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From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: linux-security-module@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@suse.com>,
	kexec@lists.infradead.org, linux-modules@vger.kernel.org,
	fsdevel@vger.kernel.org, David Howells <dhowells@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Kees Cook <keescook@chromium.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Rusty Russell <rusty@rustcorp.com.au>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Subject: [PATCH v3 07/22] vfs: define a generic function to read a file from the kernel
Date: Wed,  3 Feb 2016 14:06:15 -0500
Message-ID: <1454526390-19792-8-git-send-email-zohar@linux.vnet.ibm.com> (raw)
In-Reply-To: <1454526390-19792-1-git-send-email-zohar@linux.vnet.ibm.com>

For a while it was looked down upon to directly read files from Linux.
These days there exists a few mechanisms in the kernel that do just
this though to load a file into a local buffer.  There are minor but
important checks differences on each.  This patch set is the first
attempt at resolving some of these differences.

This patch introduces a common function for reading files from the kernel
with the corresponding security post-read hook and function.

Changelog v3:
- additional bounds checking - Luis
v2:
- To simplify patch review, re-ordered patches

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: Luis R. Rodriguez <mcgrof@suse.com>
---
 fs/exec.c                 | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h        |  1 +
 include/linux/lsm_hooks.h |  9 ++++++++
 include/linux/security.h  |  7 +++++++
 security/security.c       |  7 +++++++
 5 files changed, 77 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index b06623a..742de7a 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -56,6 +56,7 @@
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
 #include <linux/compat.h>
+#include <linux/vmalloc.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -831,6 +832,58 @@ int kernel_read(struct file *file, loff_t offset,
 
 EXPORT_SYMBOL(kernel_read);
 
+int kernel_read_file(struct file *file, void **buf, loff_t *size,
+		     loff_t max_size)
+{
+	loff_t i_size, pos;
+	ssize_t bytes = 0;
+	int ret;
+
+	if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
+		return -EINVAL;
+
+	i_size = i_size_read(file_inode(file));
+	if (max_size > 0 && i_size > max_size)
+		return -EFBIG;
+	if (i_size <= 0)
+		return -EINVAL;
+
+	*buf = vmalloc(i_size);
+	if (!*buf)
+		return -ENOMEM;
+
+	pos = 0;
+	while (pos < i_size) {
+		bytes = kernel_read(file, pos, (char *)(*buf) + pos,
+				    i_size - pos);
+		if (bytes < 0) {
+			ret = bytes;
+			goto out;
+		}
+
+		if (bytes == 0)
+			break;
+		pos += bytes;
+	}
+
+	if (pos != i_size) {
+		ret = -EIO;
+		goto out;
+	}
+
+	ret = security_kernel_post_read_file(file, *buf, i_size);
+	if (!ret)
+		*size = pos;
+
+out:
+	if (ret < 0) {
+		vfree(*buf);
+		*buf = NULL;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file);
+
 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 {
 	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3aa5142..93ca379 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2527,6 +2527,7 @@ static inline void i_readcount_inc(struct inode *inode)
 extern int do_pipe_flags(int *, int);
 
