl_paths(loadpin_sysctl_path, loadpin_sysctl_table))
 		pr_notice("sysctl registration failed!\n");
 #endif
-	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
+	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks),
+			   &loadpin_lsmid);
 
 	return 0;
 }
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index a79b985e917e..e8c41a0caf7d 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -13,6 +13,7 @@
 #include <linux/security.h>
 #include <linux/export.h>
 #include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
 
 static enum lockdown_reason kernel_locked_down;
 
@@ -75,6 +76,11 @@ static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
 };
 
+static struct lsm_id lockdown_lsmid __lsm_ro_after_init = {
+	.lsm = "lockdown",
+	.id = LSM_ID_LOCKDOWN,
+};
+
 static int __init lockdown_lsm_init(void)
 {
 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY)
@@ -83,7 +89,7 @@ static int __init lockdown_lsm_init(void)
 	lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX);
 #endif
 	security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks),
-			   "lockdown");
+			   &lockdown_lsmid);
 	return 0;
 }
 
diff --git a/security/safesetid/lsm.c b/security/safesetid/lsm.c
index e806739f7868..8d0742ba045d 100644
--- a/security/safesetid/lsm.c
+++ b/security/safesetid/lsm.c
@@ -19,6 +19,7 @@
 #include <linux/ptrace.h>
 #include <linux/sched/task_stack.h>
 #include <linux/security.h>
+#include <uapi/linux/lsm.h>
 #include "lsm.h"
 
 /* Flag indicating whether initialization completed */
@@ -261,6 +262,11 @@ static int safesetid_task_fix_setgroups(struct cred *new, const struct cred *old
 	return 0;
 }
 
+static struct lsm_id safesetid_lsmid __lsm_ro_after_init = {
+	.lsm = "safesetid",
+	.id = LSM_ID_SAFESETID,
+};
+
 static struct security_hook_list safesetid_security_hooks[] = {
 	LSM_HOOK_INIT(task_fix_setuid, safesetid_task_fix_setuid),
 	LSM_HOOK_INIT(task_fix_setgid, safesetid_task_fix_setgid),
@@ -271,7 +277,8 @@ static struct security_hook_list safesetid_security_hooks[] = {
 static int __init safesetid_security_init(void)
 {
 	security_add_hooks(safesetid_security_hooks,
-			   ARRAY_SIZE(safesetid_security_hooks), "safesetid");
+			   ARRAY_SIZE(safesetid_security_hooks),
+			   &safesetid_lsmid);
 
 	/* Report that SafeSetID successfully initialized */
 	safesetid_initialized = 1;
diff --git a/security/security.c b/security/security.c
index cf6cc576736f..58828a326024 100644
--- a/security/security.c
+++ b/security/security.c
@@ -504,17 +504,17 @@ static int lsm_append(const char *new, char **result)
  * security_add_hooks - Add a modules hooks to the hook lists.
  * @hooks: the hooks to add
  * @count: the number of hooks to add
- * @lsm: the name of the security module
+ * @lsmid: the identification information for the security module
  *
  * Each LSM has to register its hooks with the infrastructure.
  */
 void __init security_add_hooks(struct security_hook_list *hooks, int count,
-				const char *lsm)
+			       struct lsm_id *lsmid)
 {
 	int i;
 
 	for (i = 0; i < count; i++) {
-		hooks[i].lsm = lsm;
+		hooks[i].lsmid = lsmid;
 		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
 	}
 
@@ -523,7 +523,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 	 * and fix this up afterwards.
 	 */
 	if (slab_is_available()) {
-		if (lsm_append(lsm, &lsm_names) < 0)
+		if (lsm_append(lsmid->lsm, &lsm_names) < 0)
 			panic("%s - Cannot get early memory.\n", __func__);
 	}
 }
@@ -2146,7 +2146,7 @@ int security_getprocattr(struct task_struct *p, const char *lsm,
 	struct security_hook_list *hp;
 
 	hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
-		if (lsm != NULL && strcmp(lsm, hp->lsm))
+		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
 			continue;
 		return hp->hook.getprocattr(p, name, value);
 	}
@@ -2159,7 +2159,7 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
 	struct security_hook_list *hp;
 
 	hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
-		if (lsm != NULL && strcmp(lsm, hp->lsm))
+		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
 			continue;
 		return hp->hook.setprocattr(name, value, size);
 	}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9a5bdfc21314..9403aee75981 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -92,6 +92,7 @@
 #include <linux/fsnotify.h>
 #include <linux/fanotify.h>
 #include <linux/io_uring.h>
+#include <uapi/linux/lsm.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -7032,6 +7033,11 @@ static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
 }
 #endif /* CONFIG_IO_URING */
 
+static struct lsm_id selinux_lsmid __lsm_ro_after_init = {
+	.lsm = "selinux",
+	.id = LSM_ID_SELINUX,
+};
+
 /*
  * IMPORTANT NOTE: When adding new hooks, please be careful to keep this order:
  * 1. any hooks that don't belong to (2.) or (3.) below,
@@ -7355,7 +7361,8 @@ static __init int selinux_init(void)
 
 	hashtab_cache_init();
 
-	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
+	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks),
+			   &selinux_lsmid);
 
 	if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
 		panic("SELinux: Unable to register AVC netcache callback\n");
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index cfcbb748da25..3cf862fcbe08 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -43,6 +43,7 @@
 #include <linux/fs_parser.h>
 #include <linux/watch_queue.h>
 #include <linux/io_uring.h>
+#include <uapi/linux/lsm.h>
 #include "smack.h"
 
 #define TRANS_TRUE	"TRUE"
@@ -4856,6 +4857,11 @@ struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = {
 	.lbs_superblock = sizeof(struct superblock_smack),
 };
 
+static struct lsm_id smack_lsmid __lsm_ro_after_init = {
+	.lsm = "smack",
+	.id = LSM_ID_SMACK,
+};
+
 static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(ptrace_access_check, smack_ptrace_access_check),
 	LSM_HOOK_INIT(ptrace_traceme, smack_ptrace_traceme),
@@ -5062,7 +5068,7 @@ static __init int smack_init(void)
 	/*
 	 * Register with LSM
 	 */
-	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
+	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), &smack_lsmid);
 	smack_enabled = 1;
 
 	pr_info("Smack:  Initializing.\n");
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index af04a7b7eb28..a4658fb5ef0e 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
 #include "common.h"
 
 /**
@@ -542,6 +543,11 @@ static void tomoyo_task_free(struct task_struct *task)
 	}
 }
 
+static struct lsm_id tomoyo_lsmid __lsm_ro_after_init = {
+	.lsm = "tomoyo",
+	.id = LSM_ID_TOMOYO,
+};
+
 /*
  * tomoyo_security_ops is a "struct security_operations" which is used for
  * registering TOMOYO.
@@ -595,7 +601,8 @@ static int __init tomoyo_init(void)
 	struct tomoyo_task *s = tomoyo_task(current);
 
 	/* register ourselves with the security framework */
-	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
+	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks),
+			   &tomoyo_lsmid);
 	pr_info("TOMOYO Linux initialized\n");
 	s->domain_info = &tomoyo_kernel_domain;
 	atomic_inc(&tomoyo_kernel_domain.users);
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 06e226166aab..2487b8f847f3 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -18,6 +18,7 @@
 #include <linux/task_work.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
+#include <uapi/linux/lsm.h>
 
 #define YAMA_SCOPE_DISABLED	0
 #define YAMA_SCOPE_RELATIONAL	1
@@ -421,6 +422,11 @@ static int yama_ptrace_traceme(struct task_struct *parent)
 	return rc;
 }
 
+static struct lsm_id yama_lsmid __lsm_ro_after_init = {
+	.lsm = "yama",
+	.id = LSM_ID_YAMA,
+};
+
 static struct security_hook_list yama_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
 	LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
@@ -477,7 +483,7 @@ static inline void yama_init_sysctl(void) { }
 static int __init yama_init(void)
 {
 	pr_info("Yama: becoming mindful.\n");
-	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
+	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), &yama_lsmid);
 	yama_init_sysctl();
 	return 0;
 }
-- 
2.39.2

[PATCH v7 02/11] LSM: Maintain a table of LSM attribute data

[Casey Schaufler]

As LSMs are registered add their lsm_id pointers to a table.
This will be used later for attribute reporting.

Determine the number of possible security modules based on
their respective CONFIG options. This allows the number to be
known at build time. This allows data structures and tables
to use the constant.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/security.h |  2 ++
 security/security.c      | 44 ++++++++++++++++++++++++++++++++--------
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 5984d0d550b4..e70fc863b04a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -138,6 +138,8 @@ enum lockdown_reason {
 };
 
 extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
+extern u32 lsm_active_cnt;
+extern struct lsm_id *lsm_idlist[];
 
 /* These functions are in security/commoncap.c */
 extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
diff --git a/security/security.c b/security/security.c
index 58828a326024..aa84b1cf4253 100644
--- a/security/security.c
+++ b/security/security.c
@@ -28,12 +28,29 @@
 #include <linux/backing-dev.h>
 #include <linux/string.h>
 #include <linux/msg.h>
+#include <uapi/linux/lsm.h>
 #include <net/flow.h>
 
 #define MAX_LSM_EVM_XATTR	2
 
-/* How many LSMs were built into the kernel? */
-#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
+/*
+ * How many LSMs are built into the kernel as determined at
+ * build time. Used to determine fixed array sizes.
+ * The capability module is accounted for by CONFIG_SECURITY
+ */
+#define LSM_COUNT ( \
+	(IS_ENABLED(CONFIG_SECURITY) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_TOMOYO) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_IMA) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_APPARMOR) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_YAMA) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LOADPIN) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SAFESETID) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0))
 
 /*
  * These are descriptions of the reasons that can be passed to the
@@ -90,7 +107,7 @@ static __initdata const char *chosen_major_lsm;
 static __initconst const char * const builtin_lsm_order = CONFIG_LSM;
 
 /* Ordered list of LSMs to initialize. */
-static __initdata struct lsm_info **ordered_lsms;
+static __initdata struct lsm_info *ordered_lsms[LSM_COUNT];
 static __initdata struct lsm_info *exclusive;
 
 static __initdata bool debug;
@@ -341,13 +358,16 @@ static void __init report_lsm_order(void)
 	pr_cont("\n");
 }
 
+/*
+ * Current index to use while initializing the lsm id list.
+ */
+u32 lsm_active_cnt __lsm_ro_after_init;
+struct lsm_id *lsm_idlist[LSM_COUNT] __lsm_ro_after_init;
+
 static void __init ordered_lsm_init(void)
 {
 	struct lsm_info **lsm;
 
-	ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
-				GFP_KERNEL);
-
 	if (chosen_lsm_order) {
 		if (chosen_major_lsm) {
 			pr_warn("security=%s is ignored because it is superseded by lsm=%s\n",
@@ -387,8 +407,6 @@ static void __init ordered_lsm_init(void)
 	lsm_early_task(current);
 	for (lsm = ordered_lsms; *lsm; lsm++)
 		initialize_lsm(*lsm);
-
-	kfree(ordered_lsms);
 }
 
 int __init early_security_init(void)
@@ -513,6 +531,16 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 {
 	int i;
 
+	/*
+	 * A security module may call security_add_hooks() more
+	 * than once. Landlock is one such case.
+	 */
+	if (lsm_active_cnt == 0 || lsm_idlist[lsm_active_cnt - 1] != lsmid)
+		lsm_idlist[lsm_active_cnt++] = lsmid;
+
+	if (lsm_active_cnt > LSM_COUNT)
+		panic("%s Too many LSMs registered.\n", __func__);
+
 	for (i = 0; i < count; i++) {
 		hooks[i].lsmid = lsmid;
 		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
-- 
2.39.2

[PATCH v7 03/11] proc: Use lsmids instead of lsm names for attrs

[Casey Schaufler]

Use the LSM ID number instead of the LSM name to identify which
security module's attibute data should be shown in /proc/self/attr.
The security_[gs]etprocattr() functions have been changed to expect
the LSM ID. The change from a string comparison to an integer comparison
in these functions will provide a minor performance improvement.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-fsdevel@vger.kernel.org
---
 fs/proc/base.c           | 29 +++++++++++++++--------------
 fs/proc/internal.h       |  2 +-
 include/linux/security.h | 11 +++++------
 security/security.c      | 11 +++++------
 4 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 5e0e0ccd47aa..cb6dec7473fe 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -96,6 +96,7 @@
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
 #include <linux/cn_proc.h>
+#include <uapi/linux/lsm.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"
@@ -145,10 +146,10 @@ struct pid_entry {
 	NOD(NAME, (S_IFREG|(MODE)),			\
 		NULL, &proc_single_file_operations,	\
 		{ .proc_show = show } )
-#define ATTR(LSM, NAME, MODE)				\
+#define ATTR(LSMID, NAME, MODE)				\
 	NOD(NAME, (S_IFREG|(MODE)),			\
 		NULL, &proc_pid_attr_operations,	\
-		{ .lsm = LSM })
+		{ .lsmid = LSMID })
 
 /*
  * Count the number of hardlinks for the pid_entry table, excluding the .
@@ -2730,7 +2731,7 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
 	if (!task)
 		return -ESRCH;
 
-	length = security_getprocattr(task, PROC_I(inode)->op.lsm,
+	length = security_getprocattr(task, PROC_I(inode)->op.lsmid,
 				      file->f_path.dentry->d_name.name,
 				      &p);
 	put_task_struct(task);
@@ -2788,7 +2789,7 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
 	if (rv < 0)
 		goto out_free;
 
-	rv = security_setprocattr(PROC_I(inode)->op.lsm,
+	rv = security_setprocattr(PROC_I(inode)->op.lsmid,
 				  file->f_path.dentry->d_name.name, page,
 				  count);
 	mutex_unlock(&current->signal->cred_guard_mutex);
@@ -2837,27 +2838,27 @@ static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
 
 #ifdef CONFIG_SECURITY_SMACK
 static const struct pid_entry smack_attr_dir_stuff[] = {
-	ATTR("smack", "current",	0666),
+	ATTR(LSM_ID_SMACK, "current",	0666),
 };
 LSM_DIR_OPS(smack);
 #endif
 
 #ifdef CONFIG_SECURITY_APPARMOR
 static const struct pid_entry apparmor_attr_dir_stuff[] = {
-	ATTR("apparmor", "current",	0666),
-	ATTR("apparmor", "prev",	0444),
-	ATTR("apparmor", "exec",	0666),
+	ATTR(LSM_ID_APPARMOR, "current",	0666),
+	ATTR(LSM_ID_APPARMOR, "prev",		0444),
+	ATTR(LSM_ID_APPARMOR, "exec",		0666),
 };
 LSM_DIR_OPS(apparmor);
 #endif
 
 static const struct pid_entry attr_dir_stuff[] = {
-	ATTR(NULL, "current",		0666),
-	ATTR(NULL, "prev",		0444),
-	ATTR(NULL, "exec",		0666),
-	ATTR(NULL, "fscreate",		0666),
-	ATTR(NULL, "keycreate",		0666),
-	ATTR(NULL, "sockcreate",	0666),
+	ATTR(LSM_ID_UNDEF, "current",	0666),
+	ATTR(LSM_ID_UNDEF, "prev",		0444),
+	ATTR(LSM_ID_UNDEF, "exec",		0666),
+	ATTR(LSM_ID_UNDEF, "fscreate",	0666),
+	ATTR(LSM_ID_UNDEF, "keycreate",	0666),
+	ATTR(LSM_ID_UNDEF, "sockcreate",	0666),
 #ifdef CONFIG_SECURITY_SMACK
 	DIR("smack",			0555,
 	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 9dda7e54b2d0..a889d9ef9584 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -92,7 +92,7 @@ union proc_op {
 	int (*proc_show)(struct seq_file *m,
 		struct pid_namespace *ns, struct pid *pid,
 		struct task_struct *task);
-	const char *lsm;
+	int lsmid;
 };
 
 struct proc_inode {
diff --git a/include/linux/security.h b/include/linux/security.h
index e70fc863b04a..8faed81fc3b4 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -473,10 +473,9 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
 int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
 			unsigned nsops, int alter);
 void security_d_instantiate(struct dentry *dentry, struct inode *inode);
-int security_getprocattr(struct task_struct *p, const char *lsm, const char *name,
+int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
 			 char **value);
-int security_setprocattr(const char *lsm, const char *name, void *value,
-			 size_t size);
+int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
@@ -1344,14 +1343,14 @@ static inline void security_d_instantiate(struct dentry *dentry,
 					  struct inode *inode)
 { }
 
-static inline int security_getprocattr(struct task_struct *p, const char *lsm,
+static inline int security_getprocattr(struct task_struct *p, int lsmid,
 				       const char *name, char **value)
 {
 	return -EINVAL;
 }
 
-static inline int security_setprocattr(const char *lsm, char *name,
-				       void *value, size_t size)
+static inline int security_setprocattr(int lsmid, char *name, void *value,
+				       size_t size)
 {
 	return -EINVAL;
 }
diff --git a/security/security.c b/security/security.c
index aa84b1cf4253..87c8796c3c46 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2168,26 +2168,25 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
 }
 EXPORT_SYMBOL(security_d_instantiate);
 
-int security_getprocattr(struct task_struct *p, const char *lsm,
-			 const char *name, char **value)
+int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
+			 char **value)
 {
 	struct security_hook_list *hp;
 
 	hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
-		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
+		if (lsmid != 0 && lsmid != hp->lsmid->id)
 			continue;
 		return hp->hook.getprocattr(p, name, value);
 	}
 	return LSM_RET_DEFAULT(getprocattr);
 }
 
-int security_setprocattr(const char *lsm, const char *name, void *value,
-			 size_t size)
+int security_setprocattr(int lsmid, const char *name, void *value, size_t size)
 {
 	struct security_hook_list *hp;
 
 	hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
-		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
+		if (lsmid != 0 && lsmid != hp->lsmid->id)
 			continue;
 		return hp->hook.setprocattr(name, value, size);
 	}
-- 
2.39.2

[PATCH v7 04/11] LSM: syscalls for current process attributes

[Casey Schaufler]

Create a system call lsm_get_self_attr() to provide the security
module maintained attributes of the current process.
Create a system call lsm_set_self_attr() to set a security
module maintained attribute of the current process.
Historically these attributes have been exposed to user space via
entries in procfs under /proc/self/attr.

The attribute value is provided in a lsm_ctx structure. The structure
identifys the size of the attribute, and the attribute value. The format
of the attribute value is defined by the security module. A flags field
is included for LSM specific information. It is currently unused and must
be 0. The total size of the data, including the lsm_ctx structure and any
padding, is maintained as well.

struct lsm_ctx {
        __u64   id;
        __u64   flags;
        __u64   len;
        __u64   ctx_len;
        __u8    ctx[];
};

Two new LSM hooks are used to interface with the LSMs.
security_getselfattr() collects the lsm_ctx values from the
LSMs that support the hook, accounting for space requirements.
security_setselfattr() identifies which LSM the attribute is
intended for and passes it along.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/userspace-api/lsm.rst | 15 +++++
 include/linux/lsm_hook_defs.h       |  4 ++
 include/linux/lsm_hooks.h           |  9 +++
 include/linux/security.h            | 19 ++++++
 include/linux/syscalls.h            |  5 ++
 include/uapi/linux/lsm.h            | 33 ++++++++++
 kernel/sys_ni.c                     |  4 ++
 security/Makefile                   |  1 +
 security/lsm_syscalls.c             | 55 ++++++++++++++++
 security/security.c                 | 97 +++++++++++++++++++++++++++++
 10 files changed, 242 insertions(+)
 create mode 100644 security/lsm_syscalls.c

diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
index 6ddf5506110b..b45e402302b3 100644
--- a/Documentation/userspace-api/lsm.rst
+++ b/Documentation/userspace-api/lsm.rst
@@ -48,6 +48,21 @@ creating socket objects.
 The proc filesystem provides this value in ``/proc/self/attr/sockcreate``.
 This is supported by the SELinux security module.
 
+Kernel interface
+================
+
+Set a security attribute of the current process
+--------------------------------------------------
+
+.. kernel-doc:: security/lsm_syscalls.c
+    :identifiers: sys_lsm_set_self_attr
+
+Get the specified security attributes of the current process
+--------------------------------------------------
+
+.. kernel-doc:: security/lsm_syscalls.c
+    :identifiers: sys_lsm_get_self_attr
+
 Additional documentation
 ========================
 
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 094b76dc7164..7177d9554f4a 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -261,6 +261,10 @@ LSM_HOOK(int, 0, sem_semop, struct kern_ipc_perm *perm, struct sembuf *sops,
 LSM_HOOK(int, 0, netlink_send, struct sock *sk, struct sk_buff *skb)
 LSM_HOOK(void, LSM_RET_VOID, d_instantiate, struct dentry *dentry,
 	 struct inode *inode)
+LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int __user attr,
+	 struct lsm_ctx __user *ctx, size_t *size, u32 __user flags)
+LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int __user attr,
+	 struct lsm_ctx __user *ctx, size_t size, u32 __user flags)
 LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name,
 	 char **value)
 LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 32285ce65419..3c2c4916bd53 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -25,6 +25,7 @@
 #ifndef __LINUX_LSM_HOOKS_H
 #define __LINUX_LSM_HOOKS_H
 
+#include <uapi/linux/lsm.h>
 #include <linux/security.h>
 #include <linux/init.h>
 #include <linux/rculist.h>
@@ -503,6 +504,14 @@
  *	and writing the xattrs as this hook is merely a filter.
  * @d_instantiate:
  *	Fill in @inode security information for a @dentry if allowed.
+ * @getselfattr:
+ *	Read attribute @attr for the current process and store it into @ctx.
+ *	Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
+ *	or another negative value otherwise.
+ * @setselfattr:
+ *	Set attribute @attr for the current process.
+ *	Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
+ *	or another negative value otherwise.
  * @getprocattr:
  *	Read attribute @name for process @p and store it into @value if allowed.
  *	Return the length of @value on success, a negative value otherwise.
diff --git a/include/linux/security.h b/include/linux/security.h
index 8faed81fc3b4..329cd9d2be50 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -60,6 +60,7 @@ struct fs_parameter;
 enum fs_value_type;
 struct watch;
 struct watch_notification;
+struct lsm_ctx;
 
 /* Default (no) options for the capable function */
 #define CAP_OPT_NONE 0x0
@@ -473,6 +474,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
 int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
 			unsigned nsops, int alter);
 void security_d_instantiate(struct dentry *dentry, struct inode *inode);
+int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+			 size_t __user *size, u32 __user flags);
+int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+			 size_t __user size, u32 __user flags);
 int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
 			 char **value);
 int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
@@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
 					  struct inode *inode)
 { }
 
+static inline int security_getselfattr(unsigned int __user attr,
+				       struct lsm_ctx __user *ctx,
+				       size_t __user *size, u32 __user flags)
+{
+	return -EINVAL;
+}
+
+static inline int security_setselfattr(unsigned int __user attr,
+				       struct lsm_ctx __user *ctx,
+				       size_t __user size, u32 __user flags)
+{
+	return -EINVAL;
+}
+
 static inline int security_getprocattr(struct task_struct *p, int lsmid,
 				       const char *name, char **value)
 {
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 33a0ee3bcb2e..3feca00cb0c1 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -71,6 +71,7 @@ struct clone_args;
 struct open_how;
 struct mount_attr;
 struct landlock_ruleset_attr;
+struct lsm_ctx;
 enum landlock_rule_type;
 
 #include <linux/types.h>
@@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
 asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
 					    unsigned long home_node,
 					    unsigned long flags);
+asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+				      size_t *size, __u64 flags);
+asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+				      __u64 flags);
 
 /*
  * Architecture-specific system calls
diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
index aa3e01867739..adfb55dce2fd 100644
--- a/include/uapi/linux/lsm.h
+++ b/include/uapi/linux/lsm.h
@@ -9,6 +9,39 @@
 #ifndef _UAPI_LINUX_LSM_H
 #define _UAPI_LINUX_LSM_H
 
+#include <linux/types.h>
+#include <linux/unistd.h>
+
+/**
+ * struct lsm_ctx - LSM context information
+ * @id: the LSM id number, see LSM_ID_XXX
+ * @flags: LSM specific flags
+ * @len: length of the lsm_ctx struct, @ctx and any other data or padding
+ * @ctx_len: the size of @ctx
+ * @ctx: the LSM context value
+ *
+ * The @len field MUST be equal to the size of the lsm_ctx struct
+ * plus any additional padding and/or data placed after @ctx.
+ *
+ * In all cases @ctx_len MUST be equal to the length of @ctx.
+ * If @ctx is a string value it should be nul terminated with
+ * @ctx_len equal to `strlen(@ctx) + 1`.  Binary values are
+ * supported.
+ *
+ * The @flags and @ctx fields SHOULD only be interpreted by the
+ * LSM specified by @id; they MUST be set to zero/0 when not used.
+ */
+struct lsm_ctx {
+	__u64	id;
+	__u64	flags;
+	__u64	len;
+	__u64	ctx_len;
+	__u8	ctx[];
+};
+
+#include <linux/types.h>
+#include <linux/unistd.h>
+
 /*
  * ID tokens to identify Linux Security Modules (LSMs)
  *
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 860b2dcf3ac4..d03c78ef1562 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -262,6 +262,10 @@ COND_SYSCALL_COMPAT(recvmsg);
 /* mm/nommu.c, also with MMU */
 COND_SYSCALL(mremap);
 
+/* security/lsm_syscalls.c */
+COND_SYSCALL(lsm_get_self_attr);
+COND_SYSCALL(lsm_set_self_attr);
+
 /* security/keys/keyctl.c */
 COND_SYSCALL(add_key);
 COND_SYSCALL(request_key);
diff --git a/security/Makefile b/security/Makefile
index 18121f8f85cd..59f238490665 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_KEYS)			+= keys/
 
 # always enable default capabilities
 obj-y					+= commoncap.o
+obj-$(CONFIG_SECURITY) 			+= lsm_syscalls.o
 obj-$(CONFIG_MMU)			+= min_addr.o
 
 # Object file lists
diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
new file mode 100644
index 000000000000..feee31600219
--- /dev/null
+++ b/security/lsm_syscalls.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * System calls implementing the Linux Security Module API.
+ *
+ *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
+ *  Copyright (C) 2022 Intel Corporation
+ */
+
+#include <asm/current.h>
+#include <linux/compiler_types.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/security.h>
+#include <linux/stddef.h>
+#include <linux/syscalls.h>
+#include <linux/types.h>
+#include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
+
+/**
+ * sys_lsm_set_self_attr - Set current task's security module attribute
+ * @attr: which attribute to set
+ * @ctx: the LSM contexts
+ * @size: size of @ctx
+ * @flags: reserved for future use
+ *
+ * Sets the calling task's LSM context. On success this function
+ * returns 0. If the attribute specified cannot be set a negative
+ * value indicating the reason for the error is returned.
+ */
+SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
+		ctx, size_t __user, size, u32, flags)
+{
+	return security_setselfattr(attr, ctx, size, flags);
+}
+
+/**
+ * sys_lsm_get_self_attr - Return current task's security module attributes
+ * @attr: which attribute to set
+ * @ctx: the LSM contexts
+ * @size: size of @ctx, updated on return
+ * @flags: reserved for future use
+ *
+ * Returns the calling task's LSM contexts. On success this
+ * function returns the number of @ctx array elements. This value
+ * may be zero if there are no LSM contexts assigned. If @size is
+ * insufficient to contain the return data -E2BIG is returned and
+ * @size is set to the minimum required size. In all other cases
+ * a negative value indicating the error is returned.
+ */
+SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
+		ctx, size_t __user *, size, u32, flags)
+{
+	return security_getselfattr(attr, ctx, size, flags);
+}
diff --git a/security/security.c b/security/security.c
index 87c8796c3c46..2c57fe28c4f7 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
 }
 EXPORT_SYMBOL(security_d_instantiate);
 
+/**
+ * security_getselfattr - Read an LSM attribute of the current process.
+ * @attr: which attribute to return
+ * @ctx: the user-space destination for the information, or NULL
+ * @size: the size of space available to receive the data
+ * @flags: reserved for future use, must be 0
+ *
+ * Returns the number of attributes found on success, negative value
+ * on error. @size is reset to the total size of the data.
+ * If @size is insufficient to contain the data -E2BIG is returned.
+ */
+int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+			 size_t __user *size, u32 __user flags)
+{
+	struct security_hook_list *hp;
+	void __user *base = (void *)ctx;
+	size_t total = 0;
+	size_t this;
+	size_t left;
+	bool istoobig = false;
+	int count = 0;
+	int rc;
+
+	if (attr == 0)
+		return -EINVAL;
+	if (flags != 0)
+		return -EINVAL;
+	if (size == NULL)
+		return -EINVAL;
+	if (get_user(left, size))
+		return -EFAULT;
+
+	hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
+		this = left;
+		if (base)
+			ctx = (struct lsm_ctx __user *)(base + total);
+		rc = hp->hook.getselfattr(attr, ctx, &this, flags);
+		switch (rc) {
+		case -EOPNOTSUPP:
+			rc = 0;
+			continue;
+		case -E2BIG:
+			istoobig = true;
+			left = 0;
+			break;
+		case 0:
+			left -= this;
+			break;
+		default:
+			return rc;
+		}
+		total += this;
+		count++;
+	}
+	if (count == 0)
+		return LSM_RET_DEFAULT(getselfattr);
+	if (put_user(total, size))
+		return -EFAULT;
+	if (rc)
+		return rc;
+	if (istoobig)
+		return -E2BIG;
+	return count;
+}
+
+/**
+ * security_setselfattr - Set an LSM attribute on the current process.
+ * @attr: which attribute to set
+ * @ctx: the user-space source for the information
+ * @size: the size of the data
+ * @flags: reserved for future use, must be 0
+ *
+ * Set an LSM attribute for the current process. The LSM, attribute
+ * and new value are included in @ctx.
+ *
+ * Returns 0 on success, an LSM specific value on failure.
+ */
+int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+			 size_t __user size, u32 __user flags)
+{
+	struct security_hook_list *hp;
+	struct lsm_ctx lctx;
+
+	if (flags != 0)
+		return -EINVAL;
+	if (size < sizeof(*ctx))
+		return -EINVAL;
+	if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
+		return -EFAULT;
+
+	hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
+		if ((hp->lsmid->id) == lctx.id)
+			return hp->hook.setselfattr(attr, ctx, size, flags);
+
+	return LSM_RET_DEFAULT(setselfattr);
+}
+
 int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
 			 char **value)
 {
-- 
2.39.2

[PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Casey Schaufler]

Create a system call to report the list of Linux Security Modules
that are active on the system. The list is provided as an array
of LSM ID numbers.

