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* [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2]
@ 2019-11-07 13:35 David Howells
  2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
                   ` (14 more replies)
  0 siblings, 15 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:35 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel


Here's a set of patches to add a general notification queue concept and to
add event sources such as:

 (1) Keys/keyrings, such as linking and unlinking keys and changing their
     attributes.

 (2) General device events (single common queue) including:

     - Block layer events, such as device errors

     - USB subsystem events, such as device attach/remove, device reset,
       device errors.

I have patches for adding superblock and mount topology watches also,
though those are not in this set as there are other dependencies.

LSM hooks are included:

 (1) A set of hooks are provided that allow an LSM to rule on whether or
     not a watch may be set.  Each of these hooks takes a different
     "watched object" parameter, so they're not really shareable.  The LSM
     should use current's credentials.  [Wanted by SELinux & Smack]

 (2) A hook is provided to allow an LSM to rule on whether or not a
     particular message may be posted to a particular queue.  This is given
     the credentials from the event generator (which may be the system) and
     the watch setter.  [Wanted by Smack]

I've provided SELinux and Smack with implementations of some of these hooks.


Design decisions:

 (1) The notification queue is built on top of a standard pipe.  Messages
     are effectively spliced in.  The pipe is opened with a special flag:

	pipe2(fds, O_NOTIFICATION_PIPE);

     The special flag has the same value as O_EXCL (which doesn't seem like
     it will ever be applicable in this context)[?].  It is given up front
     to make it a lot easier to prohibit splice and co. from accessing the
     pipe.

     [?] Should this be done some other way?  I'd rather not use up a new
     O_* flag if I can avoid it - should I add a pipe3() system call
     instead?

     The pipe is then configured::

	ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);

     Messages are then read out of the pipe using read().

 (2) It should be possible to allow write() to insert data into the
     notification pipes too, but this is currently disabled as the kernel
     has to be able to insert messages into the pipe *without* holding
     pipe->mutex and the code to make this work needs careful auditing.

 (3) sendfile(), splice() and vmsplice() are disabled on notification pipes
     because of the pipe->mutex issue and also because they sometimes want
     to revert what they just did - but one or more notification messages
     might've been interleaved in the ring.

 (4) The kernel inserts messages with the wait queue spinlock held.  This
     means that pipe_read() and pipe_write() have to take the spinlock to
     update the queue pointers.

 (5) Records in the buffer are binary, typed and have a length so that they
     can be of varying size.

     This allows multiple heterogeneous sources to share a common buffer;
     there are 16 million types available, of which I've used just a few,
     so there is scope for others to be used.  Tags may be specified when a
     watchpoint is created to help distinguish the sources.

 (6) Records are filterable as types have up to 256 subtypes that can be
     individually filtered.  Other filtration is also available.

 (7) Notification pipes don't interfere with each other; each may be bound
     to a different set of watches.  Any particular notification will be
     copied to all the queues that are currently watching for it - and only
     those that are watching for it.

 (8) When recording a notification, the kernel will not sleep, but will
     rather mark a queue as having lost a message if there's insufficient
     space.  read() will fabricate a loss notification message at an
     appropriate point later.

 (9) The notification pipe is created and then watchpoints are attached to
     it, using one of:

	keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
	watch_devices(fds[1], 0x02, 0);

     where in both cases, fd indicates the queue and the number after is a
     tag between 0 and 255.

(10) Watches are removed if either the notification pipe is destroyed or
     the watched object is destroyed.  In the latter case, a message will
     be generated indicating the enforced watch removal.


Things I want to avoid:

 (1) Introducing features that make the core VFS dependent on the network
     stack or networking namespaces (ie. usage of netlink).

 (2) Dumping all this stuff into dmesg and having a daemon that sits there
     parsing the output and distributing it as this then puts the
     responsibility for security into userspace and makes handling
     namespaces tricky.  Further, dmesg might not exist or might be
     inaccessible inside a container.

 (3) Letting users see events they shouldn't be able to see.


Testing and manpages:

 (*) The keyutils tree has a pipe-watch branch that has keyctl commands for
     making use of notifications.  Proposed manual pages can also be found
     on this branch, though a couple of them really need to go to the main
     manpages repository instead.

     If the kernel supports the watching of keys, then running "make test"
     on that branch will cause the testing infrastructure to spawn a
     monitoring process on the side that monitors a notifications pipe for
     all the key/keyring changes induced by the tests and they'll all be
     checked off to make sure they happened.

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=pipe-watch

The kernel patches can also be found here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=notifications-pipe-core

Changes:

 ver #2:

 (*) Declare O_NOTIFICATION_PIPE to use and switch it to be the same value
     as O_EXCL rather then O_TMPFILE (the latter is a bit nasty in its
     implementation).

 ver #1:

 (*) Build on top of standard pipes instead of having a driver.

David
---
David Howells (14):
      uapi: General notification queue definitions
      security: Add hooks to rule on setting a watch
      security: Add a hook for the point of notification insertion
      pipe: Add O_NOTIFICATION_PIPE
      pipe: Add general notification queue support
      keys: Add a notification facility
      Add sample notification program
      pipe: Allow buffers to be marked read-whole-or-error for notifications
      pipe: Add notification lossage handling
      Add a general, global device notification watch list
      block: Add block layer notifications
      usb: Add USB subsystem notifications
      selinux: Implement the watch_key security hook
      smack: Implement the watch_key and post_notification hooks


 Documentation/ioctl/ioctl-number.rst        |    1 
 Documentation/security/keys/core.rst        |   58 ++
 Documentation/watch_queue.rst               |  385 ++++++++++++++++
 arch/alpha/kernel/syscalls/syscall.tbl      |    1 
 arch/arm/tools/syscall.tbl                  |    1 
 arch/arm64/include/asm/unistd.h             |    2 
 arch/arm64/include/asm/unistd32.h           |    2 
 arch/ia64/kernel/syscalls/syscall.tbl       |    1 
 arch/m68k/kernel/syscalls/syscall.tbl       |    1 
 arch/microblaze/kernel/syscalls/syscall.tbl |    1 
 arch/mips/kernel/syscalls/syscall_n32.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_n64.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_o32.tbl   |    1 
 arch/parisc/kernel/syscalls/syscall.tbl     |    1 
 arch/powerpc/kernel/syscalls/syscall.tbl    |    1 
 arch/s390/kernel/syscalls/syscall.tbl       |    1 
 arch/sh/kernel/syscalls/syscall.tbl         |    1 
 arch/sparc/kernel/syscalls/syscall.tbl      |    1 
 arch/x86/entry/syscalls/syscall_32.tbl      |    1 
 arch/x86/entry/syscalls/syscall_64.tbl      |    1 
 arch/xtensa/kernel/syscalls/syscall.tbl     |    1 
 block/Kconfig                               |    9 
 block/blk-core.c                            |   29 +
 drivers/base/Kconfig                        |    9 
 drivers/base/Makefile                       |    1 
 drivers/base/watch.c                        |   90 ++++
 drivers/usb/core/Kconfig                    |    9 
 drivers/usb/core/devio.c                    |   47 ++
 drivers/usb/core/hub.c                      |    4 
 fs/pipe.c                                   |  229 ++++++---
 fs/splice.c                                 |   12 
 include/linux/blkdev.h                      |   15 +
 include/linux/device.h                      |    7 
 include/linux/key.h                         |    3 
 include/linux/lsm_audit.h                   |    1 
 include/linux/lsm_hooks.h                   |   38 ++
 include/linux/pipe_fs_i.h                   |   27 +
 include/linux/security.h                    |   32 +
 include/linux/syscalls.h                    |    1 
 include/linux/usb.h                         |   18 +
 include/linux/watch_queue.h                 |  127 +++++
 include/uapi/asm-generic/unistd.h           |    4 
 include/uapi/linux/keyctl.h                 |    2 
 include/uapi/linux/watch_queue.h            |  158 ++++++
 init/Kconfig                                |   12 
 kernel/Makefile                             |    1 
 kernel/sys_ni.c                             |    1 
 kernel/watch_queue.c                        |  658 +++++++++++++++++++++++++++
 samples/Kconfig                             |    7 
 samples/Makefile                            |    1 
 samples/watch_queue/Makefile                |    7 
 samples/watch_queue/watch_test.c            |  251 ++++++++++
 security/keys/Kconfig                       |    9 
 security/keys/compat.c                      |    3 
 security/keys/gc.c                          |    5 
 security/keys/internal.h                    |   30 +
 security/keys/key.c                         |   38 +-
 security/keys/keyctl.c                      |   99 ++++
 security/keys/keyring.c                     |   20 +
 security/keys/request_key.c                 |    4 
 security/security.c                         |   23 +
 security/selinux/hooks.c                    |   14 +
 security/smack/smack_lsm.c                  |   82 +++
 63 files changed, 2492 insertions(+), 109 deletions(-)
 create mode 100644 Documentation/watch_queue.rst
 create mode 100644 drivers/base/watch.c
 create mode 100644 include/linux/watch_queue.h
 create mode 100644 include/uapi/linux/watch_queue.h
 create mode 100644 kernel/watch_queue.c
 create mode 100644 samples/watch_queue/Makefile
 create mode 100644 samples/watch_queue/watch_test.c


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 01/14] uapi: General notification queue definitions [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
@ 2019-11-07 13:35 ` " David Howells
  2019-11-07 13:35 ` [RFC PATCH 02/14] security: Add hooks to rule on setting a watch " David Howells
                   ` (13 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:35 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add UAPI definitions for the general notification queue, including the
following pieces:

 (*) struct watch_notification.

     This is the metadata header for notification messages.  It includes a
     type and subtype that indicate the source of the message
     (eg. WATCH_TYPE_MOUNT_NOTIFY) and the kind of the message
     (eg. NOTIFY_MOUNT_NEW_MOUNT).

     The header also contains an information field that conveys the
     following information:

	- WATCH_INFO_LENGTH.  The size of the entry (entries are variable
          length).

	- WATCH_INFO_ID.  The watch ID specified when the watchpoint was
          set.

	- WATCH_INFO_TYPE_INFO.  (Sub)type-specific information.

	- WATCH_INFO_FLAG_*.  Flag bits overlain on the type-specific
          information.  For use by the type.

     All the information in the header can be used in filtering messages at
     the point of writing into the buffer.

 (*) struct watch_notification_removal

     This is an extended watch-removal notification record that includes an
     'id' field that can indicate the identifier of the object being
     removed if available (for instance, a keyring serial number).

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/uapi/linux/watch_queue.h |   55 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 include/uapi/linux/watch_queue.h

diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
new file mode 100644
index 000000000000..5f3d21e8a34b
--- /dev/null
+++ b/include/uapi/linux/watch_queue.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_WATCH_QUEUE_H
+#define _UAPI_LINUX_WATCH_QUEUE_H
+
+#include <linux/types.h>
+
+enum watch_notification_type {
+	WATCH_TYPE_META		= 0,	/* Special record */
+	WATCH_TYPE__NR		= 1
+};
+
+enum watch_meta_notification_subtype {
+	WATCH_META_REMOVAL_NOTIFICATION	= 0,	/* Watched object was removed */
+	WATCH_META_LOSS_NOTIFICATION	= 1,	/* Data loss occurred */
+};
+
+/*
+ * Notification record header.  This is aligned to 64-bits so that subclasses
+ * can contain __u64 fields.
+ */
+struct watch_notification {
+	__u32			type:24;	/* enum watch_notification_type */
+	__u32			subtype:8;	/* Type-specific subtype (filterable) */
+	__u32			info;
+#define WATCH_INFO_LENGTH	0x0000007f	/* Length of record */
+#define WATCH_INFO_LENGTH__SHIFT 0
+#define WATCH_INFO_ID		0x0000ff00	/* ID of watchpoint */
+#define WATCH_INFO_ID__SHIFT	8
+#define WATCH_INFO_TYPE_INFO	0xffff0000	/* Type-specific info */
+#define WATCH_INFO_TYPE_INFO__SHIFT 16
+#define WATCH_INFO_FLAG_0	0x00010000	/* Type-specific info, flag bit 0 */
+#define WATCH_INFO_FLAG_1	0x00020000	/* ... */
+#define WATCH_INFO_FLAG_2	0x00040000
+#define WATCH_INFO_FLAG_3	0x00080000
+#define WATCH_INFO_FLAG_4	0x00100000
+#define WATCH_INFO_FLAG_5	0x00200000
+#define WATCH_INFO_FLAG_6	0x00400000
+#define WATCH_INFO_FLAG_7	0x00800000
+};
+
+
+/*
+ * Extended watch removal notification.  This is used optionally if the type
+ * wants to indicate an identifier for the object being watched, if there is
+ * such.  This can be distinguished by the length.
+ *
+ * type -> WATCH_TYPE_META
+ * subtype -> WATCH_META_REMOVAL_NOTIFICATION
+ */
+struct watch_notification_removal {
+	struct watch_notification watch;
+	__u64	id;		/* Type-dependent identifier */
+};
+
+#endif /* _UAPI_LINUX_WATCH_QUEUE_H */


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 02/14] security: Add hooks to rule on setting a watch [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
  2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
@ 2019-11-07 13:35 ` " David Howells
  2019-11-07 13:35 ` [RFC PATCH 03/14] security: Add a hook for the point of notification insertion " David Howells
                   ` (12 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:35 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add security hooks that will allow an LSM to rule on whether or not a watch
may be set.  More than one hook is required as the watches watch different
types of object.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Casey Schaufler <casey@schaufler-ca.com>
cc: Stephen Smalley <sds@tycho.nsa.gov>
cc: linux-security-module@vger.kernel.org
---

 include/linux/lsm_hooks.h |   24 ++++++++++++++++++++++++
 include/linux/security.h  |   17 +++++++++++++++++
 security/security.c       |   14 ++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index a3763247547c..d62e92b768c4 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1416,6 +1416,18 @@
  *	@ctx is a pointer in which to place the allocated security context.
  *	@ctxlen points to the place to put the length of @ctx.
  *
+ * Security hooks for the general notification queue:
+ *
+ * @watch_key:
+ *	Check to see if a process is allowed to watch for event notifications
+ *	from a key or keyring.
+ *	@key: The key to watch.
+ *
+ * @watch_devices:
+ *	Check to see if a process is allowed to watch for event notifications
+ *	from devices (as a global set).
+ *
+ *
  * Security hooks for using the eBPF maps and programs functionalities through
  * eBPF syscalls.
  *
@@ -1698,6 +1710,12 @@ union security_list_options {
 	int (*inode_notifysecctx)(struct inode *inode, void *ctx, u32 ctxlen);
 	int (*inode_setsecctx)(struct dentry *dentry, void *ctx, u32 ctxlen);
 	int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	int (*watch_key)(struct key *key);
+#endif
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+	int (*watch_devices)(void);
+#endif
 
 #ifdef CONFIG_SECURITY_NETWORK
 	int (*unix_stream_connect)(struct sock *sock, struct sock *other,
@@ -1977,6 +1995,12 @@ struct security_hook_heads {
 	struct hlist_head inode_notifysecctx;
 	struct hlist_head inode_setsecctx;
 	struct hlist_head inode_getsecctx;
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	struct hlist_head watch_key;
+#endif
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+	struct hlist_head watch_devices;
+#endif
 #ifdef CONFIG_SECURITY_NETWORK
 	struct hlist_head unix_stream_connect;
 	struct hlist_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index a8d59d612d27..5d1867772022 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1271,6 +1271,23 @@ static inline int security_locked_down(enum lockdown_reason what)
 }
 #endif	/* CONFIG_SECURITY */
 
+#if defined(CONFIG_SECURITY) && defined(CONFIG_KEY_NOTIFICATIONS)
+int security_watch_key(struct key *key);
+#else
+static inline int security_watch_key(struct key *key)
+{
+	return 0;
+}
+#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_DEVICE_NOTIFICATIONS)
+int security_watch_devices(void);
+#else
+static inline int security_watch_devices(void)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_SECURITY_NETWORK
 
 int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk);
diff --git a/security/security.c b/security/security.c
index 1bc000f834e2..4f970716fa6c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1956,6 +1956,20 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
 }
 EXPORT_SYMBOL(security_inode_getsecctx);
 
+#ifdef CONFIG_KEY_NOTIFICATIONS
+int security_watch_key(struct key *key)
+{
+	return call_int_hook(watch_key, 0, key);
+}
+#endif
+
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+int security_watch_devices(void)
+{
+	return call_int_hook(watch_devices, 0);
+}
+#endif
+
 #ifdef CONFIG_SECURITY_NETWORK
 
 int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk)


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 03/14] security: Add a hook for the point of notification insertion [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
  2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
  2019-11-07 13:35 ` [RFC PATCH 02/14] security: Add hooks to rule on setting a watch " David Howells
@ 2019-11-07 13:35 ` " David Howells
  2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
                   ` (11 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:35 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add a security hook that allows an LSM to rule on whether a notification
message is allowed to be inserted into a particular watch queue.