 extern int kernel_read(struct file *, loff_t, char *, unsigned long);
+extern int kernel_read_file(struct file *, void **, loff_t *, loff_t);
 extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
 extern struct file * open_exec(const char *);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 71969de..f82631c 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -561,6 +561,13 @@
  *	the kernel module to load. If the module is being loaded from a blob,
  *	this argument will be NULL.
  *	Return 0 if permission is granted.
+ * @kernel_post_read_file:
+ *	Read a file specified by userspace.
+ *	@file contains the file structure pointing to the file being read
+ *	by the kernel.
+ *	@buf pointer to buffer containing the file contents.
+ *	@size length of the file contents.
+ *	Return 0 if permission is granted.
  * @task_fix_setuid:
  *	Update the module's state after setting one or more of the user
  *	identity attributes of the current process.  The @flags parameter
@@ -1457,6 +1464,7 @@ union security_list_options {
 	int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size);
 	int (*kernel_module_request)(char *kmod_name);
 	int (*kernel_module_from_file)(struct file *file);
+	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size);
 	int (*task_fix_setuid)(struct cred *new, const struct cred *old,
 				int flags);
 	int (*task_setpgid)(struct task_struct *p, pid_t pgid);
@@ -1716,6 +1724,7 @@ struct security_hook_heads {
 	struct list_head kernel_act_as;
 	struct list_head kernel_create_files_as;
 	struct list_head kernel_fw_from_file;
+	struct list_head kernel_post_read_file;
 	struct list_head kernel_module_request;
 	struct list_head kernel_module_from_file;
 	struct list_head task_fix_setuid;
diff --git a/include/linux/security.h b/include/linux/security.h
index 4824a4c..f30f564 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -301,6 +301,7 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode);
 int security_kernel_fw_from_file(struct file *file, char *buf, size_t size);
 int security_kernel_module_request(char *kmod_name);
 int security_kernel_module_from_file(struct file *file);
+int security_kernel_post_read_file(struct file *file, char *buf, loff_t size);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
 			     int flags);
 int security_task_setpgid(struct task_struct *p, pid_t pgid);
@@ -866,6 +867,12 @@ static inline int security_kernel_module_from_file(struct file *file)
 	return 0;
 }
 
+static inline int security_kernel_post_read_file(struct file *file,
+						 char *buf, loff_t size)
+{
+	return 0;
+}
+
 static inline int security_task_fix_setuid(struct cred *new,
 					   const struct cred *old,
 					   int flags)
diff --git a/security/security.c b/security/security.c
index e8ffd92..ae50730 100644
--- a/security/security.c
+++ b/security/security.c
@@ -910,6 +910,11 @@ int security_kernel_module_from_file(struct file *file)
 	return ima_module_check(file);
 }
 
+int security_kernel_post_read_file(struct file *file, char *buf, loff_t size)
+{
+	return call_int_hook(kernel_post_read_file, 0, file, buf, size);
+}
+
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
 			     int flags)
 {
@@ -1697,6 +1702,8 @@ struct security_hook_heads security_hook_heads = {
 		LIST_HEAD_INIT(security_hook_heads.kernel_module_request),
 	.kernel_module_from_file =
 		LIST_HEAD_INIT(security_hook_heads.kernel_module_from_file),
+	.kernel_post_read_file =
+		LIST_HEAD_INIT(security_hook_heads.kernel_post_read_file),
 	.task_fix_setuid =
 		LIST_HEAD_INIT(security_hook_heads.task_fix_setuid),
 	.task_setpgid =	LIST_HEAD_INIT(security_hook_heads.task_setpgid),
-- 
2.1.0