The calling application can use this list determine what LSM
specific actions it might take. That might include chosing an
output format, determining required privilege or bypassing
security module specific behavior.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/userspace-api/lsm.rst |  3 +++
 include/linux/syscalls.h            |  1 +
 kernel/sys_ni.c                     |  1 +
 security/lsm_syscalls.c             | 39 +++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+)

diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
index b45e402302b3..a86e3817f062 100644
--- a/Documentation/userspace-api/lsm.rst
+++ b/Documentation/userspace-api/lsm.rst
@@ -63,6 +63,9 @@ Get the specified security attributes of the current process
 .. kernel-doc:: security/lsm_syscalls.c
     :identifiers: sys_lsm_get_self_attr
 
+.. kernel-doc:: security/lsm_syscalls.c
+    :identifiers: sys_lsm_list_modules
+
 Additional documentation
 ========================
 
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 3feca00cb0c1..f755c583f949 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1063,6 +1063,7 @@ asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
 				      size_t *size, __u64 flags);
 asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
 				      __u64 flags);
+asmlinkage long sys_lsm_list_modules(u64 *ids, size_t *size, u32 flags);
 
 /*
  * Architecture-specific system calls
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index d03c78ef1562..ceb3d21a62d0 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -265,6 +265,7 @@ COND_SYSCALL(mremap);
 /* security/lsm_syscalls.c */
 COND_SYSCALL(lsm_get_self_attr);
 COND_SYSCALL(lsm_set_self_attr);
+COND_SYSCALL(lsm_list_modules);
 
 /* security/keys/keyctl.c */
 COND_SYSCALL(add_key);
diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
index feee31600219..6efbe244d304 100644
--- a/security/lsm_syscalls.c
+++ b/security/lsm_syscalls.c
@@ -53,3 +53,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
 {
 	return security_getselfattr(attr, ctx, size, flags);
 }
+
+/**
+ * sys_lsm_list_modules - Return a list of the active security modules
+ * @ids: the LSM module ids
+ * @size: size of @ids, updated on return
+ * @flags: reserved for future use, must be zero
+ *
+ * Returns a list of the active LSM ids. On success this function
+ * returns the number of @ids array elements. This value may be zero
+ * if there are no LSMs active. If @size is insufficient to contain
+ * the return data -E2BIG is returned and @size is set to the minimum
+ * required size. In all other cases a negative value indicating the
+ * error is returned.
+ */
+SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
+		u32, flags)
+{
+	size_t total_size = lsm_active_cnt * sizeof(*ids);
+	size_t usize;
+	int i;
+
+	if (flags)
+		return -EINVAL;
+
+	if (get_user(usize, size))
+		return -EFAULT;
+
+	if (put_user(total_size, size) != 0)
+		return -EFAULT;
+
+	if (usize < total_size)
+		return -E2BIG;
+
+	for (i = 0; i < lsm_active_cnt; i++)
+		if (put_user(lsm_idlist[i]->id, ids++))
+			return -EFAULT;
+
+	return lsm_active_cnt;
+}
-- 
2.39.2

[PATCH v7 06/11] LSM: wireup Linux Security Module syscalls

[Casey Schaufler]

Wireup lsm_get_self_attr, lsm_set_self_attr and lsm_list_modules
system calls.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: linux-api@vger.kernel.org
---
 arch/alpha/kernel/syscalls/syscall.tbl              |  3 +++
 arch/arm/tools/syscall.tbl                          |  3 +++
 arch/arm64/include/asm/unistd.h                     |  2 +-
 arch/arm64/include/asm/unistd32.h                   |  6 ++++++
 arch/ia64/kernel/syscalls/syscall.tbl               |  3 +++
 arch/m68k/kernel/syscalls/syscall.tbl               |  3 +++
 arch/microblaze/kernel/syscalls/syscall.tbl         |  3 +++
 arch/mips/kernel/syscalls/syscall_n32.tbl           |  3 +++
 arch/mips/kernel/syscalls/syscall_n64.tbl           |  3 +++
 arch/mips/kernel/syscalls/syscall_o32.tbl           |  3 +++
 arch/parisc/kernel/syscalls/syscall.tbl             |  3 +++
 arch/powerpc/kernel/syscalls/syscall.tbl            |  3 +++
 arch/s390/kernel/syscalls/syscall.tbl               |  3 +++
 arch/sh/kernel/syscalls/syscall.tbl                 |  3 +++
 arch/sparc/kernel/syscalls/syscall.tbl              |  3 +++
 arch/x86/entry/syscalls/syscall_32.tbl              |  3 +++
 arch/x86/entry/syscalls/syscall_64.tbl              |  3 +++
 arch/xtensa/kernel/syscalls/syscall.tbl             |  3 +++
 include/uapi/asm-generic/unistd.h                   | 11 ++++++++++-
 tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl |  3 +++
 tools/perf/arch/powerpc/entry/syscalls/syscall.tbl  |  3 +++
 tools/perf/arch/s390/entry/syscalls/syscall.tbl     |  3 +++
 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl   |  3 +++
 23 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 8ebacf37a8cf..178e2792c251 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -490,3 +490,6 @@
 558	common	process_mrelease		sys_process_mrelease
 559	common  futex_waitv                     sys_futex_waitv
 560	common	set_mempolicy_home_node		sys_ni_syscall
+561	common	lsm_get_self_attr		sys_lsm_get_self_attr
+562	common	lsm_list_modules		sys_lsm_list_modules
+563	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index ac964612d8b0..9cda144f9631 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -464,3 +464,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common	futex_waitv			sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 037feba03a51..6a28fb91b85d 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -39,7 +39,7 @@
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE + 5)
 #define __ARM_NR_COMPAT_END		(__ARM_NR_COMPAT_BASE + 0x800)
 
-#define __NR_compat_syscalls		451
+#define __NR_compat_syscalls		454
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 604a2053d006..72022ffd5faa 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -907,6 +907,12 @@ __SYSCALL(__NR_process_mrelease, sys_process_mrelease)
 __SYSCALL(__NR_futex_waitv, sys_futex_waitv)
 #define __NR_set_mempolicy_home_node 450
 __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node)
+#define __NR_lsm_get_self_attr 451
+__SYSCALL(__NR_lsm_get_self_attr, sys_lsm_get_self_attr)
+#define __NR_lsm_list_modules 452
+__SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules)
+#define __NR_lsm_set_self_attr 453
+__SYSCALL(__NR_lsm_set_self_attr, sys_lsm_set_self_attr)
 
 /*
  * Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index 72c929d9902b..c52e9d87f47d 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -371,3 +371,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index b1f3940bc298..31eac3c99d84 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -450,3 +450,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 820145e47350..5037fa1f74b8 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -456,3 +456,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 253ff994ed2e..29545b3ec587 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -389,3 +389,6 @@
 448	n32	process_mrelease		sys_process_mrelease
 449	n32	futex_waitv			sys_futex_waitv
 450	n32	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	n32	lsm_get_self_attr		sys_lsm_get_self_attr
+452	n32	lsm_list_modules		sys_lsm_list_modules
+453	n32	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 3f1886ad9d80..8492aa4a771f 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -365,3 +365,6 @@
 448	n64	process_mrelease		sys_process_mrelease
 449	n64	futex_waitv			sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	n64	lsm_get_self_attr		sys_lsm_get_self_attr
+452	n64	lsm_list_modules		sys_lsm_list_modules
+453	n64	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 8f243e35a7b2..d74fd86de2a2 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -438,3 +438,6 @@
 448	o32	process_mrelease		sys_process_mrelease
 449	o32	futex_waitv			sys_futex_waitv
 450	o32	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	o32	lsm_get_self_attr		sys_lsm_get_self_attr
+452	o32	lsm_list_modules		sys_lsm_list_modules
+453	032	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 0e42fceb2d5e..d1a5f3120d6c 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -448,3 +448,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common	futex_waitv			sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index a0be127475b1..a414fe8c069b 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -537,3 +537,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450 	nospu	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 799147658dee..96b7e6b72747 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -453,3 +453,6 @@
 448  common	process_mrelease	sys_process_mrelease		sys_process_mrelease
 449  common	futex_waitv		sys_futex_waitv			sys_futex_waitv
 450  common	set_mempolicy_home_node	sys_set_mempolicy_home_node	sys_set_mempolicy_home_node
+451  common	lsm_get_self_attr	sys_lsm_get_self_attr		sys_lsm_get_self_attr
+452  common	lsm_list_modules	sys_lsm_list_modules		sys_lsm_list_modules
+453  common	lsm_set_self_attr	sys_lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 2de85c977f54..1a75a599bb55 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -453,3 +453,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 4398cc6fb68d..80b165091f6f 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -496,3 +496,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 320480a8db4f..130f9feb9eb9 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -455,3 +455,6 @@
 448	i386	process_mrelease	sys_process_mrelease
 449	i386	futex_waitv		sys_futex_waitv
 450	i386	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	i386	lsm_get_self_attr	sys_lsm_get_self_attr
+452	i386	lsm_list_modules	sys_lsm_list_modules
+453	i386	lsm_set_self_attr	sys_lsm_set_self_attr
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index c84d12608cd2..96dd45bc5988 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -372,6 +372,9 @@
 448	common	process_mrelease	sys_process_mrelease
 449	common	futex_waitv		sys_futex_waitv
 450	common	set_mempolicy_home_node	sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr	sys_lsm_get_self_attr
+452	common	lsm_list_modules	sys_lsm_list_modules
+453	common	lsm_set_self_attr	sys_lsm_set_self_attr
 
 #
 # Due to a historical design error, certain syscalls are numbered differently
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 52c94ab5c205..2610aba19802 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -421,3 +421,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 45fa180cc56a..93f89fb06ef5 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -886,8 +886,17 @@ __SYSCALL(__NR_futex_waitv, sys_futex_waitv)
 #define __NR_set_mempolicy_home_node 450
 __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node)
 
+#define __NR_lsm_get_self_attr 451
+__SYSCALL(__NR_lsm_get_self_attr, sys_lsm_get_self_attr)
+
+#define __NR_lsm_list_modules 452
+__SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules)
+
+#define __NR_lsm_set_self_attr 453
+__SYSCALL(__NR_lsm_set_self_attr, sys_lsm_set_self_attr)
+
 #undef __NR_syscalls
-#define __NR_syscalls 451
+#define __NR_syscalls 454
 
 /*
  * 32 bit systems traditionally used different
diff --git a/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
index 3f1886ad9d80..8492aa4a771f 100644
--- a/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
+++ b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl
@@ -365,3 +365,6 @@
 448	n64	process_mrelease		sys_process_mrelease
 449	n64	futex_waitv			sys_futex_waitv
 450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	n64	lsm_get_self_attr		sys_lsm_get_self_attr
+452	n64	lsm_list_modules		sys_lsm_list_modules
+453	n64	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index a0be127475b1..a414fe8c069b 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -537,3 +537,6 @@
 448	common	process_mrelease		sys_process_mrelease
 449	common  futex_waitv                     sys_futex_waitv
 450 	nospu	set_mempolicy_home_node		sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr		sys_lsm_get_self_attr
+452	common	lsm_list_modules		sys_lsm_list_modules
+453	common	lsm_set_self_attr		sys_lsm_set_self_attr
diff --git a/tools/perf/arch/s390/entry/syscalls/syscall.tbl b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
index 799147658dee..f9257e040109 100644
--- a/tools/perf/arch/s390/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/s390/entry/syscalls/syscall.tbl
@@ -453,3 +453,6 @@
 448  common	process_mrelease	sys_process_mrelease		sys_process_mrelease
 449  common	futex_waitv		sys_futex_waitv			sys_futex_waitv
 450  common	set_mempolicy_home_node	sys_set_mempolicy_home_node	sys_set_mempolicy_home_node
+451  common	lsm_get_self_attr	sys_lsm_get_self_attr	sys_lsm_get_self_attr
+452  common	lsm_list_modules	sys_lsm_list_modules	sys_lsm_list_modules
+453  common	lsm_set_self_attr	sys_lsm_set_self_attr	sys_lsm_set_self_attr
diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
index c84d12608cd2..96dd45bc5988 100644
--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
@@ -372,6 +372,9 @@
 448	common	process_mrelease	sys_process_mrelease
 449	common	futex_waitv		sys_futex_waitv
 450	common	set_mempolicy_home_node	sys_set_mempolicy_home_node
+451	common	lsm_get_self_attr	sys_lsm_get_self_attr
+452	common	lsm_list_modules	sys_lsm_list_modules
+453	common	lsm_set_self_attr	sys_lsm_set_self_attr
 
 #
 # Due to a historical design error, certain syscalls are numbered differently
-- 
2.39.2

[PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

Add lsm_name_to_attr(), which translates a text string to a
LSM_ATTR value if one is available.

Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
the trailing attribute value.

All are used in module specific components of LSM system calls.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/security.h | 13 ++++++++++
 security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
 security/security.c      | 31 ++++++++++++++++++++++++
 3 files changed, 95 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 329cd9d2be50..a5e860d332b5 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -263,6 +263,7 @@ int unregister_blocking_lsm_notifier(struct notifier_block *nb);
 /* prototypes */
 extern int security_init(void);
 extern int early_security_init(void);
+extern u64 lsm_name_to_attr(const char *name);
 
 /* Security operations */
 int security_binder_set_context_mgr(const struct cred *mgr);
@@ -491,6 +492,8 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
 int security_locked_down(enum lockdown_reason what);
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags);
 #else /* CONFIG_SECURITY */
 
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -508,6 +511,11 @@ static inline  int unregister_blocking_lsm_notifier(struct notifier_block *nb)
 	return 0;
 }
 
+static inline u64 lsm_name_to_attr(const char *name)
+{
+	return 0;
+}
+
 static inline void security_free_mnt_opts(void **mnt_opts)
 {
 }
@@ -1420,6 +1428,11 @@ static inline int security_locked_down(enum lockdown_reason what)
 {
 	return 0;
 }
+static inline int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+				    size_t context_size, u64 id, u64 flags)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
index 6efbe244d304..55d849ad5d6e 100644
--- a/security/lsm_syscalls.c
+++ b/security/lsm_syscalls.c
@@ -17,6 +17,57 @@
 #include <linux/lsm_hooks.h>
 #include <uapi/linux/lsm.h>
 
+struct attr_map {
+	char *name;
+	u64 attr;
+};
+
+static const struct attr_map lsm_attr_names[] = {
+	{
+		.name = "current",
+		.attr = LSM_ATTR_CURRENT,
+	},
+	{
+		.name = "exec",
+		.attr = LSM_ATTR_EXEC,
+	},
+	{
+		.name = "fscreate",
+		.attr = LSM_ATTR_FSCREATE,
+	},
+	{
+		.name = "keycreate",
+		.attr = LSM_ATTR_KEYCREATE,
+	},
+	{
+		.name = "prev",
+		.attr = LSM_ATTR_PREV,
+	},
+	{
+		.name = "sockcreate",
+		.attr = LSM_ATTR_SOCKCREATE,
+	},
+};
+
+/**
+ * lsm_name_to_attr - map an LSM attribute name to its ID
+ * @name: name of the attribute
+ *
+ * Look the given @name up in the table of know attribute names.
+ *
+ * Returns the LSM attribute value associated with @name, or 0 if
+ * there is no mapping.
+ */
+u64 lsm_name_to_attr(const char *name)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
+		if (!strcmp(name, lsm_attr_names[i].name))
+			return lsm_attr_names[i].attr;
+	return 0;
+}
+
 /**
  * sys_lsm_set_self_attr - Set current task's security module attribute
  * @attr: which attribute to set
diff --git a/security/security.c b/security/security.c
index 2c57fe28c4f7..f7b814a3940c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
 	return 0;
 }
 
+/**
+ * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
+ * @ctx: an LSM context to be filled
+ * @context: the new context value
+ * @context_size: the size of the new context value
+ * @id: LSM id
+ * @flags: LSM defined flags
+ *
+ * Fill all of the fields in a user space lsm_ctx structure.
+ * Caller is assumed to have verified that @ctx has enough space
+ * for @context.
+ * Returns 0 on success, -EFAULT on a copyout error.
+ */
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags)
+{
+	struct lsm_ctx local;
+	void __user *vc = ctx;
+
+	local.id = id;
+	local.flags = flags;
+	local.ctx_len = context_size;
+	local.len = context_size + sizeof(local);
+	vc += sizeof(local);
+	if (copy_to_user(ctx, &local, sizeof(local)))
+		return -EFAULT;
+	if (context_size > 0 && copy_to_user(vc, context, context_size))
+		return -EFAULT;
+	return 0;
+}
+
 /*
  * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
  * can be accessed with:
-- 
2.39.2

[PATCH v7 08/11] Smack: implement setselfattr and getselfattr hooks

[Casey Schaufler]

Implement Smack support for security_[gs]etselfattr.
Refactor the setprocattr hook to avoid code duplication.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 security/smack/smack_lsm.c | 105 +++++++++++++++++++++++++++++++++++--
 1 file changed, 100 insertions(+), 5 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3cf862fcbe08..b3e72b82ced9 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3552,6 +3552,41 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 	return;
 }
 
+/**
+ * smack_getselfattr - Smack current process attribute
+ * @attr: which attribute to fetch
+ * @ctx: buffer to receive the result
+ * @size: available size in, actual size out
+ * @flags: unused
+ *
+ * Fill the passed user space @ctx with the details of the requested
+ * attribute.
+ *
+ * Returns 0 on success, an error code otherwise.
+ */
+static int smack_getselfattr(unsigned int __user attr,
+			     struct lsm_ctx __user *ctx, size_t *size,
+			     u32 __user flags)
+{
+	struct smack_known *skp = smk_of_current();
+	int total;
+	int slen;
+	int rc = 0;
+
+	if (attr != LSM_ATTR_CURRENT)
+		return -EOPNOTSUPP;
+
+	slen = strlen(skp->smk_known) + 1;
+	total = slen + sizeof(*ctx);
+	if (total > *size)
+		rc = -E2BIG;
+	else
+		lsm_fill_user_ctx(ctx, skp->smk_known, slen, LSM_ID_SMACK, 0);
+
+	*size = total;
+	return rc;
+}
+
 /**
  * smack_getprocattr - Smack process attribute access
  * @p: the object task
@@ -3581,8 +3616,8 @@ static int smack_getprocattr(struct task_struct *p, const char *name, char **val
 }
 
 /**
- * smack_setprocattr - Smack process attribute setting
- * @name: the name of the attribute in /proc/.../attr
+ * do_setattr - Smack process attribute setting
+ * @attr: the ID of the attribute
  * @value: the value to set
  * @size: the size of the value
  *
@@ -3591,7 +3626,7 @@ static int smack_getprocattr(struct task_struct *p, const char *name, char **val
  *
  * Returns the length of the smack label or an error code
  */
-static int smack_setprocattr(const char *name, void *value, size_t size)
+static int do_setattr(u64 attr, void *value, size_t size)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
 	struct cred *new;
@@ -3605,8 +3640,8 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
 	if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
 		return -EINVAL;
 
-	if (strcmp(name, "current") != 0)
-		return -EINVAL;
+	if (attr != LSM_ATTR_CURRENT)
+		return -EOPNOTSUPP;
 
 	skp = smk_import_entry(value, size);
 	if (IS_ERR(skp))
@@ -3645,6 +3680,64 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
 	return size;
 }
 
+/**
+ * smack_setselfattr - Set a Smack process attribute
+ * @attr: which attribute to set
+ * @ctx: buffer containing the data
+ * @size: size of @ctx
+ * @flags: unused
+ *
+ * Fill the passed user space @ctx with the details of the requested
+ * attribute.
+ *
+ * Returns 0 on success, an error code otherwise.
+ */
+static int smack_setselfattr(unsigned int __user attr,
+			     struct lsm_ctx __user *ctx, size_t __user size,
+			     u32 __user flags)
+{
+	struct lsm_ctx *lctx;
+	void *context;
+	int rc;
+
+	context = kmalloc(size, GFP_KERNEL);
+	if (context == NULL)
+		return -ENOMEM;
+
+	lctx = (struct lsm_ctx *)context;
+	if (copy_from_user(context, ctx, size))
+		rc = -EFAULT;
+	else if (lctx->ctx_len > size)
+		rc = -EINVAL;
+	else
+		rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
+
+	kfree(context);
+	if (rc > 0)
+		return 0;
+	return rc;
+}
+
+/**
+ * smack_setprocattr - Smack process attribute setting
+ * @name: the name of the attribute in /proc/.../attr
+ * @value: the value to set
+ * @size: the size of the value
+ *
+ * Sets the Smack value of the task. Only setting self
+ * is permitted and only with privilege
+ *
+ * Returns the length of the smack label or an error code
+ */
+static int smack_setprocattr(const char *name, void *value, size_t size)
+{
+	int attr = lsm_name_to_attr(name);
+
+	if (attr)
+		return do_setattr(attr, value, size);
+	return -EINVAL;
+}
+
 /**
  * smack_unix_stream_connect - Smack access on UDS
  * @sock: one sock
@@ -4955,6 +5048,8 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(d_instantiate, smack_d_instantiate),
 
+	LSM_HOOK_INIT(getselfattr, smack_getselfattr),
+	LSM_HOOK_INIT(setselfattr, smack_setselfattr),
 	LSM_HOOK_INIT(getprocattr, smack_getprocattr),
 	LSM_HOOK_INIT(setprocattr, smack_setprocattr),
 
-- 
2.39.2

[PATCH v7 09/11] AppArmor: Add selfattr hooks

[Casey Schaufler]

Add hooks for setselfattr and getselfattr. These hooks are not very
different from their setprocattr and getprocattr equivalents, and
much of the code is shared.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: John Johansen <john.johansen@canonical.com>
---
 security/apparmor/include/procattr.h |  2 +-
 security/apparmor/lsm.c              | 96 ++++++++++++++++++++++++++--
 security/apparmor/procattr.c         | 11 +++-
 3 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/security/apparmor/include/procattr.h b/security/apparmor/include/procattr.h
index 31689437e0e1..03dbfdb2f2c0 100644
--- a/security/apparmor/include/procattr.h
+++ b/security/apparmor/include/procattr.h
@@ -11,7 +11,7 @@
 #ifndef __AA_PROCATTR_H
 #define __AA_PROCATTR_H
 
-int aa_getprocattr(struct aa_label *label, char **string);
+int aa_getprocattr(struct aa_label *label, char **string, bool newline);
 int aa_setprocattr_changehat(char *args, size_t size, int flags);
 
 #endif /* __AA_PROCATTR_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index ce6ccb7e06ec..89ee9d71791c 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -630,6 +630,45 @@ static int apparmor_sb_pivotroot(const struct path *old_path,
 	return error;
 }
 
+static int apparmor_getselfattr(unsigned int __user attr,
+				struct lsm_ctx __user *lx, size_t *size,
+				u32 __user flags)
+{
+	int error = -ENOENT;
+	struct aa_task_ctx *ctx = task_ctx(current);
+	struct aa_label *label = NULL;
+	size_t total_len;
+	char *value;
+
+	if (attr == LSM_ATTR_CURRENT)
+		label = aa_get_newest_label(cred_label(current_cred()));
+	else if (attr == LSM_ATTR_PREV && ctx->previous)
+		label = aa_get_newest_label(ctx->previous);
+	else if (attr == LSM_ATTR_EXEC && ctx->onexec)
+		label = aa_get_newest_label(ctx->onexec);
+	else
+		error = -EOPNOTSUPP;
+
+	if (label) {
+		error = aa_getprocattr(label, &value, false);
+		if (error > 0) {
+			total_len = error + sizeof(*ctx);
+			if (total_len > *size)
+				error = -E2BIG;
+			else
+				lsm_fill_user_ctx(lx, value, error,
+						  LSM_ID_APPARMOR, 0);
+		}
+	}
+
+	aa_put_label(label);
+
+	*size = total_len;
+	if (error > 0)
+		return 0;
+	return error;
+}
+
 static int apparmor_getprocattr(struct task_struct *task, const char *name,
 				char **value)
 {
@@ -649,7 +688,7 @@ static int apparmor_getprocattr(struct task_struct *task, const char *name,
 		error = -EINVAL;
 
 	if (label)
-		error = aa_getprocattr(label, value);
+		error = aa_getprocattr(label, value, true);
 
 	aa_put_label(label);
 	put_cred(cred);
@@ -657,8 +696,7 @@ static int apparmor_getprocattr(struct task_struct *task, const char *name,
 	return error;
 }
 
-static int apparmor_setprocattr(const char *name, void *value,
-				size_t size)
+static int do_setattr(u64 attr, void *value, size_t size)
 {
 	char *command, *largs = NULL, *args = value;
 	size_t arg_size;
@@ -689,7 +727,7 @@ static int apparmor_setprocattr(const char *name, void *value,
 		goto out;
 
 	arg_size = size - (args - (largs ? largs : (char *) value));
-	if (strcmp(name, "current") == 0) {
+	if (attr == LSM_ATTR_CURRENT) {
 		if (strcmp(command, "changehat") == 0) {
 			error = aa_setprocattr_changehat(args, arg_size,
 							 AA_CHANGE_NOFLAGS);
@@ -704,7 +742,7 @@ static int apparmor_setprocattr(const char *name, void *value,
 			error = aa_change_profile(args, AA_CHANGE_STACK);
 		} else
 			goto fail;
-	} else if (strcmp(name, "exec") == 0) {
+	} else if (attr == LSM_ATTR_EXEC) {
 		if (strcmp(command, "exec") == 0)
 			error = aa_change_profile(args, AA_CHANGE_ONEXEC);
 		else if (strcmp(command, "stack") == 0)
@@ -724,13 +762,57 @@ static int apparmor_setprocattr(const char *name, void *value,
 
 fail:
 	aad(&sa)->label = begin_current_label_crit_section();
-	aad(&sa)->info = name;
+	if (attr == LSM_ATTR_CURRENT)
+		aad(&sa)->info = "current";
+	else if (attr == LSM_ATTR_EXEC)
+		aad(&sa)->info = "exec";
+	else
+		aad(&sa)->info = "invalid";
 	aad(&sa)->error = error = -EINVAL;
 	aa_audit_msg(AUDIT_APPARMOR_DENIED, &sa, NULL);
 	end_current_label_crit_section(aad(&sa)->label);
 	goto out;
 }
 
+static int apparmor_setselfattr(unsigned int __user attr,
+				struct lsm_ctx __user *ctx, size_t __user size,
+				u32 __user flags)
+{
+	struct lsm_ctx *lctx;
+	void *context;
+	int rc;
+
+	if (attr != LSM_ATTR_CURRENT && attr != LSM_ATTR_EXEC)
+		return -EOPNOTSUPP;
+
+	context = kmalloc(size, GFP_KERNEL);
+	if (context == NULL)
+		return -ENOMEM;
+
+	lctx = (struct lsm_ctx *)context;
+	if (copy_from_user(context, ctx, size))
+		rc = -EFAULT;
+	else if (lctx->ctx_len > size)
+		rc = -EINVAL;
+	else
+		rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
+
+	kfree(context);
+	if (rc > 0)
+		return 0;
+	return rc;
+}
+
+static int apparmor_setprocattr(const char *name, void *value,
+				size_t size)
+{
+	int attr = lsm_name_to_attr(name);
+
+	if (attr)
+		return do_setattr(attr, value, size);
+	return -EINVAL;
+}
+
 /**
  * apparmor_bprm_committing_creds - do task cleanup on committing new creds
  * @bprm: binprm for the exec  (NOT NULL)
@@ -1253,6 +1335,8 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(file_lock, apparmor_file_lock),
 	LSM_HOOK_INIT(file_truncate, apparmor_file_truncate),
 
+	LSM_HOOK_INIT(getselfattr, apparmor_getselfattr),
+	LSM_HOOK_INIT(setselfattr, apparmor_setselfattr),
 	LSM_HOOK_INIT(getprocattr, apparmor_getprocattr),
 	LSM_HOOK_INIT(setprocattr, apparmor_setprocattr),
 
diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c
index 197d41f9c32b..196f319aa3b2 100644
--- a/security/apparmor/procattr.c
+++ b/security/apparmor/procattr.c
@@ -20,6 +20,7 @@
  * aa_getprocattr - Return the label information for @label
  * @label: the label to print label info about  (NOT NULL)
  * @string: Returns - string containing the label info (NOT NULL)
+ * @newline: indicates that a newline should be added
  *
  * Requires: label != NULL && string != NULL
  *
@@ -27,7 +28,7 @@
  *
  * Returns: size of string placed in @string else error code on failure
  */
-int aa_getprocattr(struct aa_label *label, char **string)
+int aa_getprocattr(struct aa_label *label, char **string, bool newline)
 {
 	struct aa_ns *ns = labels_ns(label);
 	struct aa_ns *current_ns = aa_get_current_ns();
@@ -57,10 +58,14 @@ int aa_getprocattr(struct aa_label *label, char **string)
 		return len;
 	}
 
-	(*string)[len] = '\n';
-	(*string)[len + 1] = 0;
+	if (newline)
+		(*string)[len++] = '\n';
+	(*string)[len] = 0;
 
 	aa_put_ns(current_ns);
+
+	if (newline)
+		return len;
 	return len + 1;
 }
 
-- 
2.39.2

[PATCH v7 10/11] SELinux: Add selfattr hooks

[Casey Schaufler]

Add hooks for setselfattr and getselfattr. These hooks are not very
different from their setprocattr and getprocattr equivalents, and
much of the code is shared.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: selinux@vger.kernel.org
Cc: Paul Moore <paul@paul-moore.com>
---
 security/selinux/hooks.c | 147 +++++++++++++++++++++++++++++++--------
 1 file changed, 117 insertions(+), 30 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9403aee75981..8896edf80aa9 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6348,8 +6348,7 @@ static void selinux_d_instantiate(struct dentry *dentry, struct inode *inode)
 		inode_doinit_with_dentry(inode, dentry);
 }
 
-static int selinux_getprocattr(struct task_struct *p,
-			       const char *name, char **value)
+static int do_getattr(unsigned int attr, struct task_struct *p, char **value)
 {
 	const struct task_security_struct *__tsec;
 	u32 sid;
@@ -6367,20 +6366,27 @@ static int selinux_getprocattr(struct task_struct *p,
 			goto bad;
 	}
 
-	if (!strcmp(name, "current"))
+	switch (attr) {
+	case LSM_ATTR_CURRENT:
 		sid = __tsec->sid;
-	else if (!strcmp(name, "prev"))
+		break;
+	case LSM_ATTR_PREV:
 		sid = __tsec->osid;
-	else if (!strcmp(name, "exec"))
+		break;
+	case LSM_ATTR_EXEC:
 		sid = __tsec->exec_sid;
-	else if (!strcmp(name, "fscreate"))
+		break;
+	case LSM_ATTR_FSCREATE:
 		sid = __tsec->create_sid;
-	else if (!strcmp(name, "keycreate"))
+		break;
+	case LSM_ATTR_KEYCREATE:
 		sid = __tsec->keycreate_sid;
-	else if (!strcmp(name, "sockcreate"))
+		break;
+	case LSM_ATTR_SOCKCREATE:
 		sid = __tsec->sockcreate_sid;
-	else {
-		error = -EINVAL;
+		break;
+	default:
+		error = -EOPNOTSUPP;
 		goto bad;
 	}
 	rcu_read_unlock();
@@ -6398,7 +6404,7 @@ static int selinux_getprocattr(struct task_struct *p,
 	return error;
 }
 
-static int selinux_setprocattr(const char *name, void *value, size_t size)
+static int do_setattr(u64 attr, void *value, size_t size)
 {
 	struct task_security_struct *tsec;
 	struct cred *new;
@@ -6409,28 +6415,36 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 	/*
 	 * Basic control over ability to set these attributes at all.
 	 */
-	if (!strcmp(name, "exec"))
+	switch (attr) {
+	case LSM_ATTR_CURRENT:
+		error = avc_has_perm(&selinux_state,
+				     mysid, mysid, SECCLASS_PROCESS,
+				     PROCESS__SETCURRENT, NULL);
+		break;
+	case LSM_ATTR_EXEC:
 		error = avc_has_perm(&selinux_state,
 				     mysid, mysid, SECCLASS_PROCESS,
 				     PROCESS__SETEXEC, NULL);
-	else if (!strcmp(name, "fscreate"))
+		break;
+	case LSM_ATTR_FSCREATE:
 		error = avc_has_perm(&selinux_state,
 				     mysid, mysid, SECCLASS_PROCESS,
 				     PROCESS__SETFSCREATE, NULL);
-	else if (!strcmp(name, "keycreate"))
+		break;
+	case LSM_ATTR_KEYCREATE:
 		error = avc_has_perm(&selinux_state,
 				     mysid, mysid, SECCLASS_PROCESS,
 				     PROCESS__SETKEYCREATE, NULL);
-	else if (!strcmp(name, "sockcreate"))
+		break;
+	case LSM_ATTR_SOCKCREATE:
 		error = avc_has_perm(&selinux_state,
 				     mysid, mysid, SECCLASS_PROCESS,
 				     PROCESS__SETSOCKCREATE, NULL);
-	else if (!strcmp(name, "current"))
-		error = avc_has_perm(&selinux_state,
-				     mysid, mysid, SECCLASS_PROCESS,
-				     PROCESS__SETCURRENT, NULL);
-	else
-		error = -EINVAL;
+		break;
+	default:
+		error = -EOPNOTSUPP;
+		break;
+	}
 	if (error)
 		return error;
 
@@ -6442,13 +6456,14 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 		}
 		error = security_context_to_sid(&selinux_state, value, size,
 						&sid, GFP_KERNEL);
-		if (error == -EINVAL && !strcmp(name, "fscreate")) {
+		if (error == -EINVAL && attr == LSM_ATTR_FSCREATE) {
 			if (!has_cap_mac_admin(true)) {
 				struct audit_buffer *ab;
 				size_t audit_size;
 
-				/* We strip a nul only if it is at the end, otherwise the
-				 * context contains a nul and we should audit that */
+				/* We strip a nul only if it is at the end,
+				 * otherwise the context contains a nul and
+				 * we should audit that */
 				if (str[size - 1] == '\0')
 					audit_size = size - 1;
 				else
@@ -6459,7 +6474,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 				if (!ab)
 					return error;
 				audit_log_format(ab, "op=fscreate invalid_context=");
-				audit_log_n_untrustedstring(ab, value, audit_size);
+				audit_log_n_untrustedstring(ab, value,
+							    audit_size);
 				audit_log_end(ab);
 
 				return error;
@@ -6483,11 +6499,11 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 	   checks and may_create for the file creation checks. The
 	   operation will then fail if the context is not permitted. */
 	tsec = selinux_cred(new);
-	if (!strcmp(name, "exec")) {
+	if (attr == LSM_ATTR_EXEC) {
 		tsec->exec_sid = sid;
-	} else if (!strcmp(name, "fscreate")) {
+	} else if (attr == LSM_ATTR_FSCREATE) {
 		tsec->create_sid = sid;
-	} else if (!strcmp(name, "keycreate")) {
+	} else if (attr == LSM_ATTR_KEYCREATE) {
 		if (sid) {
 			error = avc_has_perm(&selinux_state, mysid, sid,
 					     SECCLASS_KEY, KEY__CREATE, NULL);
@@ -6495,9 +6511,9 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 				goto abort_change;
 		}
 		tsec->keycreate_sid = sid;
-	} else if (!strcmp(name, "sockcreate")) {
+	} else if (attr == LSM_ATTR_SOCKCREATE) {
 		tsec->sockcreate_sid = sid;
-	} else if (!strcmp(name, "current")) {
+	} else if (attr == LSM_ATTR_CURRENT) {
 		error = -EINVAL;
 		if (sid == 0)
 			goto abort_change;
@@ -6542,6 +6558,75 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 	return error;
 }
 