The hook is given the following information:

 (1) The credentials of the triggerer (which may be init_cred for a system
     notification, eg. a hardware error).

 (2) The credentials of the whoever set the watch.

 (3) The notification message.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Casey Schaufler <casey@schaufler-ca.com>
cc: Stephen Smalley <sds@tycho.nsa.gov>
cc: linux-security-module@vger.kernel.org
---

 include/linux/lsm_hooks.h |   14 ++++++++++++++
 include/linux/security.h  |   15 ++++++++++++++-
 security/security.c       |    9 +++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index d62e92b768c4..8e1cbc27fc62 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1427,6 +1427,12 @@
  *	Check to see if a process is allowed to watch for event notifications
  *	from devices (as a global set).
  *
+ * @post_notification:
+ *	Check to see if a watch notification can be posted to a particular
+ *	queue.
+ *	@w_cred: The credentials of the whoever set the watch.
+ *	@cred: The event-triggerer's credentials
+ *	@n: The notification being posted
  *
  * Security hooks for using the eBPF maps and programs functionalities through
  * eBPF syscalls.
@@ -1716,6 +1722,11 @@ union security_list_options {
 #ifdef CONFIG_DEVICE_NOTIFICATIONS
 	int (*watch_devices)(void);
 #endif
+#ifdef CONFIG_WATCH_QUEUE
+	int (*post_notification)(const struct cred *w_cred,
+				 const struct cred *cred,
+				 struct watch_notification *n);
+#endif
 
 #ifdef CONFIG_SECURITY_NETWORK
 	int (*unix_stream_connect)(struct sock *sock, struct sock *other,
@@ -2001,6 +2012,9 @@ struct security_hook_heads {
 #ifdef CONFIG_DEVICE_NOTIFICATIONS
 	struct hlist_head watch_devices;
 #endif
+#ifdef CONFIG_WATCH_QUEUE
+	struct hlist_head post_notification;
+#endif /* CONFIG_WATCH_QUEUE */
 #ifdef CONFIG_SECURITY_NETWORK
 	struct hlist_head unix_stream_connect;
 	struct hlist_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index 5d1867772022..ee98e020c749 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -57,6 +57,8 @@ struct mm_struct;
 struct fs_context;
 struct fs_parameter;
 enum fs_value_type;
+struct watch;
+struct watch_notification;
 
 /* Default (no) options for the capable function */
 #define CAP_OPT_NONE 0x0
@@ -1287,6 +1289,18 @@ static inline int security_watch_devices(void)
 	return 0;
 }
 #endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
+int security_post_notification(const struct cred *w_cred,
+			       const struct cred *cred,
+			       struct watch_notification *n);
+#else
+static inline int security_post_notification(const struct cred *w_cred,
+					     const struct cred *cred,
+					     struct watch_notification *n)
+{
+	return 0;
+}
+#endif
 
 #ifdef CONFIG_SECURITY_NETWORK
 
@@ -1912,4 +1926,3 @@ static inline void security_bpf_prog_free(struct bpf_prog_aux *aux)
 #endif /* CONFIG_BPF_SYSCALL */
 
 #endif /* ! __LINUX_SECURITY_H */
-
diff --git a/security/security.c b/security/security.c
index 4f970716fa6c..c9d5c3d5472a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1956,6 +1956,15 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
 }
 EXPORT_SYMBOL(security_inode_getsecctx);
 
+#ifdef CONFIG_WATCH_QUEUE
+int security_post_notification(const struct cred *w_cred,
+			       const struct cred *cred,
+			       struct watch_notification *n)
+{
+	return call_int_hook(post_notification, 0, w_cred, cred, n);
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
 #ifdef CONFIG_KEY_NOTIFICATIONS
 int security_watch_key(struct key *key)
 {


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (2 preceding siblings ...)
  2019-11-07 13:35 ` [RFC PATCH 03/14] security: Add a hook for the point of notification insertion " David Howells
@ 2019-11-07 13:35 ` " David Howells
  2019-11-07 18:16   ` Andy Lutomirski
  2019-11-07 18:48   ` David Howells
  2019-11-07 13:36 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
                   ` (10 subsequent siblings)
  14 siblings, 2 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:35 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add an O_NOTIFICATION_PIPE flag that can be passed to pipe2() to indicate
that the pipe being created is going to be used for notifications.  This
suppresses the use of splice(), vmsplice(), tee() and sendfile() on the
pipe as calling iov_iter_revert() on a pipe when a kernel notification
message has been inserted into the middle of a multi-buffer splice will be
messy.

The flag is given the same value as O_EXCL as it seems unlikely that
this flag will ever be applicable to pipes and I don't want to use up
another O_* bit unnecessarily.  An alternative could be to add a pipe3()
system call.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/uapi/linux/watch_queue.h |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 5f3d21e8a34b..9df72227f515 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -3,6 +3,9 @@
 #define _UAPI_LINUX_WATCH_QUEUE_H
 
 #include <linux/types.h>
+#include <linux/fcntl.h>
+
+#define O_NOTIFICATION_PIPE	O_EXCL	/* Parameter to pipe2() selecting notification pipe */
 
 enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 05/14] pipe: Add general notification queue support [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (3 preceding siblings ...)
  2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 13:36 ` [RFC PATCH 06/14] keys: Add a notification facility " David Howells
                   ` (9 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Make it possible to have a general notification queue built on top of a
standard pipe.  Notifications are 'spliced' into the pipe and then read
out.  splice(), vmsplice() and sendfile() are forbidden on pipes used for
notifications as post_one_notification() cannot take pipe->mutex.  This
means that notifications could be posted in between individual pipe
buffers, making iov_iter_revert() difficult to effect.

The way the notification queue is used is:

 (1) An application opens a pipe with a special flag and indicates the
     number of messages it wishes to be able to queue at once (this can
     only be set once):

	pipe2(fds, O_NOTIFICATION_PIPE);
	ioctl(fds[0], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);

 (2) The application then uses poll() and read() as normal to extract data
     from the pipe.  read() will return multiple notifications if the
     buffer is big enough, but it will not split a notification across
     buffers - rather it will return a short read or EMSGSIZE.

     Notification messages include a length in the header so that the
     caller can split them up.

Each message has a header that describes it:

	struct watch_notification {
		__u32	type:24;
		__u32	subtype:8;
		__u32	info;
	};

The type indicates the source (eg. mount tree changes, superblock events,
keyring changes, block layer events) and the subtype indicates the event
type (eg. mount, unmount; EIO, EDQUOT; link, unlink).  The info field
indicates a number of things, including the entry length, an ID assigned to
a watchpoint contributing to this buffer and type-specific flags.

Supplementary data, such as the key ID that generated an event, can be
attached in additional slots.  The maximum message size is 127 bytes.
Messages may not be padded or aligned, so there is no guarantee, for
example, that the notification type will be on a 4-byte bounary.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/ioctl/ioctl-number.rst |    1 
 Documentation/watch_queue.rst        |  354 ++++++++++++++++++
 fs/pipe.c                            |  193 ++++++----
 fs/splice.c                          |   12 -
 include/linux/pipe_fs_i.h            |   19 +
 include/linux/watch_queue.h          |  127 +++++++
 include/uapi/linux/watch_queue.h     |   20 +
 init/Kconfig                         |   12 +
 kernel/Makefile                      |    1 
 kernel/watch_queue.c                 |  656 ++++++++++++++++++++++++++++++++++
 10 files changed, 1318 insertions(+), 77 deletions(-)
 create mode 100644 Documentation/watch_queue.rst
 create mode 100644 include/linux/watch_queue.h
 create mode 100644 kernel/watch_queue.c