  parent reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-03 19:06 [PATCH v3 00/22] vfs: support for a common kernel file loader Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 01/22] ima: separate 'security.ima' reading functionality from collect Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 02/22] ima: refactor ima_policy_show() to display "ima_hooks" rules Mimi Zohar
2016-02-07 19:45   ` Petko Manolov
2016-02-10 19:33   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 03/22] ima: use "ima_hooks" enum as function argument Mimi Zohar
2016-02-07 19:46   ` Petko Manolov
2016-02-10 19:35   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 04/22] firmware: simplify dev_*() print messages for generic helpers Mimi Zohar
2016-02-04 17:26   ` Kees Cook
2016-02-03 19:06 ` [PATCH v3 05/22] firmware: move completing fw into a helper Mimi Zohar
2016-02-04 17:27   ` Kees Cook
2016-02-03 19:06 ` [PATCH v3 06/22] firmware: fold successful fw read early Mimi Zohar
2016-02-04 17:36   ` Kees Cook
2016-02-04 20:26     ` Luis R. Rodriguez
2016-02-03 19:06 ` Mimi Zohar [this message]
2016-02-04 17:41   ` [PATCH v3 07/22] vfs: define a generic function to read a file from the kernel Kees Cook
2016-02-03 19:06 ` [PATCH v3 08/22] vfs: define kernel_read_file_id enumeration Mimi Zohar
2016-02-04 17:41   ` Kees Cook
2016-02-04 19:45   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 09/22] ima: provide buffer hash calculation function Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 10/22] ima: calculate the hash of a buffer using aynchronous hash(ahash) Mimi Zohar
2016-02-10 19:58   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 11/22] ima: define a new hook to measure and appraise a file already in memory Mimi Zohar
2016-02-10 20:27   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 12/22] vfs: define kernel_read_file_from_path Mimi Zohar
2016-02-04 17:46   ` Kees Cook
2016-02-04 19:47   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 13/22] firmware: replace call to fw_read_file_contents() with kernel version Mimi Zohar
2016-02-04 17:56   ` Kees Cook
2016-02-04 19:51   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 14/22] security: define kernel_read_file hook Mimi Zohar
2016-02-04 17:57   ` Kees Cook
2016-02-04 19:54   ` Luis R. Rodriguez
2016-02-11 16:54   ` Casey Schaufler
2016-02-11 19:35     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 15/22] vfs: define kernel_copy_file_from_fd() Mimi Zohar
2016-02-04 17:58   ` Kees Cook
2016-02-04 19:55   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 16/22] module: replace copy_module_from_fd with kernel version Mimi Zohar
2016-02-04 18:04   ` Kees Cook
2016-02-04 19:56   ` Luis R. Rodriguez
2016-02-05  0:19     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 17/22] ima: remove firmware and module specific cached status info Mimi Zohar
2016-02-07 19:56   ` Petko Manolov
2016-02-10 20:18   ` Dmitry Kasatkin
2016-02-10 23:14     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 18/22] kexec: replace call to copy_file_from_fd() with kernel version Mimi Zohar
2016-02-04 18:05   ` Kees Cook
2016-02-04 19:57   ` Luis R. Rodriguez
2016-02-12 12:50   ` Dave Young
2016-02-03 19:06 ` [PATCH v3 19/22] ima: support for kexec image and initramfs Mimi Zohar
2016-02-07 20:10   ` Petko Manolov
2016-02-08 23:34     ` Mimi Zohar
2016-02-10 21:09   ` Dmitry Kasatkin
2016-02-10 23:21     ` Mimi Zohar
     [not found]       ` <CACE9dm8OJ1cgbKszUG-pCiEMVarUFLLWi_jewVV-JEMGAJsA-g@mail.gmail.com>
2016-02-11  2:08         ` Mimi Zohar
2016-02-11  8:47           ` Dmitry Kasatkin
2016-02-11 12:16             ` Mimi Zohar
2016-02-12 12:53   ` Dave Young
2016-02-12 13:09     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 20/22] ima: load policy using path Mimi Zohar
2016-02-07 19:59   ` Petko Manolov
2016-02-08  9:58     ` Dmitry Kasatkin
2016-02-08 10:35       ` Petko Manolov
2016-02-08 10:45         ` Dmitry Kasatkin
2016-02-08 21:12           ` Mimi Zohar
2016-02-09  7:47             ` Petko Manolov
2016-02-03 19:06 ` [PATCH v3 21/22] ima: measure and appraise the IMA policy itself Mimi Zohar
2016-02-07 20:01   ` Petko Manolov
2016-02-10 20:22   ` Dmitry Kasatkin
2016-02-10 23:15     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 22/22] ima: require signed IMA policy Mimi Zohar
2016-02-07 20:02   ` Petko Manolov
2016-02-10 20:24   ` Dmitry Kasatkin
2016-02-04 18:15 ` [PATCH v3 00/22] vfs: support for a common kernel file loader Kees Cook
2016-02-04 23:54   ` Mimi Zohar

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