+static int selinux_getselfattr(unsigned int __user attr,
+			       struct lsm_ctx __user *ctx, size_t *size,
+			       u32 __user flags)
+{
+	char *value;
+	size_t total_len;
+	int len;
+	int rc = 0;
+
+	len = do_getattr(attr, current, &value);
+	if (len < 0)
+		return len;
+
+	total_len = len + sizeof(*ctx);
+
+	if (total_len > *size)
+		rc = -E2BIG;
+	else
+		lsm_fill_user_ctx(ctx, value, len, LSM_ID_SELINUX, 0);
+
+	*size = total_len;
+	return rc;
+}
+
+static int selinux_setselfattr(unsigned int __user attr,
+			       struct lsm_ctx __user *ctx, size_t __user size,
+			       u32 __user flags)
+{
+	struct lsm_ctx *lctx;
+	void *context;
+	int rc;
+
+	context = kmalloc(size, GFP_KERNEL);
+	if (context == NULL)
+		return -ENOMEM;
+
+	lctx = (struct lsm_ctx *)context;
+	if (copy_from_user(context, ctx, size))
+		rc = -EFAULT;
+	else if (lctx->ctx_len > size)
+		rc = -EINVAL;
+	else
+		rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
+
+	kfree(context);
+	if (rc > 0)
+		return 0;
+	return rc;
+}
+
+static int selinux_getprocattr(struct task_struct *p,
+			       const char *name, char **value)
+{
+	unsigned int attr = lsm_name_to_attr(name);
+
+	if (attr)
+		return do_getattr(attr, p, value);
+	return -EINVAL;
+}
+
+static int selinux_setprocattr(const char *name, void *value, size_t size)
+{
+	int attr = lsm_name_to_attr(name);
+
+	if (attr)
+		return do_setattr(attr, value, size);
+	return -EINVAL;
+}
+
 static int selinux_ismaclabel(const char *name)
 {
 	return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
@@ -7183,6 +7268,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(d_instantiate, selinux_d_instantiate),
 
+	LSM_HOOK_INIT(getselfattr, selinux_getselfattr),
+	LSM_HOOK_INIT(setselfattr, selinux_setselfattr),
 	LSM_HOOK_INIT(getprocattr, selinux_getprocattr),
 	LSM_HOOK_INIT(setprocattr, selinux_setprocattr),
 
-- 
2.39.2

[PATCH v7 11/11] LSM: selftests for Linux Security Module syscalls

[Casey Schaufler]

Add selftests for the three system calls supporting the LSM
infrastructure.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/lsm/Makefile          |  12 +
 tools/testing/selftests/lsm/config            |   2 +
 .../selftests/lsm/lsm_get_self_attr_test.c    | 268 ++++++++++++++++++
 .../selftests/lsm/lsm_list_modules_test.c     | 149 ++++++++++
 .../selftests/lsm/lsm_set_self_attr_test.c    |  70 +++++
 6 files changed, 502 insertions(+)
 create mode 100644 tools/testing/selftests/lsm/Makefile
 create mode 100644 tools/testing/selftests/lsm/config
 create mode 100644 tools/testing/selftests/lsm/lsm_get_self_attr_test.c
 create mode 100644 tools/testing/selftests/lsm/lsm_list_modules_test.c
 create mode 100644 tools/testing/selftests/lsm/lsm_set_self_attr_test.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 13a6837a0c6b..b18d133a1141 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -38,6 +38,7 @@ TARGETS += landlock
 TARGETS += lib
 TARGETS += livepatch
 TARGETS += lkdtm
+TARGETS += lsm
 TARGETS += membarrier
 TARGETS += memfd
 TARGETS += memory-hotplug
diff --git a/tools/testing/selftests/lsm/Makefile b/tools/testing/selftests/lsm/Makefile
new file mode 100644
index 000000000000..f39a75212b78
--- /dev/null
+++ b/tools/testing/selftests/lsm/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# First run: make -C ../../../.. headers_install
+
+CFLAGS += -Wall -O2 $(KHDR_INCLUDES)
+
+TEST_GEN_PROGS := lsm_get_self_attr_test lsm_list_modules_test \
+		  lsm_set_self_attr_test
+
+include ../lib.mk
+
+$(TEST_GEN_PROGS):
diff --git a/tools/testing/selftests/lsm/config b/tools/testing/selftests/lsm/config
new file mode 100644
index 000000000000..afb887715f64
--- /dev/null
+++ b/tools/testing/selftests/lsm/config
@@ -0,0 +1,2 @@
+CONFIG_SYSFS=y
+CONFIG_SECURITY=y
diff --git a/tools/testing/selftests/lsm/lsm_get_self_attr_test.c b/tools/testing/selftests/lsm/lsm_get_self_attr_test.c
new file mode 100644
index 000000000000..2c61a1411c54
--- /dev/null
+++ b/tools/testing/selftests/lsm/lsm_get_self_attr_test.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_get_self_attr system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ * Copyright © 2022 Intel Corporation
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+
+#define PROCATTR	"/proc/self/attr/"
+
+static int read_proc_attr(const char *attr, char *value, __kernel_size_t size)
+{
+	int fd;
+	int len;
+	char *path;
+
+	len = strlen(PROCATTR) + strlen(attr) + 1;
+	path = calloc(len, 1);
+	if (path == NULL)
+		return -1;
+	sprintf(path, "%s%s", PROCATTR, attr);
+
+	fd = open(path, O_RDONLY);
+	free(path);
+
+	if (fd < 0)
+		return -1;
+	len = read(fd, value, size);
+	if (len <= 0)
+		return -1;
+fprintf(stderr, "len=%d\n", len);
+	close(fd);
+
+	path = strchr(value, '\n');
+	if (path)
+		*path = '\0';
+
+	return 0;
+}
+
+static struct lsm_ctx *next_ctx(struct lsm_ctx *ctxp)
+{
+	void *vp;
+
+	vp = (void *)ctxp + sizeof(*ctxp) + ctxp->ctx_len;
+	return (struct lsm_ctx *)vp;
+}
+
+TEST(size_null_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+			      NULL, 0));
+	ASSERT_EQ(EINVAL, errno);
+
+	free(ctx);
+}
+
+TEST(ctx_null_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, NULL,
+			      &size, 0));
+	ASSERT_NE(1, size);
+}
+
+TEST(size_too_small_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	__kernel_size_t size = 1;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+			      &size, 0));
+	ASSERT_EQ(E2BIG, errno);
+	ASSERT_NE(1, size);
+
+	free(ctx);
+}
+
+TEST(flags_zero_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+			      &size, 1));
+	ASSERT_EQ(EINVAL, errno);
+	ASSERT_EQ(page_size, size);
+
+	free(ctx);
+}
+
+TEST(flags_overset_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr,
+			      LSM_ATTR_CURRENT | LSM_ATTR_PREV, ctx, &size, 0));
+	ASSERT_EQ(EOPNOTSUPP, errno);
+	ASSERT_EQ(page_size, size);
+
+	free(ctx);
+}
+
+TEST(basic_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__kernel_size_t size = page_size;
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	struct lsm_ctx *tctx = NULL;
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	char *attr = calloc(page_size, 1);
+	int cnt_current = 0;
+	int cnt_exec = 0;
+	int cnt_fscreate = 0;
+	int cnt_keycreate = 0;
+	int cnt_prev = 0;
+	int cnt_sockcreate = 0;
+	int lsmcount;
+	int count;
+	int i;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_NE(NULL, syscall_lsms);
+
+	lsmcount = syscall(__NR_lsm_list_modules, syscall_lsms, &size, 0);
+	ASSERT_LE(1, lsmcount);
+
+	for (i = 0; i < lsmcount; i++) {
+		switch (syscall_lsms[i]) {
+		case LSM_ID_SELINUX:
+			cnt_current++;
+			cnt_exec++;
+			cnt_fscreate++;
+			cnt_keycreate++;
+			cnt_prev++;
+			cnt_sockcreate++;
+			break;
+		case LSM_ID_SMACK:
+			cnt_current++;
+			break;
+		case LSM_ID_APPARMOR:
+			cnt_current++;
+			cnt_exec++;
+			cnt_prev++;
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (cnt_current) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+				&size, 0);
+		ASSERT_EQ(cnt_current, count);
+		tctx = ctx;
+		ASSERT_EQ(0, read_proc_attr("current", attr, page_size));
+		ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_exec) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_EXEC, ctx,
+				&size, 0);
+		ASSERT_GE(cnt_exec, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("exec", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_fscreate) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_FSCREATE, ctx,
+				&size, 0);
+		ASSERT_GE(cnt_fscreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("fscreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_keycreate) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_KEYCREATE, ctx,
+				&size, 0);
+		ASSERT_GE(cnt_keycreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("keycreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_prev) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_PREV, ctx,
+				&size, 0);
+		ASSERT_GE(cnt_prev, count);
+		if (count > 0) {
+			tctx = ctx;
+			ASSERT_EQ(0, read_proc_attr("prev", attr, page_size));
+			ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+			for (i = 1; i < count; i++) {
+				tctx = next_ctx(tctx);
+				ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+			}
+		}
+	}
+	if (cnt_sockcreate) {
+		size = page_size;
+		count = syscall(__NR_lsm_get_self_attr, LSM_ATTR_SOCKCREATE,
+				ctx, &size, 0);
+		ASSERT_GE(cnt_sockcreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("sockcreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+
+	free(ctx);
+	free(attr);
+	free(syscall_lsms);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/lsm/lsm_list_modules_test.c b/tools/testing/selftests/lsm/lsm_list_modules_test.c
new file mode 100644
index 000000000000..3ec814002710
--- /dev/null
+++ b/tools/testing/selftests/lsm/lsm_list_modules_test.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_list_modules system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ * Copyright © 2022 Intel Corporation
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+
+static int read_sysfs_lsms(char *lsms, __kernel_size_t size)
+{
+	FILE *fp;
+
+	fp = fopen("/sys/kernel/security/lsm", "r");
+	if (fp == NULL)
+		return -1;
+	if (fread(lsms, 1, size, fp) <= 0)
+		return -1;
+	fclose(fp);
+	return 0;
+}
+
+TEST(size_null_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *syscall_lsms = calloc(page_size, 1);
+
+	ASSERT_NE(NULL, syscall_lsms);
+	ASSERT_EQ(-1, syscall(__NR_lsm_list_modules, syscall_lsms, NULL, 0));
+	ASSERT_EQ(EFAULT, errno);
+
+	free(syscall_lsms);
+}
+
+TEST(ids_null_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__kernel_size_t size = page_size;
+
+	ASSERT_EQ(-1, syscall(__NR_lsm_list_modules, NULL, &size, 0));
+	ASSERT_EQ(EFAULT, errno);
+	ASSERT_NE(1, size);
+}
+
+TEST(size_too_small_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *syscall_lsms = calloc(page_size, 1);
+	__kernel_size_t size = 1;
+
+	ASSERT_NE(NULL, syscall_lsms);
+	ASSERT_EQ(-1, syscall(__NR_lsm_list_modules, syscall_lsms, &size, 0));
+	ASSERT_EQ(E2BIG, errno);
+	ASSERT_NE(1, size);
+
+	free(syscall_lsms);
+}
+
+TEST(flags_set_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *syscall_lsms = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(NULL, syscall_lsms);
+	ASSERT_EQ(-1, syscall(__NR_lsm_list_modules, syscall_lsms, &size, 7));
+	ASSERT_EQ(EINVAL, errno);
+	ASSERT_EQ(page_size, size);
+
+	free(syscall_lsms);
+}
+
+TEST(correct_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__kernel_size_t size = page_size;
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	char *sysfs_lsms = calloc(page_size, 1);
+	char *name;
+	char *cp;
+	int count;
+	int i;
+
+	ASSERT_NE(NULL, sysfs_lsms);
+	ASSERT_NE(NULL, syscall_lsms);
+	ASSERT_EQ(0, read_sysfs_lsms(sysfs_lsms, page_size));
+
+	count = syscall(__NR_lsm_list_modules, syscall_lsms, &size, 0);
+	ASSERT_LE(1, count);
+	cp = sysfs_lsms;
+	for (i = 0; i < count; i++) {
+		switch (syscall_lsms[i]) {
+		case LSM_ID_CAPABILITY:
+			name = "capability";
+			break;
+		case LSM_ID_SELINUX:
+			name = "selinux";
+			break;
+		case LSM_ID_SMACK:
+			name = "smack";
+			break;
+		case LSM_ID_TOMOYO:
+			name = "tomoyo";
+			break;
+		case LSM_ID_IMA:
+			name = "ima";
+			break;
+		case LSM_ID_APPARMOR:
+			name = "apparmor";
+			break;
+		case LSM_ID_YAMA:
+			name = "yama";
+			break;
+		case LSM_ID_LOADPIN:
+			name = "loadpin";
+			break;
+		case LSM_ID_SAFESETID:
+			name = "safesetid";
+			break;
+		case LSM_ID_LOCKDOWN:
+			name = "lockdown";
+			break;
+		case LSM_ID_BPF:
+			name = "bpf";
+			break;
+		case LSM_ID_LANDLOCK:
+			name = "landlock";
+			break;
+		default:
+			name = "INVALID";
+			break;
+		}
+		ASSERT_EQ(0, strncmp(cp, name, strlen(name)));
+		cp += strlen(name) + 1;
+	}
+
+	free(sysfs_lsms);
+	free(syscall_lsms);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/lsm/lsm_set_self_attr_test.c b/tools/testing/selftests/lsm/lsm_set_self_attr_test.c
new file mode 100644
index 000000000000..ca538a703168
--- /dev/null
+++ b/tools/testing/selftests/lsm/lsm_set_self_attr_test.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_set_self_attr system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ * Copyright © 2022 Intel Corporation
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+
+TEST(ctx_null_lsm_set_self_attr)
+{
+	ASSERT_EQ(-1, syscall(__NR_lsm_set_self_attr, LSM_ATTR_CURRENT, NULL,
+			      sizeof(struct lsm_ctx), 0));
+}
+
+TEST(size_too_small_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+			     &size, 0));
+	ASSERT_EQ(-1, syscall(__NR_lsm_set_self_attr, LSM_ATTR_CURRENT, ctx, 1,
+			      0));
+
+	free(ctx);
+}
+
+TEST(flags_zero_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
+			     &size, 0));
+	ASSERT_EQ(-1, syscall(__NR_lsm_set_self_attr, LSM_ATTR_CURRENT, ctx,
+			      size, 1));
+
+	free(ctx);
+}
+
+TEST(flags_overset_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	__kernel_size_t size = page_size;
+	struct lsm_ctx *tctx = (struct lsm_ctx *)ctx;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, tctx,
+			     &size, 0));
+	ASSERT_EQ(-1, syscall(__NR_lsm_set_self_attr,
+			      LSM_ATTR_CURRENT | LSM_ATTR_PREV, tctx, size, 0));
+
+	free(ctx);
+}
+
+TEST_HARNESS_MAIN
-- 
2.39.2

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[kernel test robot]

Hi Casey,

I love your patch! Yet something to improve:

[auto build test ERROR on shuah-kselftest/next]
[also build test ERROR on shuah-kselftest/fixes linus/master v6.3-rc2]
[cannot apply to tip/perf/core acme/perf/core next-20230316]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230316-074751
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
patch link:    https://lore.kernel.org/r/20230315224704.2672-5-casey%40schaufler-ca.com
patch subject: [PATCH v7 04/11] LSM: syscalls for current process attributes
config: sh-allmodconfig (https://download.01.org/0day-ci/archive/20230316/202303162018.FY1iL9wN-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/0883a93af669a6fcb80a9cc74737d5285a1c46ae
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230316-074751
        git checkout 0883a93af669a6fcb80a9cc74737d5285a1c46ae
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sh olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sh SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303162018.FY1iL9wN-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from security/lsm_syscalls.c:15:
>> include/linux/syscalls.h:243:25: error: conflicting types for 'sys_lsm_set_self_attr'; have 'long int(unsigned int,  struct lsm_ctx *, size_t,  u32)' {aka 'long int(unsigned int,  struct lsm_ctx *, unsigned int,  unsigned int)'}
     243 |         asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
         |                         ^~~
   include/linux/syscalls.h:229:9: note: in expansion of macro '__SYSCALL_DEFINEx'
     229 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
         |         ^~~~~~~~~~~~~~~~~
   include/linux/syscalls.h:221:36: note: in expansion of macro 'SYSCALL_DEFINEx'
     221 | #define SYSCALL_DEFINE4(name, ...) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
         |                                    ^~~~~~~~~~~~~~~
   security/lsm_syscalls.c:31:1: note: in expansion of macro 'SYSCALL_DEFINE4'
      31 | SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
         | ^~~~~~~~~~~~~~~
   include/linux/syscalls.h:1064:17: note: previous declaration of 'sys_lsm_set_self_attr' with type 'long int(unsigned int,  struct lsm_ctx *, __u64)' {aka 'long int(unsigned int,  struct lsm_ctx *, long long unsigned int)'}
    1064 | asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
         |                 ^~~~~~~~~~~~~~~~~~~~~
>> include/linux/syscalls.h:243:25: error: conflicting types for 'sys_lsm_get_self_attr'; have 'long int(unsigned int,  struct lsm_ctx *, size_t *, u32)' {aka 'long int(unsigned int,  struct lsm_ctx *, unsigned int *, unsigned int)'}
     243 |         asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
         |                         ^~~
   include/linux/syscalls.h:229:9: note: in expansion of macro '__SYSCALL_DEFINEx'
     229 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
         |         ^~~~~~~~~~~~~~~~~
   include/linux/syscalls.h:221:36: note: in expansion of macro 'SYSCALL_DEFINEx'
     221 | #define SYSCALL_DEFINE4(name, ...) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
         |                                    ^~~~~~~~~~~~~~~
   security/lsm_syscalls.c:51:1: note: in expansion of macro 'SYSCALL_DEFINE4'
      51 | SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
         | ^~~~~~~~~~~~~~~
   include/linux/syscalls.h:1062:17: note: previous declaration of 'sys_lsm_get_self_attr' with type 'long int(unsigned int,  struct lsm_ctx *, size_t *, __u64)' {aka 'long int(unsigned int,  struct lsm_ctx *, unsigned int *, long long unsigned int)'}
    1062 | asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
         |                 ^~~~~~~~~~~~~~~~~~~~~


vim +243 include/linux/syscalls.h

1bd21c6c21e848 Dominik Brodowski   2018-04-05  232  
e145242ea0df6b Dominik Brodowski   2018-04-09  233  /*
e145242ea0df6b Dominik Brodowski   2018-04-09  234   * The asmlinkage stub is aliased to a function named __se_sys_*() which
e145242ea0df6b Dominik Brodowski   2018-04-09  235   * sign-extends 32-bit ints to longs whenever needed. The actual work is
e145242ea0df6b Dominik Brodowski   2018-04-09  236   * done within __do_sys_*().
e145242ea0df6b Dominik Brodowski   2018-04-09  237   */
1bd21c6c21e848 Dominik Brodowski   2018-04-05  238  #ifndef __SYSCALL_DEFINEx
bed1ffca022cc8 Frederic Weisbecker 2009-03-13  239  #define __SYSCALL_DEFINEx(x, name, ...)					\
bee20031772af3 Arnd Bergmann       2018-06-19  240  	__diag_push();							\
bee20031772af3 Arnd Bergmann       2018-06-19  241  	__diag_ignore(GCC, 8, "-Wattribute-alias",			\
bee20031772af3 Arnd Bergmann       2018-06-19  242  		      "Type aliasing is used to sanitize syscall arguments");\
83460ec8dcac14 Andi Kleen          2013-11-12 @243  	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
e145242ea0df6b Dominik Brodowski   2018-04-09  244  		__attribute__((alias(__stringify(__se_sys##name))));	\
c9a211951c7c79 Howard McLauchlan   2018-03-21  245  	ALLOW_ERROR_INJECTION(sys##name, ERRNO);			\
e145242ea0df6b Dominik Brodowski   2018-04-09  246  	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
e145242ea0df6b Dominik Brodowski   2018-04-09  247  	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
e145242ea0df6b Dominik Brodowski   2018-04-09  248  	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
1a94bc34768e46 Heiko Carstens      2009-01-14  249  	{								\
e145242ea0df6b Dominik Brodowski   2018-04-09  250  		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
07fe6e00f6cca6 Al Viro             2013-01-21  251  		__MAP(x,__SC_TEST,__VA_ARGS__);				\
2cf0966683430b Al Viro             2013-01-21  252  		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));	\
2cf0966683430b Al Viro             2013-01-21  253  		return ret;						\
1a94bc34768e46 Heiko Carstens      2009-01-14  254  	}								\
bee20031772af3 Arnd Bergmann       2018-06-19  255  	__diag_pop();							\
e145242ea0df6b Dominik Brodowski   2018-04-09  256  	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
1bd21c6c21e848 Dominik Brodowski   2018-04-05  257  #endif /* __SYSCALL_DEFINEx */
1a94bc34768e46 Heiko Carstens      2009-01-14  258  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH v7 01/11] LSM: Identify modules by more than name

[Paul Moore]

On Wed, Mar 15, 2023 at 6:47 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Create a struct lsm_id to contain identifying information
> about Linux Security Modules (LSMs). At inception this contains
> the name of the module, an identifier associated with the security
> module and an integer member "attrs" which identifies the API
> related data associated with each security module. The initial set
> of features maps to information that has traditionaly been available
> in /proc/self/attr. They are documented in a new userspace-api file.
> Change the security_add_hooks() interface to use this structure.
> Change the individual modules to maintain their own struct lsm_id
> and pass it to security_add_hooks().
>
> The values are for LSM identifiers are defined in a new UAPI
> header file linux/lsm.h. Each existing LSM has been updated to
> include it's LSMID in the lsm_id.
>
> The LSM ID values are sequential, with the oldest module
> LSM_ID_CAPABILITY being the lowest value and the existing modules
> numbered in the order they were included in the main line kernel.
> This is an arbitrary convention for assigning the values, but
> none better presents itself. The value 0 is defined as being invalid.
> The values 1-99 are reserved for any special case uses which may
> arise in the future. This may include attributes of the LSM
> infrastructure itself, possibly related to namespacing or network
> attribute management. A special range is identified for such attributes
> to help reduce confusion for developers unfamiliar with LSMs.
>
> LSM attribute values are defined for the attributes presented by
> modules that are available today. As with the LSM IDs, The value 0
> is defined as being invalid. The values 1-99 are reserved for any
> special case uses which may arise in the future.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Cc: linux-security-module <linux-security-module@vger.kernel.org>
> ---
>  Documentation/userspace-api/index.rst |  1 +
>  Documentation/userspace-api/lsm.rst   | 55 +++++++++++++++++++++++++++
>  MAINTAINERS                           |  1 +
>  include/linux/lsm_hooks.h             | 18 ++++++++-
>  include/uapi/linux/lsm.h              | 53 ++++++++++++++++++++++++++
>  security/apparmor/lsm.c               |  8 +++-
>  security/bpf/hooks.c                  |  9 ++++-
>  security/commoncap.c                  |  8 +++-
>  security/landlock/cred.c              |  2 +-
>  security/landlock/fs.c                |  2 +-
>  security/landlock/ptrace.c            |  2 +-
>  security/landlock/setup.c             |  6 +++
>  security/landlock/setup.h             |  1 +
>  security/loadpin/loadpin.c            |  9 ++++-
>  security/lockdown/lockdown.c          |  8 +++-
>  security/safesetid/lsm.c              |  9 ++++-
>  security/security.c                   | 12 +++---
>  security/selinux/hooks.c              |  9 ++++-
>  security/smack/smack_lsm.c            |  8 +++-
>  security/tomoyo/tomoyo.c              |  9 ++++-
>  security/yama/yama_lsm.c              |  8 +++-
>  21 files changed, 217 insertions(+), 21 deletions(-)
>  create mode 100644 Documentation/userspace-api/lsm.rst
>  create mode 100644 include/uapi/linux/lsm.h

...

> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 6e156d2acffc..32285ce65419 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1665,6 +1665,20 @@ struct security_hook_heads {
>         #undef LSM_HOOK
>  } __randomize_layout;
>
> +/**
> + * struct lsm_id - Identify a Linux Security Module.
> + * @lsm: name of the LSM, must be approved by the LSM maintainers
> + * @id: LSM ID number from uapi/linux/lsm.h
> + * @attrs: which attributes this LSM supports
> + *
> + * Contains the information that identifies the LSM.
> + */
> +struct lsm_id {
> +       const u8        *lsm;
> +       u64             id;
> +       u64             attrs;
> +};

I would either start setting the 'attrs' field values in the LSMs when
their 'lsm_id' struct is defined or I would leave it out of this patch
and add it later in the patchset when it is used.

> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
> new file mode 100644
> index 000000000000..aa3e01867739
> --- /dev/null
> +++ b/include/uapi/linux/lsm.h
> @@ -0,0 +1,53 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * Linux Security Modules (LSM) - User space API
> + *
> + * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
> + * Copyright (C) 2022 Intel Corporation
> + */
> +
> +#ifndef _UAPI_LINUX_LSM_H
> +#define _UAPI_LINUX_LSM_H
> +
> +/*
> + * ID tokens to identify Linux Security Modules (LSMs)
> + *
> + * These token values are used to uniquely identify specific LSMs
> + * in the kernel as well as in the kernel's LSM userspace API.
> + *
> + * A value of zero/0 is considered undefined and should not be used
> + * outside the kernel. Values 1-99 are reserved for potential
> + * future use.
> + */
> +#define LSM_ID_UNDEF           0
> +#define LSM_ID_CAPABILITY      100
> +#define LSM_ID_SELINUX         101
> +#define LSM_ID_SMACK           102
> +#define LSM_ID_TOMOYO          103
> +#define LSM_ID_IMA             104
> +#define LSM_ID_APPARMOR                105
> +#define LSM_ID_YAMA            106
> +#define LSM_ID_LOADPIN         107
> +#define LSM_ID_SAFESETID       108
> +#define LSM_ID_LOCKDOWN                109
> +#define LSM_ID_BPF             110
> +#define LSM_ID_LANDLOCK                111
> +
> +/*
> + * LSM_ATTR_XXX definitions identify different LSM attributes
> + * which are used in the kernel's LSM userspace API. Support
> + * for these attributes vary across the different LSMs. None
> + * are required.
> + *
> + * A value of zero/0 is considered undefined and should not be used
> + * outside the kernel. Values 1-99 are reserved for potential
> + * future use.
> + */
> +#define LSM_ATTR_CURRENT       100
> +#define LSM_ATTR_EXEC          101
> +#define LSM_ATTR_FSCREATE      102
> +#define LSM_ATTR_KEYCREATE     103
> +#define LSM_ATTR_PREV          104
> +#define LSM_ATTR_SOCKCREATE    105

We might as well add a LSM_ATTR_UNDEF for zero/0.

> +#endif /* _UAPI_LINUX_LSM_H */

--
paul-moore.com

Re: [PATCH v7 02/11] LSM: Maintain a table of LSM attribute data

[Paul Moore]

On Wed, Mar 15, 2023 at 6:47 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> As LSMs are registered add their lsm_id pointers to a table.
> This will be used later for attribute reporting.
>
> Determine the number of possible security modules based on
> their respective CONFIG options. This allows the number to be
> known at build time. This allows data structures and tables
> to use the constant.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  include/linux/security.h |  2 ++
>  security/security.c      | 44 ++++++++++++++++++++++++++++++++--------
>  2 files changed, 38 insertions(+), 8 deletions(-)

...

> diff --git a/security/security.c b/security/security.c
> index 58828a326024..aa84b1cf4253 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -513,6 +531,16 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
>  {
>         int i;
>
> +       /*
> +        * A security module may call security_add_hooks() more
> +        * than once. Landlock is one such case.
> +        */
> +       if (lsm_active_cnt == 0 || lsm_idlist[lsm_active_cnt - 1] != lsmid)
> +               lsm_idlist[lsm_active_cnt++] = lsmid;
> +
> +       if (lsm_active_cnt > LSM_COUNT)
> +               panic("%s Too many LSMs registered.\n", __func__);

In addition to the fixes needed to resolve the bug identified by the
kernel test robot, I think it might be wise to do the @lsm_active_cnt
check *before* potentially adding it to the @lsm_idlist array.

>         for (i = 0; i < count; i++) {
>                 hooks[i].lsmid = lsmid;
>                 hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
> --
> 2.39.2

--
paul-moore.com

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Paul Moore]

On Wed, Mar 15, 2023 at 6:48 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Create a system call lsm_get_self_attr() to provide the security
> module maintained attributes of the current process.
> Create a system call lsm_set_self_attr() to set a security
> module maintained attribute of the current process.
> Historically these attributes have been exposed to user space via
> entries in procfs under /proc/self/attr.
>
> The attribute value is provided in a lsm_ctx structure. The structure
> identifys the size of the attribute, and the attribute value. The format

"identifies"

> of the attribute value is defined by the security module. A flags field
> is included for LSM specific information. It is currently unused and must
> be 0. The total size of the data, including the lsm_ctx structure and any
> padding, is maintained as well.
>
> struct lsm_ctx {
>         __u64   id;
>         __u64   flags;
>         __u64   len;
>         __u64   ctx_len;
>         __u8    ctx[];
> };
>
> Two new LSM hooks are used to interface with the LSMs.
> security_getselfattr() collects the lsm_ctx values from the
> LSMs that support the hook, accounting for space requirements.
> security_setselfattr() identifies which LSM the attribute is
> intended for and passes it along.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  Documentation/userspace-api/lsm.rst | 15 +++++
>  include/linux/lsm_hook_defs.h       |  4 ++
>  include/linux/lsm_hooks.h           |  9 +++
>  include/linux/security.h            | 19 ++++++
>  include/linux/syscalls.h            |  5 ++
>  include/uapi/linux/lsm.h            | 33 ++++++++++
>  kernel/sys_ni.c                     |  4 ++
>  security/Makefile                   |  1 +
>  security/lsm_syscalls.c             | 55 ++++++++++++++++
>  security/security.c                 | 97 +++++++++++++++++++++++++++++
>  10 files changed, 242 insertions(+)
>  create mode 100644 security/lsm_syscalls.c

...

> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 32285ce65419..3c2c4916bd53 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -503,6 +504,14 @@
>   *     and writing the xattrs as this hook is merely a filter.
>   * @d_instantiate:
>   *     Fill in @inode security information for a @dentry if allowed.
> + * @getselfattr:
> + *     Read attribute @attr for the current process and store it into @ctx.
> + *     Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
> + *     or another negative value otherwise.
> + * @setselfattr:
> + *     Set attribute @attr for the current process.
> + *     Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
> + *     or another negative value otherwise.
>   * @getprocattr:
>   *     Read attribute @name for process @p and store it into @value if allowed.
>   *     Return the length of @value on success, a negative value otherwise.

I'm sure you're already aware of this, but the above will need to be
moved to security.c due to the changes in the lsm/next branch.  That
said, if you're basing on Linus' tree that's fine too, I'll fix it up
during the merge; thankfully it's not a significant merge conflict.

> diff --git a/include/linux/security.h b/include/linux/security.h
> index 8faed81fc3b4..329cd9d2be50 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
>                                           struct inode *inode)
>  { }
>
> +static inline int security_getselfattr(unsigned int __user attr,
> +                                      struct lsm_ctx __user *ctx,
> +                                      size_t __user *size, u32 __user flags)
> +{
> +       return -EINVAL;
> +}
> +
> +static inline int security_setselfattr(unsigned int __user attr,
> +                                      struct lsm_ctx __user *ctx,
> +                                      size_t __user size, u32 __user flags)
> +{
> +       return -EINVAL;
> +}

It seems like EOPNOTSUPP might be more appropriate than EINVAL for
both of these dummy implementations.

> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 33a0ee3bcb2e..3feca00cb0c1 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
>  asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
>                                             unsigned long home_node,
>                                             unsigned long flags);
> +asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> +                                     size_t *size, __u64 flags);
> +asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> +                                     __u64 flags);

As the kernel test robot already pointed out, the above needs to be updated.