diff --git a/Documentation/ioctl/ioctl-number.rst b/Documentation/ioctl/ioctl-number.rst
index bef79cd4c6b4..303fe17d871e 100644
--- a/Documentation/ioctl/ioctl-number.rst
+++ b/Documentation/ioctl/ioctl-number.rst
@@ -202,6 +202,7 @@ Code  Seq#    Include File                                           Comments
 'W'   00-1F  linux/wanrouter.h                                       conflict! (pre 3.9)
 'W'   00-3F  sound/asound.h                                          conflict!
 'W'   40-5F  drivers/pci/switch/switchtec.c
+'W'   60-61  linux/watch_queue.h
 'X'   all    fs/xfs/xfs_fs.h,                                        conflict!
              fs/xfs/linux-2.6/xfs_ioctl32.h,
              include/linux/falloc.h,
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
new file mode 100644
index 000000000000..d8f70282d247
--- /dev/null
+++ b/Documentation/watch_queue.rst
@@ -0,0 +1,354 @@
+==============================
+General notification mechanism
+==============================
+
+The general notification mechanism is built on top of the standard pipe driver
+whereby it effectively splices notification messages from the kernel into pipes
+opened by userspace.  This can be used in conjunction with::
+
+  * Key/keyring notifications
+
+  * General device event notifications
+
+
+The notifications buffers can be enabled by:
+
+	"General setup"/"General notification queue"
+	(CONFIG_WATCH_QUEUE)
+
+This document has the following sections:
+
+.. contents:: :local:
+
+
+Overview
+========
+
+This facility appears as a pipe that is opened in a special mode.  The pipe's
+internal ring buffer is used to hold messages that are generated by the kernel.
+These messages are then read out by read().  Splice and similar are disabled on
+such pipes due to them wanting to, under some circumstances, revert their
+additions to the ring - which might end up interleaved with notification
+messages.
+
+The owner of the pipe has to tell the kernel which sources it would like to
+watch through that pipe.  Only sources that have been connected to a pipe will
+insert messages into it.  Note that a source may be bound to multiple pipes and
+insert messages into all of them simultaneously.
+
+Filters may also be emplaced on a pipe so that certain source types and
+subevents can be ignored if they're not of interest.
+
+A message will be discarded if there isn't a slot available in the ring or if
+no preallocated message buffer is available.  In both of these cases, read()
+will insert a WATCH_META_LOSS_NOTIFICATION message into the output buffer after
+the last message currently in the buffer has been read.
+
+Note that when producing a notification, the kernel does not wait for the
+consumers to collect it, but rather just continues on.  This means that
+notifications can be generated whilst spinlocks are held and also protects the
+kernel from being held up indefinitely by a userspace malfunction.
+
+
+Message Structure
+=================
+
+Notification messages begin with a short header::
+
+	struct watch_notification {
+		__u32	type:24;
+		__u32	subtype:8;
+		__u32	info;
+	};
+
+"type" indicates the source of the notification record and "subtype" indicates
+the type of record from that source (see the Watch Sources section below).  The
+type may also be "WATCH_TYPE_META".  This is a special record type generated
+internally by the watch queue itself.  There are two subtypes:
+
+  * WATCH_META_REMOVAL_NOTIFICATION
+  * WATCH_META_LOSS_NOTIFICATION
+
+The first indicates that an object on which a watch was installed was removed
+or destroyed and the second indicates that some messages have been lost.
+
+"info" indicates a bunch of things, including:
+
+  * The length of the message in bytes, including the header (mask with
+    WATCH_INFO_LENGTH and shift by WATCH_INFO_LENGTH__SHIFT).  This indicates
+    the size of the record, which may be between 8 and 127 bytes.
+
+  * The watch ID (mask with WATCH_INFO_ID and shift by WATCH_INFO_ID__SHIFT).
+    This indicates that caller's ID of the watch, which may be between 0
+    and 255.  Multiple watches may share a queue, and this provides a means to
+    distinguish them.
+
+  * A type-specific field (WATCH_INFO_TYPE_INFO).  This is set by the
+    notification producer to indicate some meaning specific to the type and
+    subtype.
+
+Everything in info apart from the length can be used for filtering.
+
+The header can be followed by supplementary information.  The format of this is
+at the discretion is defined by the type and subtype.
+
+
+Watch List (Notification Source) API
+====================================
+
+A "watch list" is a list of watchers that are subscribed to a source of
+notifications.  A list may be attached to an object (say a key or a superblock)
+or may be global (say for device events).  From a userspace perspective, a
+non-global watch list is typically referred to by reference to the object it
+belongs to (such as using KEYCTL_NOTIFY and giving it a key serial number to
+watch that specific key).
+
+To manage a watch list, the following functions are provided:
+
+  * ``void init_watch_list(struct watch_list *wlist,
+			   void (*release_watch)(struct watch *wlist));``
+
+    Initialise a watch list.  If ``release_watch`` is not NULL, then this
+    indicates a function that should be called when the watch_list object is
+    destroyed to discard any references the watch list holds on the watched
+    object.
+
+  * ``void remove_watch_list(struct watch_list *wlist);``
+
+    This removes all of the watches subscribed to a watch_list and frees them
+    and then destroys the watch_list object itself.
+
+
+Watch Queue (Notification Output) API
+=====================================
+
+A "watch queue" is the buffer allocated by an application that notification
+records will be written into.  The workings of this are hidden entirely inside
+of the watch_queue device driver, but it is necessary to gain a reference to it
+to set a watch.  These can be managed with:
+
+  * ``struct watch_queue *get_watch_queue(int fd);``
+
+    Since watch queues are indicated to the kernel by the fd of the pipe that
+    implements the buffer, userspace must hand that fd through a system call.
+    This can be used to look up an opaque pointer to the watch queue from the
+    system call.
+
+  * ``void put_watch_queue(struct watch_queue *wqueue);``
+
+    This discards the reference obtained from ``get_watch_queue()``.
+
+
+Watch Subscription API
+======================
+
+A "watch" is a subscription on a watch list, indicating the watch queue, and
+thus the buffer, into which notification records should be written.  The watch
+queue object may also carry filtering rules for that object, as set by
+userspace.  Some parts of the watch struct can be set by the driver::
+
+	struct watch {
+		union {
+			u32		info_id;	/* ID to be OR'd in to info field */
+			...
+		};
+		void			*private;	/* Private data for the watched object */
+		u64			id;		/* Internal identifier */
+		...
+	};
+
+The ``info_id`` value should be an 8-bit number obtained from userspace and
+shifted by WATCH_INFO_ID__SHIFT.  This is OR'd into the WATCH_INFO_ID field of
+struct watch_notification::info when and if the notification is written into
+the associated watch queue buffer.
+
+The ``private`` field is the driver's data associated with the watch_list and
+is cleaned up by the ``watch_list::release_watch()`` method.
+
+The ``id`` field is the source's ID.  Notifications that are posted with a
+different ID are ignored.
+
+The following functions are provided to manage watches:
+
+  * ``void init_watch(struct watch *watch, struct watch_queue *wqueue);``
+
+    Initialise a watch object, setting its pointer to the watch queue, using
+    appropriate barriering to avoid lockdep complaints.
+
+  * ``int add_watch_to_object(struct watch *watch, struct watch_list *wlist);``
+
+    Subscribe a watch to a watch list (notification source).  The
+    driver-settable fields in the watch struct must have been set before this
+    is called.
+
+  * ``int remove_watch_from_object(struct watch_list *wlist,
+				   struct watch_queue *wqueue,
+				   u64 id, false);``
+
+    Remove a watch from a watch list, where the watch must match the specified
+    watch queue (``wqueue``) and object identifier (``id``).  A notification
+    (``WATCH_META_REMOVAL_NOTIFICATION``) is sent to the watch queue to
+    indicate that the watch got removed.
+
+  * ``int remove_watch_from_object(struct watch_list *wlist, NULL, 0, true);``
+
+    Remove all the watches from a watch list.  It is expected that this will be
+    called preparatory to destruction and that the watch list will be
+    inaccessible to new watches by this point.  A notification
+    (``WATCH_META_REMOVAL_NOTIFICATION``) is sent to the watch queue of each
+    subscribed watch to indicate that the watch got removed.
+
+
+Notification Posting API
+========================
+
+To post a notification to watch list so that the subscribed watches can see it,
+the following function should be used::
+
+	void post_watch_notification(struct watch_list *wlist,
+				     struct watch_notification *n,
+				     const struct cred *cred,
+				     u64 id);
+
+The notification should be preformatted and a pointer to the header (``n``)
+should be passed in.  The notification may be larger than this and the size in
+units of buffer slots is noted in ``n->info & WATCH_INFO_LENGTH``.
+
+The ``cred`` struct indicates the credentials of the source (subject) and is
+passed to the LSMs, such as SELinux, to allow or suppress the recording of the
+note in each individual queue according to the credentials of that queue
+(object).
+
+The ``id`` is the ID of the source object (such as the serial number on a key).
+Only watches that have the same ID set in them will see this notification.
+
+
+Watch Sources
+=============
+
+Any particular buffer can be fed from multiple sources.  Sources include:
+
+  * WATCH_TYPE_KEY_NOTIFY
+
+    Notifications of this type indicate changes to keys and keyrings, including
+    the changes of keyring contents or the attributes of keys.
+
+    See Documentation/security/keys/core.rst for more information.
+
+  * WATCH_TYPE_BLOCK_NOTIFY
+
+    Notifications of this type indicate block layer events, such as I/O errors
+    or temporary link loss.  Watches of this type are set on a global queue.
+
+
+Event Filtering
+===============
+
+Once a watch queue has been created, a set of filters can be applied to limit
+the events that are received using::
+
+	struct watch_notification_filter filter = {
+		...
+	};
+	ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter)
+
+The filter description is a variable of type::
+
+	struct watch_notification_filter {
+		__u32	nr_filters;
+		__u32	__reserved;
+		struct watch_notification_type_filter filters[];
+	};
+
+Where "nr_filters" is the number of filters in filters[] and "__reserved"
+should be 0.  The "filters" array has elements of the following type::
+
+	struct watch_notification_type_filter {
+		__u32	type;
+		__u32	info_filter;
+		__u32	info_mask;
+		__u32	subtype_filter[8];
+	};
+
+Where:
+
+  * ``type`` is the event type to filter for and should be something like
+    "WATCH_TYPE_KEY_NOTIFY"
+
+  * ``info_filter`` and ``info_mask`` act as a filter on the info field of the
+    notification record.  The notification is only written into the buffer if::
+
+	(watch.info & info_mask) == info_filter
+
+    This could be used, for example, to ignore events that are not exactly on
+    the watched point in a mount tree.
+
+  * ``subtype_filter`` is a bitmask indicating the subtypes that are of
+    interest.  Bit 0 of subtype_filter[0] corresponds to subtype 0, bit 1 to
+    subtype 1, and so on.
+
+If the argument to the ioctl() is NULL, then the filters will be removed and
+all events from the watched sources will come through.
+
+
+Userspace Code Example
+======================
+
+A buffer is created with something like the following::
+
+	pipe2(fds, O_TMPFILE);
+	ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
+
+It can then be set to receive keyring change notifications and device event
+notifications::
+
+	keyctl(KEYCTL_WATCH_KEY, KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
+	watch_devices(fds[1], 0x2);
+
+The notifications can then be consumed by something like the following::
+
+	static void consumer(int rfd, struct watch_queue_buffer *buf)
+	{
+		unsigned char buffer[128];
+		ssize_t buf_len;
+
+		while (buf_len = read(rfd, buffer, sizeof(buffer)),
+		       buf_len > 0
+		       ) {
+			void *p = buffer;
+			void *end = buffer + buf_len;
+			while (p < end) {
+				union {
+					struct watch_notification n;
+					unsigned char buf1[128];
+				} n;
+				size_t largest, len;
+
+				largest = end - p;
+				if (largest > 128)
+					largest = 128;
+				memcpy(&n, p, largest);
+
+				len = (n->info & WATCH_INFO_LENGTH) >>
+					WATCH_INFO_LENGTH__SHIFT;
+				if (len == 0 || len > largest)
+					return;
+
+				switch (n.n.type) {
+				case WATCH_TYPE_META:
+					got_meta(&n.n);
+				case WATCH_TYPE_KEY_NOTIFY:
+					saw_key_change(&n.n);
+					break;
+				case WATCH_TYPE_BLOCK_NOTIFY:
+					saw_block_event(&n.n);
+					break;
+				case WATCH_TYPE_USB_NOTIFY:
+					saw_usb_event(&n.n);
+					break;
+				}
+
+				p += len;
+			}
+		}
+	}
diff --git a/fs/pipe.c b/fs/pipe.c
index 9cd5cbef9552..099bf4b657dd 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -24,6 +24,7 @@
 #include <linux/syscalls.h>
 #include <linux/fcntl.h>
 #include <linux/memcontrol.h>
+#include <linux/watch_queue.h>
 
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
@@ -407,6 +408,11 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
 		goto out;
 	}
 
+	if (pipe->watch_queue) {
+		ret = -EXDEV;
+		goto out;
+	}
+
 	head = pipe->head;
 	max_usage = pipe->max_usage;
 	mask = pipe->ring_size - 1;
@@ -546,25 +552,37 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct pipe_inode_info *pipe = filp->private_data;
-	int count, head, tail, mask;
+	int count, head, tail, mask, ret;
 
 	switch (cmd) {
-		case FIONREAD:
-			__pipe_lock(pipe);
-			count = 0;
-			head = pipe->head;
-			tail = pipe->tail;
-			mask = pipe->ring_size - 1;
+	case FIONREAD:
+		__pipe_lock(pipe);
+		count = 0;
+		head = pipe->head;
+		tail = pipe->tail;
+		mask = pipe->ring_size - 1;
 
-			while (tail != head) {
-				count += pipe->bufs[tail & mask].len;
-				tail++;
-			}
-			__pipe_unlock(pipe);
+		while (tail != head) {
+			count += pipe->bufs[tail & mask].len;
+			tail++;
+		}
+		__pipe_unlock(pipe);
+
+		return put_user(count, (int __user *)arg);
 
-			return put_user(count, (int __user *)arg);
-		default:
-			return -ENOIOCTLCMD;
+	case IOC_WATCH_QUEUE_SET_SIZE:
+		__pipe_lock(pipe);
+		ret = watch_queue_set_size(pipe, arg);
+		__pipe_unlock(pipe);
+		return ret;
+
+	case IOC_WATCH_QUEUE_SET_FILTER:
+		ret = watch_queue_set_filter(
+			pipe, (struct watch_notification_filter __user *)arg);
+		return ret;
+
+	default:
+		return -ENOIOCTLCMD;
 	}
 }
 
@@ -660,27 +678,27 @@ pipe_fasync(int fd, struct file *filp, int on)
 	return retval;
 }
 
-static unsigned long account_pipe_buffers(struct user_struct *user,
-                                 unsigned long old, unsigned long new)
+unsigned long account_pipe_buffers(struct user_struct *user,
+				   unsigned long old, unsigned long new)
 {
 	return atomic_long_add_return(new - old, &user->pipe_bufs);
 }
 
-static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
+bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 {
 	unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 
 	return soft_limit && user_bufs > soft_limit;
 }
 
-static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
+bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 {
 	unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 
 	return hard_limit && user_bufs > hard_limit;
 }
 
-static bool is_unprivileged_user(void)
+bool pipe_is_unprivileged_user(void)
 {
 	return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 }
@@ -702,12 +720,12 @@ struct pipe_inode_info *alloc_pipe_info(void)
 
 	user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 
-	if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
+	if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
 		user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
 		pipe_bufs = 1;
 	}
 
-	if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
+	if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
 		goto out_revert_acct;
 
 	pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
@@ -718,6 +736,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
 		pipe->r_counter = pipe->w_counter = 1;
 		pipe->max_usage = pipe_bufs;
 		pipe->ring_size = pipe_bufs;
+		pipe->nr_accounted = pipe_bufs;
 		pipe->user = user;
 		mutex_init(&pipe->mutex);
 		return pipe;
@@ -735,7 +754,12 @@ void free_pipe_info(struct pipe_inode_info *pipe)
 {
 	int i;
 
-	(void) account_pipe_buffers(pipe->user, pipe->ring_size, 0);
+	if (pipe->watch_queue) {
+		watch_queue_clear(pipe->watch_queue);
+		put_watch_queue(pipe->watch_queue);
+	}
+
+	(void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
 	free_uid(pipe->user);
 	for (i = 0; i < pipe->ring_size; i++) {
 		struct pipe_buffer *buf = pipe->bufs + i;
@@ -811,6 +835,13 @@ int create_pipe_files(struct file **res, int flags)
 	if (!inode)
 		return -ENFILE;
 
+	if (flags & O_NOTIFICATION_PIPE) {
+		if (watch_queue_init(inode->i_pipe) < 0) {
+			iput(inode);
+			return -ENOMEM;
+		}
+	}
+
 	f = alloc_file_pseudo(inode, pipe_mnt, "",
 				O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 				&pipefifo_fops);
@@ -839,7 +870,7 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags)
 	int error;
 	int fdw, fdr;
 
-	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
+	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
 		return -EINVAL;
 
 	error = create_pipe_files(files, flags);
@@ -1086,42 +1117,12 @@ unsigned int round_pipe_size(unsigned long size)
 }
 
 /*
- * Allocate a new array of pipe buffers and copy the info over. Returns the
- * pipe size if successful, or return -ERROR on error.
+ * Resize the pipe ring to a number of slots.
  */
-static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
 {
 	struct pipe_buffer *bufs;
-	unsigned int size, nr_slots, head, tail, mask, n;
-	unsigned long user_bufs;
-	long ret = 0;
-
-	size = round_pipe_size(arg);
-	nr_slots = size >> PAGE_SHIFT;
-
-	if (!nr_slots)
-		return -EINVAL;
-
-	/*
-	 * If trying to increase the pipe capacity, check that an
-	 * unprivileged user is not trying to exceed various limits
-	 * (soft limit check here, hard limit check just below).
-	 * Decreasing the pipe capacity is always permitted, even
-	 * if the user is currently over a limit.
-	 */
-	if (nr_slots > pipe->ring_size &&
-			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
-		return -EPERM;
-
-	user_bufs = account_pipe_buffers(pipe->user, pipe->ring_size, nr_slots);
-
-	if (nr_slots > pipe->ring_size &&
-			(too_many_pipe_buffers_hard(user_bufs) ||
-			 too_many_pipe_buffers_soft(user_bufs)) &&
-			is_unprivileged_user()) {
-		ret = -EPERM;
-		goto out_revert_acct;
-	}
+	unsigned int head, tail, mask, n;
 
 	/*
 	 * We can shrink the pipe, if arg is greater than the ring occupancy.
@@ -1133,17 +1134,13 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
 	head = pipe->head;
 	tail = pipe->tail;
 	n = pipe_occupancy(pipe->head, pipe->tail);
-	if (nr_slots < n) {
-		ret = -EBUSY;
-		goto out_revert_acct;
-	}
+	if (nr_slots < n)
+		return -EBUSY;
 
 	bufs = kcalloc(nr_slots, sizeof(*bufs),
 		       GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
-	if (unlikely(!bufs)) {
-		ret = -ENOMEM;
-		goto out_revert_acct;
-	}
+	if (unlikely(!bufs))
+		return -ENOMEM;
 
 	/*
 	 * The pipe array wraps around, so just start the new one at zero
@@ -1171,13 +1168,63 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
 	kfree(pipe->bufs);
 	pipe->bufs = bufs;
 	pipe->ring_size = nr_slots;
-	pipe->max_usage = nr_slots;
+	if (pipe->max_usage > nr_slots)
+		pipe->max_usage = nr_slots;
 	pipe->tail = tail;
 	pipe->head = head;
+	return 0;
+}
+
+/*
+ * Allocate a new array of pipe buffers and copy the info over. Returns the
+ * pipe size if successful, or return -ERROR on error.
+ */
+long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+{
+	unsigned long user_bufs;
+	unsigned int nr_slots, size;
+	long ret = 0;
+
+	if (pipe->watch_queue)
+		return -EBUSY;
+
+	size = round_pipe_size(arg);
+	nr_slots = size >> PAGE_SHIFT;
+
+	if (!nr_slots)
+		return -EINVAL;
+
+	/*
+	 * If trying to increase the pipe capacity, check that an
+	 * unprivileged user is not trying to exceed various limits
+	 * (soft limit check here, hard limit check just below).
+	 * Decreasing the pipe capacity is always permitted, even
+	 * if the user is currently over a limit.
+	 */
+	if (nr_slots > pipe->max_usage &&
+			size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+
+	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
+
+	if (nr_slots > pipe->max_usage &&
+			(too_many_pipe_buffers_hard(user_bufs) ||
+			 too_many_pipe_buffers_soft(user_bufs)) &&
+			pipe_is_unprivileged_user()) {
+		ret = -EPERM;
+		goto out_revert_acct;
+	}
+
+	ret = pipe_resize_ring(pipe, nr_slots);
+	if (ret < 0)
+		goto out_revert_acct;
+
+	pipe->max_usage = nr_slots;
+	pipe->nr_accounted = nr_slots;
 	return pipe->max_usage * PAGE_SIZE;
 
 out_revert_acct:
-	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->ring_size);
+	(void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
 	return ret;
 }
 