>  /*
>   * Architecture-specific system calls
> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
> index aa3e01867739..adfb55dce2fd 100644
> --- a/include/uapi/linux/lsm.h
> +++ b/include/uapi/linux/lsm.h
> @@ -9,6 +9,39 @@
>  #ifndef _UAPI_LINUX_LSM_H
>  #define _UAPI_LINUX_LSM_H
>
> +#include <linux/types.h>
> +#include <linux/unistd.h>
> +
> +/**
> + * struct lsm_ctx - LSM context information
> + * @id: the LSM id number, see LSM_ID_XXX
> + * @flags: LSM specific flags
> + * @len: length of the lsm_ctx struct, @ctx and any other data or padding
> + * @ctx_len: the size of @ctx
> + * @ctx: the LSM context value
> + *
> + * The @len field MUST be equal to the size of the lsm_ctx struct
> + * plus any additional padding and/or data placed after @ctx.
> + *
> + * In all cases @ctx_len MUST be equal to the length of @ctx.
> + * If @ctx is a string value it should be nul terminated with
> + * @ctx_len equal to `strlen(@ctx) + 1`.  Binary values are
> + * supported.
> + *
> + * The @flags and @ctx fields SHOULD only be interpreted by the
> + * LSM specified by @id; they MUST be set to zero/0 when not used.
> + */
> +struct lsm_ctx {
> +       __u64   id;
> +       __u64   flags;
> +       __u64   len;
> +       __u64   ctx_len;
> +       __u8    ctx[];
> +};
> +
> +#include <linux/types.h>
> +#include <linux/unistd.h>

I'm pretty sure the repeated #includes are a typo, right?  Or is there
some uapi trick I'm missing ...

> diff --git a/security/security.c b/security/security.c
> index 87c8796c3c46..2c57fe28c4f7 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
>  }
>  EXPORT_SYMBOL(security_d_instantiate);
>
> +/**
> + * security_getselfattr - Read an LSM attribute of the current process.
> + * @attr: which attribute to return
> + * @ctx: the user-space destination for the information, or NULL
> + * @size: the size of space available to receive the data
> + * @flags: reserved for future use, must be 0
> + *
> + * Returns the number of attributes found on success, negative value
> + * on error. @size is reset to the total size of the data.
> + * If @size is insufficient to contain the data -E2BIG is returned.
> + */
> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> +                        size_t __user *size, u32 __user flags)
> +{
> +       struct security_hook_list *hp;
> +       void __user *base = (void *)ctx;

The casting seems wrong for a couple of reasons: I don't believe you
need to cast the right side when the left side is a void pointer, and
the right side cast drops the '__user' attribute when the left side is
also a '__user' pointer value.

That said, I think we may want @base to be 'u8 __user *base', more on
that below ...

> +       size_t total = 0;
> +       size_t this;

Naming is hard, but 'this'?  You can do better ...

> +       size_t left;
> +       bool istoobig = false;

Sorry, more naming nits and since it looks like you need to respin
anyway ... please rename @istoobig to @toobig or something else.  The
phrases-as-variable-names has always grated on me.

> +       int count = 0;
> +       int rc;
> +
> +       if (attr == 0)
> +               return -EINVAL;
> +       if (flags != 0)
> +               return -EINVAL;
> +       if (size == NULL)
> +               return -EINVAL;
> +       if (get_user(left, size))
> +               return -EFAULT;
> +
> +       hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
> +               this = left;
> +               if (base)
> +                       ctx = (struct lsm_ctx __user *)(base + total);

Pointer math on void pointers always makes me nervous.  Why not set
@base's type to a 'u8' just to remove any concerns?

> +               rc = hp->hook.getselfattr(attr, ctx, &this, flags);
> +               switch (rc) {
> +               case -EOPNOTSUPP:
> +                       rc = 0;
> +                       continue;
> +               case -E2BIG:
> +                       istoobig = true;
> +                       left = 0;
> +                       break;
> +               case 0:
> +                       left -= this;
> +                       break;
> +               default:
> +                       return rc;

I think the @getselfattr hook should behave similarly to the
associated syscall, returning a non-negative number should indicate
that @rc entries have been added to the @ctx array.  Right now all the
LSMs would just be adding one entry to the array, but we might as well
code this up to be flexible.

> +               }
> +               total += this;
> +               count++;
> +       }
> +       if (count == 0)
> +               return LSM_RET_DEFAULT(getselfattr);
> +       if (put_user(total, size))
> +               return -EFAULT;
> +       if (rc)
> +               return rc;

Is the 'if (rc)' check needed here?  Shouldn't the switch-statement
after the hook catch everything that this check would catch?

> +       if (istoobig)
> +               return -E2BIG;
> +       return count;
> +}
> +
> +/**
> + * security_setselfattr - Set an LSM attribute on the current process.
> + * @attr: which attribute to set
> + * @ctx: the user-space source for the information
> + * @size: the size of the data
> + * @flags: reserved for future use, must be 0
> + *
> + * Set an LSM attribute for the current process. The LSM, attribute
> + * and new value are included in @ctx.
> + *
> + * Returns 0 on success, an LSM specific value on failure.
> + */
> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> +                        size_t __user size, u32 __user flags)
> +{
> +       struct security_hook_list *hp;
> +       struct lsm_ctx lctx;

Shouldn't we check @attr for valid values and return -EINVAL if bogus?

> +       if (flags != 0)
> +               return -EINVAL;
> +       if (size < sizeof(*ctx))
> +               return -EINVAL;

If we're only going to support on 'lsm_ctx' entry in this function we
should verify that the 'len' and 'ctx_len' fields are sane.  Although
more on this below ...

> +       if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
> +               return -EFAULT;
> +
> +       hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
> +               if ((hp->lsmid->id) == lctx.id)
> +                       return hp->hook.setselfattr(attr, ctx, size, flags);

Can anyone think of any good reason why we shouldn't support setting
multiple LSMs in one call, similar to what we do with
security_getselfattr()?  It seems like it might be a nice thing to
have ...

> +       return LSM_RET_DEFAULT(setselfattr);
> +}
> +
>  int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
>                          char **value)
>  {
> --
> 2.39.2

--
paul-moore.com

Re: [PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Paul Moore]

On Wed, Mar 15, 2023 at 6:48 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Create a system call to report the list of Linux Security Modules
> that are active on the system. The list is provided as an array
> of LSM ID numbers.
>
> The calling application can use this list determine what LSM
> specific actions it might take. That might include chosing an
> output format, determining required privilege or bypassing
> security module specific behavior.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  Documentation/userspace-api/lsm.rst |  3 +++
>  include/linux/syscalls.h            |  1 +
>  kernel/sys_ni.c                     |  1 +
>  security/lsm_syscalls.c             | 39 +++++++++++++++++++++++++++++
>  4 files changed, 44 insertions(+)

...

> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index feee31600219..6efbe244d304 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -53,3 +53,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
>  {
>         return security_getselfattr(attr, ctx, size, flags);
>  }
> +
> +/**
> + * sys_lsm_list_modules - Return a list of the active security modules
> + * @ids: the LSM module ids
> + * @size: size of @ids, updated on return
> + * @flags: reserved for future use, must be zero
> + *
> + * Returns a list of the active LSM ids. On success this function
> + * returns the number of @ids array elements. This value may be zero
> + * if there are no LSMs active. If @size is insufficient to contain
> + * the return data -E2BIG is returned and @size is set to the minimum
> + * required size. In all other cases a negative value indicating the
> + * error is returned.
> + */
> +SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
> +               u32, flags)
> +{
> +       size_t total_size = lsm_active_cnt * sizeof(*ids);
> +       size_t usize;
> +       int i;
> +
> +       if (flags)
> +               return -EINVAL;

In other patches in this patchset you use 'if (flags != 0)'; I don't
care too much which approach you take, but please be consistent.

Actually, I guess you might as well just go with 'if (flags)' since
I'm pretty sure someone later down the line will end up wasting
reviewer time by changing '(flags != 0)' into '(flags)' ...


> +       if (get_user(usize, size))
> +               return -EFAULT;
> +
> +       if (put_user(total_size, size) != 0)
> +               return -EFAULT;
> +
> +       if (usize < total_size)
> +               return -E2BIG;
> +
> +       for (i = 0; i < lsm_active_cnt; i++)
> +               if (put_user(lsm_idlist[i]->id, ids++))
> +                       return -EFAULT;
> +
> +       return lsm_active_cnt;
> +}
> --
> 2.39.2

--
paul-moore.com

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Paul Moore]

On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Add lsm_name_to_attr(), which translates a text string to a
> LSM_ATTR value if one is available.
>
> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
> the trailing attribute value.
>
> All are used in module specific components of LSM system calls.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  include/linux/security.h | 13 ++++++++++
>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>  security/security.c      | 31 ++++++++++++++++++++++++
>  3 files changed, 95 insertions(+)

...

> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index 6efbe244d304..55d849ad5d6e 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -17,6 +17,57 @@
>  #include <linux/lsm_hooks.h>
>  #include <uapi/linux/lsm.h>
>
> +struct attr_map {
> +       char *name;
> +       u64 attr;
> +};
> +
> +static const struct attr_map lsm_attr_names[] = {
> +       {
> +               .name = "current",
> +               .attr = LSM_ATTR_CURRENT,
> +       },
> +       {
> +               .name = "exec",
> +               .attr = LSM_ATTR_EXEC,
> +       },
> +       {
> +               .name = "fscreate",
> +               .attr = LSM_ATTR_FSCREATE,
> +       },
> +       {
> +               .name = "keycreate",
> +               .attr = LSM_ATTR_KEYCREATE,
> +       },
> +       {
> +               .name = "prev",
> +               .attr = LSM_ATTR_PREV,
> +       },
> +       {
> +               .name = "sockcreate",
> +               .attr = LSM_ATTR_SOCKCREATE,
> +       },
> +};
> +
> +/**
> + * lsm_name_to_attr - map an LSM attribute name to its ID
> + * @name: name of the attribute
> + *
> + * Look the given @name up in the table of know attribute names.
> + *
> + * Returns the LSM attribute value associated with @name, or 0 if
> + * there is no mapping.
> + */
> +u64 lsm_name_to_attr(const char *name)
> +{
> +       int i;
> +
> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
> +               if (!strcmp(name, lsm_attr_names[i].name))
> +                       return lsm_attr_names[i].attr;

I'm pretty sure this is the only place where @lsm_attr_names is used,
right?  If true, when coupled with the idea that these syscalls are
going to close the door on new LSM attributes in procfs I think we can
just put the mapping directly in this function via a series of
if-statements.

> +       return 0;
> +}
> +
>  /**
>   * sys_lsm_set_self_attr - Set current task's security module attribute
>   * @attr: which attribute to set
> diff --git a/security/security.c b/security/security.c
> index 2c57fe28c4f7..f7b814a3940c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
>         return 0;
>  }
>
> +/**
> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> + * @ctx: an LSM context to be filled
> + * @context: the new context value
> + * @context_size: the size of the new context value
> + * @id: LSM id
> + * @flags: LSM defined flags
> + *
> + * Fill all of the fields in a user space lsm_ctx structure.
> + * Caller is assumed to have verified that @ctx has enough space
> + * for @context.
> + * Returns 0 on success, -EFAULT on a copyout error.
> + */
> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
> +                     size_t context_size, u64 id, u64 flags)
> +{
> +       struct lsm_ctx local;
> +       void __user *vc = ctx;
> +
> +       local.id = id;
> +       local.flags = flags;
> +       local.ctx_len = context_size;
> +       local.len = context_size + sizeof(local);
> +       vc += sizeof(local);

See my prior comments about void pointer math.

> +       if (copy_to_user(ctx, &local, sizeof(local)))
> +               return -EFAULT;
> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
> +               return -EFAULT;

Should we handle the padding in this function?

> +       return 0;
> +}

--
paul-moore.com

Re: [PATCH v7 10/11] SELinux: Add selfattr hooks

[Paul Moore]

On Wed, Mar 15, 2023 at 6:52 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Add hooks for setselfattr and getselfattr. These hooks are not very
> different from their setprocattr and getprocattr equivalents, and
> much of the code is shared.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Cc: selinux@vger.kernel.org
> Cc: Paul Moore <paul@paul-moore.com>
> ---
>  security/selinux/hooks.c | 147 +++++++++++++++++++++++++++++++--------
>  1 file changed, 117 insertions(+), 30 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 9403aee75981..8896edf80aa9 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6348,8 +6348,7 @@ static void selinux_d_instantiate(struct dentry *dentry, struct inode *inode)
>                 inode_doinit_with_dentry(inode, dentry);
>  }
>
> -static int selinux_getprocattr(struct task_struct *p,
> -                              const char *name, char **value)
> +static int do_getattr(unsigned int attr, struct task_struct *p, char **value)

Are you ready for more naming nitpicks? ;)

Let's call this 'selinux_lsm_getattr()', and the matching setter
should be 'selinux_lsm_setattr()'.

>  {
>         const struct task_security_struct *__tsec;
>         u32 sid;
> @@ -6367,20 +6366,27 @@ static int selinux_getprocattr(struct task_struct *p,
>                         goto bad;
>         }
>
> -       if (!strcmp(name, "current"))
> +       switch (attr) {
> +       case LSM_ATTR_CURRENT:
>                 sid = __tsec->sid;
> -       else if (!strcmp(name, "prev"))
> +               break;
> +       case LSM_ATTR_PREV:
>                 sid = __tsec->osid;
> -       else if (!strcmp(name, "exec"))
> +               break;
> +       case LSM_ATTR_EXEC:
>                 sid = __tsec->exec_sid;
> -       else if (!strcmp(name, "fscreate"))
> +               break;
> +       case LSM_ATTR_FSCREATE:
>                 sid = __tsec->create_sid;
> -       else if (!strcmp(name, "keycreate"))
> +               break;
> +       case LSM_ATTR_KEYCREATE:
>                 sid = __tsec->keycreate_sid;
> -       else if (!strcmp(name, "sockcreate"))
> +               break;
> +       case LSM_ATTR_SOCKCREATE:
>                 sid = __tsec->sockcreate_sid;
> -       else {
> -               error = -EINVAL;
> +               break;
> +       default:
> +               error = -EOPNOTSUPP;

The error should probably be -EINVAL.

>                 goto bad;
>         }
>         rcu_read_unlock();
> @@ -6398,7 +6404,7 @@ static int selinux_getprocattr(struct task_struct *p,
>         return error;
>  }
>
> -static int selinux_setprocattr(const char *name, void *value, size_t size)
> +static int do_setattr(u64 attr, void *value, size_t size)
>  {
>         struct task_security_struct *tsec;
>         struct cred *new;
> @@ -6409,28 +6415,36 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>         /*
>          * Basic control over ability to set these attributes at all.
>          */
> -       if (!strcmp(name, "exec"))
> +       switch (attr) {
> +       case LSM_ATTR_CURRENT:
> +               error = avc_has_perm(&selinux_state,
> +                                    mysid, mysid, SECCLASS_PROCESS,
> +                                    PROCESS__SETCURRENT, NULL);
> +               break;
> +       case LSM_ATTR_EXEC:
>                 error = avc_has_perm(&selinux_state,
>                                      mysid, mysid, SECCLASS_PROCESS,
>                                      PROCESS__SETEXEC, NULL);
> -       else if (!strcmp(name, "fscreate"))
> +               break;
> +       case LSM_ATTR_FSCREATE:
>                 error = avc_has_perm(&selinux_state,
>                                      mysid, mysid, SECCLASS_PROCESS,
>                                      PROCESS__SETFSCREATE, NULL);
> -       else if (!strcmp(name, "keycreate"))
> +               break;
> +       case LSM_ATTR_KEYCREATE:
>                 error = avc_has_perm(&selinux_state,
>                                      mysid, mysid, SECCLASS_PROCESS,
>                                      PROCESS__SETKEYCREATE, NULL);
> -       else if (!strcmp(name, "sockcreate"))
> +               break;
> +       case LSM_ATTR_SOCKCREATE:
>                 error = avc_has_perm(&selinux_state,
>                                      mysid, mysid, SECCLASS_PROCESS,
>                                      PROCESS__SETSOCKCREATE, NULL);
> -       else if (!strcmp(name, "current"))
> -               error = avc_has_perm(&selinux_state,
> -                                    mysid, mysid, SECCLASS_PROCESS,
> -                                    PROCESS__SETCURRENT, NULL);
> -       else
> -               error = -EINVAL;
> +               break;
> +       default:
> +               error = -EOPNOTSUPP;

Same as above, should be -EINVAL.

> +               break;
> +       }
>         if (error)
>                 return error;
>
> @@ -6442,13 +6456,14 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>                 }
>                 error = security_context_to_sid(&selinux_state, value, size,
>                                                 &sid, GFP_KERNEL);
> -               if (error == -EINVAL && !strcmp(name, "fscreate")) {
> +               if (error == -EINVAL && attr == LSM_ATTR_FSCREATE) {
>                         if (!has_cap_mac_admin(true)) {
>                                 struct audit_buffer *ab;
>                                 size_t audit_size;
>
> -                               /* We strip a nul only if it is at the end, otherwise the
> -                                * context contains a nul and we should audit that */
> +                               /* We strip a nul only if it is at the end,
> +                                * otherwise the context contains a nul and
> +                                * we should audit that */

You *do* get gold stars for fixing line lengths in close proximity ;)


>                                 if (str[size - 1] == '\0')
>                                         audit_size = size - 1;
>                                 else
> @@ -6459,7 +6474,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>                                 if (!ab)
>                                         return error;
>                                 audit_log_format(ab, "op=fscreate invalid_context=");
> -                               audit_log_n_untrustedstring(ab, value, audit_size);
> +                               audit_log_n_untrustedstring(ab, value,
> +                                                           audit_size);
>                                 audit_log_end(ab);
>
>                                 return error;
> @@ -6483,11 +6499,11 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>            checks and may_create for the file creation checks. The
>            operation will then fail if the context is not permitted. */
>         tsec = selinux_cred(new);
> -       if (!strcmp(name, "exec")) {
> +       if (attr == LSM_ATTR_EXEC) {
>                 tsec->exec_sid = sid;
> -       } else if (!strcmp(name, "fscreate")) {
> +       } else if (attr == LSM_ATTR_FSCREATE) {
>                 tsec->create_sid = sid;
> -       } else if (!strcmp(name, "keycreate")) {
> +       } else if (attr == LSM_ATTR_KEYCREATE) {
>                 if (sid) {
>                         error = avc_has_perm(&selinux_state, mysid, sid,
>                                              SECCLASS_KEY, KEY__CREATE, NULL);
> @@ -6495,9 +6511,9 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>                                 goto abort_change;
>                 }
>                 tsec->keycreate_sid = sid;
> -       } else if (!strcmp(name, "sockcreate")) {
> +       } else if (attr == LSM_ATTR_SOCKCREATE) {
>                 tsec->sockcreate_sid = sid;
> -       } else if (!strcmp(name, "current")) {
> +       } else if (attr == LSM_ATTR_CURRENT) {
>                 error = -EINVAL;
>                 if (sid == 0)
>                         goto abort_change;
> @@ -6542,6 +6558,75 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>         return error;
>  }
>
> +static int selinux_getselfattr(unsigned int __user attr,
> +                              struct lsm_ctx __user *ctx, size_t *size,
> +                              u32 __user flags)
> +{
> +       char *value;
> +       size_t total_len;
> +       int len;
> +       int rc = 0;
> +
> +       len = do_getattr(attr, current, &value);
> +       if (len < 0)
> +               return len;
> +
> +       total_len = len + sizeof(*ctx);
> +
> +       if (total_len > *size)
> +               rc = -E2BIG;
> +       else
> +               lsm_fill_user_ctx(ctx, value, len, LSM_ID_SELINUX, 0);
> +
> +       *size = total_len;
> +       return rc;
> +}
> +
> +static int selinux_setselfattr(unsigned int __user attr,
> +                              struct lsm_ctx __user *ctx, size_t __user size,
> +                              u32 __user flags)
> +{
> +       struct lsm_ctx *lctx;
> +       void *context;
> +       int rc;
> +
> +       context = kmalloc(size, GFP_KERNEL);
> +       if (context == NULL)
> +               return -ENOMEM;
> +
> +       lctx = (struct lsm_ctx *)context;
> +       if (copy_from_user(context, ctx, size))
> +               rc = -EFAULT;
> +       else if (lctx->ctx_len > size)
> +               rc = -EINVAL;
> +       else
> +               rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
> +
> +       kfree(context);
> +       if (rc > 0)
> +               return 0;
> +       return rc;
> +}
> +
> +static int selinux_getprocattr(struct task_struct *p,
> +                              const char *name, char **value)
> +{
> +       unsigned int attr = lsm_name_to_attr(name);
> +
> +       if (attr)
> +               return do_getattr(attr, p, value);
> +       return -EINVAL;
> +}
> +
> +static int selinux_setprocattr(const char *name, void *value, size_t size)
> +{
> +       int attr = lsm_name_to_attr(name);
> +
> +       if (attr)
> +               return do_setattr(attr, value, size);
> +       return -EINVAL;
> +}
> +
>  static int selinux_ismaclabel(const char *name)
>  {
>         return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
> @@ -7183,6 +7268,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
>
>         LSM_HOOK_INIT(d_instantiate, selinux_d_instantiate),
>
> +       LSM_HOOK_INIT(getselfattr, selinux_getselfattr),
> +       LSM_HOOK_INIT(setselfattr, selinux_setselfattr),
>         LSM_HOOK_INIT(getprocattr, selinux_getprocattr),
>         LSM_HOOK_INIT(setprocattr, selinux_setprocattr),
>
> --
> 2.39.2

--
paul-moore.com

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Paul Moore]

On March 29, 2023 9:12:19 PM Paul Moore <paul@paul-moore.com> wrote:
> On Wed, Mar 15, 2023 at 6:48 PM Casey Schaufler <casey@schaufler-ca.com> wrote:

...

>
>> +/**
>> + * security_setselfattr - Set an LSM attribute on the current process.
>> + * @attr: which attribute to set
>> + * @ctx: the user-space source for the information
>> + * @size: the size of the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Set an LSM attribute for the current process. The LSM, attribute
>> + * and new value are included in @ctx.
>> + *
>> + * Returns 0 on success, an LSM specific value on failure.
>> + */
>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> +                        size_t __user size, u32 __user flags)
>> +{
>> +       struct security_hook_list *hp;
>> +       struct lsm_ctx lctx;
>
> Shouldn't we check @attr for valid values and return -EINVAL if bogus?
>
>> +       if (flags != 0)
>> +               return -EINVAL;
>> +       if (size < sizeof(*ctx))
>> +               return -EINVAL;
>
> If we're only going to support on 'lsm_ctx' entry in this function we
> should verify that the 'len' and 'ctx_len' fields are sane.  Although
> more on this below ...
>
>> +       if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>> +               return -EFAULT;
>> +
>> +       hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>> +               if ((hp->lsmid->id) == lctx.id)
>> +                       return hp->hook.setselfattr(attr, ctx, size, flags);
>
> Can anyone think of any good reason why we shouldn't support setting
> multiple LSMs in one call, similar to what we do with
> security_getselfattr()?  It seems like it might be a nice thing to
> have ...

Scratch that, I just reminded myself why attempting to set an attribute on 
multiple LSMs in one operation would be a nightmare. Sorry about the confusion.

--
paul-moore.com

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Casey Schaufler]

On 3/29/2023 6:12 PM, Paul Moore wrote:
> On Wed, Mar 15, 2023 at 6:48 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Create a system call lsm_get_self_attr() to provide the security
>> module maintained attributes of the current process.
>> Create a system call lsm_set_self_attr() to set a security
>> module maintained attribute of the current process.
>> Historically these attributes have been exposed to user space via
>> entries in procfs under /proc/self/attr.
>>
>> The attribute value is provided in a lsm_ctx structure. The structure
>> identifys the size of the attribute, and the attribute value. The format
> "identifies"
>
>> of the attribute value is defined by the security module. A flags field
>> is included for LSM specific information. It is currently unused and must
>> be 0. The total size of the data, including the lsm_ctx structure and any
>> padding, is maintained as well.
>>
>> struct lsm_ctx {
>>         __u64   id;
>>         __u64   flags;
>>         __u64   len;
>>         __u64   ctx_len;
>>         __u8    ctx[];
>> };
>>
>> Two new LSM hooks are used to interface with the LSMs.
>> security_getselfattr() collects the lsm_ctx values from the
>> LSMs that support the hook, accounting for space requirements.
>> security_setselfattr() identifies which LSM the attribute is
>> intended for and passes it along.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> ---
>>  Documentation/userspace-api/lsm.rst | 15 +++++
>>  include/linux/lsm_hook_defs.h       |  4 ++
>>  include/linux/lsm_hooks.h           |  9 +++
>>  include/linux/security.h            | 19 ++++++
>>  include/linux/syscalls.h            |  5 ++
>>  include/uapi/linux/lsm.h            | 33 ++++++++++
>>  kernel/sys_ni.c                     |  4 ++
>>  security/Makefile                   |  1 +
>>  security/lsm_syscalls.c             | 55 ++++++++++++++++
>>  security/security.c                 | 97 +++++++++++++++++++++++++++++
>>  10 files changed, 242 insertions(+)
>>  create mode 100644 security/lsm_syscalls.c
> ..
>
>> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
>> index 32285ce65419..3c2c4916bd53 100644
>> --- a/include/linux/lsm_hooks.h
>> +++ b/include/linux/lsm_hooks.h
>> @@ -503,6 +504,14 @@
>>   *     and writing the xattrs as this hook is merely a filter.
>>   * @d_instantiate:
>>   *     Fill in @inode security information for a @dentry if allowed.
>> + * @getselfattr:
>> + *     Read attribute @attr for the current process and store it into @ctx.
>> + *     Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
>> + *     or another negative value otherwise.
>> + * @setselfattr:
>> + *     Set attribute @attr for the current process.
>> + *     Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
>> + *     or another negative value otherwise.
>>   * @getprocattr:
>>   *     Read attribute @name for process @p and store it into @value if allowed.
>>   *     Return the length of @value on success, a negative value otherwise.
> I'm sure you're already aware of this, but the above will need to be
> moved to security.c due to the changes in the lsm/next branch.  That
> said, if you're basing on Linus' tree that's fine too, I'll fix it up
> during the merge; thankfully it's not a significant merge conflict.

I'm based on Linus' tree.

>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 8faed81fc3b4..329cd9d2be50 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
>>                                           struct inode *inode)
>>  { }
>>
>> +static inline int security_getselfattr(unsigned int __user attr,
>> +                                      struct lsm_ctx __user *ctx,
>> +                                      size_t __user *size, u32 __user flags)
>> +{
>> +       return -EINVAL;
>> +}
>> +
>> +static inline int security_setselfattr(unsigned int __user attr,
>> +                                      struct lsm_ctx __user *ctx,
>> +                                      size_t __user size, u32 __user flags)
>> +{
>> +       return -EINVAL;
>> +}
> It seems like EOPNOTSUPP might be more appropriate than EINVAL for
> both of these dummy implementations.

Sure.

>> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
>> index 33a0ee3bcb2e..3feca00cb0c1 100644
>> --- a/include/linux/syscalls.h
>> +++ b/include/linux/syscalls.h
>> @@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
>>  asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
>>                                             unsigned long home_node,
>>                                             unsigned long flags);
>> +asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>> +                                     size_t *size, __u64 flags);
>> +asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>> +                                     __u64 flags);
> As the kernel test robot already pointed out, the above needs to be updated.
>
>>  /*
>>   * Architecture-specific system calls
>> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
>> index aa3e01867739..adfb55dce2fd 100644
>> --- a/include/uapi/linux/lsm.h
>> +++ b/include/uapi/linux/lsm.h
>> @@ -9,6 +9,39 @@
>>  #ifndef _UAPI_LINUX_LSM_H
>>  #define _UAPI_LINUX_LSM_H
>>
>> +#include <linux/types.h>
>> +#include <linux/unistd.h>
>> +
>> +/**
>> + * struct lsm_ctx - LSM context information
>> + * @id: the LSM id number, see LSM_ID_XXX
>> + * @flags: LSM specific flags
>> + * @len: length of the lsm_ctx struct, @ctx and any other data or padding
>> + * @ctx_len: the size of @ctx
>> + * @ctx: the LSM context value
>> + *
>> + * The @len field MUST be equal to the size of the lsm_ctx struct
>> + * plus any additional padding and/or data placed after @ctx.
>> + *
>> + * In all cases @ctx_len MUST be equal to the length of @ctx.
>> + * If @ctx is a string value it should be nul terminated with
>> + * @ctx_len equal to `strlen(@ctx) + 1`.  Binary values are
>> + * supported.
>> + *
>> + * The @flags and @ctx fields SHOULD only be interpreted by the
>> + * LSM specified by @id; they MUST be set to zero/0 when not used.
>> + */
>> +struct lsm_ctx {
>> +       __u64   id;
>> +       __u64   flags;
>> +       __u64   len;
>> +       __u64   ctx_len;
>> +       __u8    ctx[];
>> +};
>> +
>> +#include <linux/types.h>
>> +#include <linux/unistd.h>
> I'm pretty sure the repeated #includes are a typo, right?  Or is there
> some uapi trick I'm missing ...

An artifact of patch (mis)management. Thanks for noticing.

>> diff --git a/security/security.c b/security/security.c
>> index 87c8796c3c46..2c57fe28c4f7 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
>>  }
>>  EXPORT_SYMBOL(security_d_instantiate);
>>
>> +/**
>> + * security_getselfattr - Read an LSM attribute of the current process.
>> + * @attr: which attribute to return
>> + * @ctx: the user-space destination for the information, or NULL
>> + * @size: the size of space available to receive the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Returns the number of attributes found on success, negative value
>> + * on error. @size is reset to the total size of the data.
>> + * If @size is insufficient to contain the data -E2BIG is returned.
>> + */
>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> +                        size_t __user *size, u32 __user flags)
>> +{
>> +       struct security_hook_list *hp;
>> +       void __user *base = (void *)ctx;
> The casting seems wrong for a couple of reasons: I don't believe you
> need to cast the right side when the left side is a void pointer, and
> the right side cast drops the '__user' attribute when the left side is
> also a '__user' pointer value.
>
> That said, I think we may want @base to be 'u8 __user *base', more on
> that below ...
>
>> +       size_t total = 0;
>> +       size_t this;
> Naming is hard, but 'this'?  You can do better ...

It seemed like a good idea at the time, but a rose by any other
name still has thorns. I'll come up with something "better".


>> +       size_t left;
>> +       bool istoobig = false;
> Sorry, more naming nits and since it looks like you need to respin
> anyway ... please rename @istoobig to @toobig or something else.  The
> phrases-as-variable-names has always grated on me.

Sure.

>> +       int count = 0;
>> +       int rc;
>> +
>> +       if (attr == 0)
>> +               return -EINVAL;
>> +       if (flags != 0)
>> +               return -EINVAL;
>> +       if (size == NULL)
>> +               return -EINVAL;
>> +       if (get_user(left, size))
>> +               return -EFAULT;
>> +
>> +       hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
>> +               this = left;
>> +               if (base)
>> +                       ctx = (struct lsm_ctx __user *)(base + total);
> Pointer math on void pointers always makes me nervous.  Why not set
> @base's type to a 'u8' just to remove any concerns?

I can do that. I made it a void pointer to reflect the notion that
the attributes aren't necessarily strings. Making it a u8 may suggest that
the data is a string to some developers.

>> +               rc = hp->hook.getselfattr(attr, ctx, &this, flags);
>> +               switch (rc) {
>> +               case -EOPNOTSUPP:
>> +                       rc = 0;
>> +                       continue;
>> +               case -E2BIG:
>> +                       istoobig = true;
>> +                       left = 0;
>> +                       break;
>> +               case 0:
>> +                       left -= this;
>> +                       break;
>> +               default:
>> +                       return rc;
> I think the @getselfattr hook should behave similarly to the
> associated syscall, returning a non-negative number should indicate
> that @rc entries have been added to the @ctx array.  Right now all the
> LSMs would just be adding one entry to the array, but we might as well
> code this up to be flexible.

Yes, some LSM may decide to have multiple "contexts".

>> +               }
>> +               total += this;
>> +               count++;
>> +       }
>> +       if (count == 0)
>> +               return LSM_RET_DEFAULT(getselfattr);
>> +       if (put_user(total, size))
>> +               return -EFAULT;
>> +       if (rc)
>> +               return rc;
> Is the 'if (rc)' check needed here?  Shouldn't the switch-statement
> after the hook catch everything that this check would catch?

It's necessary because of BPF, which doesn't follow the LSM rules.

>> +       if (istoobig)
>> +               return -E2BIG;
>> +       return count;
>> +}
>> +
>> +/**
>> + * security_setselfattr - Set an LSM attribute on the current process.
>> + * @attr: which attribute to set
>> + * @ctx: the user-space source for the information
>> + * @size: the size of the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Set an LSM attribute for the current process. The LSM, attribute
>> + * and new value are included in @ctx.
>> + *
>> + * Returns 0 on success, an LSM specific value on failure.
>> + */
>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> +                        size_t __user size, u32 __user flags)
>> +{
>> +       struct security_hook_list *hp;
>> +       struct lsm_ctx lctx;
> Shouldn't we check @attr for valid values and return -EINVAL if bogus?

Sure.

>> +       if (flags != 0)
>> +               return -EINVAL;
>> +       if (size < sizeof(*ctx))
>> +               return -EINVAL;
> If we're only going to support on 'lsm_ctx' entry in this function we
> should verify that the 'len' and 'ctx_len' fields are sane.  Although
> more on this below ...

The LSM is going to have to do its own version of sanity checking. Having
sanity checking here as well seems excessive.