@@ -1186,9 +1233,15 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
  * location, so checking ->i_pipe is not enough to verify that this is a
  * pipe.
  */
-struct pipe_inode_info *get_pipe_info(struct file *file)
+struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
 {
-	return file->f_op == &pipefifo_fops ? file->private_data : NULL;
+	struct pipe_inode_info *pipe = file->private_data;
+
+	if (file->f_op != &pipefifo_fops || !pipe)
+		return NULL;
+	if (for_splice && pipe->watch_queue)
+		return NULL;
+	return pipe;
 }
 
 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -1196,7 +1249,7 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct pipe_inode_info *pipe;
 	long ret;
 
-	pipe = get_pipe_info(file);
+	pipe = get_pipe_info(file, false);
 	if (!pipe)
 		return -EBADF;
 
diff --git a/fs/splice.c b/fs/splice.c
index c521090a0469..01eb34e0dfac 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1118,8 +1118,8 @@ static long do_splice(struct file *in, loff_t __user *off_in,
 	loff_t offset;
 	long ret;
 
-	ipipe = get_pipe_info(in);
-	opipe = get_pipe_info(out);
+	ipipe = get_pipe_info(in, true);
+	opipe = get_pipe_info(out, true);
 
 	if (ipipe && opipe) {
 		if (off_in || off_out)
@@ -1271,7 +1271,7 @@ static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
 			     unsigned int flags)
 {
-	struct pipe_inode_info *pipe = get_pipe_info(file);
+	struct pipe_inode_info *pipe = get_pipe_info(file, true);
 	struct splice_desc sd = {
 		.total_len = iov_iter_count(iter),
 		.flags = flags,
@@ -1306,7 +1306,7 @@ static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
 	if (flags & SPLICE_F_GIFT)
 		buf_flag = PIPE_BUF_FLAG_GIFT;
 
-	pipe = get_pipe_info(file);
+	pipe = get_pipe_info(file, true);
 	if (!pipe)
 		return -EBADF;
 
@@ -1770,8 +1770,8 @@ static int link_pipe(struct pipe_inode_info *ipipe,
 static long do_tee(struct file *in, struct file *out, size_t len,
 		   unsigned int flags)
 {
-	struct pipe_inode_info *ipipe = get_pipe_info(in);
-	struct pipe_inode_info *opipe = get_pipe_info(out);
+	struct pipe_inode_info *ipipe = get_pipe_info(in, true);
+	struct pipe_inode_info *opipe = get_pipe_info(out, true);
 	int ret = -EINVAL;
 
 	/*
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 44f2245debda..816bc0d3aecd 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -34,6 +34,7 @@ struct pipe_buffer {
  *	@tail: The point of buffer consumption
  *	@max_usage: The maximum number of slots that may be used in the ring
  *	@ring_size: total number of buffers (should be a power of 2)
+ *	@nr_accounted: The amount this pipe accounts for in user->pipe_bufs
  *	@tmp_page: cached released page
  *	@readers: number of current readers of this pipe
  *	@writers: number of current writers of this pipe
@@ -45,6 +46,7 @@ struct pipe_buffer {
  *	@fasync_writers: writer side fasync
  *	@bufs: the circular array of pipe buffers
  *	@user: the user who created this pipe
+ *	@watch_queue: If this pipe is a watch_queue, this is the stuff for that
  **/
 struct pipe_inode_info {
 	struct mutex mutex;
@@ -53,6 +55,7 @@ struct pipe_inode_info {
 	unsigned int tail;
 	unsigned int max_usage;
 	unsigned int ring_size;
+	unsigned int nr_accounted;
 	unsigned int readers;
 	unsigned int writers;
 	unsigned int files;
@@ -64,6 +67,9 @@ struct pipe_inode_info {
 	struct fasync_struct *fasync_writers;
 	struct pipe_buffer *bufs;
 	struct user_struct *user;
+#ifdef CONFIG_WATCH_QUEUE
+	struct watch_queue *watch_queue;
+#endif
 };
 
 /*
@@ -238,9 +244,20 @@ void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
 
 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
 
+#ifdef CONFIG_WATCH_QUEUE
+unsigned long account_pipe_buffers(struct user_struct *user,
+				   unsigned long old, unsigned long new);
+bool too_many_pipe_buffers_soft(unsigned long user_bufs);
+bool too_many_pipe_buffers_hard(unsigned long user_bufs);
+bool pipe_is_unprivileged_user(void);
+#endif
+
 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
+#ifdef CONFIG_WATCH_QUEUE
+int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
+#endif
 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
-struct pipe_inode_info *get_pipe_info(struct file *file);
+struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
 
 int create_pipe_files(struct file **, int);
 unsigned int round_pipe_size(unsigned long size);
diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
new file mode 100644
index 000000000000..b705db0a2868
--- /dev/null
+++ b/include/linux/watch_queue.h
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/* User-mappable watch queue
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See Documentation/watch_queue.rst
+ */
+
+#ifndef _LINUX_WATCH_QUEUE_H
+#define _LINUX_WATCH_QUEUE_H
+
+#include <uapi/linux/watch_queue.h>
+#include <linux/kref.h>
+#include <linux/rcupdate.h>
+
+#ifdef CONFIG_WATCH_QUEUE
+
+struct cred;
+
+struct watch_type_filter {
+	enum watch_notification_type type;
+	__u32		subtype_filter[1];	/* Bitmask of subtypes to filter on */
+	__u32		info_filter;		/* Filter on watch_notification::info */
+	__u32		info_mask;		/* Mask of relevant bits in info_filter */
+};
+
+struct watch_filter {
+	union {
+		struct rcu_head	rcu;
+		unsigned long	type_filter[2];	/* Bitmask of accepted types */
+	};
+	u32			nr_filters;	/* Number of filters */
+	struct watch_type_filter filters[];
+};
+
+struct watch_queue {
+	struct rcu_head		rcu;
+	struct watch_filter __rcu *filter;
+	struct pipe_inode_info	*pipe;		/* The pipe we're using as a buffer */
+	struct hlist_head	watches;	/* Contributory watches */
+	struct page		**notes;	/* Preallocated notifications */
+	unsigned long		*notes_bitmap;	/* Allocation bitmap for notes */
+	struct kref		usage;		/* Object usage count */
+	spinlock_t		lock;
+	unsigned int		nr_notes;	/* Number of notes */
+	unsigned int		nr_pages;	/* Number of pages in notes[] */
+	bool			defunct;	/* T when queues closed */
+};
+
+/*
+ * Representation of a watch on an object.
+ */
+struct watch {
+	union {
+		struct rcu_head	rcu;
+		u32		info_id;	/* ID to be OR'd in to info field */
+	};
+	struct watch_queue __rcu *queue;	/* Queue to post events to */
+	struct hlist_node	queue_node;	/* Link in queue->watches */
+	struct watch_list __rcu	*watch_list;
+	struct hlist_node	list_node;	/* Link in watch_list->watchers */
+	const struct cred	*cred;		/* Creds of the owner of the watch */
+	void			*private;	/* Private data for the watched object */
+	u64			id;		/* Internal identifier */
+	struct kref		usage;		/* Object usage count */
+};
+
+/*
+ * List of watches on an object.
+ */
+struct watch_list {
+	struct rcu_head		rcu;
+	struct hlist_head	watchers;
+	void (*release_watch)(struct watch *);
+	spinlock_t		lock;
+};
+
+extern void __post_watch_notification(struct watch_list *,
+				      struct watch_notification *,
+				      const struct cred *,
+				      u64);
+extern struct watch_queue *get_watch_queue(int);
+extern void put_watch_queue(struct watch_queue *);
+extern void init_watch(struct watch *, struct watch_queue *);
+extern int add_watch_to_object(struct watch *, struct watch_list *);
+extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
+extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int);
+extern long watch_queue_set_filter(struct pipe_inode_info *,
+				   struct watch_notification_filter __user *);
+extern int watch_queue_init(struct pipe_inode_info *);
+extern void watch_queue_clear(struct watch_queue *);
+
+static inline void init_watch_list(struct watch_list *wlist,
+				   void (*release_watch)(struct watch *))
+{
+	INIT_HLIST_HEAD(&wlist->watchers);
+	spin_lock_init(&wlist->lock);
+	wlist->release_watch = release_watch;
+}
+
+static inline void post_watch_notification(struct watch_list *wlist,
+					   struct watch_notification *n,
+					   const struct cred *cred,
+					   u64 id)
+{
+	if (unlikely(wlist))
+		__post_watch_notification(wlist, n, cred, id);
+}
+
+static inline void remove_watch_list(struct watch_list *wlist, u64 id)
+{
+	if (wlist) {
+		remove_watch_from_object(wlist, NULL, id, true);
+		kfree_rcu(wlist, rcu);
+	}
+}
+
+/**
+ * watch_sizeof - Calculate the information part of the size of a watch record,
+ * given the structure size.
+ */
+#define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)
+
+#endif
+
+#endif /* _LINUX_WATCH_QUEUE_H */
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 9df72227f515..3a5790f1f05d 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -4,9 +4,13 @@
 
 #include <linux/types.h>
 #include <linux/fcntl.h>
+#include <linux/ioctl.h>
 
 #define O_NOTIFICATION_PIPE	O_EXCL	/* Parameter to pipe2() selecting notification pipe */
 
+#define IOC_WATCH_QUEUE_SET_SIZE	_IO('W', 0x60)	/* Set the size in pages */
+#define IOC_WATCH_QUEUE_SET_FILTER	_IO('W', 0x61)	/* Set the filter */
+
 enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */
 	WATCH_TYPE__NR		= 1
@@ -41,6 +45,22 @@ struct watch_notification {
 #define WATCH_INFO_FLAG_7	0x00800000
 };
 
+/*
+ * Notification filtering rules (IOC_WATCH_QUEUE_SET_FILTER).
+ */
+struct watch_notification_type_filter {
+	__u32	type;			/* Type to apply filter to */
+	__u32	info_filter;		/* Filter on watch_notification::info */
+	__u32	info_mask;		/* Mask of relevant bits in info_filter */
+	__u32	subtype_filter[8];	/* Bitmask of subtypes to filter on */
+};
+
+struct watch_notification_filter {
+	__u32	nr_filters;		/* Number of filters */
+	__u32	__reserved;		/* Must be 0 */
+	struct watch_notification_type_filter filters[];
+};
+
 
 /*
  * Extended watch removal notification.  This is used optionally if the type
diff --git a/init/Kconfig b/init/Kconfig
index b4daad2bac23..eb177b78f560 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -358,6 +358,18 @@ config POSIX_MQUEUE_SYSCTL
 	depends on SYSCTL
 	default y
 
+config WATCH_QUEUE
+	bool "General notification queue"
+	default n
+	help
+
+	  This is a general notification queue for the kernel to pass events to
+	  userspace by splicing them into pipes.  It can be used in conjunction
+	  with watches for key/keyring change notifications and device
+	  notifications.
+
+	  See Documentation/watch_queue.rst
+
 config CROSS_MEMORY_ATTACH
 	bool "Enable process_vm_readv/writev syscalls"
 	depends on MMU
diff --git a/kernel/Makefile b/kernel/Makefile
index daad787fb795..067975dd2e0c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
 
 obj-$(CONFIG_HAS_IOMEM) += iomem.o
 obj-$(CONFIG_RSEQ) += rseq.o
+obj-$(CONFIG_WATCH_QUEUE) += watch_queue.o
 
 obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
 KASAN_SANITIZE_stackleak.o := n
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
new file mode 100644
index 000000000000..b73fbfe0d467
--- /dev/null
+++ b/kernel/watch_queue.c
@@ -0,0 +1,656 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Watch queue and general notification mechanism, built on pipes
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See Documentation/watch_queue.rst
+ */
+
+#define pr_fmt(fmt) "watchq: " fmt
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/printk.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/poll.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/file.h>
+#include <linux/security.h>
+#include <linux/cred.h>
+#include <linux/sched/signal.h>
+#include <linux/watch_queue.h>
+#include <linux/pipe_fs_i.h>
+
+MODULE_DESCRIPTION("Watch queue");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+#define WATCH_QUEUE_NOTE_SIZE 128
+#define WATCH_QUEUE_NOTES_PER_PAGE (PAGE_SIZE / WATCH_QUEUE_NOTE_SIZE)
+
+static void watch_queue_pipe_buf_release(struct pipe_inode_info *pipe,
+					 struct pipe_buffer *buf)
+{
+	struct watch_queue *wqueue = (struct watch_queue *)buf->private;
+	struct page *page;
+	unsigned int bit;
+
+	/* We need to work out which note within the page this refers to, but
+	 * the note might have been maximum size, so merely ANDing the offset
+	 * off doesn't work.  OTOH, the note must've been more than zero size.
+	 */
+	bit = buf->offset + buf->len;
+	if ((bit & (WATCH_QUEUE_NOTE_SIZE - 1)) == 0)
+		bit -= WATCH_QUEUE_NOTE_SIZE;
+	bit /= WATCH_QUEUE_NOTE_SIZE;
+
+	page = buf->page;
+	bit += page->index;
+
+	set_bit(bit, wqueue->notes_bitmap);
+}
+
+static int watch_queue_pipe_buf_steal(struct pipe_inode_info *pipe,
+				      struct pipe_buffer *buf)
+{
+	return -1; /* No. */
+}
+
+/* New data written to a pipe may be appended to a buffer with this type. */
+static const struct pipe_buf_operations watch_queue_pipe_buf_ops = {
+	.confirm	= generic_pipe_buf_confirm,
+	.release	= watch_queue_pipe_buf_release,
+	.steal		= watch_queue_pipe_buf_steal,
+	.get		= generic_pipe_buf_get,
+};
+
+/*
+ * Post a notification to a watch queue.
+ */
+static bool post_one_notification(struct watch_queue *wqueue,
+				  struct watch_notification *n)
+{
+	void *p;
+	struct pipe_inode_info *pipe = wqueue->pipe;
+	struct pipe_buffer *buf;
+	struct page *page;
+	unsigned int head, tail, mask, note, offset, len;
+	bool done = false;
+
+	if (!pipe)
+		return false;
+
+	spin_lock_irq(&pipe->wait.lock);
+
+	if (wqueue->defunct)
+		goto out;
+
+	mask = pipe->ring_size - 1;
+	head = pipe->head;
+	tail = pipe->tail;
+	if (pipe_full(head, tail, pipe->ring_size))
+		goto lost;
+
+	note = find_first_bit(wqueue->notes_bitmap, wqueue->nr_notes);
+	if (note >= wqueue->nr_notes)
+		goto lost;
+
+	page = wqueue->notes[note / WATCH_QUEUE_NOTES_PER_PAGE];
+	offset = note % WATCH_QUEUE_NOTES_PER_PAGE * WATCH_QUEUE_NOTE_SIZE;
+	get_page(page);
+	len = n->info & WATCH_INFO_LENGTH;
+	p = kmap_atomic(page);
+	memcpy(p + offset, n, len);
+	kunmap_atomic(p);
+
+	buf = &pipe->bufs[head & mask];
+	buf->page = page;
+	buf->private = (unsigned long)wqueue;
+	buf->ops = &watch_queue_pipe_buf_ops;
+	buf->offset = offset;
+	buf->len = len;
+	buf->flags = 0;
+	pipe->head = head + 1;
+
+	if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
+		spin_unlock_irq(&pipe->wait.lock);
+		BUG();
+	}
+	wake_up_interruptible_sync_poll_locked(&pipe->wait, EPOLLIN | EPOLLRDNORM);
+	done = true;
+
+out:
+	spin_unlock_irq(&pipe->wait.lock);
+	if (done)
+		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+	return done;
+
+lost:
+	goto out;
+}
+
+/*
+ * Apply filter rules to a notification.
+ */
+static bool filter_watch_notification(const struct watch_filter *wf,
+				      const struct watch_notification *n)
+{
+	const struct watch_type_filter *wt;
+	unsigned int st_bits = sizeof(wt->subtype_filter[0]) * 8;
+	unsigned int st_index = n->subtype / st_bits;
+	unsigned int st_bit = 1U << (n->subtype % st_bits);
+	int i;
+
+	if (!test_bit(n->type, wf->type_filter))
+		return false;
+
+	for (i = 0; i < wf->nr_filters; i++) {
+		wt = &wf->filters[i];
+		if (n->type == wt->type &&
+		    (wt->subtype_filter[st_index] & st_bit) &&
+		    (n->info & wt->info_mask) == wt->info_filter)
+			return true;
+	}
+
+	return false; /* If there is a filter, the default is to reject. */
+}
+
+/**
+ * __post_watch_notification - Post an event notification
+ * @wlist: The watch list to post the event to.
+ * @n: The notification record to post.
+ * @cred: The creds of the process that triggered the notification.
+ * @id: The ID to match on the watch.
+ *
+ * Post a notification of an event into a set of watch queues and let the users
+ * know.
+ *
+ * The size of the notification should be set in n->info & WATCH_INFO_LENGTH and
+ * should be in units of sizeof(*n).
+ */
+void __post_watch_notification(struct watch_list *wlist,
+			       struct watch_notification *n,
+			       const struct cred *cred,
+			       u64 id)
+{
+	const struct watch_filter *wf;
+	struct watch_queue *wqueue;
+	struct watch *watch;
+
+	if (((n->info & WATCH_INFO_LENGTH) >> WATCH_INFO_LENGTH__SHIFT) == 0) {
+		WARN_ON(1);
+		return;
+	}
+
+	rcu_read_lock();
+
+	hlist_for_each_entry_rcu(watch, &wlist->watchers, list_node) {
+		if (watch->id != id)
+			continue;
+		n->info &= ~WATCH_INFO_ID;
+		n->info |= watch->info_id;
+
+		wqueue = rcu_dereference(watch->queue);
+		wf = rcu_dereference(wqueue->filter);
+		if (wf && !filter_watch_notification(wf, n))
+			continue;
+
+		if (security_post_notification(watch->cred, cred, n) < 0)
+			continue;
+
+		post_one_notification(wqueue, n);
+	}
+
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL(__post_watch_notification);
+
+/*
+ * Allocate sufficient pages to preallocation for the requested number of
+ * notifications.
+ */
+long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
+{
+	struct watch_queue *wqueue = pipe->watch_queue;
+	struct page **pages;
+	unsigned long *bitmap;
+	unsigned long user_bufs;
+	unsigned int bmsize;
+	int ret, i, nr_pages;
+
+	if (!wqueue)
+		return -ENODEV;
+	if (wqueue->notes)
+		return -EBUSY;
+
+	if (nr_notes < 1 ||
+	    nr_notes > 512) /* TODO: choose a better hard limit */
+		return -EINVAL;
+
+	nr_pages = (nr_notes + WATCH_QUEUE_NOTES_PER_PAGE - 1);
+	nr_pages /= WATCH_QUEUE_NOTES_PER_PAGE;
+	user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_pages);
+
+	if (nr_pages > pipe->max_usage &&
+	    (too_many_pipe_buffers_hard(user_bufs) ||
+	     too_many_pipe_buffers_soft(user_bufs)) &&
+	    pipe_is_unprivileged_user()) {
+		ret = -EPERM;
+		goto error;
+	}
+
+	ret = pipe_resize_ring(pipe, nr_notes);
+	if (ret < 0)
+		goto error;
+
+	pages = kcalloc(sizeof(struct page *), nr_pages, GFP_KERNEL);
+	if (!pages)
+		goto error;
+
+	for (i = 0; i < nr_pages; i++) {
+		pages[i] = alloc_page(GFP_KERNEL);
+		if (!pages[i])
+			goto error_p;
+		pages[i]->index = i * WATCH_QUEUE_NOTES_PER_PAGE;
+	}
+
+	bmsize = (nr_notes + BITS_PER_LONG - 1) / BITS_PER_LONG;
+	bmsize *= sizeof(unsigned long);
+	bitmap = kmalloc(bmsize, GFP_KERNEL);
+	if (!bitmap)
+		goto error_p;
+
+	memset(bitmap, 0xff, bmsize);
+	wqueue->notes = pages;
+	wqueue->notes_bitmap = bitmap;
+	wqueue->nr_pages = nr_pages;
+	wqueue->nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
+	return 0;
+
+error_p:
+	for (i = 0; i < nr_pages; i++)
+		__free_page(pages[i]);
+	kfree(pages);
+error:
+	(void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
+	return ret;
+}
+
+/*
+ * Set the filter on a watch queue.
+ */
+long watch_queue_set_filter(struct pipe_inode_info *pipe,
+			    struct watch_notification_filter __user *_filter)
+{
+	struct watch_notification_type_filter *tf;
+	struct watch_notification_filter filter;
+	struct watch_type_filter *q;
+	struct watch_filter *wfilter;
+	struct watch_queue *wqueue = pipe->watch_queue;
+	int ret, nr_filter = 0, i;
+
+	if (!wqueue)
+		return -ENODEV;
+
+	if (!_filter) {
+		/* Remove the old filter */
+		wfilter = NULL;
+		goto set;
+	}
+
+	/* Grab the user's filter specification */
+	if (copy_from_user(&filter, _filter, sizeof(filter)) != 0)
+		return -EFAULT;
+	if (filter.nr_filters == 0 ||
+	    filter.nr_filters > 16 ||
+	    filter.__reserved != 0)
+		return -EINVAL;
+
+	tf = memdup_user(_filter->filters, filter.nr_filters * sizeof(*tf));
+	if (IS_ERR(tf))
+		return PTR_ERR(tf);
+
+	ret = -EINVAL;
+	for (i = 0; i < filter.nr_filters; i++) {
+		if ((tf[i].info_filter & ~tf[i].info_mask) ||
+		    tf[i].info_mask & WATCH_INFO_LENGTH)
+			goto err_filter;
+		/* Ignore any unknown types */
+		if (tf[i].type >= sizeof(wfilter->type_filter) * 8)
+			continue;
+		nr_filter++;
+	}
+
+	/* Now we need to build the internal filter from only the relevant
+	 * user-specified filters.
+	 */
+	ret = -ENOMEM;
+	wfilter = kzalloc(struct_size(wfilter, filters, nr_filter), GFP_KERNEL);
+	if (!wfilter)
+		goto err_filter;
+	wfilter->nr_filters = nr_filter;
+
+	q = wfilter->filters;
+	for (i = 0; i < filter.nr_filters; i++) {
+		if (tf[i].type >= sizeof(wfilter->type_filter) * BITS_PER_LONG)
+			continue;
+
+		q->type			= tf[i].type;
+		q->info_filter		= tf[i].info_filter;
+		q->info_mask		= tf[i].info_mask;
+		q->subtype_filter[0]	= tf[i].subtype_filter[0];
+		__set_bit(q->type, wfilter->type_filter);
+		q++;
+	}
+
+	kfree(tf);
+set:
+	pipe_lock(pipe);
+	rcu_swap_protected(wqueue->filter, wfilter,
+			   lockdep_is_held(&pipe->mutex));
+	pipe_unlock(pipe);
+	if (wfilter)
+		kfree_rcu(wfilter, rcu);
+	return 0;
+
+err_filter:
+	kfree(tf);
+	return ret;
+}
+
+static void __put_watch_queue(struct kref *kref)
+{
+	struct watch_queue *wqueue =
+		container_of(kref, struct watch_queue, usage);
+	struct watch_filter *wfilter;
+	int i;
+
+	for (i = 0; i < wqueue->nr_pages; i++)
+		__free_page(wqueue->notes[i]);
+
+	wfilter = rcu_access_pointer(wqueue->filter);
+	if (wfilter)
+		kfree_rcu(wfilter, rcu);
+	kfree_rcu(wqueue, rcu);
+}
+
+/**
+ * put_watch_queue - Dispose of a ref on a watchqueue.
+ * @wqueue: The watch queue to unref.
+ */
+void put_watch_queue(struct watch_queue *wqueue)
+{
+	kref_put(&wqueue->usage, __put_watch_queue);
+}
+EXPORT_SYMBOL(put_watch_queue);
+
+static void free_watch(struct rcu_head *rcu)
+{
+	struct watch *watch = container_of(rcu, struct watch, rcu);
+
+	put_watch_queue(rcu_access_pointer(watch->queue));
+	put_cred(watch->cred);
+}
+
+static void __put_watch(struct kref *kref)
+{
+	struct watch *watch = container_of(kref, struct watch, usage);
+
+	call_rcu(&watch->rcu, free_watch);
+}
+
+/*
+ * Discard a watch.
+ */
+static void put_watch(struct watch *watch)
+{
+	kref_put(&watch->usage, __put_watch);
+}
+
+/**
+ * init_watch_queue - Initialise a watch
+ * @watch: The watch to initialise.
+ * @wqueue: The queue to assign.
+ *
+ * Initialise a watch and set the watch queue.
+ */
+void init_watch(struct watch *watch, struct watch_queue *wqueue)
+{
+	kref_init(&watch->usage);
+	INIT_HLIST_NODE(&watch->list_node);
+	INIT_HLIST_NODE(&watch->queue_node);
+	rcu_assign_pointer(watch->queue, wqueue);
+}
+
+/**
+ * add_watch_to_object - Add a watch on an object to a watch list
+ * @watch: The watch to add
+ * @wlist: The watch list to add to
+ *
+ * @watch->queue must have been set to point to the queue to post notifications
+ * to and the watch list of the object to be watched.  @watch->cred must also
+ * have been set to the appropriate credentials and a ref taken on them.
+ *
+ * The caller must pin the queue and the list both and must hold the list
+ * locked against racing watch additions/removals.
+ */
+int add_watch_to_object(struct watch *watch, struct watch_list *wlist)
+{
+	struct watch_queue *wqueue = rcu_access_pointer(watch->queue);
+	struct watch *w;
+
+	hlist_for_each_entry(w, &wlist->watchers, list_node) {
+		struct watch_queue *wq = rcu_access_pointer(w->queue);
+		if (wqueue == wq && watch->id == w->id)
+			return -EBUSY;
+	}
+
+	watch->cred = get_current_cred();
+	rcu_assign_pointer(watch->watch_list, wlist);
+
+	spin_lock_bh(&wqueue->lock);
+	kref_get(&wqueue->usage);
+	hlist_add_head(&watch->queue_node, &wqueue->watches);
+	spin_unlock_bh(&wqueue->lock);
+
+	hlist_add_head(&watch->list_node, &wlist->watchers);
+	return 0;
+}
+EXPORT_SYMBOL(add_watch_to_object);
+
+/**
+ * remove_watch_from_object - Remove a watch or all watches from an object.
+ * @wlist: The watch list to remove from
+ * @wq: The watch queue of interest (ignored if @all is true)
+ * @id: The ID of the watch to remove (ignored if @all is true)
+ * @all: True to remove all objects
+ *
+ * Remove a specific watch or all watches from an object.  A notification is
+ * sent to the watcher to tell them that this happened.
+ */
+int remove_watch_from_object(struct watch_list *wlist, struct watch_queue *wq,
+			     u64 id, bool all)
+{
+	struct watch_notification_removal n;
+	struct watch_queue *wqueue;
+	struct watch *watch;
+	int ret = -EBADSLT;
+
+	rcu_read_lock();
+
+again:
+	spin_lock(&wlist->lock);
+	hlist_for_each_entry(watch, &wlist->watchers, list_node) {
+		if (all ||
+		    (watch->id == id && rcu_access_pointer(watch->queue) == wq))
+			goto found;
+	}
+	spin_unlock(&wlist->lock);
+	goto out;
+
+found:
+	ret = 0;
+	hlist_del_init_rcu(&watch->list_node);
+	rcu_assign_pointer(watch->watch_list, NULL);
+	spin_unlock(&wlist->lock);
+
+	/* We now own the reference on watch that used to belong to wlist. */
+
+	n.watch.type = WATCH_TYPE_META;
+	n.watch.subtype = WATCH_META_REMOVAL_NOTIFICATION;
+	n.watch.info = watch->info_id | watch_sizeof(n.watch);
+	n.id = id;
+	if (id != 0)
+		n.watch.info = watch->info_id | watch_sizeof(n);
+
+	wqueue = rcu_dereference(watch->queue);
+
+	/* We don't need the watch list lock for the next bit as RCU is
+	 * protecting *wqueue from deallocation.
+	 */
+	if (wqueue) {
+		post_one_notification(wqueue, &n.watch);
+
+		spin_lock_bh(&wqueue->lock);
+
+		if (!hlist_unhashed(&watch->queue_node)) {
+			hlist_del_init_rcu(&watch->queue_node);
+			put_watch(watch);
+		}
+
+		spin_unlock_bh(&wqueue->lock);
+	}
+
+	if (wlist->release_watch) {
+		void (*release_watch)(struct watch *);
+
+		release_watch = wlist->release_watch;
+		rcu_read_unlock();
+		(*release_watch)(watch);
+		rcu_read_lock();
+	}
+	put_watch(watch);
+
+	if (all && !hlist_empty(&wlist->watchers))
+		goto again;
+out:
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL(remove_watch_from_object);
+
+/*
+ * Remove all the watches that are contributory to a queue.  This has the
+ * potential to race with removal of the watches by the destruction of the
+ * objects being watched or with the distribution of notifications.
+ */
+void watch_queue_clear(struct watch_queue *wqueue)
+{
+	struct watch_list *wlist;
+	struct watch *watch;
+	bool release;
+
+	rcu_read_lock();
+	spin_lock_bh(&wqueue->lock);
+
+	/* Prevent new additions and prevent notifications from happening */
+	wqueue->defunct = true;
+
+	while (!hlist_empty(&wqueue->watches)) {
+		watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);
+		hlist_del_init_rcu(&watch->queue_node);
+		/* We now own a ref on the watch. */
+		spin_unlock_bh(&wqueue->lock);
+
+		/* We can't do the next bit under the queue lock as we need to
+		 * get the list lock - which would cause a deadlock if someone
+		 * was removing from the opposite direction at the same time or
+		 * posting a notification.
+		 */
+		wlist = rcu_dereference(watch->watch_list);
+		if (wlist) {
+			void (*release_watch)(struct watch *);
+
+			spin_lock(&wlist->lock);
+
+			release = !hlist_unhashed(&watch->list_node);
+			if (release) {
+				hlist_del_init_rcu(&watch->list_node);
+				rcu_assign_pointer(watch->watch_list, NULL);
+
+				/* We now own a second ref on the watch. */
+			}
+
+			release_watch = wlist->release_watch;
+			spin_unlock(&wlist->lock);
+
+			if (release) {
+				if (release_watch) {
+					rcu_read_unlock();
+					/* This might need to call dput(), so
+					 * we have to drop all the locks.
+					 */
+					(*release_watch)(watch);
+					rcu_read_lock();
+				}
+				put_watch(watch);
+			}
+		}
+
+		put_watch(watch);
+		spin_lock_bh(&wqueue->lock);
+	}
+
+	spin_unlock_bh(&wqueue->lock);
+	rcu_read_unlock();
+}
+
+/**
+ * get_watch_queue - Get a watch queue from its file descriptor.
+ * @fd: The fd to query.
+ */
+struct watch_queue *get_watch_queue(int fd)
+{
+	struct pipe_inode_info *pipe;
+	struct watch_queue *wqueue = ERR_PTR(-EINVAL);
+	struct fd f;
+
+	f = fdget(fd);
+	if (f.file) {
+		pipe = get_pipe_info(f.file, false);
+		if (pipe && pipe->watch_queue) {
+			wqueue = pipe->watch_queue;
+			kref_get(&wqueue->usage);
+		}
+		fdput(f);
+	}
+
+	return wqueue;
+}
+EXPORT_SYMBOL(get_watch_queue);
+
+/*
+ * Initialise a watch queue
+ */
+int watch_queue_init(struct pipe_inode_info *pipe)
+{
+	struct watch_queue *wqueue;
+
+	wqueue = kzalloc(sizeof(*wqueue), GFP_KERNEL);
+	if (!wqueue)
+		return -ENOMEM;
+
+	wqueue->pipe = pipe;
+	kref_init(&wqueue->usage);
+	spin_lock_init(&wqueue->lock);
+	INIT_HLIST_HEAD(&wqueue->watches);
+
+	pipe->watch_queue = wqueue;
+	return 0;
+}