>> +       if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>> +               return -EFAULT;
>> +
>> +       hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>> +               if ((hp->lsmid->id) == lctx.id)
>> +                       return hp->hook.setselfattr(attr, ctx, size, flags);
> Can anyone think of any good reason why we shouldn't support setting
> multiple LSMs in one call, similar to what we do with
> security_getselfattr()?  It seems like it might be a nice thing to
> have ...

If you're setting the context for multiple LSMs and one fails the recovery
process is horrendous. Putting values you've already changed back to their
previous state may not even be possible. We could have a two pass scheme, one
to verify that the request would succeed and a second to do the work. That
doesn't address all the issues, including how to report which attribute failed.
I had planned to do multiple settings, but the weight of the mechanism to
deal with the failure case is considerable for a "nice to have".

>> +       return LSM_RET_DEFAULT(setselfattr);
>> +}
>> +
>>  int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
>>                          char **value)
>>  {
>> --
>> 2.39.2
> --
> paul-moore.com

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 3/29/2023 6:13 PM, Paul Moore wrote:
> On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Add lsm_name_to_attr(), which translates a text string to a
>> LSM_ATTR value if one is available.
>>
>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>> the trailing attribute value.
>>
>> All are used in module specific components of LSM system calls.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> ---
>>  include/linux/security.h | 13 ++++++++++
>>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>  security/security.c      | 31 ++++++++++++++++++++++++
>>  3 files changed, 95 insertions(+)
> ..
>
>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>> index 6efbe244d304..55d849ad5d6e 100644
>> --- a/security/lsm_syscalls.c
>> +++ b/security/lsm_syscalls.c
>> @@ -17,6 +17,57 @@
>>  #include <linux/lsm_hooks.h>
>>  #include <uapi/linux/lsm.h>
>>
>> +struct attr_map {
>> +       char *name;
>> +       u64 attr;
>> +};
>> +
>> +static const struct attr_map lsm_attr_names[] = {
>> +       {
>> +               .name = "current",
>> +               .attr = LSM_ATTR_CURRENT,
>> +       },
>> +       {
>> +               .name = "exec",
>> +               .attr = LSM_ATTR_EXEC,
>> +       },
>> +       {
>> +               .name = "fscreate",
>> +               .attr = LSM_ATTR_FSCREATE,
>> +       },
>> +       {
>> +               .name = "keycreate",
>> +               .attr = LSM_ATTR_KEYCREATE,
>> +       },
>> +       {
>> +               .name = "prev",
>> +               .attr = LSM_ATTR_PREV,
>> +       },
>> +       {
>> +               .name = "sockcreate",
>> +               .attr = LSM_ATTR_SOCKCREATE,
>> +       },
>> +};
>> +
>> +/**
>> + * lsm_name_to_attr - map an LSM attribute name to its ID
>> + * @name: name of the attribute
>> + *
>> + * Look the given @name up in the table of know attribute names.
>> + *
>> + * Returns the LSM attribute value associated with @name, or 0 if
>> + * there is no mapping.
>> + */
>> +u64 lsm_name_to_attr(const char *name)
>> +{
>> +       int i;
>> +
>> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
>> +               if (!strcmp(name, lsm_attr_names[i].name))
>> +                       return lsm_attr_names[i].attr;
> I'm pretty sure this is the only place where @lsm_attr_names is used,
> right?  If true, when coupled with the idea that these syscalls are
> going to close the door on new LSM attributes in procfs I think we can
> just put the mapping directly in this function via a series of
> if-statements.

Ick. You're not wrong, but the hard coded if-statement approach goes
against all sorts of coding principles. I'll do it, but I can't say I
like it.

>> +       return 0;
>> +}
>> +
>>  /**
>>   * sys_lsm_set_self_attr - Set current task's security module attribute
>>   * @attr: which attribute to set
>> diff --git a/security/security.c b/security/security.c
>> index 2c57fe28c4f7..f7b814a3940c 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
>>         return 0;
>>  }
>>
>> +/**
>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>> + * @ctx: an LSM context to be filled
>> + * @context: the new context value
>> + * @context_size: the size of the new context value
>> + * @id: LSM id
>> + * @flags: LSM defined flags
>> + *
>> + * Fill all of the fields in a user space lsm_ctx structure.
>> + * Caller is assumed to have verified that @ctx has enough space
>> + * for @context.
>> + * Returns 0 on success, -EFAULT on a copyout error.
>> + */
>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>> +                     size_t context_size, u64 id, u64 flags)
>> +{
>> +       struct lsm_ctx local;
>> +       void __user *vc = ctx;
>> +
>> +       local.id = id;
>> +       local.flags = flags;
>> +       local.ctx_len = context_size;
>> +       local.len = context_size + sizeof(local);
>> +       vc += sizeof(local);
> See my prior comments about void pointer math.
>
>> +       if (copy_to_user(ctx, &local, sizeof(local)))
>> +               return -EFAULT;
>> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
>> +               return -EFAULT;
> Should we handle the padding in this function?

This function fills in a lsm_ctx. The padding, if any, is in addition to
the lsm_ctx, not part of it.

>> +       return 0;
>> +}
> --
> paul-moore.com

Re: [PATCH v7 10/11] SELinux: Add selfattr hooks

[Casey Schaufler]

On 3/29/2023 6:13 PM, Paul Moore wrote:
> On Wed, Mar 15, 2023 at 6:52 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Add hooks for setselfattr and getselfattr. These hooks are not very
>> different from their setprocattr and getprocattr equivalents, and
>> much of the code is shared.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> Cc: selinux@vger.kernel.org
>> Cc: Paul Moore <paul@paul-moore.com>
>> ---
>>  security/selinux/hooks.c | 147 +++++++++++++++++++++++++++++++--------
>>  1 file changed, 117 insertions(+), 30 deletions(-)
>>
>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
>> index 9403aee75981..8896edf80aa9 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -6348,8 +6348,7 @@ static void selinux_d_instantiate(struct dentry *dentry, struct inode *inode)
>>                 inode_doinit_with_dentry(inode, dentry);
>>  }
>>
>> -static int selinux_getprocattr(struct task_struct *p,
>> -                              const char *name, char **value)
>> +static int do_getattr(unsigned int attr, struct task_struct *p, char **value)
> Are you ready for more naming nitpicks? ;)

I would expect nothing less. :)

> Let's call this 'selinux_lsm_getattr()', and the matching setter
> should be 'selinux_lsm_setattr()'.

As you wish. It's your LSM.


>>  {
>>         const struct task_security_struct *__tsec;
>>         u32 sid;
>> @@ -6367,20 +6366,27 @@ static int selinux_getprocattr(struct task_struct *p,
>>                         goto bad;
>>         }
>>
>> -       if (!strcmp(name, "current"))
>> +       switch (attr) {
>> +       case LSM_ATTR_CURRENT:
>>                 sid = __tsec->sid;
>> -       else if (!strcmp(name, "prev"))
>> +               break;
>> +       case LSM_ATTR_PREV:
>>                 sid = __tsec->osid;
>> -       else if (!strcmp(name, "exec"))
>> +               break;
>> +       case LSM_ATTR_EXEC:
>>                 sid = __tsec->exec_sid;
>> -       else if (!strcmp(name, "fscreate"))
>> +               break;
>> +       case LSM_ATTR_FSCREATE:
>>                 sid = __tsec->create_sid;
>> -       else if (!strcmp(name, "keycreate"))
>> +               break;
>> +       case LSM_ATTR_KEYCREATE:
>>                 sid = __tsec->keycreate_sid;
>> -       else if (!strcmp(name, "sockcreate"))
>> +               break;
>> +       case LSM_ATTR_SOCKCREATE:
>>                 sid = __tsec->sockcreate_sid;
>> -       else {
>> -               error = -EINVAL;
>> +               break;
>> +       default:
>> +               error = -EOPNOTSUPP;
> The error should probably be -EINVAL.

It's possible that we may add an attribute that SELinux doesn't
support, say LSM_ATTR_CRYPTO_KEY, that another LSM does. This is
the same behavior the other LSMs exhibit in the face of a request
for attributes such as LSM_ATTR_KEYCREATE that they don't support.


>>                 goto bad;
>>         }
>>         rcu_read_unlock();
>> @@ -6398,7 +6404,7 @@ static int selinux_getprocattr(struct task_struct *p,
>>         return error;
>>  }
>>
>> -static int selinux_setprocattr(const char *name, void *value, size_t size)
>> +static int do_setattr(u64 attr, void *value, size_t size)
>>  {
>>         struct task_security_struct *tsec;
>>         struct cred *new;
>> @@ -6409,28 +6415,36 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>         /*
>>          * Basic control over ability to set these attributes at all.
>>          */
>> -       if (!strcmp(name, "exec"))
>> +       switch (attr) {
>> +       case LSM_ATTR_CURRENT:
>> +               error = avc_has_perm(&selinux_state,
>> +                                    mysid, mysid, SECCLASS_PROCESS,
>> +                                    PROCESS__SETCURRENT, NULL);
>> +               break;
>> +       case LSM_ATTR_EXEC:
>>                 error = avc_has_perm(&selinux_state,
>>                                      mysid, mysid, SECCLASS_PROCESS,
>>                                      PROCESS__SETEXEC, NULL);
>> -       else if (!strcmp(name, "fscreate"))
>> +               break;
>> +       case LSM_ATTR_FSCREATE:
>>                 error = avc_has_perm(&selinux_state,
>>                                      mysid, mysid, SECCLASS_PROCESS,
>>                                      PROCESS__SETFSCREATE, NULL);
>> -       else if (!strcmp(name, "keycreate"))
>> +               break;
>> +       case LSM_ATTR_KEYCREATE:
>>                 error = avc_has_perm(&selinux_state,
>>                                      mysid, mysid, SECCLASS_PROCESS,
>>                                      PROCESS__SETKEYCREATE, NULL);
>> -       else if (!strcmp(name, "sockcreate"))
>> +               break;
>> +       case LSM_ATTR_SOCKCREATE:
>>                 error = avc_has_perm(&selinux_state,
>>                                      mysid, mysid, SECCLASS_PROCESS,
>>                                      PROCESS__SETSOCKCREATE, NULL);
>> -       else if (!strcmp(name, "current"))
>> -               error = avc_has_perm(&selinux_state,
>> -                                    mysid, mysid, SECCLASS_PROCESS,
>> -                                    PROCESS__SETCURRENT, NULL);
>> -       else
>> -               error = -EINVAL;
>> +               break;
>> +       default:
>> +               error = -EOPNOTSUPP;
> Same as above, should be -EINVAL.

Same as above, there may be attributes SELinux doesn't support.


>> +               break;
>> +       }
>>         if (error)
>>                 return error;
>>
>> @@ -6442,13 +6456,14 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>                 }
>>                 error = security_context_to_sid(&selinux_state, value, size,
>>                                                 &sid, GFP_KERNEL);
>> -               if (error == -EINVAL && !strcmp(name, "fscreate")) {
>> +               if (error == -EINVAL && attr == LSM_ATTR_FSCREATE) {
>>                         if (!has_cap_mac_admin(true)) {
>>                                 struct audit_buffer *ab;
>>                                 size_t audit_size;
>>
>> -                               /* We strip a nul only if it is at the end, otherwise the
>> -                                * context contains a nul and we should audit that */
>> +                               /* We strip a nul only if it is at the end,
>> +                                * otherwise the context contains a nul and
>> +                                * we should audit that */
> You *do* get gold stars for fixing line lengths in close proximity ;)

I guess I'm the Last User of the 80 character terminal.

>>                                 if (str[size - 1] == '\0')
>>                                         audit_size = size - 1;
>>                                 else
>> @@ -6459,7 +6474,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>                                 if (!ab)
>>                                         return error;
>>                                 audit_log_format(ab, "op=fscreate invalid_context=");
>> -                               audit_log_n_untrustedstring(ab, value, audit_size);
>> +                               audit_log_n_untrustedstring(ab, value,
>> +                                                           audit_size);
>>                                 audit_log_end(ab);
>>
>>                                 return error;
>> @@ -6483,11 +6499,11 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>            checks and may_create for the file creation checks. The
>>            operation will then fail if the context is not permitted. */
>>         tsec = selinux_cred(new);
>> -       if (!strcmp(name, "exec")) {
>> +       if (attr == LSM_ATTR_EXEC) {
>>                 tsec->exec_sid = sid;
>> -       } else if (!strcmp(name, "fscreate")) {
>> +       } else if (attr == LSM_ATTR_FSCREATE) {
>>                 tsec->create_sid = sid;
>> -       } else if (!strcmp(name, "keycreate")) {
>> +       } else if (attr == LSM_ATTR_KEYCREATE) {
>>                 if (sid) {
>>                         error = avc_has_perm(&selinux_state, mysid, sid,
>>                                              SECCLASS_KEY, KEY__CREATE, NULL);
>> @@ -6495,9 +6511,9 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>                                 goto abort_change;
>>                 }
>>                 tsec->keycreate_sid = sid;
>> -       } else if (!strcmp(name, "sockcreate")) {
>> +       } else if (attr == LSM_ATTR_SOCKCREATE) {
>>                 tsec->sockcreate_sid = sid;
>> -       } else if (!strcmp(name, "current")) {
>> +       } else if (attr == LSM_ATTR_CURRENT) {
>>                 error = -EINVAL;
>>                 if (sid == 0)
>>                         goto abort_change;
>> @@ -6542,6 +6558,75 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>>         return error;
>>  }
>>
>> +static int selinux_getselfattr(unsigned int __user attr,
>> +                              struct lsm_ctx __user *ctx, size_t *size,
>> +                              u32 __user flags)
>> +{
>> +       char *value;
>> +       size_t total_len;
>> +       int len;
>> +       int rc = 0;
>> +
>> +       len = do_getattr(attr, current, &value);
>> +       if (len < 0)
>> +               return len;
>> +
>> +       total_len = len + sizeof(*ctx);
>> +
>> +       if (total_len > *size)
>> +               rc = -E2BIG;
>> +       else
>> +               lsm_fill_user_ctx(ctx, value, len, LSM_ID_SELINUX, 0);
>> +
>> +       *size = total_len;
>> +       return rc;
>> +}
>> +
>> +static int selinux_setselfattr(unsigned int __user attr,
>> +                              struct lsm_ctx __user *ctx, size_t __user size,
>> +                              u32 __user flags)
>> +{
>> +       struct lsm_ctx *lctx;
>> +       void *context;
>> +       int rc;
>> +
>> +       context = kmalloc(size, GFP_KERNEL);
>> +       if (context == NULL)
>> +               return -ENOMEM;
>> +
>> +       lctx = (struct lsm_ctx *)context;
>> +       if (copy_from_user(context, ctx, size))
>> +               rc = -EFAULT;
>> +       else if (lctx->ctx_len > size)
>> +               rc = -EINVAL;
>> +       else
>> +               rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
>> +
>> +       kfree(context);
>> +       if (rc > 0)
>> +               return 0;
>> +       return rc;
>> +}
>> +
>> +static int selinux_getprocattr(struct task_struct *p,
>> +                              const char *name, char **value)
>> +{
>> +       unsigned int attr = lsm_name_to_attr(name);
>> +
>> +       if (attr)
>> +               return do_getattr(attr, p, value);
>> +       return -EINVAL;
>> +}
>> +
>> +static int selinux_setprocattr(const char *name, void *value, size_t size)
>> +{
>> +       int attr = lsm_name_to_attr(name);
>> +
>> +       if (attr)
>> +               return do_setattr(attr, value, size);
>> +       return -EINVAL;
>> +}
>> +
>>  static int selinux_ismaclabel(const char *name)
>>  {
>>         return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
>> @@ -7183,6 +7268,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
>>
>>         LSM_HOOK_INIT(d_instantiate, selinux_d_instantiate),
>>
>> +       LSM_HOOK_INIT(getselfattr, selinux_getselfattr),
>> +       LSM_HOOK_INIT(setselfattr, selinux_setselfattr),
>>         LSM_HOOK_INIT(getprocattr, selinux_getprocattr),
>>         LSM_HOOK_INIT(setprocattr, selinux_setprocattr),
>>
>> --
>> 2.39.2
> --
> paul-moore.com

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Paul Moore]

On Thu, Mar 30, 2023 at 4:00 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 3/29/2023 6:12 PM, Paul Moore wrote:
> > On Wed, Mar 15, 2023 at 6:48 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >> Create a system call lsm_get_self_attr() to provide the security
> >> module maintained attributes of the current process.
> >> Create a system call lsm_set_self_attr() to set a security
> >> module maintained attribute of the current process.
> >> Historically these attributes have been exposed to user space via
> >> entries in procfs under /proc/self/attr.
> >>
> >> The attribute value is provided in a lsm_ctx structure. The structure
> >> identifys the size of the attribute, and the attribute value. The format
> > "identifies"
> >
> >> of the attribute value is defined by the security module. A flags field
> >> is included for LSM specific information. It is currently unused and must
> >> be 0. The total size of the data, including the lsm_ctx structure and any
> >> padding, is maintained as well.
> >>
> >> struct lsm_ctx {
> >>         __u64   id;
> >>         __u64   flags;
> >>         __u64   len;
> >>         __u64   ctx_len;
> >>         __u8    ctx[];
> >> };
> >>
> >> Two new LSM hooks are used to interface with the LSMs.
> >> security_getselfattr() collects the lsm_ctx values from the
> >> LSMs that support the hook, accounting for space requirements.
> >> security_setselfattr() identifies which LSM the attribute is
> >> intended for and passes it along.
> >>
> >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> >> ---
> >>  Documentation/userspace-api/lsm.rst | 15 +++++
> >>  include/linux/lsm_hook_defs.h       |  4 ++
> >>  include/linux/lsm_hooks.h           |  9 +++
> >>  include/linux/security.h            | 19 ++++++
> >>  include/linux/syscalls.h            |  5 ++
> >>  include/uapi/linux/lsm.h            | 33 ++++++++++
> >>  kernel/sys_ni.c                     |  4 ++
> >>  security/Makefile                   |  1 +
> >>  security/lsm_syscalls.c             | 55 ++++++++++++++++
> >>  security/security.c                 | 97 +++++++++++++++++++++++++++++
> >>  10 files changed, 242 insertions(+)
> >>  create mode 100644 security/lsm_syscalls.c

...

> >> +       int count = 0;
> >> +       int rc;
> >> +
> >> +       if (attr == 0)
> >> +               return -EINVAL;
> >> +       if (flags != 0)
> >> +               return -EINVAL;
> >> +       if (size == NULL)
> >> +               return -EINVAL;
> >> +       if (get_user(left, size))
> >> +               return -EFAULT;
> >> +
> >> +       hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
> >> +               this = left;
> >> +               if (base)
> >> +                       ctx = (struct lsm_ctx __user *)(base + total);
> > Pointer math on void pointers always makes me nervous.  Why not set
> > @base's type to a 'u8' just to remove any concerns?
>
> I can do that. I made it a void pointer to reflect the notion that
> the attributes aren't necessarily strings. Making it a u8 may suggest that
> the data is a string to some developers.

That's a fair concern, but there is plenty of precedence of binary
blobs being stored in 'unsigned char' arrays to make it easier to
pluck data out at random byte offsets.

> >> +               rc = hp->hook.getselfattr(attr, ctx, &this, flags);
> >> +               switch (rc) {
> >> +               case -EOPNOTSUPP:
> >> +                       rc = 0;
> >> +                       continue;
> >> +               case -E2BIG:
> >> +                       istoobig = true;
> >> +                       left = 0;
> >> +                       break;
> >> +               case 0:
> >> +                       left -= this;
> >> +                       break;
> >> +               default:
> >> +                       return rc;
> > I think the @getselfattr hook should behave similarly to the
> > associated syscall, returning a non-negative number should indicate
> > that @rc entries have been added to the @ctx array.  Right now all the
> > LSMs would just be adding one entry to the array, but we might as well
> > code this up to be flexible.
>
> Yes, some LSM may decide to have multiple "contexts".
>
> >> +               }
> >> +               total += this;
> >> +               count++;
> >> +       }
> >> +       if (count == 0)
> >> +               return LSM_RET_DEFAULT(getselfattr);
> >> +       if (put_user(total, size))
> >> +               return -EFAULT;
> >> +       if (rc)
> >> +               return rc;
> > Is the 'if (rc)' check needed here?  Shouldn't the switch-statement
> > after the hook catch everything that this check would catch?
>
> It's necessary because of BPF, which doesn't follow the LSM rules.

I thought if it made it this far in the function the LSM, BPF or not,
would still have gone through the switch statement above which would
have returned early if the the value was something other than one of
the accepted return codes ... right?

> >> +       if (istoobig)
> >> +               return -E2BIG;
> >> +       return count;
> >> +}
> >> +
> >> +/**
> >> + * security_setselfattr - Set an LSM attribute on the current process.
> >> + * @attr: which attribute to set
> >> + * @ctx: the user-space source for the information
> >> + * @size: the size of the data
> >> + * @flags: reserved for future use, must be 0
> >> + *
> >> + * Set an LSM attribute for the current process. The LSM, attribute
> >> + * and new value are included in @ctx.
> >> + *
> >> + * Returns 0 on success, an LSM specific value on failure.
> >> + */
> >> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> >> +                        size_t __user size, u32 __user flags)
> >> +{
> >> +       struct security_hook_list *hp;
> >> +       struct lsm_ctx lctx;
> > Shouldn't we check @attr for valid values and return -EINVAL if bogus?
>
> Sure.
>
> >> +       if (flags != 0)
> >> +               return -EINVAL;
> >> +       if (size < sizeof(*ctx))
> >> +               return -EINVAL;
> > If we're only going to support on 'lsm_ctx' entry in this function we
> > should verify that the 'len' and 'ctx_len' fields are sane.  Although
> > more on this below ...
>
> The LSM is going to have to do its own version of sanity checking. Having
> sanity checking here as well seems excessive.

Yes, the LSM will probably need to do some checks, but we can safely
do the length checking here so we might as well do it simply so every
LSM doesn't have to duplicate the length checks.

> >> +       if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
> >> +               return -EFAULT;
> >> +
> >> +       hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
> >> +               if ((hp->lsmid->id) == lctx.id)
> >> +                       return hp->hook.setselfattr(attr, ctx, size, flags);
> > Can anyone think of any good reason why we shouldn't support setting
> > multiple LSMs in one call, similar to what we do with
> > security_getselfattr()?  It seems like it might be a nice thing to
> > have ...
>
> If you're setting the context for multiple LSMs ...

See my follow-up to my original reply sent earlier today.

-- 
paul-moore.com

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Paul Moore]

On Thu, Mar 30, 2023 at 4:42 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 3/29/2023 6:13 PM, Paul Moore wrote:
> > On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >> Add lsm_name_to_attr(), which translates a text string to a
> >> LSM_ATTR value if one is available.
> >>
> >> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
> >> the trailing attribute value.
> >>
> >> All are used in module specific components of LSM system calls.
> >>
> >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> >> ---
> >>  include/linux/security.h | 13 ++++++++++
> >>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
> >>  security/security.c      | 31 ++++++++++++++++++++++++
> >>  3 files changed, 95 insertions(+)
> > ..
> >
> >> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> >> index 6efbe244d304..55d849ad5d6e 100644
> >> --- a/security/lsm_syscalls.c
> >> +++ b/security/lsm_syscalls.c
> >> @@ -17,6 +17,57 @@
> >>  #include <linux/lsm_hooks.h>
> >>  #include <uapi/linux/lsm.h>
> >>
> >> +struct attr_map {
> >> +       char *name;
> >> +       u64 attr;
> >> +};
> >> +
> >> +static const struct attr_map lsm_attr_names[] = {
> >> +       {
> >> +               .name = "current",
> >> +               .attr = LSM_ATTR_CURRENT,
> >> +       },
> >> +       {
> >> +               .name = "exec",
> >> +               .attr = LSM_ATTR_EXEC,
> >> +       },
> >> +       {
> >> +               .name = "fscreate",
> >> +               .attr = LSM_ATTR_FSCREATE,
> >> +       },
> >> +       {
> >> +               .name = "keycreate",
> >> +               .attr = LSM_ATTR_KEYCREATE,
> >> +       },
> >> +       {
> >> +               .name = "prev",
> >> +               .attr = LSM_ATTR_PREV,
> >> +       },
> >> +       {
> >> +               .name = "sockcreate",
> >> +               .attr = LSM_ATTR_SOCKCREATE,
> >> +       },
> >> +};
> >> +
> >> +/**
> >> + * lsm_name_to_attr - map an LSM attribute name to its ID
> >> + * @name: name of the attribute
> >> + *
> >> + * Look the given @name up in the table of know attribute names.
> >> + *
> >> + * Returns the LSM attribute value associated with @name, or 0 if
> >> + * there is no mapping.
> >> + */
> >> +u64 lsm_name_to_attr(const char *name)
> >> +{
> >> +       int i;
> >> +
> >> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
> >> +               if (!strcmp(name, lsm_attr_names[i].name))
> >> +                       return lsm_attr_names[i].attr;
> > I'm pretty sure this is the only place where @lsm_attr_names is used,
> > right?  If true, when coupled with the idea that these syscalls are
> > going to close the door on new LSM attributes in procfs I think we can
> > just put the mapping directly in this function via a series of
> > if-statements.
>
> Ick. You're not wrong, but the hard coded if-statement approach goes
> against all sorts of coding principles. I'll do it, but I can't say I
> like it.

If it helps any, I understand and am sympathetic.  I guess I've gotten
to that point where in addition to "code elegance", I'm also very
concerned about defending against "code abuse", and something like an
nicely defined mapping array is ripe for someone to come along and use
that to justify further use of the attribute string names in some
other function/API.

If you want to stick with the array - I have no problem with that -
make it local to lsm_name_to_attr().

> >> +/**
> >> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> >> + * @ctx: an LSM context to be filled
> >> + * @context: the new context value
> >> + * @context_size: the size of the new context value
> >> + * @id: LSM id
> >> + * @flags: LSM defined flags
> >> + *
> >> + * Fill all of the fields in a user space lsm_ctx structure.
> >> + * Caller is assumed to have verified that @ctx has enough space
> >> + * for @context.
> >> + * Returns 0 on success, -EFAULT on a copyout error.
> >> + */
> >> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
> >> +                     size_t context_size, u64 id, u64 flags)
> >> +{
> >> +       struct lsm_ctx local;
> >> +       void __user *vc = ctx;
> >> +
> >> +       local.id = id;
> >> +       local.flags = flags;
> >> +       local.ctx_len = context_size;
> >> +       local.len = context_size + sizeof(local);
> >> +       vc += sizeof(local);
> > See my prior comments about void pointer math.
> >
> >> +       if (copy_to_user(ctx, &local, sizeof(local)))
> >> +               return -EFAULT;
> >> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
> >> +               return -EFAULT;
> > Should we handle the padding in this function?
>
> This function fills in a lsm_ctx. The padding, if any, is in addition to
> the lsm_ctx, not part of it.

Okay, so where is the padding managed?  I may have missed it, but I
don't recall seeing it anywhere in this patchset ...

-- 
paul-moore.com

Re: [PATCH v7 10/11] SELinux: Add selfattr hooks

[Paul Moore]

On Thu, Mar 30, 2023 at 4:55 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 3/29/2023 6:13 PM, Paul Moore wrote:
> > On Wed, Mar 15, 2023 at 6:52 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >> Add hooks for setselfattr and getselfattr. These hooks are not very
> >> different from their setprocattr and getprocattr equivalents, and
> >> much of the code is shared.
> >>
> >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> >> Cc: selinux@vger.kernel.org
> >> Cc: Paul Moore <paul@paul-moore.com>
> >> ---
> >>  security/selinux/hooks.c | 147 +++++++++++++++++++++++++++++++--------
> >>  1 file changed, 117 insertions(+), 30 deletions(-)
> >>
> >> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> >> index 9403aee75981..8896edf80aa9 100644
> >> --- a/security/selinux/hooks.c
> >> +++ b/security/selinux/hooks.c
> >> @@ -6348,8 +6348,7 @@ static void selinux_d_instantiate(struct dentry *dentry, struct inode *inode)
> >>                 inode_doinit_with_dentry(inode, dentry);
> >>  }
> >>
> >> -static int selinux_getprocattr(struct task_struct *p,
> >> -                              const char *name, char **value)
> >> +static int do_getattr(unsigned int attr, struct task_struct *p, char **value)
> > Are you ready for more naming nitpicks? ;)
>
> I would expect nothing less. :)
>
> > Let's call this 'selinux_lsm_getattr()', and the matching setter
> > should be 'selinux_lsm_setattr()'.
>
> As you wish. It's your LSM.
>
>
> >>  {
> >>         const struct task_security_struct *__tsec;
> >>         u32 sid;
> >> @@ -6367,20 +6366,27 @@ static int selinux_getprocattr(struct task_struct *p,
> >>                         goto bad;
> >>         }
> >>
> >> -       if (!strcmp(name, "current"))
> >> +       switch (attr) {
> >> +       case LSM_ATTR_CURRENT:
> >>                 sid = __tsec->sid;
> >> -       else if (!strcmp(name, "prev"))
> >> +               break;
> >> +       case LSM_ATTR_PREV:
> >>                 sid = __tsec->osid;
> >> -       else if (!strcmp(name, "exec"))
> >> +               break;
> >> +       case LSM_ATTR_EXEC:
> >>                 sid = __tsec->exec_sid;
> >> -       else if (!strcmp(name, "fscreate"))
> >> +               break;
> >> +       case LSM_ATTR_FSCREATE:
> >>                 sid = __tsec->create_sid;
> >> -       else if (!strcmp(name, "keycreate"))
> >> +               break;
> >> +       case LSM_ATTR_KEYCREATE:
> >>                 sid = __tsec->keycreate_sid;
> >> -       else if (!strcmp(name, "sockcreate"))
> >> +               break;
> >> +       case LSM_ATTR_SOCKCREATE:
> >>                 sid = __tsec->sockcreate_sid;
> >> -       else {
> >> -               error = -EINVAL;
> >> +               break;
> >> +       default:
> >> +               error = -EOPNOTSUPP;
> > The error should probably be -EINVAL.
>
> It's possible that we may add an attribute that SELinux doesn't
> support, say LSM_ATTR_CRYPTO_KEY, that another LSM does. This is
> the same behavior the other LSMs exhibit in the face of a request
> for attributes such as LSM_ATTR_KEYCREATE that they don't support.

Okay, I'll accept that argument, but I would ask that add some
additional handling in selinux_getprocattr() so that it returns
-EINVAL in this case just as it does today.

> >>                 goto bad;
> >>         }
> >>         rcu_read_unlock();
> >> @@ -6398,7 +6404,7 @@ static int selinux_getprocattr(struct task_struct *p,
> >>         return error;
> >>  }
> >>
> >> -static int selinux_setprocattr(const char *name, void *value, size_t size)
> >> +static int do_setattr(u64 attr, void *value, size_t size)
> >>  {
> >>         struct task_security_struct *tsec;
> >>         struct cred *new;
> >> @@ -6409,28 +6415,36 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
> >>         /*
> >>          * Basic control over ability to set these attributes at all.
> >>          */
> >> -       if (!strcmp(name, "exec"))
> >> +       switch (attr) {
> >> +       case LSM_ATTR_CURRENT:
> >> +               error = avc_has_perm(&selinux_state,
> >> +                                    mysid, mysid, SECCLASS_PROCESS,
> >> +                                    PROCESS__SETCURRENT, NULL);
> >> +               break;
> >> +       case LSM_ATTR_EXEC:
> >>                 error = avc_has_perm(&selinux_state,
> >>                                      mysid, mysid, SECCLASS_PROCESS,
> >>                                      PROCESS__SETEXEC, NULL);
> >> -       else if (!strcmp(name, "fscreate"))
> >> +               break;
> >> +       case LSM_ATTR_FSCREATE:
> >>                 error = avc_has_perm(&selinux_state,
> >>                                      mysid, mysid, SECCLASS_PROCESS,
> >>                                      PROCESS__SETFSCREATE, NULL);
> >> -       else if (!strcmp(name, "keycreate"))
> >> +               break;
> >> +       case LSM_ATTR_KEYCREATE:
> >>                 error = avc_has_perm(&selinux_state,
> >>                                      mysid, mysid, SECCLASS_PROCESS,
> >>                                      PROCESS__SETKEYCREATE, NULL);
> >> -       else if (!strcmp(name, "sockcreate"))
> >> +               break;
> >> +       case LSM_ATTR_SOCKCREATE:
> >>                 error = avc_has_perm(&selinux_state,
> >>                                      mysid, mysid, SECCLASS_PROCESS,
> >>                                      PROCESS__SETSOCKCREATE, NULL);
> >> -       else if (!strcmp(name, "current"))
> >> -               error = avc_has_perm(&selinux_state,
> >> -                                    mysid, mysid, SECCLASS_PROCESS,
> >> -                                    PROCESS__SETCURRENT, NULL);
> >> -       else
> >> -               error = -EINVAL;
> >> +               break;
> >> +       default:
> >> +               error = -EOPNOTSUPP;
> > Same as above, should be -EINVAL.
>
> Same as above, there may be attributes SELinux doesn't support.