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 06/14] keys: Add a notification facility [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (4 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 13:36 ` [RFC PATCH 07/14] Add sample notification program " David Howells
                   ` (8 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add a key/keyring change notification facility whereby notifications about
changes in key and keyring content and attributes can be received.

Firstly, an event queue needs to be created:

	pipe2(fds, O_NOTIFICATION_PIPE);
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);

then a notification can be set up to report notifications via that queue:

	struct watch_notification_filter filter = {
		.nr_filters = 1,
		.filters = {
			[0] = {
				.type = WATCH_TYPE_KEY_NOTIFY,
				.subtype_filter[0] = UINT_MAX,
			},
		},
	};
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
	keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);

After that, records will be placed into the queue when events occur in
which keys are changed in some way.  Records are of the following format:

	struct key_notification {
		struct watch_notification watch;
		__u32	key_id;
		__u32	aux;
	} *n;

Where:

	n->watch.type will be WATCH_TYPE_KEY_NOTIFY.

	n->watch.subtype will indicate the type of event, such as
	NOTIFY_KEY_REVOKED.

	n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
	record.

	n->watch.info & WATCH_INFO_ID will be the second argument to
	keyctl_watch_key(), shifted.

	n->key will be the ID of the affected key.

	n->aux will hold subtype-dependent information, such as the key
	being linked into the keyring specified by n->key in the case of
	NOTIFY_KEY_LINKED.

Note that it is permissible for event records to be of variable length -
or, at least, the length may be dependent on the subtype.  Note also that
the queue can be shared between multiple notifications of various types.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/security/keys/core.rst |   58 ++++++++++++++++++++
 include/linux/key.h                  |    3 +
 include/uapi/linux/keyctl.h          |    2 +
 include/uapi/linux/watch_queue.h     |   28 +++++++++-
 security/keys/Kconfig                |    9 +++
 security/keys/compat.c               |    3 +
 security/keys/gc.c                   |    5 ++
 security/keys/internal.h             |   30 ++++++++++
 security/keys/key.c                  |   38 ++++++++-----
 security/keys/keyctl.c               |   99 +++++++++++++++++++++++++++++++++-
 security/keys/keyring.c              |   20 ++++---
 security/keys/request_key.c          |    4 +
 12 files changed, 271 insertions(+), 28 deletions(-)

diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
index d6d8b0b756b6..957179f8cea9 100644
--- a/Documentation/security/keys/core.rst
+++ b/Documentation/security/keys/core.rst
@@ -833,6 +833,7 @@ The keyctl syscall functions are:
      A process must have search permission on the key for this function to be
      successful.
 
+
   *  Compute a Diffie-Hellman shared secret or public key::
 
 	long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params,
@@ -1026,6 +1027,63 @@ The keyctl syscall functions are:
      written into the output buffer.  Verification returns 0 on success.
 
 
+  *  Watch a key or keyring for changes::
+
+	long keyctl(KEYCTL_WATCH_KEY, key_serial_t key, int queue_fd,
+		    const struct watch_notification_filter *filter);
+
+     This will set or remove a watch for changes on the specified key or
+     keyring.
+
+     "key" is the ID of the key to be watched.
+
+     "queue_fd" is a file descriptor referring to an open "/dev/watch_queue"
+     which manages the buffer into which notifications will be delivered.
+
+     "filter" is either NULL to remove a watch or a filter specification to
+     indicate what events are required from the key.
+
+     See Documentation/watch_queue.rst for more information.
+
+     Note that only one watch may be emplaced for any particular { key,
+     queue_fd } combination.
+
+     Notification records look like::
+
+	struct key_notification {
+		struct watch_notification watch;
+		__u32	key_id;
+		__u32	aux;
+	};
+
+     In this, watch::type will be "WATCH_TYPE_KEY_NOTIFY" and subtype will be
+     one of::
+
+	NOTIFY_KEY_INSTANTIATED
+	NOTIFY_KEY_UPDATED
+	NOTIFY_KEY_LINKED
+	NOTIFY_KEY_UNLINKED
+	NOTIFY_KEY_CLEARED
+	NOTIFY_KEY_REVOKED
+	NOTIFY_KEY_INVALIDATED
+	NOTIFY_KEY_SETATTR
+
+     Where these indicate a key being instantiated/rejected, updated, a link
+     being made in a keyring, a link being removed from a keyring, a keyring
+     being cleared, a key being revoked, a key being invalidated or a key
+     having one of its attributes changed (user, group, perm, timeout,
+     restriction).
+
+     If a watched key is deleted, a basic watch_notification will be issued
+     with "type" set to WATCH_TYPE_META and "subtype" set to
+     watch_meta_removal_notification.  The watchpoint ID will be set in the
+     "info" field.
+
+     This needs to be configured by enabling:
+
+	"Provide key/keyring change notifications" (KEY_NOTIFICATIONS)
+
+
 Kernel Services
 ===============
 
diff --git a/include/linux/key.h b/include/linux/key.h
index 6cf8e71cf8b7..b99b40db08fc 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -176,6 +176,9 @@ struct key {
 		struct list_head graveyard_link;
 		struct rb_node	serial_node;
 	};
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	struct watch_list	*watchers;	/* Entities watching this key for changes */
+#endif
 	struct rw_semaphore	sem;		/* change vs change sem */
 	struct key_user		*user;		/* owner of this key */
 	void			*security;	/* security data for this key */
diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index ed3d5893830d..4c8884eea808 100644
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -69,6 +69,7 @@
 #define KEYCTL_RESTRICT_KEYRING		29	/* Restrict keys allowed to link to a keyring */
 #define KEYCTL_MOVE			30	/* Move keys between keyrings */
 #define KEYCTL_CAPABILITIES		31	/* Find capabilities of keyrings subsystem */
+#define KEYCTL_WATCH_KEY		32	/* Watch a key or ring of keys for changes */
 
 /* keyctl structures */
 struct keyctl_dh_params {
@@ -130,5 +131,6 @@ struct keyctl_pkey_params {
 #define KEYCTL_CAPS0_MOVE		0x80 /* KEYCTL_MOVE supported */
 #define KEYCTL_CAPS1_NS_KEYRING_NAME	0x01 /* Keyring names are per-user_namespace */
 #define KEYCTL_CAPS1_NS_KEY_TAG		0x02 /* Key indexing can include a namespace tag */
+#define KEYCTL_CAPS1_NOTIFICATIONS	0x04 /* Keys generate watchable notifications */
 
 #endif /*  _LINUX_KEYCTL_H */
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 3a5790f1f05d..c3d8320b5d3a 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -13,7 +13,8 @@
 
 enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */
-	WATCH_TYPE__NR		= 1
+	WATCH_TYPE_KEY_NOTIFY	= 1,	/* Key change event notification */
+	WATCH_TYPE__NR		= 2
 };
 
 enum watch_meta_notification_subtype {
@@ -75,4 +76,29 @@ struct watch_notification_removal {
 	__u64	id;		/* Type-dependent identifier */
 };
 
+/*
+ * Type of key/keyring change notification.
+ */
+enum key_notification_subtype {
+	NOTIFY_KEY_INSTANTIATED	= 0, /* Key was instantiated (aux is error code) */
+	NOTIFY_KEY_UPDATED	= 1, /* Key was updated */
+	NOTIFY_KEY_LINKED	= 2, /* Key (aux) was added to watched keyring */
+	NOTIFY_KEY_UNLINKED	= 3, /* Key (aux) was removed from watched keyring */
+	NOTIFY_KEY_CLEARED	= 4, /* Keyring was cleared */
+	NOTIFY_KEY_REVOKED	= 5, /* Key was revoked */
+	NOTIFY_KEY_INVALIDATED	= 6, /* Key was invalidated */
+	NOTIFY_KEY_SETATTR	= 7, /* Key's attributes got changed */
+};
+
+/*
+ * Key/keyring notification record.
+ * - watch.type = WATCH_TYPE_KEY_NOTIFY
+ * - watch.subtype = enum key_notification_type
+ */
+struct key_notification {
+	struct watch_notification watch;
+	__u32	key_id;		/* The key/keyring affected */
+	__u32	aux;		/* Per-type auxiliary data */
+};
+
 #endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index dd313438fecf..20791a556b58 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -120,3 +120,12 @@ config KEY_DH_OPERATIONS
 	 in the kernel.
 
 	 If you are unsure as to whether this is required, answer N.
+
+config KEY_NOTIFICATIONS
+	bool "Provide key/keyring change notifications"
+	depends on KEYS && WATCH_QUEUE
+	help
+	  This option provides support for getting change notifications on keys
+	  and keyrings on which the caller has View permission.  This makes use
+	  of the /dev/watch_queue misc device to handle the notification
+	  buffer and provides KEYCTL_WATCH_KEY to enable/disable watches.
diff --git a/security/keys/compat.c b/security/keys/compat.c
index 9bcc404131aa..ac5a4fd0d7ea 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -161,6 +161,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
 	case KEYCTL_CAPABILITIES:
 		return keyctl_capabilities(compat_ptr(arg2), arg3);
 
+	case KEYCTL_WATCH_KEY:
+		return keyctl_watch_key(arg2, arg3, arg4);
+
 	default:
 		return -EOPNOTSUPP;
 	}
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 671dd730ecfc..3c90807476eb 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -131,6 +131,11 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
 		kdebug("- %u", key->serial);
 		key_check(key);
 
+#ifdef CONFIG_KEY_NOTIFICATIONS
+		remove_watch_list(key->watchers, key->serial);
+		key->watchers = NULL;
+#endif
+
 		/* Throw away the key data if the key is instantiated */
 		if (state == KEY_IS_POSITIVE && key->type->destroy)
 			key->type->destroy(key);
diff --git a/security/keys/internal.h b/security/keys/internal.h
index c039373488bd..240f55c7b4a2 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -15,6 +15,7 @@
 #include <linux/task_work.h>
 #include <linux/keyctl.h>
 #include <linux/refcount.h>
+#include <linux/watch_queue.h>
 #include <linux/compat.h>
 
 struct iovec;
@@ -97,7 +98,8 @@ extern int __key_link_begin(struct key *keyring,
 			    const struct keyring_index_key *index_key,
 			    struct assoc_array_edit **_edit);
 extern int __key_link_check_live_key(struct key *keyring, struct key *key);
-extern void __key_link(struct key *key, struct assoc_array_edit **_edit);
+extern void __key_link(struct key *keyring, struct key *key,
+		       struct assoc_array_edit **_edit);
 extern void __key_link_end(struct key *keyring,
 			   const struct keyring_index_key *index_key,
 			   struct assoc_array_edit *edit);
@@ -181,6 +183,23 @@ extern int key_task_permission(const key_ref_t key_ref,
 			       const struct cred *cred,
 			       key_perm_t perm);
 
+static inline void notify_key(struct key *key,
+			      enum key_notification_subtype subtype, u32 aux)
+{
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	struct key_notification n = {
+		.watch.type	= WATCH_TYPE_KEY_NOTIFY,
+		.watch.subtype	= subtype,
+		.watch.info	= watch_sizeof(n),
+		.key_id		= key_serial(key),
+		.aux		= aux,
+	};
+
+	post_watch_notification(key->watchers, &n.watch, current_cred(),
+				n.key_id);
+#endif
+}
+
 /*
  * Check to see whether permission is granted to use a key in the desired way.
  */
@@ -331,6 +350,15 @@ static inline long keyctl_pkey_e_d_s(int op,
 
 extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen);
 
+#ifdef CONFIG_KEY_NOTIFICATIONS
+extern long keyctl_watch_key(key_serial_t, int, int);
+#else
+static inline long keyctl_watch_key(key_serial_t key_id, int watch_fd, int watch_id)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 /*
  * Debugging key validation
  */
diff --git a/security/keys/key.c b/security/keys/key.c
index 764f4c57913e..83e8d7c4bb6f 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -443,6 +443,7 @@ static int __key_instantiate_and_link(struct key *key,
 			/* mark the key as being instantiated */
 			atomic_inc(&key->user->nikeys);
 			mark_key_instantiated(key, 0);
+			notify_key(key, NOTIFY_KEY_INSTANTIATED, 0);
 
 			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 				awaken = 1;
@@ -452,7 +453,7 @@ static int __key_instantiate_and_link(struct key *key,
 				if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
 					set_bit(KEY_FLAG_KEEP, &key->flags);
 