Also, same as above.

> >> +               break;
> >> +       }
> >>         if (error)
> >>                 return error;
> >>
> >> @@ -6442,13 +6456,14 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
> >>                 }
> >>                 error = security_context_to_sid(&selinux_state, value, size,
> >>                                                 &sid, GFP_KERNEL);
> >> -               if (error == -EINVAL && !strcmp(name, "fscreate")) {
> >> +               if (error == -EINVAL && attr == LSM_ATTR_FSCREATE) {
> >>                         if (!has_cap_mac_admin(true)) {
> >>                                 struct audit_buffer *ab;
> >>                                 size_t audit_size;
> >>
> >> -                               /* We strip a nul only if it is at the end, otherwise the
> >> -                                * context contains a nul and we should audit that */
> >> +                               /* We strip a nul only if it is at the end,
> >> +                                * otherwise the context contains a nul and
> >> +                                * we should audit that */
> > You *do* get gold stars for fixing line lengths in close proximity ;)
>
> I guess I'm the Last User of the 80 character terminal.

I'm still a big fan and I'm sticking to the 80 char limit for the LSM
layer as well as the SELinux, audit, and labeled networking
subsystems.  Longer lines either predate me or I simply didn't catch
them during review/merge.

-- 
paul-moore.com

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 3/30/2023 4:28 PM, Paul Moore wrote:
> On Thu, Mar 30, 2023 at 4:42 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> On 3/29/2023 6:13 PM, Paul Moore wrote:
>>> On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>> Add lsm_name_to_attr(), which translates a text string to a
>>>> LSM_ATTR value if one is available.
>>>>
>>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>>> the trailing attribute value.
>>>>
>>>> All are used in module specific components of LSM system calls.
>>>>
>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>> ---
>>>>  include/linux/security.h | 13 ++++++++++
>>>>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>>>  security/security.c      | 31 ++++++++++++++++++++++++
>>>>  3 files changed, 95 insertions(+)
>>> ..
>>>
>>>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>>>> index 6efbe244d304..55d849ad5d6e 100644
>>>> --- a/security/lsm_syscalls.c
>>>> +++ b/security/lsm_syscalls.c
>>>> @@ -17,6 +17,57 @@
>>>>  #include <linux/lsm_hooks.h>
>>>>  #include <uapi/linux/lsm.h>
>>>>
>>>> +struct attr_map {
>>>> +       char *name;
>>>> +       u64 attr;
>>>> +};
>>>> +
>>>> +static const struct attr_map lsm_attr_names[] = {
>>>> +       {
>>>> +               .name = "current",
>>>> +               .attr = LSM_ATTR_CURRENT,
>>>> +       },
>>>> +       {
>>>> +               .name = "exec",
>>>> +               .attr = LSM_ATTR_EXEC,
>>>> +       },
>>>> +       {
>>>> +               .name = "fscreate",
>>>> +               .attr = LSM_ATTR_FSCREATE,
>>>> +       },
>>>> +       {
>>>> +               .name = "keycreate",
>>>> +               .attr = LSM_ATTR_KEYCREATE,
>>>> +       },
>>>> +       {
>>>> +               .name = "prev",
>>>> +               .attr = LSM_ATTR_PREV,
>>>> +       },
>>>> +       {
>>>> +               .name = "sockcreate",
>>>> +               .attr = LSM_ATTR_SOCKCREATE,
>>>> +       },
>>>> +};
>>>> +
>>>> +/**
>>>> + * lsm_name_to_attr - map an LSM attribute name to its ID
>>>> + * @name: name of the attribute
>>>> + *
>>>> + * Look the given @name up in the table of know attribute names.
>>>> + *
>>>> + * Returns the LSM attribute value associated with @name, or 0 if
>>>> + * there is no mapping.
>>>> + */
>>>> +u64 lsm_name_to_attr(const char *name)
>>>> +{
>>>> +       int i;
>>>> +
>>>> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
>>>> +               if (!strcmp(name, lsm_attr_names[i].name))
>>>> +                       return lsm_attr_names[i].attr;
>>> I'm pretty sure this is the only place where @lsm_attr_names is used,
>>> right?  If true, when coupled with the idea that these syscalls are
>>> going to close the door on new LSM attributes in procfs I think we can
>>> just put the mapping directly in this function via a series of
>>> if-statements.
>> Ick. You're not wrong, but the hard coded if-statement approach goes
>> against all sorts of coding principles. I'll do it, but I can't say I
>> like it.
> If it helps any, I understand and am sympathetic.  I guess I've gotten
> to that point where in addition to "code elegance", I'm also very
> concerned about defending against "code abuse", and something like an
> nicely defined mapping array is ripe for someone to come along and use
> that to justify further use of the attribute string names in some
> other function/API.
>
> If you want to stick with the array - I have no problem with that -
> make it local to lsm_name_to_attr().
>
>>>> +/**
>>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>>> + * @ctx: an LSM context to be filled
>>>> + * @context: the new context value
>>>> + * @context_size: the size of the new context value
>>>> + * @id: LSM id
>>>> + * @flags: LSM defined flags
>>>> + *
>>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>>> + * Caller is assumed to have verified that @ctx has enough space
>>>> + * for @context.
>>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>>> + */
>>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>>> +                     size_t context_size, u64 id, u64 flags)
>>>> +{
>>>> +       struct lsm_ctx local;
>>>> +       void __user *vc = ctx;
>>>> +
>>>> +       local.id = id;
>>>> +       local.flags = flags;
>>>> +       local.ctx_len = context_size;
>>>> +       local.len = context_size + sizeof(local);
>>>> +       vc += sizeof(local);
>>> See my prior comments about void pointer math.
>>>
>>>> +       if (copy_to_user(ctx, &local, sizeof(local)))
>>>> +               return -EFAULT;
>>>> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
>>>> +               return -EFAULT;
>>> Should we handle the padding in this function?
>> This function fills in a lsm_ctx. The padding, if any, is in addition to
>> the lsm_ctx, not part of it.
> Okay, so where is the padding managed?  I may have missed it, but I
> don't recall seeing it anywhere in this patchset ...

Padding isn't being managed. There has been talk about using padding to
expand the API, but there is no use for it now. Or is there?

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Paul Moore]

On Fri, Mar 31, 2023 at 12:56 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 3/30/2023 4:28 PM, Paul Moore wrote:
> > On Thu, Mar 30, 2023 at 4:42 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >> On 3/29/2023 6:13 PM, Paul Moore wrote:
> >>> On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >>>> Add lsm_name_to_attr(), which translates a text string to a
> >>>> LSM_ATTR value if one is available.
> >>>>
> >>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
> >>>> the trailing attribute value.
> >>>>
> >>>> All are used in module specific components of LSM system calls.
> >>>>
> >>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> >>>> ---
> >>>>  include/linux/security.h | 13 ++++++++++
> >>>>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
> >>>>  security/security.c      | 31 ++++++++++++++++++++++++
> >>>>  3 files changed, 95 insertions(+)
> >>> ..
> >>>
> >>>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> >>>> index 6efbe244d304..55d849ad5d6e 100644
> >>>> --- a/security/lsm_syscalls.c
> >>>> +++ b/security/lsm_syscalls.c
> >>>> @@ -17,6 +17,57 @@
> >>>>  #include <linux/lsm_hooks.h>
> >>>>  #include <uapi/linux/lsm.h>
> >>>>
> >>>> +struct attr_map {
> >>>> +       char *name;
> >>>> +       u64 attr;
> >>>> +};
> >>>> +
> >>>> +static const struct attr_map lsm_attr_names[] = {
> >>>> +       {
> >>>> +               .name = "current",
> >>>> +               .attr = LSM_ATTR_CURRENT,
> >>>> +       },
> >>>> +       {
> >>>> +               .name = "exec",
> >>>> +               .attr = LSM_ATTR_EXEC,
> >>>> +       },
> >>>> +       {
> >>>> +               .name = "fscreate",
> >>>> +               .attr = LSM_ATTR_FSCREATE,
> >>>> +       },
> >>>> +       {
> >>>> +               .name = "keycreate",
> >>>> +               .attr = LSM_ATTR_KEYCREATE,
> >>>> +       },
> >>>> +       {
> >>>> +               .name = "prev",
> >>>> +               .attr = LSM_ATTR_PREV,
> >>>> +       },
> >>>> +       {
> >>>> +               .name = "sockcreate",
> >>>> +               .attr = LSM_ATTR_SOCKCREATE,
> >>>> +       },
> >>>> +};
> >>>> +
> >>>> +/**
> >>>> + * lsm_name_to_attr - map an LSM attribute name to its ID
> >>>> + * @name: name of the attribute
> >>>> + *
> >>>> + * Look the given @name up in the table of know attribute names.
> >>>> + *
> >>>> + * Returns the LSM attribute value associated with @name, or 0 if
> >>>> + * there is no mapping.
> >>>> + */
> >>>> +u64 lsm_name_to_attr(const char *name)
> >>>> +{
> >>>> +       int i;
> >>>> +
> >>>> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
> >>>> +               if (!strcmp(name, lsm_attr_names[i].name))
> >>>> +                       return lsm_attr_names[i].attr;
> >>> I'm pretty sure this is the only place where @lsm_attr_names is used,
> >>> right?  If true, when coupled with the idea that these syscalls are
> >>> going to close the door on new LSM attributes in procfs I think we can
> >>> just put the mapping directly in this function via a series of
> >>> if-statements.
> >> Ick. You're not wrong, but the hard coded if-statement approach goes
> >> against all sorts of coding principles. I'll do it, but I can't say I
> >> like it.
> > If it helps any, I understand and am sympathetic.  I guess I've gotten
> > to that point where in addition to "code elegance", I'm also very
> > concerned about defending against "code abuse", and something like an
> > nicely defined mapping array is ripe for someone to come along and use
> > that to justify further use of the attribute string names in some
> > other function/API.
> >
> > If you want to stick with the array - I have no problem with that -
> > make it local to lsm_name_to_attr().
> >
> >>>> +/**
> >>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> >>>> + * @ctx: an LSM context to be filled
> >>>> + * @context: the new context value
> >>>> + * @context_size: the size of the new context value
> >>>> + * @id: LSM id
> >>>> + * @flags: LSM defined flags
> >>>> + *
> >>>> + * Fill all of the fields in a user space lsm_ctx structure.
> >>>> + * Caller is assumed to have verified that @ctx has enough space
> >>>> + * for @context.
> >>>> + * Returns 0 on success, -EFAULT on a copyout error.
> >>>> + */
> >>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
> >>>> +                     size_t context_size, u64 id, u64 flags)
> >>>> +{
> >>>> +       struct lsm_ctx local;
> >>>> +       void __user *vc = ctx;
> >>>> +
> >>>> +       local.id = id;
> >>>> +       local.flags = flags;
> >>>> +       local.ctx_len = context_size;
> >>>> +       local.len = context_size + sizeof(local);
> >>>> +       vc += sizeof(local);
> >>> See my prior comments about void pointer math.
> >>>
> >>>> +       if (copy_to_user(ctx, &local, sizeof(local)))
> >>>> +               return -EFAULT;
> >>>> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
> >>>> +               return -EFAULT;
> >>> Should we handle the padding in this function?
> >> This function fills in a lsm_ctx. The padding, if any, is in addition to
> >> the lsm_ctx, not part of it.
> > Okay, so where is the padding managed?  I may have missed it, but I
> > don't recall seeing it anywhere in this patchset ...
>
> Padding isn't being managed. There has been talk about using padding to
> expand the API, but there is no use for it now. Or is there?

I think two separate ideas are getting conflated, likely because the
'len' field is involved in both.

THe first issue is padding at the end of the lsm_ctx struct to ensure
that the next array element is aligned.  The second issue is the
potential for extending the lsm_ctx struct on a per-LSM basis through
creative use of the 'flags' and 'len' fields; in this case additional
information could be stashed at the end of the lsm_ctx struct after
the 'ctx' field.  The latter issue (extending the lsm_ctx) isn't
something we want to jump into, but it is something the syscall/struct
API would allow, and I don't want to exclude it as a possible future
solution to a yet unknown future problem.  The former issue (padding
array elements) isn't a strict requirement as the syscall/struct API
works either way, but it seems like a good thing to do.

-- 
paul-moore.com

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 3/31/2023 12:24 PM, Paul Moore wrote:
> On Fri, Mar 31, 2023 at 12:56 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> On 3/30/2023 4:28 PM, Paul Moore wrote:
>>> On Thu, Mar 30, 2023 at 4:42 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>> On 3/29/2023 6:13 PM, Paul Moore wrote:
>>>>> On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>>>> Add lsm_name_to_attr(), which translates a text string to a
>>>>>> LSM_ATTR value if one is available.
>>>>>>
>>>>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>>>>> the trailing attribute value.
>>>>>>
>>>>>> All are used in module specific components of LSM system calls.
>>>>>>
>>>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>>>> ---
>>>>>>  include/linux/security.h | 13 ++++++++++
>>>>>>  security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>>>>>  security/security.c      | 31 ++++++++++++++++++++++++
>>>>>>  3 files changed, 95 insertions(+)
>>>>> ..
>>>>>
>>>>>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>>>>>> index 6efbe244d304..55d849ad5d6e 100644
>>>>>> --- a/security/lsm_syscalls.c
>>>>>> +++ b/security/lsm_syscalls.c
>>>>>> @@ -17,6 +17,57 @@
>>>>>>  #include <linux/lsm_hooks.h>
>>>>>>  #include <uapi/linux/lsm.h>
>>>>>>
>>>>>> +struct attr_map {
>>>>>> +       char *name;
>>>>>> +       u64 attr;
>>>>>> +};
>>>>>> +
>>>>>> +static const struct attr_map lsm_attr_names[] = {
>>>>>> +       {
>>>>>> +               .name = "current",
>>>>>> +               .attr = LSM_ATTR_CURRENT,
>>>>>> +       },
>>>>>> +       {
>>>>>> +               .name = "exec",
>>>>>> +               .attr = LSM_ATTR_EXEC,
>>>>>> +       },
>>>>>> +       {
>>>>>> +               .name = "fscreate",
>>>>>> +               .attr = LSM_ATTR_FSCREATE,
>>>>>> +       },
>>>>>> +       {
>>>>>> +               .name = "keycreate",
>>>>>> +               .attr = LSM_ATTR_KEYCREATE,
>>>>>> +       },
>>>>>> +       {
>>>>>> +               .name = "prev",
>>>>>> +               .attr = LSM_ATTR_PREV,
>>>>>> +       },
>>>>>> +       {
>>>>>> +               .name = "sockcreate",
>>>>>> +               .attr = LSM_ATTR_SOCKCREATE,
>>>>>> +       },
>>>>>> +};
>>>>>> +
>>>>>> +/**
>>>>>> + * lsm_name_to_attr - map an LSM attribute name to its ID
>>>>>> + * @name: name of the attribute
>>>>>> + *
>>>>>> + * Look the given @name up in the table of know attribute names.
>>>>>> + *
>>>>>> + * Returns the LSM attribute value associated with @name, or 0 if
>>>>>> + * there is no mapping.
>>>>>> + */
>>>>>> +u64 lsm_name_to_attr(const char *name)
>>>>>> +{
>>>>>> +       int i;
>>>>>> +
>>>>>> +       for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
>>>>>> +               if (!strcmp(name, lsm_attr_names[i].name))
>>>>>> +                       return lsm_attr_names[i].attr;
>>>>> I'm pretty sure this is the only place where @lsm_attr_names is used,
>>>>> right?  If true, when coupled with the idea that these syscalls are
>>>>> going to close the door on new LSM attributes in procfs I think we can
>>>>> just put the mapping directly in this function via a series of
>>>>> if-statements.
>>>> Ick. You're not wrong, but the hard coded if-statement approach goes
>>>> against all sorts of coding principles. I'll do it, but I can't say I
>>>> like it.
>>> If it helps any, I understand and am sympathetic.  I guess I've gotten
>>> to that point where in addition to "code elegance", I'm also very
>>> concerned about defending against "code abuse", and something like an
>>> nicely defined mapping array is ripe for someone to come along and use
>>> that to justify further use of the attribute string names in some
>>> other function/API.
>>>
>>> If you want to stick with the array - I have no problem with that -
>>> make it local to lsm_name_to_attr().
>>>
>>>>>> +/**
>>>>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>>>>> + * @ctx: an LSM context to be filled
>>>>>> + * @context: the new context value
>>>>>> + * @context_size: the size of the new context value
>>>>>> + * @id: LSM id
>>>>>> + * @flags: LSM defined flags
>>>>>> + *
>>>>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>>>>> + * Caller is assumed to have verified that @ctx has enough space
>>>>>> + * for @context.
>>>>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>>>>> + */
>>>>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>>>>> +                     size_t context_size, u64 id, u64 flags)
>>>>>> +{
>>>>>> +       struct lsm_ctx local;
>>>>>> +       void __user *vc = ctx;
>>>>>> +
>>>>>> +       local.id = id;
>>>>>> +       local.flags = flags;
>>>>>> +       local.ctx_len = context_size;
>>>>>> +       local.len = context_size + sizeof(local);
>>>>>> +       vc += sizeof(local);
>>>>> See my prior comments about void pointer math.
>>>>>
>>>>>> +       if (copy_to_user(ctx, &local, sizeof(local)))
>>>>>> +               return -EFAULT;
>>>>>> +       if (context_size > 0 && copy_to_user(vc, context, context_size))
>>>>>> +               return -EFAULT;
>>>>> Should we handle the padding in this function?
>>>> This function fills in a lsm_ctx. The padding, if any, is in addition to
>>>> the lsm_ctx, not part of it.
>>> Okay, so where is the padding managed?  I may have missed it, but I
>>> don't recall seeing it anywhere in this patchset ...
>> Padding isn't being managed. There has been talk about using padding to
>> expand the API, but there is no use for it now. Or is there?
> I think two separate ideas are getting conflated, likely because the
> 'len' field is involved in both.
>
> THe first issue is padding at the end of the lsm_ctx struct to ensure
> that the next array element is aligned.  The second issue is the
> potential for extending the lsm_ctx struct on a per-LSM basis through
> creative use of the 'flags' and 'len' fields; in this case additional
> information could be stashed at the end of the lsm_ctx struct after
> the 'ctx' field.  The latter issue (extending the lsm_ctx) isn't
> something we want to jump into, but it is something the syscall/struct
> API would allow, and I don't want to exclude it as a possible future
> solution to a yet unknown future problem.  The former issue (padding
> array elements) isn't a strict requirement as the syscall/struct API
> works either way, but it seems like a good thing to do.

Reasonable. Thanks for the clarification.

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Mickaël Salaün]

On 15/03/2023 23:47, Casey Schaufler wrote:
> Add lsm_name_to_attr(), which translates a text string to a
> LSM_ATTR value if one is available.
> 
> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
> the trailing attribute value.
> 
> All are used in module specific components of LSM system calls.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>   include/linux/security.h | 13 ++++++++++
>   security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>   security/security.c      | 31 ++++++++++++++++++++++++
>   3 files changed, 95 insertions(+)

[...]

> diff --git a/security/security.c b/security/security.c
> index 2c57fe28c4f7..f7b814a3940c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
>   	return 0;
>   }
>   
> +/**
> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> + * @ctx: an LSM context to be filled
> + * @context: the new context value
> + * @context_size: the size of the new context value
> + * @id: LSM id
> + * @flags: LSM defined flags
> + *
> + * Fill all of the fields in a user space lsm_ctx structure.
> + * Caller is assumed to have verified that @ctx has enough space
> + * for @context.
> + * Returns 0 on success, -EFAULT on a copyout error.
> + */
> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
> +		      size_t context_size, u64 id, u64 flags)
> +{
> +	struct lsm_ctx local;
> +	void __user *vc = ctx;
> +
> +	local.id = id;
> +	local.flags = flags;
> +	local.ctx_len = context_size;
> +	local.len = context_size + sizeof(local);
> +	vc += sizeof(local);
> +	if (copy_to_user(ctx, &local, sizeof(local)))
> +		return -EFAULT;
> +	if (context_size > 0 && copy_to_user(vc, context, context_size))
> +		return -EFAULT;

Can we do a single copy_to_user() call? That would avoid inconsistent 
user space data, could speed up a bit the operation, and make the code 
easier to understand. To use the stack, we need to know the maximum size 
of context_size for all use cases, which seems reasonable and can be 
checked at build time (on each LSM side, and potentially with specific 
context type passed as enum instead of context_size) and run time (for 
this generic helper).


> +	return 0;
> +}
> +
>   /*
>    * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
>    * can be accessed with:

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Mickaël Salaün]

On 03/04/2023 11:47, Mickaël Salaün wrote:
> 
> On 15/03/2023 23:47, Casey Schaufler wrote:
>> Add lsm_name_to_attr(), which translates a text string to a
>> LSM_ATTR value if one is available.
>>
>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>> the trailing attribute value.
>>
>> All are used in module specific components of LSM system calls.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> ---
>>    include/linux/security.h | 13 ++++++++++
>>    security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>    security/security.c      | 31 ++++++++++++++++++++++++
>>    3 files changed, 95 insertions(+)
> 
> [...]
> 
>> diff --git a/security/security.c b/security/security.c
>> index 2c57fe28c4f7..f7b814a3940c 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
>>    	return 0;
>>    }
>>    
>> +/**
>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>> + * @ctx: an LSM context to be filled
>> + * @context: the new context value
>> + * @context_size: the size of the new context value
>> + * @id: LSM id
>> + * @flags: LSM defined flags
>> + *
>> + * Fill all of the fields in a user space lsm_ctx structure.
>> + * Caller is assumed to have verified that @ctx has enough space
>> + * for @context.
>> + * Returns 0 on success, -EFAULT on a copyout error.
>> + */
>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>> +		      size_t context_size, u64 id, u64 flags)
>> +{
>> +	struct lsm_ctx local;
>> +	void __user *vc = ctx;
>> +
>> +	local.id = id;
>> +	local.flags = flags;
>> +	local.ctx_len = context_size;
>> +	local.len = context_size + sizeof(local);
>> +	vc += sizeof(local);
>> +	if (copy_to_user(ctx, &local, sizeof(local)))
>> +		return -EFAULT;
>> +	if (context_size > 0 && copy_to_user(vc, context, context_size))
>> +		return -EFAULT;
> 
> Can we do a single copy_to_user() call? That would avoid inconsistent
> user space data, could speed up a bit the operation, and make the code
> easier to understand. To use the stack, we need to know the maximum size
> of context_size for all use cases, which seems reasonable and can be
> checked at build time (on each LSM side, and potentially with specific
> context type passed as enum instead of context_size) and run time (for
> this generic helper).

Well, actually the context_size should be inferred from id, and the 
"local" size should be defined and check at build time against all 
context ID sizes.

> 
> 
>> +	return 0;
>> +}
>> +
>>    /*
>>     * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
>>     * can be accessed with:

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Mickaël Salaün]

On 03/04/2023 11:54, Mickaël Salaün wrote:
> 
> On 03/04/2023 11:47, Mickaël Salaün wrote:
>>
>> On 15/03/2023 23:47, Casey Schaufler wrote:
>>> Add lsm_name_to_attr(), which translates a text string to a
>>> LSM_ATTR value if one is available.
>>>
>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>> the trailing attribute value.
>>>
>>> All are used in module specific components of LSM system calls.
>>>
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>> ---
>>>     include/linux/security.h | 13 ++++++++++
>>>     security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>>     security/security.c      | 31 ++++++++++++++++++++++++
>>>     3 files changed, 95 insertions(+)
>>
>> [...]
>>
>>> diff --git a/security/security.c b/security/security.c
>>> index 2c57fe28c4f7..f7b814a3940c 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
>>>     	return 0;
>>>     }
>>>     
>>> +/**
>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>> + * @ctx: an LSM context to be filled
>>> + * @context: the new context value
>>> + * @context_size: the size of the new context value
>>> + * @id: LSM id
>>> + * @flags: LSM defined flags
>>> + *
>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>> + * Caller is assumed to have verified that @ctx has enough space
>>> + * for @context.
>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>> + */
>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>> +		      size_t context_size, u64 id, u64 flags)
>>> +{
>>> +	struct lsm_ctx local;
>>> +	void __user *vc = ctx;
>>> +
>>> +	local.id = id;
>>> +	local.flags = flags;
>>> +	local.ctx_len = context_size;
>>> +	local.len = context_size + sizeof(local);
>>> +	vc += sizeof(local);
>>> +	if (copy_to_user(ctx, &local, sizeof(local)))
>>> +		return -EFAULT;
>>> +	if (context_size > 0 && copy_to_user(vc, context, context_size))
>>> +		return -EFAULT;
>>
>> Can we do a single copy_to_user() call? That would avoid inconsistent
>> user space data, could speed up a bit the operation, and make the code
>> easier to understand. To use the stack, we need to know the maximum size
>> of context_size for all use cases, which seems reasonable and can be
>> checked at build time (on each LSM side, and potentially with specific
>> context type passed as enum instead of context_size) and run time (for
>> this generic helper).
> 
> Well, actually the context_size should be inferred from id, and the
> "local" size should be defined and check at build time against all
> context ID sizes.

@ctx_len should already be known by user space according to the LSM ID 
and the requested attribute. @len should already be known by user space 
because lsm_ctx is part of the ABI.

The only reason I can think of the rationale for @len and @ctx_len is 
that struct lsm_ctx could gain more fields. If this happen, they would 
then need to be inserted before @ctx. This would make this struct 
lsm_ctx too flexible and complex for user space to parse correctly (e.g. 
for strace, gdb).

I don't see where we could use @flags instead of relying on a new 
attribute type.

I think security_getselfattr() and lsm_fill_user_ctx() could be changed 
to avoid each LSM to pass their own ID to lsm_fill_user_ctx(). We could 
have a lsm_get_attr_size(lsm_id, attr) helper (called by 
security_getselfattr) to group these relations, based on fixed values, 
exposed in the UAPI, and checked at build time with the size of the 
related LSM-specific attribute type. This would also allow to factor out 
the total size calculation needed before calling the getselfattr() 
implementers, and then rely on a common consistent behavior. That could 
also be used to not call getselfattr() implementers if they don't handle 
a specific attribute, and then remove their related error handling for 
this case.

For now, the getselfattr() hook (not the related syscall) doesn't need 
to pass a "flags" argument to each LSM because there is no use of it.


> 
>>
>>
>>> +	return 0;
>>> +}
>>> +
>>>     /*
>>>      * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
>>>      * can be accessed with:

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Mickaël Salaün]

On 15/03/2023 23:46, Casey Schaufler wrote:
> Create a system call lsm_get_self_attr() to provide the security
> module maintained attributes of the current process.
> Create a system call lsm_set_self_attr() to set a security
> module maintained attribute of the current process.
> Historically these attributes have been exposed to user space via
> entries in procfs under /proc/self/attr.
> 
> The attribute value is provided in a lsm_ctx structure. The structure
> identifys the size of the attribute, and the attribute value. The format
> of the attribute value is defined by the security module. A flags field
> is included for LSM specific information. It is currently unused and must
> be 0. The total size of the data, including the lsm_ctx structure and any
> padding, is maintained as well.
> 
> struct lsm_ctx {
>          __u64   id;
>          __u64   flags;
>          __u64   len;
>          __u64   ctx_len;
>          __u8    ctx[];
> };
> 
> Two new LSM hooks are used to interface with the LSMs.
> security_getselfattr() collects the lsm_ctx values from the
> LSMs that support the hook, accounting for space requirements.
> security_setselfattr() identifies which LSM the attribute is
> intended for and passes it along.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>   Documentation/userspace-api/lsm.rst | 15 +++++
>   include/linux/lsm_hook_defs.h       |  4 ++
>   include/linux/lsm_hooks.h           |  9 +++
>   include/linux/security.h            | 19 ++++++
>   include/linux/syscalls.h            |  5 ++
>   include/uapi/linux/lsm.h            | 33 ++++++++++
>   kernel/sys_ni.c                     |  4 ++
>   security/Makefile                   |  1 +
>   security/lsm_syscalls.c             | 55 ++++++++++++++++
>   security/security.c                 | 97 +++++++++++++++++++++++++++++
>   10 files changed, 242 insertions(+)
>   create mode 100644 security/lsm_syscalls.c

[...]

> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> new file mode 100644
> index 000000000000..feee31600219
> --- /dev/null
> +++ b/security/lsm_syscalls.c
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * System calls implementing the Linux Security Module API.
> + *
> + *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
> + *  Copyright (C) 2022 Intel Corporation
> + */
> +
> +#include <asm/current.h>
> +#include <linux/compiler_types.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/security.h>
> +#include <linux/stddef.h>
> +#include <linux/syscalls.h>
> +#include <linux/types.h>
> +#include <linux/lsm_hooks.h>
> +#include <uapi/linux/lsm.h>
> +
> +/**
> + * sys_lsm_set_self_attr - Set current task's security module attribute
> + * @attr: which attribute to set
> + * @ctx: the LSM contexts
> + * @size: size of @ctx
> + * @flags: reserved for future use
> + *
> + * Sets the calling task's LSM context. On success this function
> + * returns 0. If the attribute specified cannot be set a negative
> + * value indicating the reason for the error is returned.

Do you think it is really worth it to implement syscalls that can get 
and set attributes to several LSMs at the same time, instead of one at a 
time? LSM-specific tools don't care about other LSMs. I still think it 
would be much simpler (for kernel and user space) to pass an LSM ID to 
both syscalls. This would avoid dealing with variable arrays of variable 
element lengths, to both get or set attributes.

Furthermore, considering the hypotetical LSM_ATTR_MAGICFD that was 
previously talked about, getting an unknown number of file descriptor 
doesn't look good neither.


> + */
> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> +		ctx, size_t __user, size, u32, flags)
> +{
> +	return security_setselfattr(attr, ctx, size, flags);
> +}
> +
> +/**
> + * sys_lsm_get_self_attr - Return current task's security module attributes
> + * @attr: which attribute to set

attribute to *get*

> + * @ctx: the LSM contexts
> + * @size: size of @ctx, updated on return

I suggest to use a dedicated argument to read the allocated size, and 
another to write the actual/written size.

This would not be required with an LSM ID passed to the syscall because 
attribute sizes should be known by user space, and there is no need to 
help them probe this information.


> + * @flags: reserved for future use
> + *
> + * Returns the calling task's LSM contexts. On success this
> + * function returns the number of @ctx array elements. This value
> + * may be zero if there are no LSM contexts assigned. If @size is
> + * insufficient to contain the return data -E2BIG is returned and
> + * @size is set to the minimum required size.

Doing something (updating a buffer) even when returning an error doesn't 
look right. These sizes should be well-known to user space and part of 
the ABI/UAPI.


> In all other cases
> + * a negative value indicating the error is returned.
> + */
> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> +		ctx, size_t __user *, size, u32, flags)
> +{
> +	return security_getselfattr(attr, ctx, size, flags);
> +}
> diff --git a/security/security.c b/security/security.c
> index 87c8796c3c46..2c57fe28c4f7 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
>   }
>   EXPORT_SYMBOL(security_d_instantiate);
>   
> +/**
> + * security_getselfattr - Read an LSM attribute of the current process.
> + * @attr: which attribute to return
> + * @ctx: the user-space destination for the information, or NULL
> + * @size: the size of space available to receive the data
> + * @flags: reserved for future use, must be 0
> + *
> + * Returns the number of attributes found on success, negative value
> + * on error. @size is reset to the total size of the data.
> + * If @size is insufficient to contain the data -E2BIG is returned.
> + */
> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> +			 size_t __user *size, u32 __user flags)
> +{
> +	struct security_hook_list *hp;
> +	void __user *base = (void *)ctx;
> +	size_t total = 0;
> +	size_t this;
> +	size_t left;
> +	bool istoobig = false;
> +	int count = 0;
> +	int rc;
> +
> +	if (attr == 0)
> +		return -EINVAL;
> +	if (flags != 0)
> +		return -EINVAL;
> +	if (size == NULL)
> +		return -EINVAL;
> +	if (get_user(left, size))
> +		return -EFAULT;
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
> +		this = left;
> +		if (base)
> +			ctx = (struct lsm_ctx __user *)(base + total);
> +		rc = hp->hook.getselfattr(attr, ctx, &this, flags);
> +		switch (rc) {
> +		case -EOPNOTSUPP:
> +			rc = 0;
> +			continue;
> +		case -E2BIG:
> +			istoobig = true;
> +			left = 0;
> +			break;

These two error cases could be directly handled by 
security_getselfattr() instead of relying on each LSM-specific 
implementations. See my suggestion on patch 7/11 (lsm_get_attr_size).