-				__key_link(key, _edit);
+				__key_link(keyring, key, _edit);
 			}
 
 			/* disable the authorisation key */
@@ -600,6 +601,7 @@ int key_reject_and_link(struct key *key,
 		/* mark the key as being negatively instantiated */
 		atomic_inc(&key->user->nikeys);
 		mark_key_instantiated(key, -error);
+		notify_key(key, NOTIFY_KEY_INSTANTIATED, -error);
 		key->expiry = ktime_get_real_seconds() + timeout;
 		key_schedule_gc(key->expiry + key_gc_delay);
 
@@ -610,7 +612,7 @@ int key_reject_and_link(struct key *key,
 
 		/* and link it into the destination keyring */
 		if (keyring && link_ret == 0)
-			__key_link(key, &edit);
+			__key_link(keyring, key, &edit);
 
 		/* disable the authorisation key */
 		if (authkey)
@@ -763,9 +765,11 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
 	down_write(&key->sem);
 
 	ret = key->type->update(key, prep);
-	if (ret == 0)
+	if (ret == 0) {
 		/* Updating a negative key positively instantiates it */
 		mark_key_instantiated(key, 0);
+		notify_key(key, NOTIFY_KEY_UPDATED, 0);
+	}
 
 	up_write(&key->sem);
 
@@ -1013,9 +1017,11 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 	down_write(&key->sem);
 
 	ret = key->type->update(key, &prep);
-	if (ret == 0)
+	if (ret == 0) {
 		/* Updating a negative key positively instantiates it */
 		mark_key_instantiated(key, 0);
+		notify_key(key, NOTIFY_KEY_UPDATED, 0);
+	}
 
 	up_write(&key->sem);
 
@@ -1047,15 +1053,17 @@ void key_revoke(struct key *key)
 	 *   instantiated
 	 */
 	down_write_nested(&key->sem, 1);
-	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
-	    key->type->revoke)
-		key->type->revoke(key);
-
-	/* set the death time to no more than the expiry time */
-	time = ktime_get_real_seconds();
-	if (key->revoked_at == 0 || key->revoked_at > time) {
-		key->revoked_at = time;
-		key_schedule_gc(key->revoked_at + key_gc_delay);
+	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags)) {
+		notify_key(key, NOTIFY_KEY_REVOKED, 0);
+		if (key->type->revoke)
+			key->type->revoke(key);
+
+		/* set the death time to no more than the expiry time */
+		time = ktime_get_real_seconds();
+		if (key->revoked_at == 0 || key->revoked_at > time) {
+			key->revoked_at = time;
+			key_schedule_gc(key->revoked_at + key_gc_delay);
+		}
 	}
 
 	up_write(&key->sem);
@@ -1077,8 +1085,10 @@ void key_invalidate(struct key *key)
 
 	if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
 		down_write_nested(&key->sem, 1);
-		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
+		if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
+			notify_key(key, NOTIFY_KEY_INVALIDATED, 0);
 			key_schedule_gc_links();
+		}
 		up_write(&key->sem);
 	}
 }
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 9b898c969558..6610649514fb 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -37,7 +37,9 @@ static const unsigned char keyrings_capabilities[2] = {
 	       KEYCTL_CAPS0_MOVE
 	       ),
 	[1] = (KEYCTL_CAPS1_NS_KEYRING_NAME |
-	       KEYCTL_CAPS1_NS_KEY_TAG),
+	       KEYCTL_CAPS1_NS_KEY_TAG |
+	       (IS_ENABLED(CONFIG_KEY_NOTIFICATIONS)	? KEYCTL_CAPS1_NOTIFICATIONS : 0)
+	       ),
 };
 
 static int key_get_type_from_user(char *type,
@@ -970,6 +972,7 @@ long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
 	if (group != (gid_t) -1)
 		key->gid = gid;
 
+	notify_key(key, NOTIFY_KEY_SETATTR, 0);
 	ret = 0;
 
 error_put:
@@ -1020,6 +1023,7 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
 	/* if we're not the sysadmin, we can only change a key that we own */
 	if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
 		key->perm = perm;
+		notify_key(key, NOTIFY_KEY_SETATTR, 0);
 		ret = 0;
 	}
 
@@ -1411,10 +1415,12 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 okay:
 	key = key_ref_to_ptr(key_ref);
 	ret = 0;
-	if (test_bit(KEY_FLAG_KEEP, &key->flags))
+	if (test_bit(KEY_FLAG_KEEP, &key->flags)) {
 		ret = -EPERM;
-	else
+	} else {
 		key_set_timeout(key, timeout);
+		notify_key(key, NOTIFY_KEY_SETATTR, 0);
+	}
 	key_put(key);
 
 error:
@@ -1688,6 +1694,90 @@ long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
 	return ret;
 }
 
+#ifdef CONFIG_KEY_NOTIFICATIONS
+/*
+ * Watch for changes to a key.
+ *
+ * The caller must have View permission to watch a key or keyring.
+ */
+long keyctl_watch_key(key_serial_t id, int watch_queue_fd, int watch_id)
+{
+	struct watch_queue *wqueue;
+	struct watch_list *wlist = NULL;
+	struct watch *watch = NULL;
+	struct key *key;
+	key_ref_t key_ref;
+	long ret;
+
+	if (watch_id < -1 || watch_id > 0xff)
+		return -EINVAL;
+
+	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_VIEW);
+	if (IS_ERR(key_ref))
+		return PTR_ERR(key_ref);
+	key = key_ref_to_ptr(key_ref);
+
+	wqueue = get_watch_queue(watch_queue_fd);
+	if (IS_ERR(wqueue)) {
+		ret = PTR_ERR(wqueue);
+		goto err_key;
+	}
+
+	if (watch_id >= 0) {
+		ret = -ENOMEM;
+		if (!key->watchers) {
+			wlist = kzalloc(sizeof(*wlist), GFP_KERNEL);
+			if (!wlist)
+				goto err_wqueue;
+			init_watch_list(wlist, NULL);
+		}
+
+		watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+		if (!watch)
+			goto err_wlist;
+
+		init_watch(watch, wqueue);
+		watch->id	= key->serial;
+		watch->info_id	= (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+		ret = security_watch_key(key);
+		if (ret < 0)
+			goto err_watch;
+
+		down_write(&key->sem);
+		if (!key->watchers) {
+			key->watchers = wlist;
+			wlist = NULL;
+		}
+
+		ret = add_watch_to_object(watch, key->watchers);
+		up_write(&key->sem);
+
+		if (ret == 0)
+			watch = NULL;
+	} else {
+		ret = -EBADSLT;
+		if (key->watchers) {
+			down_write(&key->sem);
+			ret = remove_watch_from_object(key->watchers,
+						       wqueue, key_serial(key),
+						       false);
+			up_write(&key->sem);
+		}
+	}
+
+err_watch:
+	kfree(watch);
+err_wlist:
+	kfree(wlist);
+err_wqueue:
+	put_watch_queue(wqueue);
+err_key:
+	key_put(key);
+	return ret;
+}
+#endif /* CONFIG_KEY_NOTIFICATIONS */
+
 /*
  * Get keyrings subsystem capabilities.
  */
@@ -1857,6 +1947,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	case KEYCTL_CAPABILITIES:
 		return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);
 
+	case KEYCTL_WATCH_KEY:
+		return keyctl_watch_key((key_serial_t)arg2, (int)arg3, (int)arg4);
+
 	default:
 		return -EOPNOTSUPP;
 	}
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index febf36c6ddc5..40a0dcdfda44 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1060,12 +1060,14 @@ int keyring_restrict(key_ref_t keyring_ref, const char *type,
 	down_write(&keyring->sem);
 	down_write(&keyring_serialise_restrict_sem);
 
-	if (keyring->restrict_link)
+	if (keyring->restrict_link) {
 		ret = -EEXIST;
-	else if (keyring_detect_restriction_cycle(keyring, restrict_link))
+	} else if (keyring_detect_restriction_cycle(keyring, restrict_link)) {
 		ret = -EDEADLK;
-	else
+	} else {
 		keyring->restrict_link = restrict_link;
+		notify_key(keyring, NOTIFY_KEY_SETATTR, 0);
+	}
 
 	up_write(&keyring_serialise_restrict_sem);
 	up_write(&keyring->sem);
@@ -1366,12 +1368,14 @@ int __key_link_check_live_key(struct key *keyring, struct key *key)
  * holds at most one link to any given key of a particular type+description
  * combination.
  */
-void __key_link(struct key *key, struct assoc_array_edit **_edit)
+void __key_link(struct key *keyring, struct key *key,
+		struct assoc_array_edit **_edit)
 {
 	__key_get(key);
 	assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
 	assoc_array_apply_edit(*_edit);
 	*_edit = NULL;
+	notify_key(keyring, NOTIFY_KEY_LINKED, key_serial(key));
 }
 
 /*
@@ -1455,7 +1459,7 @@ int key_link(struct key *keyring, struct key *key)
 	if (ret == 0)
 		ret = __key_link_check_live_key(keyring, key);
 	if (ret == 0)
-		__key_link(key, &edit);
+		__key_link(keyring, key, &edit);
 
 error_end:
 	__key_link_end(keyring, &key->index_key, edit);
@@ -1487,7 +1491,7 @@ static int __key_unlink_begin(struct key *keyring, struct key *key,
 	struct assoc_array_edit *edit;
 
 	BUG_ON(*_edit != NULL);
-	
+
 	edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
 				  &key->index_key);
 	if (IS_ERR(edit))
@@ -1507,6 +1511,7 @@ static void __key_unlink(struct key *keyring, struct key *key,
 			 struct assoc_array_edit **_edit)
 {
 	assoc_array_apply_edit(*_edit);
+	notify_key(keyring, NOTIFY_KEY_UNLINKED, key_serial(key));
 	*_edit = NULL;
 	key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
 }
@@ -1625,7 +1630,7 @@ int key_move(struct key *key,
 		goto error;
 
 	__key_unlink(from_keyring, key, &from_edit);
-	__key_link(key, &to_edit);
+	__key_link(to_keyring, key, &to_edit);
 error:
 	__key_link_end(to_keyring, &key->index_key, to_edit);
 	__key_unlink_end(from_keyring, key, from_edit);
@@ -1659,6 +1664,7 @@ int keyring_clear(struct key *keyring)
 	} else {
 		if (edit)
 			assoc_array_apply_edit(edit);
+		notify_key(keyring, NOTIFY_KEY_CLEARED, 0);
 		key_payload_reserve(keyring, 0);
 		ret = 0;
 	}
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 957b9e3e1492..e1b9f1a80676 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -418,7 +418,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
 		goto key_already_present;
 
 	if (dest_keyring)
-		__key_link(key, &edit);
+		__key_link(dest_keyring, key, &edit);
 
 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
@@ -437,7 +437,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
 	if (dest_keyring) {
 		ret = __key_link_check_live_key(dest_keyring, key);
 		if (ret == 0)
-			__key_link(key, &edit);
+			__key_link(dest_keyring, key, &edit);
 		__key_link_end(dest_keyring, &ctx->index_key, edit);
 		if (ret < 0)
 			goto link_check_failed;


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 07/14] Add sample notification program [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (5 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 06/14] keys: Add a notification facility " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 13:36 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
                   ` (7 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

The sample program is run like:

	./samples/watch_queue/watch_test

and watches "/" for mount changes and the current session keyring for key
changes:

	# keyctl add user a a @s
	1035096409
	# keyctl unlink 1035096409 @s

producing:

	# ./watch_test
	read() = 16
	NOTIFY[000]: ty=000001 sy=02 i=00000110
	KEY 2ffc2e5d change=2[linked] aux=1035096409
	read() = 16
	NOTIFY[000]: ty=000001 sy=02 i=00000110
	KEY 2ffc2e5d change=3[unlinked] aux=1035096409

Other events may be produced, such as with a failing disk:

	read() = 22
	NOTIFY[000]: ty=000003 sy=02 i=00000416
	USB 3-7.7 dev-reset e=0 r=0
	read() = 24
	NOTIFY[000]: ty=000002 sy=06 i=00000418
	BLOCK 00800050 e=6[critical medium] s=64000ef8

This corresponds to:

	blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0

in dmesg.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 samples/Kconfig                  |    7 +
 samples/Makefile                 |    1 
 samples/watch_queue/Makefile     |    7 +
 samples/watch_queue/watch_test.c |  183 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 198 insertions(+)
 create mode 100644 samples/watch_queue/Makefile
 create mode 100644 samples/watch_queue/watch_test.c

diff --git a/samples/Kconfig b/samples/Kconfig
index c8dacb4dda80..d0761f29ccb0 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -169,4 +169,11 @@ config SAMPLE_VFS
 	  as mount API and statx().  Note that this is restricted to the x86
 	  arch whilst it accesses system calls that aren't yet in all arches.
 