> +		case 0:
> +			left -= this;
> +			break;
> +		default:
> +			return rc;
> +		}
> +		total += this;
> +		count++;
> +	}
> +	if (count == 0)
> +		return LSM_RET_DEFAULT(getselfattr);
> +	if (put_user(total, size))
> +		return -EFAULT;
> +	if (rc)
> +		return rc;
> +	if (istoobig)
> +		return -E2BIG;
> +	return count;
> +}
> +
> +/**
> + * security_setselfattr - Set an LSM attribute on the current process.
> + * @attr: which attribute to set
> + * @ctx: the user-space source for the information
> + * @size: the size of the data
> + * @flags: reserved for future use, must be 0
> + *
> + * Set an LSM attribute for the current process. The LSM, attribute
> + * and new value are included in @ctx.
> + *
> + * Returns 0 on success, an LSM specific value on failure.
> + */
> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> +			 size_t __user size, u32 __user flags)
> +{
> +	struct security_hook_list *hp;
> +	struct lsm_ctx lctx;
> +
> +	if (flags != 0)
> +		return -EINVAL;
> +	if (size < sizeof(*ctx))
> +		return -EINVAL;
> +	if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
> +		return -EFAULT;
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
> +		if ((hp->lsmid->id) == lctx.id)
> +			return hp->hook.setselfattr(attr, ctx, size, flags);
> +
> +	return LSM_RET_DEFAULT(setselfattr);
> +}
> +
>   int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
>   			 char **value)
>   {

Re: [PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Mickaël Salaün]

It looks like you missed my preview reviews on these patches.

On 15/03/2023 23:46, Casey Schaufler wrote:
> Create a system call to report the list of Linux Security Modules
> that are active on the system. The list is provided as an array
> of LSM ID numbers.
> 
> The calling application can use this list determine what LSM
> specific actions it might take. That might include chosing an
> output format, determining required privilege or bypassing
> security module specific behavior.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>   Documentation/userspace-api/lsm.rst |  3 +++
>   include/linux/syscalls.h            |  1 +
>   kernel/sys_ni.c                     |  1 +
>   security/lsm_syscalls.c             | 39 +++++++++++++++++++++++++++++
>   4 files changed, 44 insertions(+)
> 
> diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
> index b45e402302b3..a86e3817f062 100644
> --- a/Documentation/userspace-api/lsm.rst
> +++ b/Documentation/userspace-api/lsm.rst
> @@ -63,6 +63,9 @@ Get the specified security attributes of the current process
>   .. kernel-doc:: security/lsm_syscalls.c
>       :identifiers: sys_lsm_get_self_attr
>   
> +.. kernel-doc:: security/lsm_syscalls.c
> +    :identifiers: sys_lsm_list_modules
> +
>   Additional documentation
>   ========================
>   
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 3feca00cb0c1..f755c583f949 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -1063,6 +1063,7 @@ asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>   				      size_t *size, __u64 flags);
>   asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>   				      __u64 flags);
> +asmlinkage long sys_lsm_list_modules(u64 *ids, size_t *size, u32 flags);
>   
>   /*
>    * Architecture-specific system calls
> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> index d03c78ef1562..ceb3d21a62d0 100644
> --- a/kernel/sys_ni.c
> +++ b/kernel/sys_ni.c
> @@ -265,6 +265,7 @@ COND_SYSCALL(mremap);
>   /* security/lsm_syscalls.c */
>   COND_SYSCALL(lsm_get_self_attr);
>   COND_SYSCALL(lsm_set_self_attr);
> +COND_SYSCALL(lsm_list_modules);
>   
>   /* security/keys/keyctl.c */
>   COND_SYSCALL(add_key);
> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index feee31600219..6efbe244d304 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -53,3 +53,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
>   {
>   	return security_getselfattr(attr, ctx, size, flags);
>   }
> +
> +/**
> + * sys_lsm_list_modules - Return a list of the active security modules
> + * @ids: the LSM module ids
> + * @size: size of @ids, updated on return
> + * @flags: reserved for future use, must be zero
> + *
> + * Returns a list of the active LSM ids. On success this function
> + * returns the number of @ids array elements. This value may be zero
> + * if there are no LSMs active. If @size is insufficient to contain
> + * the return data -E2BIG is returned and @size is set to the minimum
> + * required size. In all other cases a negative value indicating the
> + * error is returned.
> + */
> +SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
> +		u32, flags)
> +{
> +	size_t total_size = lsm_active_cnt * sizeof(*ids);
> +	size_t usize;
> +	int i;
> +
> +	if (flags)
> +		return -EINVAL;
> +
> +	if (get_user(usize, size))
> +		return -EFAULT;
> +
> +	if (put_user(total_size, size) != 0)
> +		return -EFAULT;
> +
> +	if (usize < total_size)
> +		return -E2BIG;
> +
> +	for (i = 0; i < lsm_active_cnt; i++)
> +		if (put_user(lsm_idlist[i]->id, ids++))
> +			return -EFAULT;
> +
> +	return lsm_active_cnt;
> +}

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Casey Schaufler]

On 4/3/2023 5:04 AM, Mickaël Salaün wrote:
>
> On 15/03/2023 23:46, Casey Schaufler wrote:
>> Create a system call lsm_get_self_attr() to provide the security
>> module maintained attributes of the current process.
>> Create a system call lsm_set_self_attr() to set a security
>> module maintained attribute of the current process.
>> Historically these attributes have been exposed to user space via
>> entries in procfs under /proc/self/attr.
>>
>> The attribute value is provided in a lsm_ctx structure. The structure
>> identifys the size of the attribute, and the attribute value. The format
>> of the attribute value is defined by the security module. A flags field
>> is included for LSM specific information. It is currently unused and
>> must
>> be 0. The total size of the data, including the lsm_ctx structure and
>> any
>> padding, is maintained as well.
>>
>> struct lsm_ctx {
>>          __u64   id;
>>          __u64   flags;
>>          __u64   len;
>>          __u64   ctx_len;
>>          __u8    ctx[];
>> };
>>
>> Two new LSM hooks are used to interface with the LSMs.
>> security_getselfattr() collects the lsm_ctx values from the
>> LSMs that support the hook, accounting for space requirements.
>> security_setselfattr() identifies which LSM the attribute is
>> intended for and passes it along.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> ---
>>   Documentation/userspace-api/lsm.rst | 15 +++++
>>   include/linux/lsm_hook_defs.h       |  4 ++
>>   include/linux/lsm_hooks.h           |  9 +++
>>   include/linux/security.h            | 19 ++++++
>>   include/linux/syscalls.h            |  5 ++
>>   include/uapi/linux/lsm.h            | 33 ++++++++++
>>   kernel/sys_ni.c                     |  4 ++
>>   security/Makefile                   |  1 +
>>   security/lsm_syscalls.c             | 55 ++++++++++++++++
>>   security/security.c                 | 97 +++++++++++++++++++++++++++++
>>   10 files changed, 242 insertions(+)
>>   create mode 100644 security/lsm_syscalls.c
>
> [...]
>
>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>> new file mode 100644
>> index 000000000000..feee31600219
>> --- /dev/null
>> +++ b/security/lsm_syscalls.c
>> @@ -0,0 +1,55 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * System calls implementing the Linux Security Module API.
>> + *
>> + *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
>> + *  Copyright (C) 2022 Intel Corporation
>> + */
>> +
>> +#include <asm/current.h>
>> +#include <linux/compiler_types.h>
>> +#include <linux/err.h>
>> +#include <linux/errno.h>
>> +#include <linux/security.h>
>> +#include <linux/stddef.h>
>> +#include <linux/syscalls.h>
>> +#include <linux/types.h>
>> +#include <linux/lsm_hooks.h>
>> +#include <uapi/linux/lsm.h>
>> +
>> +/**
>> + * sys_lsm_set_self_attr - Set current task's security module attribute
>> + * @attr: which attribute to set
>> + * @ctx: the LSM contexts
>> + * @size: size of @ctx
>> + * @flags: reserved for future use
>> + *
>> + * Sets the calling task's LSM context. On success this function
>> + * returns 0. If the attribute specified cannot be set a negative
>> + * value indicating the reason for the error is returned.
>
> Do you think it is really worth it to implement syscalls that can get
> and set attributes to several LSMs at the same time, instead of one at
> a time? 

Setting the values for more than one LSM is impractical due to the possibility
that the Nth value may fail, and unwinding the N-1 values may not be possible.

> LSM-specific tools don't care about other LSMs.

That's part of the problem. Are systemd, dbusd, ps and id LSM specific tools?
They shouldn't be.

> I still think it would be much simpler (for kernel and user space) to
> pass an LSM ID to both syscalls. This would avoid dealing with
> variable arrays of variable element lengths, to both get or set
> attributes.

ps and id should both work regardless of which and how many LSMs provide
context attributes. They shouldn't need to know which LSMs are active in
advance. If a new LSM is introduced, they shouldn't need to be updated to
support it.

>
> Furthermore, considering the hypotetical LSM_ATTR_MAGICFD that was
> previously talked about, getting an unknown number of file descriptor
> doesn't look good neither.

If you have multiple LSM_ATTR_MAGICFD values and can only get one at
a time you have to do something convoluted with flags to get them all.
I don't see that as a good thing.

>
>
>> + */
>> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct
>> lsm_ctx __user *,
>> +        ctx, size_t __user, size, u32, flags)
>> +{
>> +    return security_setselfattr(attr, ctx, size, flags);
>> +}
>> +
>> +/**
>> + * sys_lsm_get_self_attr - Return current task's security module
>> attributes
>> + * @attr: which attribute to set
>
> attribute to *get*
>
>> + * @ctx: the LSM contexts
>> + * @size: size of @ctx, updated on return
>
> I suggest to use a dedicated argument to read the allocated size, and
> another to write the actual/written size.
>
> This would not be required with an LSM ID passed to the syscall
> because attribute sizes should be known by user space, and there is no
> need to help them probe this information.
>
>
>> + * @flags: reserved for future use
>> + *
>> + * Returns the calling task's LSM contexts. On success this
>> + * function returns the number of @ctx array elements. This value
>> + * may be zero if there are no LSM contexts assigned. If @size is
>> + * insufficient to contain the return data -E2BIG is returned and
>> + * @size is set to the minimum required size.
>
> Doing something (updating a buffer) even when returning an error
> doesn't look right. These sizes should be well-known to user space and
> part of the ABI/UAPI.

No. The size of attributes is not well known to user space.
They are usually text strings. The maximum size will be known,
but that's putting additional burden on user space to know
about all possible LSMs. It's not always necessary.

>
>
>> In all other cases
>> + * a negative value indicating the error is returned.
>> + */
>> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct
>> lsm_ctx __user *,
>> +        ctx, size_t __user *, size, u32, flags)
>> +{
>> +    return security_getselfattr(attr, ctx, size, flags);
>> +}
>> diff --git a/security/security.c b/security/security.c
>> index 87c8796c3c46..2c57fe28c4f7 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry
>> *dentry, struct inode *inode)
>>   }
>>   EXPORT_SYMBOL(security_d_instantiate);
>>   +/**
>> + * security_getselfattr - Read an LSM attribute of the current process.
>> + * @attr: which attribute to return
>> + * @ctx: the user-space destination for the information, or NULL
>> + * @size: the size of space available to receive the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Returns the number of attributes found on success, negative value
>> + * on error. @size is reset to the total size of the data.
>> + * If @size is insufficient to contain the data -E2BIG is returned.
>> + */
>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx
>> __user *ctx,
>> +             size_t __user *size, u32 __user flags)
>> +{
>> +    struct security_hook_list *hp;
>> +    void __user *base = (void *)ctx;
>> +    size_t total = 0;
>> +    size_t this;
>> +    size_t left;
>> +    bool istoobig = false;
>> +    int count = 0;
>> +    int rc;
>> +
>> +    if (attr == 0)
>> +        return -EINVAL;
>> +    if (flags != 0)
>> +        return -EINVAL;
>> +    if (size == NULL)
>> +        return -EINVAL;
>> +    if (get_user(left, size))
>> +        return -EFAULT;
>> +
>> +    hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
>> +        this = left;
>> +        if (base)
>> +            ctx = (struct lsm_ctx __user *)(base + total);
>> +        rc = hp->hook.getselfattr(attr, ctx, &this, flags);
>> +        switch (rc) {
>> +        case -EOPNOTSUPP:
>> +            rc = 0;
>> +            continue;
>> +        case -E2BIG:
>> +            istoobig = true;
>> +            left = 0;
>> +            break;
>
> These two error cases could be directly handled by
> security_getselfattr() instead of relying on each LSM-specific
> implementations. See my suggestion on patch 7/11 (lsm_get_attr_size).

Yes, they could. My understanding is that Paul wants the LSM layer
to be "thin". Where possible and not insane, the logic should be in
the LSM, not the infrastructure.

>
>
>> +        case 0:
>> +            left -= this;
>> +            break;
>> +        default:
>> +            return rc;
>> +        }
>> +        total += this;
>> +        count++;
>> +    }
>> +    if (count == 0)
>> +        return LSM_RET_DEFAULT(getselfattr);
>> +    if (put_user(total, size))
>> +        return -EFAULT;
>> +    if (rc)
>> +        return rc;
>> +    if (istoobig)
>> +        return -E2BIG;
>> +    return count;
>> +}
>> +
>> +/**
>> + * security_setselfattr - Set an LSM attribute on the current process.
>> + * @attr: which attribute to set
>> + * @ctx: the user-space source for the information
>> + * @size: the size of the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Set an LSM attribute for the current process. The LSM, attribute
>> + * and new value are included in @ctx.
>> + *
>> + * Returns 0 on success, an LSM specific value on failure.
>> + */
>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx
>> __user *ctx,
>> +             size_t __user size, u32 __user flags)
>> +{
>> +    struct security_hook_list *hp;
>> +    struct lsm_ctx lctx;
>> +
>> +    if (flags != 0)
>> +        return -EINVAL;
>> +    if (size < sizeof(*ctx))
>> +        return -EINVAL;
>> +    if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>> +        return -EFAULT;
>> +
>> +    hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>> +        if ((hp->lsmid->id) == lctx.id)
>> +            return hp->hook.setselfattr(attr, ctx, size, flags);
>> +
>> +    return LSM_RET_DEFAULT(setselfattr);
>> +}
>> +
>>   int security_getprocattr(struct task_struct *p, int lsmid, const
>> char *name,
>>                char **value)
>>   {

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 4/3/2023 2:47 AM, Mickaël Salaün wrote:
>
> On 15/03/2023 23:47, Casey Schaufler wrote:
>> Add lsm_name_to_attr(), which translates a text string to a
>> LSM_ATTR value if one is available.
>>
>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>> the trailing attribute value.
>>
>> All are used in module specific components of LSM system calls.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> ---
>>   include/linux/security.h | 13 ++++++++++
>>   security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>   security/security.c      | 31 ++++++++++++++++++++++++
>>   3 files changed, 95 insertions(+)
>
> [...]
>
>> diff --git a/security/security.c b/security/security.c
>> index 2c57fe28c4f7..f7b814a3940c 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct
>> super_block *sb)
>>       return 0;
>>   }
>>   +/**
>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>> + * @ctx: an LSM context to be filled
>> + * @context: the new context value
>> + * @context_size: the size of the new context value
>> + * @id: LSM id
>> + * @flags: LSM defined flags
>> + *
>> + * Fill all of the fields in a user space lsm_ctx structure.
>> + * Caller is assumed to have verified that @ctx has enough space
>> + * for @context.
>> + * Returns 0 on success, -EFAULT on a copyout error.
>> + */
>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>> +              size_t context_size, u64 id, u64 flags)
>> +{
>> +    struct lsm_ctx local;
>> +    void __user *vc = ctx;
>> +
>> +    local.id = id;
>> +    local.flags = flags;
>> +    local.ctx_len = context_size;
>> +    local.len = context_size + sizeof(local);
>> +    vc += sizeof(local);
>> +    if (copy_to_user(ctx, &local, sizeof(local)))
>> +        return -EFAULT;
>> +    if (context_size > 0 && copy_to_user(vc, context, context_size))
>> +        return -EFAULT;
>
> Can we do a single copy_to_user() call? 

It would be possible, but would require allocating memory and copying
the context. I don't see that as an improvement.

> That would avoid inconsistent user space data, could speed up a bit
> the operation, and make the code easier to understand. To use the
> stack, we need to know the maximum size of context_size for all use
> cases, which seems reasonable and can be checked at build time (on
> each LSM side, and potentially with specific context type passed as
> enum instead of context_size) and run time (for this generic helper).

Knowning the maximum size of attributes for all LSMs and hard coding
that here would make maintaining this code really painful.

>
>
>> +    return 0;
>> +}
>> +
>>   /*
>>    * The default value of the LSM hook is defined in
>> linux/lsm_hook_defs.h and
>>    * can be accessed with:

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Mickaël Salaün]

On 03/04/2023 19:36, Casey Schaufler wrote:
> On 4/3/2023 5:04 AM, Mickaël Salaün wrote:
>>
>> On 15/03/2023 23:46, Casey Schaufler wrote:
>>> Create a system call lsm_get_self_attr() to provide the security
>>> module maintained attributes of the current process.
>>> Create a system call lsm_set_self_attr() to set a security
>>> module maintained attribute of the current process.
>>> Historically these attributes have been exposed to user space via
>>> entries in procfs under /proc/self/attr.
>>>
>>> The attribute value is provided in a lsm_ctx structure. The structure
>>> identifys the size of the attribute, and the attribute value. The format
>>> of the attribute value is defined by the security module. A flags field
>>> is included for LSM specific information. It is currently unused and
>>> must
>>> be 0. The total size of the data, including the lsm_ctx structure and
>>> any
>>> padding, is maintained as well.
>>>
>>> struct lsm_ctx {
>>>           __u64   id;
>>>           __u64   flags;
>>>           __u64   len;
>>>           __u64   ctx_len;
>>>           __u8    ctx[];
>>> };
>>>
>>> Two new LSM hooks are used to interface with the LSMs.
>>> security_getselfattr() collects the lsm_ctx values from the
>>> LSMs that support the hook, accounting for space requirements.
>>> security_setselfattr() identifies which LSM the attribute is
>>> intended for and passes it along.
>>>
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>> ---
>>>    Documentation/userspace-api/lsm.rst | 15 +++++
>>>    include/linux/lsm_hook_defs.h       |  4 ++
>>>    include/linux/lsm_hooks.h           |  9 +++
>>>    include/linux/security.h            | 19 ++++++
>>>    include/linux/syscalls.h            |  5 ++
>>>    include/uapi/linux/lsm.h            | 33 ++++++++++
>>>    kernel/sys_ni.c                     |  4 ++
>>>    security/Makefile                   |  1 +
>>>    security/lsm_syscalls.c             | 55 ++++++++++++++++
>>>    security/security.c                 | 97 +++++++++++++++++++++++++++++
>>>    10 files changed, 242 insertions(+)
>>>    create mode 100644 security/lsm_syscalls.c
>>
>> [...]
>>
>>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>>> new file mode 100644
>>> index 000000000000..feee31600219
>>> --- /dev/null
>>> +++ b/security/lsm_syscalls.c
>>> @@ -0,0 +1,55 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +/*
>>> + * System calls implementing the Linux Security Module API.
>>> + *
>>> + *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
>>> + *  Copyright (C) 2022 Intel Corporation
>>> + */
>>> +
>>> +#include <asm/current.h>
>>> +#include <linux/compiler_types.h>
>>> +#include <linux/err.h>
>>> +#include <linux/errno.h>
>>> +#include <linux/security.h>
>>> +#include <linux/stddef.h>
>>> +#include <linux/syscalls.h>
>>> +#include <linux/types.h>
>>> +#include <linux/lsm_hooks.h>
>>> +#include <uapi/linux/lsm.h>
>>> +
>>> +/**
>>> + * sys_lsm_set_self_attr - Set current task's security module attribute
>>> + * @attr: which attribute to set
>>> + * @ctx: the LSM contexts
>>> + * @size: size of @ctx
>>> + * @flags: reserved for future use
>>> + *
>>> + * Sets the calling task's LSM context. On success this function
>>> + * returns 0. If the attribute specified cannot be set a negative
>>> + * value indicating the reason for the error is returned.
>>
>> Do you think it is really worth it to implement syscalls that can get
>> and set attributes to several LSMs at the same time, instead of one at
>> a time?
> 
> Setting the values for more than one LSM is impractical due to the possibility
> that the Nth value may fail, and unwinding the N-1 values may not be possible.

Indeed, so unless I missed something, why not passing the LSM ID as a 
syscall argument for lsm_set_self_attr() and lsm_get_self_attr(), and 
avoid managing a set of contexts but instead only managing one context 
at a time (to get or set)?


> 
>> LSM-specific tools don't care about other LSMs.
> 
> That's part of the problem. Are systemd, dbusd, ps and id LSM specific tools?
> They shouldn't be.
> 
>> I still think it would be much simpler (for kernel and user space) to
>> pass an LSM ID to both syscalls. This would avoid dealing with
>> variable arrays of variable element lengths, to both get or set
>> attributes.
> 
> ps and id should both work regardless of which and how many LSMs provide
> context attributes. They shouldn't need to know which LSMs are active in
> advance. If a new LSM is introduced, they shouldn't need to be updated to
> support it.

I agree, and making the syscalls simpler doesn't change that.

> 
>>
>> Furthermore, considering the hypotetical LSM_ATTR_MAGICFD that was
>> previously talked about, getting an unknown number of file descriptor
>> doesn't look good neither.
> 
> If you have multiple LSM_ATTR_MAGICFD values and can only get one at
> a time you have to do something convoluted with flags to get them all.
> I don't see that as a good thing.

Yes, that was another argument to *not* deal with a set of contexts.


> 
>>
>>
>>> + */
>>> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct
>>> lsm_ctx __user *,
>>> +        ctx, size_t __user, size, u32, flags)
>>> +{
>>> +    return security_setselfattr(attr, ctx, size, flags);
>>> +}
>>> +
>>> +/**
>>> + * sys_lsm_get_self_attr - Return current task's security module
>>> attributes
>>> + * @attr: which attribute to set
>>
>> attribute to *get*
>>
>>> + * @ctx: the LSM contexts
>>> + * @size: size of @ctx, updated on return
>>
>> I suggest to use a dedicated argument to read the allocated size, and
>> another to write the actual/written size.
>>
>> This would not be required with an LSM ID passed to the syscall
>> because attribute sizes should be known by user space, and there is no
>> need to help them probe this information.
>>
>>
>>> + * @flags: reserved for future use
>>> + *
>>> + * Returns the calling task's LSM contexts. On success this
>>> + * function returns the number of @ctx array elements. This value
>>> + * may be zero if there are no LSM contexts assigned. If @size is
>>> + * insufficient to contain the return data -E2BIG is returned and
>>> + * @size is set to the minimum required size.
>>
>> Doing something (updating a buffer) even when returning an error
>> doesn't look right. These sizes should be well-known to user space and
>> part of the ABI/UAPI.
> 
> No. The size of attributes is not well known to user space.
> They are usually text strings. The maximum size will be known,
> but that's putting additional burden on user space to know
> about all possible LSMs. It's not always necessary.

Right, I forgot the strings stuff… The lsm_get_self_attr() syscall could 
then return a ctx_actual_size (as one argument), and a ctx pointer (as 
another argument). Similarly, the lsm_set_self_attr() syscall could use 
a dedicated argument for ctx_size and another for the ctx pointer.

> 
>>
>>
>>> In all other cases
>>> + * a negative value indicating the error is returned.
>>> + */
>>> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct
>>> lsm_ctx __user *,
>>> +        ctx, size_t __user *, size, u32, flags)
>>> +{
>>> +    return security_getselfattr(attr, ctx, size, flags);
>>> +}
>>> diff --git a/security/security.c b/security/security.c
>>> index 87c8796c3c46..2c57fe28c4f7 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry
>>> *dentry, struct inode *inode)
>>>    }
>>>    EXPORT_SYMBOL(security_d_instantiate);
>>>    +/**
>>> + * security_getselfattr - Read an LSM attribute of the current process.
>>> + * @attr: which attribute to return
>>> + * @ctx: the user-space destination for the information, or NULL
>>> + * @size: the size of space available to receive the data
>>> + * @flags: reserved for future use, must be 0
>>> + *
>>> + * Returns the number of attributes found on success, negative value
>>> + * on error. @size is reset to the total size of the data.
>>> + * If @size is insufficient to contain the data -E2BIG is returned.
>>> + */
>>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx
>>> __user *ctx,
>>> +             size_t __user *size, u32 __user flags)
>>> +{
>>> +    struct security_hook_list *hp;
>>> +    void __user *base = (void *)ctx;
>>> +    size_t total = 0;
>>> +    size_t this;
>>> +    size_t left;
>>> +    bool istoobig = false;
>>> +    int count = 0;
>>> +    int rc;
>>> +
>>> +    if (attr == 0)
>>> +        return -EINVAL;
>>> +    if (flags != 0)
>>> +        return -EINVAL;
>>> +    if (size == NULL)
>>> +        return -EINVAL;
>>> +    if (get_user(left, size))
>>> +        return -EFAULT;
>>> +
>>> +    hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
>>> +        this = left;
>>> +        if (base)
>>> +            ctx = (struct lsm_ctx __user *)(base + total);
>>> +        rc = hp->hook.getselfattr(attr, ctx, &this, flags);
>>> +        switch (rc) {
>>> +        case -EOPNOTSUPP:
>>> +            rc = 0;
>>> +            continue;
>>> +        case -E2BIG:
>>> +            istoobig = true;
>>> +            left = 0;
>>> +            break;
>>
>> These two error cases could be directly handled by
>> security_getselfattr() instead of relying on each LSM-specific
>> implementations. See my suggestion on patch 7/11 (lsm_get_attr_size).
> 
> Yes, they could. My understanding is that Paul wants the LSM layer
> to be "thin". Where possible and not insane, the logic should be in
> the LSM, not the infrastructure.

FWIW, since we are defining new syscalls to make user space's life 
easier, I'm in favor of a well defined common behavior (e.g. returned 
errno) and factoring common code to make each LSM-specific code thin.

> 
>>
>>
>>> +        case 0:
>>> +            left -= this;
>>> +            break;
>>> +        default:
>>> +            return rc;
>>> +        }
>>> +        total += this;
>>> +        count++;
>>> +    }
>>> +    if (count == 0)
>>> +        return LSM_RET_DEFAULT(getselfattr);
>>> +    if (put_user(total, size))
>>> +        return -EFAULT;
>>> +    if (rc)
>>> +        return rc;
>>> +    if (istoobig)
>>> +        return -E2BIG;
>>> +    return count;
>>> +}
>>> +
>>> +/**
>>> + * security_setselfattr - Set an LSM attribute on the current process.
>>> + * @attr: which attribute to set
>>> + * @ctx: the user-space source for the information
>>> + * @size: the size of the data
>>> + * @flags: reserved for future use, must be 0
>>> + *
>>> + * Set an LSM attribute for the current process. The LSM, attribute
>>> + * and new value are included in @ctx.
>>> + *
>>> + * Returns 0 on success, an LSM specific value on failure.
>>> + */
>>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx
>>> __user *ctx,
>>> +             size_t __user size, u32 __user flags)
>>> +{
>>> +    struct security_hook_list *hp;
>>> +    struct lsm_ctx lctx;
>>> +
>>> +    if (flags != 0)
>>> +        return -EINVAL;
>>> +    if (size < sizeof(*ctx))
>>> +        return -EINVAL;
>>> +    if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>>> +        return -EFAULT;
>>> +
>>> +    hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>>> +        if ((hp->lsmid->id) == lctx.id)
>>> +            return hp->hook.setselfattr(attr, ctx, size, flags);
>>> +
>>> +    return LSM_RET_DEFAULT(setselfattr);
>>> +}
>>> +
>>>    int security_getprocattr(struct task_struct *p, int lsmid, const
>>> char *name,
>>>                 char **value)
>>>    {

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 4/3/2023 2:54 AM, Mickaël Salaün wrote:
>
> On 03/04/2023 11:47, Mickaël Salaün wrote:
>>
>> On 15/03/2023 23:47, Casey Schaufler wrote:
>>> Add lsm_name_to_attr(), which translates a text string to a
>>> LSM_ATTR value if one is available.
>>>
>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>> the trailing attribute value.
>>>
>>> All are used in module specific components of LSM system calls.
>>>
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>> ---
>>>    include/linux/security.h | 13 ++++++++++
>>>    security/lsm_syscalls.c  | 51
>>> ++++++++++++++++++++++++++++++++++++++++
>>>    security/security.c      | 31 ++++++++++++++++++++++++
>>>    3 files changed, 95 insertions(+)
>>
>> [...]
>>
>>> diff --git a/security/security.c b/security/security.c
>>> index 2c57fe28c4f7..f7b814a3940c 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct
>>> super_block *sb)
>>>        return 0;
>>>    }
>>>    +/**
>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>> + * @ctx: an LSM context to be filled
>>> + * @context: the new context value
>>> + * @context_size: the size of the new context value
>>> + * @id: LSM id
>>> + * @flags: LSM defined flags
>>> + *
>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>> + * Caller is assumed to have verified that @ctx has enough space
>>> + * for @context.
>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>> + */
>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>> +              size_t context_size, u64 id, u64 flags)
>>> +{
>>> +    struct lsm_ctx local;
>>> +    void __user *vc = ctx;
>>> +
>>> +    local.id = id;
>>> +    local.flags = flags;
>>> +    local.ctx_len = context_size;
>>> +    local.len = context_size + sizeof(local);
>>> +    vc += sizeof(local);
>>> +    if (copy_to_user(ctx, &local, sizeof(local)))
>>> +        return -EFAULT;
>>> +    if (context_size > 0 && copy_to_user(vc, context, context_size))
>>> +        return -EFAULT;
>>
>> Can we do a single copy_to_user() call? That would avoid inconsistent
>> user space data, could speed up a bit the operation, and make the code
>> easier to understand. To use the stack, we need to know the maximum size
>> of context_size for all use cases, which seems reasonable and can be
>> checked at build time (on each LSM side, and potentially with specific
>> context type passed as enum instead of context_size) and run time (for
>> this generic helper).
>
> Well, actually the context_size should be inferred from id, and the
> "local" size should be defined and check at build time against all
> context ID sizes.

Again, no, I don't see this as an improvement.

>
>>
>>
>>> +    return 0;
>>> +}
>>> +
>>>    /*
>>>     * The default value of the LSM hook is defined in
>>> linux/lsm_hook_defs.h and
>>>     * can be accessed with:

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Mickaël Salaün]

On 03/04/2023 20:03, Casey Schaufler wrote:
> On 4/3/2023 2:47 AM, Mickaël Salaün wrote:
>>
>> On 15/03/2023 23:47, Casey Schaufler wrote:
>>> Add lsm_name_to_attr(), which translates a text string to a
>>> LSM_ATTR value if one is available.
>>>
>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>> the trailing attribute value.
>>>
>>> All are used in module specific components of LSM system calls.
>>>
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>> ---
>>>    include/linux/security.h | 13 ++++++++++
>>>    security/lsm_syscalls.c  | 51 ++++++++++++++++++++++++++++++++++++++++
>>>    security/security.c      | 31 ++++++++++++++++++++++++
>>>    3 files changed, 95 insertions(+)
>>
>> [...]
>>
>>> diff --git a/security/security.c b/security/security.c
>>> index 2c57fe28c4f7..f7b814a3940c 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct
>>> super_block *sb)
>>>        return 0;
>>>    }
>>>    +/**
>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>> + * @ctx: an LSM context to be filled
>>> + * @context: the new context value
>>> + * @context_size: the size of the new context value
>>> + * @id: LSM id
>>> + * @flags: LSM defined flags
>>> + *
>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>> + * Caller is assumed to have verified that @ctx has enough space
>>> + * for @context.
>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>> + */
>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>> +              size_t context_size, u64 id, u64 flags)
>>> +{
>>> +    struct lsm_ctx local;
>>> +    void __user *vc = ctx;
>>> +
>>> +    local.id = id;
>>> +    local.flags = flags;
>>> +    local.ctx_len = context_size;
>>> +    local.len = context_size + sizeof(local);
>>> +    vc += sizeof(local);
>>> +    if (copy_to_user(ctx, &local, sizeof(local)))
>>> +        return -EFAULT;
>>> +    if (context_size > 0 && copy_to_user(vc, context, context_size))
>>> +        return -EFAULT;
>>
>> Can we do a single copy_to_user() call?
> 
> It would be possible, but would require allocating memory and copying
> the context. I don't see that as an improvement.
> 
>> That would avoid inconsistent user space data, could speed up a bit
>> the operation, and make the code easier to understand. To use the
>> stack, we need to know the maximum size of context_size for all use
>> cases, which seems reasonable and can be checked at build time (on
>> each LSM side, and potentially with specific context type passed as
>> enum instead of context_size) and run time (for this generic helper).
> 
> Knowning the maximum size of attributes for all LSMs and hard coding
> that here would make maintaining this code really painful.

Hmm, I forgot about variable-length strings, but maybe a reasonable 
common maximum size (that could fit on the stack) could be found?

> 
>>
>>
>>> +    return 0;
>>> +}
>>> +
>>>    /*
>>>     * The default value of the LSM hook is defined in
>>> linux/lsm_hook_defs.h and
>>>     * can be accessed with:

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Casey Schaufler]

On 4/3/2023 11:04 AM, Mickaël Salaün wrote:
>
> On 03/04/2023 19:36, Casey Schaufler wrote:
>> On 4/3/2023 5:04 AM, Mickaël Salaün wrote:
>>>
>>> On 15/03/2023 23:46, Casey Schaufler wrote:
>>>> Create a system call lsm_get_self_attr() to provide the security
>>>> module maintained attributes of the current process.
>>>> Create a system call lsm_set_self_attr() to set a security
>>>> module maintained attribute of the current process.
>>>> Historically these attributes have been exposed to user space via
>>>> entries in procfs under /proc/self/attr.
>>>>
>>>> The attribute value is provided in a lsm_ctx structure. The structure
>>>> identifys the size of the attribute, and the attribute value. The
>>>> format
>>>> of the attribute value is defined by the security module. A flags
>>>> field
>>>> is included for LSM specific information. It is currently unused and
>>>> must
>>>> be 0. The total size of the data, including the lsm_ctx structure and
>>>> any
>>>> padding, is maintained as well.
>>>>
>>>> struct lsm_ctx {
>>>>           __u64   id;
>>>>           __u64   flags;
>>>>           __u64   len;
>>>>           __u64   ctx_len;
>>>>           __u8    ctx[];
>>>> };
>>>>
>>>> Two new LSM hooks are used to interface with the LSMs.
>>>> security_getselfattr() collects the lsm_ctx values from the
>>>> LSMs that support the hook, accounting for space requirements.
>>>> security_setselfattr() identifies which LSM the attribute is
>>>> intended for and passes it along.
>>>>
>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>> ---
>>>>    Documentation/userspace-api/lsm.rst | 15 +++++
>>>>    include/linux/lsm_hook_defs.h       |  4 ++
>>>>    include/linux/lsm_hooks.h           |  9 +++
>>>>    include/linux/security.h            | 19 ++++++
>>>>    include/linux/syscalls.h            |  5 ++
>>>>    include/uapi/linux/lsm.h            | 33 ++++++++++
>>>>    kernel/sys_ni.c                     |  4 ++
>>>>    security/Makefile                   |  1 +
>>>>    security/lsm_syscalls.c             | 55 ++++++++++++++++
>>>>    security/security.c                 | 97
>>>> +++++++++++++++++++++++++++++
>>>>    10 files changed, 242 insertions(+)
>>>>    create mode 100644 security/lsm_syscalls.c
>>>
>>> [...]
>>>
>>>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>>>> new file mode 100644
>>>> index 000000000000..feee31600219
>>>> --- /dev/null
>>>> +++ b/security/lsm_syscalls.c
>>>> @@ -0,0 +1,55 @@
>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>> +/*
>>>> + * System calls implementing the Linux Security Module API.
>>>> + *
>>>> + *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
>>>> + *  Copyright (C) 2022 Intel Corporation
>>>> + */
>>>> +
>>>> +#include <asm/current.h>
>>>> +#include <linux/compiler_types.h>
>>>> +#include <linux/err.h>
>>>> +#include <linux/errno.h>
>>>> +#include <linux/security.h>
>>>> +#include <linux/stddef.h>
>>>> +#include <linux/syscalls.h>
>>>> +#include <linux/types.h>
>>>> +#include <linux/lsm_hooks.h>
>>>> +#include <uapi/linux/lsm.h>
>>>> +
>>>> +/**
>>>> + * sys_lsm_set_self_attr - Set current task's security module
>>>> attribute
>>>> + * @attr: which attribute to set
>>>> + * @ctx: the LSM contexts
>>>> + * @size: size of @ctx
>>>> + * @flags: reserved for future use
>>>> + *
>>>> + * Sets the calling task's LSM context. On success this function
>>>> + * returns 0. If the attribute specified cannot be set a negative
>>>> + * value indicating the reason for the error is returned.
>>>
>>> Do you think it is really worth it to implement syscalls that can get
>>> and set attributes to several LSMs at the same time, instead of one at
>>> a time?
>>
>> Setting the values for more than one LSM is impractical due to the
>> possibility
>> that the Nth value may fail, and unwinding the N-1 values may not be
>> possible.
>
> Indeed, so unless I missed something, why not passing the LSM ID as a
> syscall argument for lsm_set_self_attr() and lsm_get_self_attr(), and
> avoid managing a set of contexts but instead only managing one context
> at a time (to get or set)?

The LSM ID is already in the lsm_attr being passed. An additional argument
would be redundant and introduce a potential error when the two values don't
match.

>
>
>>
>>> LSM-specific tools don't care about other LSMs.
>>
>> That's part of the problem. Are systemd, dbusd, ps and id LSM
>> specific tools?
>> They shouldn't be.
>>
>>> I still think it would be much simpler (for kernel and user space) to
>>> pass an LSM ID to both syscalls. This would avoid dealing with
>>> variable arrays of variable element lengths, to both get or set
>>> attributes.
>>
>> ps and id should both work regardless of which and how many LSMs provide
>> context attributes. They shouldn't need to know which LSMs are active in
>> advance. If a new LSM is introduced, they shouldn't need to be
>> updated to
>> support it.
>
> I agree, and making the syscalls simpler doesn't change that.
>
>>
>>>
>>> Furthermore, considering the hypotetical LSM_ATTR_MAGICFD that was
>>> previously talked about, getting an unknown number of file descriptor
>>> doesn't look good neither.
>>
>> If you have multiple LSM_ATTR_MAGICFD values and can only get one at
>> a time you have to do something convoluted with flags to get them all.
>> I don't see that as a good thing.
>
> Yes, that was another argument to *not* deal with a set of contexts.

User space is going to have to deal with multiple values somehow,
either by fetching each possible value independently or by getting
them all at once in a set. Neither is pretty.

>
>>
>>>
>>>
>>>> + */
>>>> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct
>>>> lsm_ctx __user *,
>>>> +        ctx, size_t __user, size, u32, flags)
>>>> +{
>>>> +    return security_setselfattr(attr, ctx, size, flags);
>>>> +}
>>>> +
>>>> +/**
>>>> + * sys_lsm_get_self_attr - Return current task's security module
>>>> attributes
>>>> + * @attr: which attribute to set
>>>
>>> attribute to *get*
>>>
>>>> + * @ctx: the LSM contexts
>>>> + * @size: size of @ctx, updated on return
>>>
>>> I suggest to use a dedicated argument to read the allocated size, and
>>> another to write the actual/written size.
>>>
>>> This would not be required with an LSM ID passed to the syscall
>>> because attribute sizes should be known by user space, and there is no
>>> need to help them probe this information.
>>>
>>>
>>>> + * @flags: reserved for future use
>>>> + *
>>>> + * Returns the calling task's LSM contexts. On success this
>>>> + * function returns the number of @ctx array elements. This value
>>>> + * may be zero if there are no LSM contexts assigned. If @size is
>>>> + * insufficient to contain the return data -E2BIG is returned and
>>>> + * @size is set to the minimum required size.
>>>
>>> Doing something (updating a buffer) even when returning an error
>>> doesn't look right. These sizes should be well-known to user space and
>>> part of the ABI/UAPI.
>>
>> No. The size of attributes is not well known to user space.
>> They are usually text strings. The maximum size will be known,
>> but that's putting additional burden on user space to know
>> about all possible LSMs. It's not always necessary.
>
> Right, I forgot the strings stuff… The lsm_get_self_attr() syscall
> could then return a ctx_actual_size (as one argument), and a ctx
> pointer (as another argument). Similarly, the lsm_set_self_attr()
> syscall could use a dedicated argument for ctx_size and another for
> the ctx pointer.

That does not meet the design requirement. Paul wants a lsm_attr structure.
I'm not going to deviate from that.

>
>>
>>>
>>>
>>>> In all other cases
>>>> + * a negative value indicating the error is returned.
>>>> + */
>>>> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct
>>>> lsm_ctx __user *,
>>>> +        ctx, size_t __user *, size, u32, flags)
>>>> +{
>>>> +    return security_getselfattr(attr, ctx, size, flags);
>>>> +}
>>>> diff --git a/security/security.c b/security/security.c
>>>> index 87c8796c3c46..2c57fe28c4f7 100644
>>>> --- a/security/security.c
>>>> +++ b/security/security.c
>>>> @@ -2168,6 +2168,103 @@ void security_d_instantiate(struct dentry
>>>> *dentry, struct inode *inode)
>>>>    }
>>>>    EXPORT_SYMBOL(security_d_instantiate);
>>>>    +/**
>>>> + * security_getselfattr - Read an LSM attribute of the current
>>>> process.
>>>> + * @attr: which attribute to return
>>>> + * @ctx: the user-space destination for the information, or NULL
>>>> + * @size: the size of space available to receive the data
>>>> + * @flags: reserved for future use, must be 0
>>>> + *
>>>> + * Returns the number of attributes found on success, negative value
>>>> + * on error. @size is reset to the total size of the data.
>>>> + * If @size is insufficient to contain the data -E2BIG is returned.
>>>> + */
>>>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx
>>>> __user *ctx,
>>>> +             size_t __user *size, u32 __user flags)
>>>> +{
>>>> +    struct security_hook_list *hp;
>>>> +    void __user *base = (void *)ctx;
>>>> +    size_t total = 0;
>>>> +    size_t this;
>>>> +    size_t left;
>>>> +    bool istoobig = false;
>>>> +    int count = 0;
>>>> +    int rc;
>>>> +
>>>> +    if (attr == 0)
>>>> +        return -EINVAL;
>>>> +    if (flags != 0)
>>>> +        return -EINVAL;
>>>> +    if (size == NULL)
>>>> +        return -EINVAL;
>>>> +    if (get_user(left, size))
>>>> +        return -EFAULT;
>>>> +
>>>> +    hlist_for_each_entry(hp, &security_hook_heads.getselfattr,
>>>> list) {
>>>> +        this = left;
>>>> +        if (base)
>>>> +            ctx = (struct lsm_ctx __user *)(base + total);
>>>> +        rc = hp->hook.getselfattr(attr, ctx, &this, flags);
>>>> +        switch (rc) {
>>>> +        case -EOPNOTSUPP:
>>>> +            rc = 0;
>>>> +            continue;
>>>> +        case -E2BIG:
>>>> +            istoobig = true;
>>>> +            left = 0;
>>>> +            break;
>>>
>>> These two error cases could be directly handled by
>>> security_getselfattr() instead of relying on each LSM-specific
>>> implementations. See my suggestion on patch 7/11 (lsm_get_attr_size).
>>
>> Yes, they could. My understanding is that Paul wants the LSM layer
>> to be "thin". Where possible and not insane, the logic should be in
>> the LSM, not the infrastructure.
>
> FWIW, since we are defining new syscalls to make user space's life
> easier, I'm in favor of a well defined common behavior (e.g. returned
> errno) and factoring common code to make each LSM-specific code thin.

I appreciate the viewpoint. It's not what I understand the maintainer wants.

>
>>
>>>
>>>
>>>> +        case 0:
>>>> +            left -= this;
>>>> +            break;
>>>> +        default:
>>>> +            return rc;
>>>> +        }
>>>> +        total += this;
>>>> +        count++;
>>>> +    }
>>>> +    if (count == 0)
>>>> +        return LSM_RET_DEFAULT(getselfattr);
>>>> +    if (put_user(total, size))
>>>> +        return -EFAULT;
>>>> +    if (rc)
>>>> +        return rc;
>>>> +    if (istoobig)
>>>> +        return -E2BIG;
>>>> +    return count;
>>>> +}
>>>> +
>>>> +/**
>>>> + * security_setselfattr - Set an LSM attribute on the current
>>>> process.
>>>> + * @attr: which attribute to set
>>>> + * @ctx: the user-space source for the information
>>>> + * @size: the size of the data
>>>> + * @flags: reserved for future use, must be 0
>>>> + *
>>>> + * Set an LSM attribute for the current process. The LSM, attribute
>>>> + * and new value are included in @ctx.
>>>> + *
>>>> + * Returns 0 on success, an LSM specific value on failure.
>>>> + */
>>>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx
>>>> __user *ctx,
>>>> +             size_t __user size, u32 __user flags)
>>>> +{
>>>> +    struct security_hook_list *hp;
>>>> +    struct lsm_ctx lctx;
>>>> +
>>>> +    if (flags != 0)
>>>> +        return -EINVAL;
>>>> +    if (size < sizeof(*ctx))
>>>> +        return -EINVAL;
>>>> +    if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>>>> +        return -EFAULT;
>>>> +
>>>> +    hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>>>> +        if ((hp->lsmid->id) == lctx.id)
>>>> +            return hp->hook.setselfattr(attr, ctx, size, flags);
>>>> +
>>>> +    return LSM_RET_DEFAULT(setselfattr);
>>>> +}
>>>> +
>>>>    int security_getprocattr(struct task_struct *p, int lsmid, const
>>>> char *name,
>>>>                 char **value)
>>>>    {

Re: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

[Casey Schaufler]

On 4/3/2023 11:06 AM, Mickaël Salaün wrote:
>
> On 03/04/2023 20:03, Casey Schaufler wrote:
>> On 4/3/2023 2:47 AM, Mickaël Salaün wrote:
>>>
>>> On 15/03/2023 23:47, Casey Schaufler wrote:
>>>> Add lsm_name_to_attr(), which translates a text string to a
>>>> LSM_ATTR value if one is available.
>>>>
>>>> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
>>>> the trailing attribute value.
>>>>
>>>> All are used in module specific components of LSM system calls.
>>>>
>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>> ---
>>>>    include/linux/security.h | 13 ++++++++++
>>>>    security/lsm_syscalls.c  | 51
>>>> ++++++++++++++++++++++++++++++++++++++++
>>>>    security/security.c      | 31 ++++++++++++++++++++++++
>>>>    3 files changed, 95 insertions(+)
>>>
>>> [...]
>>>
>>>> diff --git a/security/security.c b/security/security.c
>>>> index 2c57fe28c4f7..f7b814a3940c 100644
>>>> --- a/security/security.c
>>>> +++ b/security/security.c
>>>> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct
>>>> super_block *sb)
>>>>        return 0;
>>>>    }
>>>>    +/**
>>>> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
>>>> + * @ctx: an LSM context to be filled
>>>> + * @context: the new context value
>>>> + * @context_size: the size of the new context value
>>>> + * @id: LSM id
>>>> + * @flags: LSM defined flags
>>>> + *
>>>> + * Fill all of the fields in a user space lsm_ctx structure.
>>>> + * Caller is assumed to have verified that @ctx has enough space
>>>> + * for @context.
>>>> + * Returns 0 on success, -EFAULT on a copyout error.
>>>> + */
>>>> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
>>>> +              size_t context_size, u64 id, u64 flags)
>>>> +{
>>>> +    struct lsm_ctx local;
>>>> +    void __user *vc = ctx;
>>>> +
>>>> +    local.id = id;
>>>> +    local.flags = flags;
>>>> +    local.ctx_len = context_size;
>>>> +    local.len = context_size + sizeof(local);
>>>> +    vc += sizeof(local);
>>>> +    if (copy_to_user(ctx, &local, sizeof(local)))
>>>> +        return -EFAULT;
>>>> +    if (context_size > 0 && copy_to_user(vc, context, context_size))
>>>> +        return -EFAULT;
>>>
>>> Can we do a single copy_to_user() call?
>>
>> It would be possible, but would require allocating memory and copying
>> the context. I don't see that as an improvement.
>>
>>> That would avoid inconsistent user space data, could speed up a bit
>>> the operation, and make the code easier to understand. To use the
>>> stack, we need to know the maximum size of context_size for all use
>>> cases, which seems reasonable and can be checked at build time (on
>>> each LSM side, and potentially with specific context type passed as
>>> enum instead of context_size) and run time (for this generic helper).
>>
>> Knowning the maximum size of attributes for all LSMs and hard coding
>> that here would make maintaining this code really painful.
>
> Hmm, I forgot about variable-length strings, but maybe a reasonable
> common maximum size (that could fit on the stack) could be found?

Putting a maximum size limit on LSM attributes just to reduce the
number of copy_to_user() calls in this helper function does not make
a whole lot of sense to me.

>
>>
>>>
>>>
>>>> +    return 0;
>>>> +}
>>>> +
>>>>    /*
>>>>     * The default value of the LSM hook is defined in
>>>> linux/lsm_hook_defs.h and
>>>>     * can be accessed with:

Re: [PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Paul Moore]

On Mon, Apr 3, 2023 at 8:04 AM Mickaël Salaün <mic@digikod.net> wrote:
>
> It looks like you missed my preview reviews on these patches.

For reference, I believe this is Mickaël's review of the associated v6 patch:

https://lore.kernel.org/linux-security-module/1ca41f67-ffa1-56c2-b4ee-f5deece95130@digikod.net/

> On 15/03/2023 23:46, Casey Schaufler wrote:
> > Create a system call to report the list of Linux Security Modules
> > that are active on the system. The list is provided as an array
> > of LSM ID numbers.
> >
> > The calling application can use this list determine what LSM
> > specific actions it might take. That might include chosing an
> > output format, determining required privilege or bypassing
> > security module specific behavior.
> >
> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> > ---
> >   Documentation/userspace-api/lsm.rst |  3 +++
> >   include/linux/syscalls.h            |  1 +
> >   kernel/sys_ni.c                     |  1 +
> >   security/lsm_syscalls.c             | 39 +++++++++++++++++++++++++++++
> >   4 files changed, 44 insertions(+)
> >
> > diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
> > index b45e402302b3..a86e3817f062 100644
> > --- a/Documentation/userspace-api/lsm.rst
> > +++ b/Documentation/userspace-api/lsm.rst
> > @@ -63,6 +63,9 @@ Get the specified security attributes of the current process
> >   .. kernel-doc:: security/lsm_syscalls.c
> >       :identifiers: sys_lsm_get_self_attr
> >
> > +.. kernel-doc:: security/lsm_syscalls.c
> > +    :identifiers: sys_lsm_list_modules
> > +
> >   Additional documentation
> >   ========================
> >
> > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> > index 3feca00cb0c1..f755c583f949 100644
> > --- a/include/linux/syscalls.h
> > +++ b/include/linux/syscalls.h
> > @@ -1063,6 +1063,7 @@ asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> >                                     size_t *size, __u64 flags);
> >   asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> >                                     __u64 flags);
> > +asmlinkage long sys_lsm_list_modules(u64 *ids, size_t *size, u32 flags);
> >
> >   /*
> >    * Architecture-specific system calls
> > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> > index d03c78ef1562..ceb3d21a62d0 100644
> > --- a/kernel/sys_ni.c
> > +++ b/kernel/sys_ni.c
> > @@ -265,6 +265,7 @@ COND_SYSCALL(mremap);
> >   /* security/lsm_syscalls.c */
> >   COND_SYSCALL(lsm_get_self_attr);
> >   COND_SYSCALL(lsm_set_self_attr);
> > +COND_SYSCALL(lsm_list_modules);
> >
> >   /* security/keys/keyctl.c */
> >   COND_SYSCALL(add_key);
> > diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> > index feee31600219..6efbe244d304 100644
> > --- a/security/lsm_syscalls.c
> > +++ b/security/lsm_syscalls.c
> > @@ -53,3 +53,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> >   {
> >       return security_getselfattr(attr, ctx, size, flags);
> >   }
> > +
> > +/**
> > + * sys_lsm_list_modules - Return a list of the active security modules
> > + * @ids: the LSM module ids
> > + * @size: size of @ids, updated on return
> > + * @flags: reserved for future use, must be zero
> > + *
> > + * Returns a list of the active LSM ids. On success this function
> > + * returns the number of @ids array elements. This value may be zero
> > + * if there are no LSMs active. If @size is insufficient to contain
> > + * the return data -E2BIG is returned and @size is set to the minimum
> > + * required size. In all other cases a negative value indicating the
> > + * error is returned.
> > + */
> > +SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
> > +             u32, flags)
> > +{
> > +     size_t total_size = lsm_active_cnt * sizeof(*ids);
> > +     size_t usize;
> > +     int i;
> > +
> > +     if (flags)
> > +             return -EINVAL;
> > +
> > +     if (get_user(usize, size))
> > +             return -EFAULT;
> > +
> > +     if (put_user(total_size, size) != 0)
> > +             return -EFAULT;
> > +
> > +     if (usize < total_size)
> > +             return -E2BIG;
> > +
> > +     for (i = 0; i < lsm_active_cnt; i++)
> > +             if (put_user(lsm_idlist[i]->id, ids++))
> > +                     return -EFAULT;
> > +
> > +     return lsm_active_cnt;
> > +}

-- 
paul-moore.com

Re: [PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Paul Moore]

On Mon, Apr 10, 2023 at 7:37 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Mon, Apr 3, 2023 at 8:04 AM Mickaël Salaün <mic@digikod.net> wrote:
> >
> > It looks like you missed my preview reviews on these patches.
>
> For reference, I believe this is Mickaël's review of the associated v6 patch:
>
> https://lore.kernel.org/linux-security-module/1ca41f67-ffa1-56c2-b4ee-f5deece95130@digikod.net/

My apologies, I hit send too soon ... Mickaël, if there are a specific
points you feel have not been addressed, but should be, it would be
helpful if you could list them in this thread.

> > On 15/03/2023 23:46, Casey Schaufler wrote:
> > > Create a system call to report the list of Linux Security Modules
> > > that are active on the system. The list is provided as an array
> > > of LSM ID numbers.
> > >
> > > The calling application can use this list determine what LSM
> > > specific actions it might take. That might include chosing an
> > > output format, determining required privilege or bypassing
> > > security module specific behavior.
> > >
> > > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> > > ---
> > >   Documentation/userspace-api/lsm.rst |  3 +++
> > >   include/linux/syscalls.h            |  1 +
> > >   kernel/sys_ni.c                     |  1 +
> > >   security/lsm_syscalls.c             | 39 +++++++++++++++++++++++++++++
> > >   4 files changed, 44 insertions(+)
> > >
> > > diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
> > > index b45e402302b3..a86e3817f062 100644
> > > --- a/Documentation/userspace-api/lsm.rst
> > > +++ b/Documentation/userspace-api/lsm.rst
> > > @@ -63,6 +63,9 @@ Get the specified security attributes of the current process
> > >   .. kernel-doc:: security/lsm_syscalls.c
> > >       :identifiers: sys_lsm_get_self_attr
> > >
> > > +.. kernel-doc:: security/lsm_syscalls.c
> > > +    :identifiers: sys_lsm_list_modules
> > > +
> > >   Additional documentation
> > >   ========================
> > >
> > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> > > index 3feca00cb0c1..f755c583f949 100644
> > > --- a/include/linux/syscalls.h
> > > +++ b/include/linux/syscalls.h
> > > @@ -1063,6 +1063,7 @@ asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> > >                                     size_t *size, __u64 flags);
> > >   asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> > >                                     __u64 flags);
> > > +asmlinkage long sys_lsm_list_modules(u64 *ids, size_t *size, u32 flags);
> > >
> > >   /*
> > >    * Architecture-specific system calls
> > > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> > > index d03c78ef1562..ceb3d21a62d0 100644
> > > --- a/kernel/sys_ni.c
> > > +++ b/kernel/sys_ni.c
> > > @@ -265,6 +265,7 @@ COND_SYSCALL(mremap);
> > >   /* security/lsm_syscalls.c */
> > >   COND_SYSCALL(lsm_get_self_attr);
> > >   COND_SYSCALL(lsm_set_self_attr);
> > > +COND_SYSCALL(lsm_list_modules);
> > >
> > >   /* security/keys/keyctl.c */
> > >   COND_SYSCALL(add_key);
> > > diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> > > index feee31600219..6efbe244d304 100644
> > > --- a/security/lsm_syscalls.c
> > > +++ b/security/lsm_syscalls.c
> > > @@ -53,3 +53,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> > >   {
> > >       return security_getselfattr(attr, ctx, size, flags);
> > >   }
> > > +
> > > +/**
> > > + * sys_lsm_list_modules - Return a list of the active security modules
> > > + * @ids: the LSM module ids
> > > + * @size: size of @ids, updated on return
> > > + * @flags: reserved for future use, must be zero
> > > + *
> > > + * Returns a list of the active LSM ids. On success this function
> > > + * returns the number of @ids array elements. This value may be zero
> > > + * if there are no LSMs active. If @size is insufficient to contain
> > > + * the return data -E2BIG is returned and @size is set to the minimum
> > > + * required size. In all other cases a negative value indicating the
> > > + * error is returned.
> > > + */
> > > +SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
> > > +             u32, flags)
> > > +{
> > > +     size_t total_size = lsm_active_cnt * sizeof(*ids);
> > > +     size_t usize;
> > > +     int i;
> > > +
> > > +     if (flags)
> > > +             return -EINVAL;
> > > +
> > > +     if (get_user(usize, size))
> > > +             return -EFAULT;
> > > +
> > > +     if (put_user(total_size, size) != 0)
> > > +             return -EFAULT;
> > > +
> > > +     if (usize < total_size)
> > > +             return -E2BIG;
> > > +
> > > +     for (i = 0; i < lsm_active_cnt; i++)
> > > +             if (put_user(lsm_idlist[i]->id, ids++))
> > > +                     return -EFAULT;
> > > +
> > > +     return lsm_active_cnt;
> > > +}
>
> --
> paul-moore.com



-- 
paul-moore.com

Re: [PATCH v7 04/11] LSM: syscalls for current process attributes

[Paul Moore]

On Mon, Apr 3, 2023 at 8:04 AM Mickaël Salaün <mic@digikod.net> wrote:
> On 15/03/2023 23:46, Casey Schaufler wrote:
> > Create a system call lsm_get_self_attr() to provide the security
> > module maintained attributes of the current process.
> > Create a system call lsm_set_self_attr() to set a security
> > module maintained attribute of the current process.
> > Historically these attributes have been exposed to user space via
> > entries in procfs under /proc/self/attr.
> >
> > The attribute value is provided in a lsm_ctx structure. The structure
> > identifys the size of the attribute, and the attribute value. The format
> > of the attribute value is defined by the security module. A flags field
> > is included for LSM specific information. It is currently unused and must
> > be 0. The total size of the data, including the lsm_ctx structure and any
> > padding, is maintained as well.
> >
> > struct lsm_ctx {
> >          __u64   id;
> >          __u64   flags;
> >          __u64   len;
> >          __u64   ctx_len;
> >          __u8    ctx[];
> > };
> >
> > Two new LSM hooks are used to interface with the LSMs.
> > security_getselfattr() collects the lsm_ctx values from the
> > LSMs that support the hook, accounting for space requirements.
> > security_setselfattr() identifies which LSM the attribute is
> > intended for and passes it along.
> >
> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> > ---
> >   Documentation/userspace-api/lsm.rst | 15 +++++
> >   include/linux/lsm_hook_defs.h       |  4 ++
> >   include/linux/lsm_hooks.h           |  9 +++
> >   include/linux/security.h            | 19 ++++++
> >   include/linux/syscalls.h            |  5 ++
> >   include/uapi/linux/lsm.h            | 33 ++++++++++
> >   kernel/sys_ni.c                     |  4 ++
> >   security/Makefile                   |  1 +
> >   security/lsm_syscalls.c             | 55 ++++++++++++++++
> >   security/security.c                 | 97 +++++++++++++++++++++++++++++
> >   10 files changed, 242 insertions(+)
> >   create mode 100644 security/lsm_syscalls.c
>
> [...]
>
> > diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> > new file mode 100644
> > index 000000000000..feee31600219
> > --- /dev/null
> > +++ b/security/lsm_syscalls.c
> > @@ -0,0 +1,55 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * System calls implementing the Linux Security Module API.
> > + *
> > + *  Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
> > + *  Copyright (C) 2022 Intel Corporation
> > + */
> > +
> > +#include <asm/current.h>
> > +#include <linux/compiler_types.h>
> > +#include <linux/err.h>
> > +#include <linux/errno.h>
> > +#include <linux/security.h>
> > +#include <linux/stddef.h>
> > +#include <linux/syscalls.h>
> > +#include <linux/types.h>
> > +#include <linux/lsm_hooks.h>
> > +#include <uapi/linux/lsm.h>
> > +
> > +/**
> > + * sys_lsm_set_self_attr - Set current task's security module attribute
> > + * @attr: which attribute to set
> > + * @ctx: the LSM contexts
> > + * @size: size of @ctx
> > + * @flags: reserved for future use
> > + *
> > + * Sets the calling task's LSM context. On success this function
> > + * returns 0. If the attribute specified cannot be set a negative
> > + * value indicating the reason for the error is returned.
>
> Do you think it is really worth it to implement syscalls that can get
> and set attributes to several LSMs at the same time, instead of one at a
> time?

As mentioned elsewhere, the "set" operations pretty much have to be
one LSM at a time; the error handling is almost impossible otherwise.

However, it would be possible to have a single LSM "get" operation.
We could do this with the proposed lsm_get_self_attr() syscall and a
flag to indicate that only a single LSM's attribute information is
being requested, and that the desired LSM is indicated by the
lsm_ctx::id field (populated by the userspace caller).  I'm imagining
something like this:

  lsm_ctx->id = LSM_ID_MYFAVORITELSM;
  lsm_get_self_attr(LSM_ATTR_CURRENT,
                    lsm_ctx, &lsm_ctx_size, LSM_FLG_SINGLE);

> LSM-specific tools don't care about other LSMs.

That's why they are called "LSM-specific tools" ;)  I think it is a
reasonable request to provide optimizations for that, the
discussion/example above, but I think we also want to support tools
which are LSM "aware" but don't need to be made specific to any one
particular LSM.  Thankfully, I think we can do both.

> I still think it
> would be much simpler (for kernel and user space) to pass an LSM ID to
> both syscalls. This would avoid dealing with variable arrays of variable
> element lengths, to both get or set attributes.

I think we should support "get" operations that support getting an
attribute from multiple LSMs, but I'm perfectly fine with also
supporting a single LSM "get" operation as described in the example
above.

> Furthermore, considering the hypotetical LSM_ATTR_MAGICFD that was
> previously talked about, getting an unknown number of file descriptor
> doesn't look good neither.

We are already in a place where not all LSMs support all of the
attributes, and we handle that.  If you are concerned about a specific
LSM returning some additional, or "richer", attribute data, the
syscall does support that; it is just a matter of the userspace caller
being able to understand the LSM-specific data ... which is true for
even the simple/standard case.

> > + */
> > +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> > +             ctx, size_t __user, size, u32, flags)
> > +{
> > +     return security_setselfattr(attr, ctx, size, flags);
> > +}
> > +
> > +/**
> > + * sys_lsm_get_self_attr - Return current task's security module attributes
> > + * @attr: which attribute to set
>
> attribute to *get*
>
> > + * @ctx: the LSM contexts
> > + * @size: size of @ctx, updated on return
>
> I suggest to use a dedicated argument to read the allocated size, and
> another to write the actual/written size.

Can you elaborate on this?  There is plenty of precedence for this approach.

> This would not be required with an LSM ID passed to the syscall because
> attribute sizes should be known by user space, and there is no need to
> help them probe this information.

No.  As we move forward, and LSMs potentially introduce additional
attribute information/types/etc., there will be cases where the kernel
could need more buffer space than userspace would realize.  Keeping
the length flexible allows this, with the extra information ignored by
"legacy" userspace, and utilized by "new" userspace.

> > + * @flags: reserved for future use
> > + *
> > + * Returns the calling task's LSM contexts. On success this
> > + * function returns the number of @ctx array elements. This value
> > + * may be zero if there are no LSM contexts assigned. If @size is
> > + * insufficient to contain the return data -E2BIG is returned and
> > + * @size is set to the minimum required size.
>
> Doing something (updating a buffer) even when returning an error doesn't
> look right.

We could zero the buffer on error/E2BIG if that is a concern, but
unfortunately due the nature of the LSM it is not possible to safely
(no races) determine the size of the buffer before populating it.

> These sizes should be well-known to user space and part of
> the ABI/UAPI.

That may be true for specific LSMs at this point in time, but I
believe it would be a serious mistake to impose that constraint on
these syscalls.

-- 
paul-moore.com

Re: [PATCH v7 05/11] LSM: Create lsm_list_modules system call

[Mickaël Salaün]

On 11/04/2023 01:38, Paul Moore wrote:
> On Mon, Apr 10, 2023 at 7:37 PM Paul Moore <paul@paul-moore.com> wrote:
>>
>> On Mon, Apr 3, 2023 at 8:04 AM Mickaël Salaün <mic@digikod.net> wrote:
>>>
>>> It looks like you missed my preview reviews on these patches.
>>
>> For reference, I believe this is Mickaël's review of the associated v6 patch:
>>
>> https://lore.kernel.org/linux-security-module/1ca41f67-ffa1-56c2-b4ee-f5deece95130@digikod.net/
> 
> My apologies, I hit send too soon ... Mickaël, if there are a specific
> points you feel have not been addressed, but should be, it would be
> helpful if you could list them in this thread.

No worries, Casey replied to the original thread: 
https://lore.kernel.org/linux-security-module/8819e4eb-1e99-bb38-6501-638677d3f4cf@schaufler-ca.com/