+config SAMPLE_WATCH_QUEUE
+	bool "Build example /dev/watch_queue notification consumer"
+	depends on HEADERS_INSTALL
+	help
+	  Build example userspace program to use the new mount_notify(),
+	  sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
+
 endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 7d6e4ca28d69..a61a39047d02 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/
 obj-$(CONFIG_VIDEO_PCI_SKELETON)	+= v4l/
 obj-y					+= vfio-mdev/
 subdir-$(CONFIG_SAMPLE_VFS)		+= vfs
+subdir-$(CONFIG_SAMPLE_WATCH_QUEUE)	+= watch_queue
diff --git a/samples/watch_queue/Makefile b/samples/watch_queue/Makefile
new file mode 100644
index 000000000000..eec00dd0a8df
--- /dev/null
+++ b/samples/watch_queue/Makefile
@@ -0,0 +1,7 @@
+# List of programs to build
+hostprogs-y := watch_test
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_watch_test.o += -I$(objtree)/usr/include
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
new file mode 100644
index 000000000000..8925593bdb9b
--- /dev/null
+++ b/samples/watch_queue/watch_test.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Use /dev/watch_queue to watch for notifications.
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define _GNU_SOURCE
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <limits.h>
+#include <linux/watch_queue.h>
+#include <linux/unistd.h>
+#include <linux/keyctl.h>
+
+#ifndef KEYCTL_WATCH_KEY
+#define KEYCTL_WATCH_KEY -1
+#endif
+#ifndef __NR_watch_devices
+#define __NR_watch_devices -1
+#endif
+
+#define BUF_SIZE 256
+
+static long keyctl_watch_key(int key, int watch_fd, int watch_id)
+{
+	return syscall(__NR_keyctl, KEYCTL_WATCH_KEY, key, watch_fd, watch_id);
+}
+
+static const char *key_subtypes[256] = {
+	[NOTIFY_KEY_INSTANTIATED]	= "instantiated",
+	[NOTIFY_KEY_UPDATED]		= "updated",
+	[NOTIFY_KEY_LINKED]		= "linked",
+	[NOTIFY_KEY_UNLINKED]		= "unlinked",
+	[NOTIFY_KEY_CLEARED]		= "cleared",
+	[NOTIFY_KEY_REVOKED]		= "revoked",
+	[NOTIFY_KEY_INVALIDATED]	= "invalidated",
+	[NOTIFY_KEY_SETATTR]		= "setattr",
+};
+
+static void saw_key_change(struct watch_notification *n, size_t len)
+{
+	struct key_notification *k = (struct key_notification *)n;
+
+	if (len != sizeof(struct key_notification)) {
+		fprintf(stderr, "Incorrect key message length\n");
+		return;
+	}
+
+	printf("KEY %08x change=%u[%s] aux=%u\n",
+	       k->key_id, n->subtype, key_subtypes[n->subtype], k->aux);
+}
+
+/*
+ * Consume and display events.
+ */
+static void consumer(int fd)
+{
+	unsigned char buffer[4096], *p, *end;
+	union {
+		struct watch_notification n;
+		unsigned char buf1[128];
+	} n;
+	ssize_t buf_len;
+
+	for (;;) {
+		buf_len = read(fd, buffer, sizeof(buffer));
+		if (buf_len == -1) {
+			perror("read");
+			exit(1);
+		}
+
+		if (buf_len == 0) {
+			printf("-- END --\n");
+			return;
+		}
+
+		if (buf_len > sizeof(buffer)) {
+			fprintf(stderr, "Read buffer overrun: %zd\n", buf_len);
+			return;
+		}
+
+		printf("read() = %zd\n", buf_len);
+
+		p = buffer;
+		end = buffer + buf_len;
+		while (p < end) {
+			size_t largest, len;
+
+			largest = end - p;
+			if (largest > 128)
+				largest = 128;
+			if (largest < sizeof(struct watch_notification)) {
+				fprintf(stderr, "Short message header: %zu\n", largest);
+				return;
+			}
+			memcpy(&n, p, largest);
+
+			printf("NOTIFY[%03zx]: ty=%06x sy=%02x i=%08x\n",
+			       p - buffer, n.n.type, n.n.subtype, n.n.info);
+
+			len = n.n.info & WATCH_INFO_LENGTH;
+			if (len < sizeof(n.n) || len > largest) {
+				fprintf(stderr, "Bad message length: %zu/%zu\n", len, largest);
+				exit(1);
+			}
+
+			switch (n.n.type) {
+			case WATCH_TYPE_META:
+				switch (n.n.subtype) {
+				case WATCH_META_REMOVAL_NOTIFICATION:
+					printf("REMOVAL of watchpoint %08x\n",
+					       (n.n.info & WATCH_INFO_ID) >>
+					       WATCH_INFO_ID__SHIFT);
+					break;
+				default:
+					printf("other meta record\n");
+					break;
+				}
+				break;
+			case WATCH_TYPE_KEY_NOTIFY:
+				saw_key_change(&n.n, len);
+				break;
+			default:
+				printf("other type\n");
+				break;
+			}
+
+			p += len;
+		}
+	}
+}
+
+static struct watch_notification_filter filter = {
+	.nr_filters	= 1,
+	.filters = {
+		[0]	= {
+			.type			= WATCH_TYPE_KEY_NOTIFY,
+			.subtype_filter[0]	= UINT_MAX,
+		},
+	},
+};
+
+int main(int argc, char **argv)
+{
+	int pipefd[2], fd;
+
+	if (pipe2(pipefd, O_NOTIFICATION_PIPE) == -1) {
+		perror("pipe2");
+		exit(1);
+	}
+	fd = pipefd[0];
+
+	if (ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, BUF_SIZE) == -1) {
+		perror("/dev/watch_queue(size)");
+		exit(1);
+	}
+
+	if (ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter) == -1) {
+		perror("/dev/watch_queue(filter)");
+		exit(1);
+	}
+
+	if (keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fd, 0x01) == -1) {
+		perror("keyctl");
+		exit(1);
+	}
+
+	if (keyctl_watch_key(KEY_SPEC_USER_KEYRING, fd, 0x02) == -1) {
+		perror("keyctl");
+		exit(1);
+	}
+
+	consumer(fd);
+	exit(0);
+}


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (6 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 07/14] Add sample notification program " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 18:15   ` Andy Lutomirski
  2019-11-07 18:23   ` David Howells
  2019-11-07 13:36 ` [RFC PATCH 09/14] pipe: Add notification lossage handling " David Howells
                   ` (6 subsequent siblings)
  14 siblings, 2 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Allow a buffer to be marked such that read() must return the entire buffer
in one go or return ENOBUFS.  Multiple buffers can be amalgamated into a
single read, but a short read will occur if the next "whole" buffer won't
fit.

This is useful for watch queue notifications to make sure we don't split a
notification across multiple reads, especially given that we need to
fabricate an overrun record under some circumstances - and that isn't in
the buffers.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/pipe.c                        |    8 +++++++-
 include/linux/pipe_fs_i.h        |    1 +
 kernel/watch_queue.c             |    2 +-
 samples/watch_queue/watch_test.c |    2 +-
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 099bf4b657dd..588355c24ee0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -298,8 +298,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 			size_t written;
 			int error;
 
-			if (chars > total_len)
+			if (chars > total_len) {
+				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
+					if (ret == 0)
+						ret = -ENOBUFS;
+					break;
+				}
 				chars = total_len;
+			}
 
 			error = pipe_buf_confirm(pipe, buf);
 			if (error) {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 816bc0d3aecd..a19d60a06869 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -8,6 +8,7 @@
 #define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
 #define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
 #define PIPE_BUF_FLAG_PACKET	0x08	/* read() as a packet */
+#define PIPE_BUF_FLAG_WHOLE	0x10	/* read() must return entire buffer or error */
 
 /**
  *	struct pipe_buffer - a linux kernel pipe buffer
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index b73fbfe0d467..b1d30296e29b 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -115,7 +115,7 @@ static bool post_one_notification(struct watch_queue *wqueue,
 	buf->ops = &watch_queue_pipe_buf_ops;
 	buf->offset = offset;
 	buf->len = len;
-	buf->flags = 0;
+	buf->flags = PIPE_BUF_FLAG_WHOLE;
 	pipe->head = head + 1;
 
 	if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 8925593bdb9b..f6fb6e813551 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -63,7 +63,7 @@ static void saw_key_change(struct watch_notification *n, size_t len)
  */
 static void consumer(int fd)
 {
-	unsigned char buffer[4096], *p, *end;
+	unsigned char buffer[433], *p, *end;
 	union {
 		struct watch_notification n;
 		unsigned char buf1[128];


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 09/14] pipe: Add notification lossage handling [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (7 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 13:36 ` [RFC PATCH 10/14] Add a general, global device notification watch list " David Howells
                   ` (5 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add handling for loss of notifications by having read() insert a
loss-notification message after it has read the pipe buffer that was last
in the ring when the loss occurred.

Lossage can come about either by running out of notification descriptors or
by running out of space in the pipe ring.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/pipe.c                        |   28 ++++++++++++++++++++++++++++
 include/linux/pipe_fs_i.h        |    7 +++++++
 kernel/watch_queue.c             |    2 ++
 samples/watch_queue/watch_test.c |    3 +++
 4 files changed, 40 insertions(+)

diff --git a/fs/pipe.c b/fs/pipe.c
index 588355c24ee0..955a4ec1dc50 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -292,6 +292,30 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 		unsigned int tail = pipe->tail;
 		unsigned int mask = pipe->ring_size - 1;
 
+#ifdef CONFIG_WATCH_QUEUE
+		if (pipe->note_loss) {
+			struct watch_notification n;
+
+			if (total_len < 8) {
+				if (ret == 0)
+					ret = -ENOBUFS;
+				break;
+			}
+
+			n.type = WATCH_TYPE_META;
+			n.subtype = WATCH_META_LOSS_NOTIFICATION;
+			n.info = watch_sizeof(n);
+			if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
+				if (ret == 0)
+					ret = -EFAULT;
+				break;
+			}
+			ret += sizeof(n);
+			total_len -= sizeof(n);
+			pipe->note_loss = false;
+		}
+#endif
+
 		if (!pipe_empty(head, tail)) {
 			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 			size_t chars = buf->len;
@@ -334,6 +358,10 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 				bool wake;
 				pipe_buf_release(pipe, buf);
 				spin_lock_irq(&pipe->wait.lock);
+#ifdef CONFIG_WATCH_QUEUE
+				if (buf->flags & PIPE_BUF_FLAG_LOSS)
+					pipe->note_loss = true;
+#endif
 				tail++;
 				pipe->tail = tail;
 				do_wakeup = 1;
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index a19d60a06869..5be6fdf5134d 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -9,6 +9,9 @@
 #define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
 #define PIPE_BUF_FLAG_PACKET	0x08	/* read() as a packet */
 #define PIPE_BUF_FLAG_WHOLE	0x10	/* read() must return entire buffer or error */
+#ifdef CONFIG_WATCH_QUEUE
+#define PIPE_BUF_FLAG_LOSS	0x20	/* Message loss happened after this buffer */
+#endif
 
 /**
  *	struct pipe_buffer - a linux kernel pipe buffer
@@ -33,6 +36,7 @@ struct pipe_buffer {
  *	@wait: reader/writer wait point in case of empty/full pipe
  *	@head: The point of buffer production
  *	@tail: The point of buffer consumption
+ *	@note_loss: The next read() should insert a data-lost message
  *	@max_usage: The maximum number of slots that may be used in the ring
  *	@ring_size: total number of buffers (should be a power of 2)
  *	@nr_accounted: The amount this pipe accounts for in user->pipe_bufs
@@ -56,6 +60,9 @@ struct pipe_inode_info {
 	unsigned int tail;
 	unsigned int max_usage;
 	unsigned int ring_size;
+#ifdef CONFIG_WATCH_QUEUE
+	bool note_loss;
+#endif
 	unsigned int nr_accounted;
 	unsigned int readers;
 	unsigned int writers;
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index b1d30296e29b..b34ad1b170a4 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -132,6 +132,8 @@ static bool post_one_notification(struct watch_queue *wqueue,
 	return done;
 
 lost:
+	buf = &pipe->bufs[(head - 1) & mask];
+	buf->flags |= PIPE_BUF_FLAG_LOSS;
 	goto out;
 }
 
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index f6fb6e813551..58e826109ecc 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -120,6 +120,9 @@ static void consumer(int fd)
 					       (n.n.info & WATCH_INFO_ID) >>
 					       WATCH_INFO_ID__SHIFT);
 					break;
+				case WATCH_META_LOSS_NOTIFICATION:
+					printf("-- LOSS --\n");
+					break;
 				default:
 					printf("other meta record\n");
 					break;


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 10/14] Add a general, global device notification watch list [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (8 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 09/14] pipe: Add notification lossage handling " David Howells
@ 2019-11-07 13:36 ` " David Howells
  2019-11-07 13:37 ` [RFC PATCH 11/14] block: Add block layer notifications " David Howells
                   ` (4 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:36 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Create a general, global watch list that can be used for the posting of
device notification events, for such things as device attachment,
detachment and errors on sources such as block devices and USB devices.
This can be enabled with:

	CONFIG_DEVICE_NOTIFICATIONS

To add a watch on this list, an event queue must be created and configured:

        pipe2(fds, O_NOTIFICATION_PIPE);
        ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);

and then a watch can be placed upon it using a system call:

        watch_devices(fds[1], 12, 0);

Unless the application wants to receive all events, it should employ
appropriate filters.  For example, to receive just USB notifications, it
could do:

	struct watch_notification_filter filter = {
		.nr_filters = 1,
		.filters = {
			[0] = {
				.type = WATCH_TYPE_USB_NOTIFY,
				.subtype_filter[0] = UINT_MAX;
			},
		},
	};
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/watch_queue.rst               |   22 ++++++-
 arch/alpha/kernel/syscalls/syscall.tbl      |    1 
 arch/arm/tools/syscall.tbl                  |    1 
 arch/arm64/include/asm/unistd.h             |    2 -
 arch/arm64/include/asm/unistd32.h           |    2 +
 arch/ia64/kernel/syscalls/syscall.tbl       |    1 
 arch/m68k/kernel/syscalls/syscall.tbl       |    1 
 arch/microblaze/kernel/syscalls/syscall.tbl |    1 
 arch/mips/kernel/syscalls/syscall_n32.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_n64.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_o32.tbl   |    1 
 arch/parisc/kernel/syscalls/syscall.tbl     |    1 
 arch/powerpc/kernel/syscalls/syscall.tbl    |    1 
 arch/s390/kernel/syscalls/syscall.tbl       |    1 
 arch/sh/kernel/syscalls/syscall.tbl         |    1 
 arch/sparc/kernel/syscalls/syscall.tbl      |    1 
 arch/x86/entry/syscalls/syscall_32.tbl      |    1 
 arch/x86/entry/syscalls/syscall_64.tbl      |    1 
 arch/xtensa/kernel/syscalls/syscall.tbl     |    1 
 drivers/base/Kconfig                        |    9 +++
 drivers/base/Makefile                       |    1 
 drivers/base/watch.c                        |   90 +++++++++++++++++++++++++++
 include/linux/device.h                      |    7 ++
 include/linux/syscalls.h                    |    1 
 include/uapi/asm-generic/unistd.h           |    4 +
 kernel/sys_ni.c                             |    1 
 26 files changed, 152 insertions(+), 3 deletions(-)
 create mode 100644 drivers/base/watch.c

diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index d8f70282d247..ed592700be0e 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -223,6 +223,25 @@ The ``id`` is the ID of the source object (such as the serial number on a key).
 Only watches that have the same ID set in them will see this notification.
 
 
+Global Device Watch List
+========================
+
+There is a global watch list that hardware generated events, such as device
+connection, disconnection, failure and error can be posted upon.  It must be
+enabled using::
+
+	CONFIG_DEVICE_NOTIFICATIONS
+
+Watchpoints are set in userspace using the device_notify(2) system call.
+Within the kernel events are posted upon it using::
+
+	void post_device_notification(struct watch_notification *n, u64 id);
+
+where ``n`` is the formatted notification record to post.  ``id`` is an
+identifier that can be used to direct to specific watches, but it should be 0
+for general use on this queue.
+
+
 Watch Sources
 =============
 
@@ -238,7 +257,8 @@ Any particular buffer can be fed from multiple sources.  Sources include:
   * WATCH_TYPE_BLOCK_NOTIFY
 
     Notifications of this type indicate block layer events, such as I/O errors
-    or temporary link loss.  Watches of this type are set on a global queue.
+    or temporary link loss.  Watches of this type are set on the global device
+    watch list.
 
 
 Event Filtering
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 728fe028c02c..8e841d8e4c22 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -475,3 +475,4 @@
 543	common	fspick				sys_fspick
 544	common	pidfd_open			sys_pidfd_open
 # 545 reserved for clone3
+546	common	watch_devices			sys_watch_devices
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 6da7dc4d79cc..0f080cf44cc9 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -449,3 +449,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 435	common	clone3				sys_clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 2629a68b8724..368761302768 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -38,7 +38,7 @@
 #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		436
+#define __NR_compat_syscalls		437
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 94ab29cf4f00..b5310789ce7a 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -879,6 +879,8 @@ __SYSCALL(__NR_fspick, sys_fspick)
 __SYSCALL(__NR_pidfd_open, sys_pidfd_open)
 #define __NR_clone3 435
 __SYSCALL(__NR_clone3, sys_clone3)
+#define __NR_watch_devices 436
+__SYSCALL(__NR_watch_devices, sys_watch_devices)
 
 /*
  * 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 36d5faf4c86c..2f33f5db2fed 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -356,3 +356,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 # 435 reserved for clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index a88a285a0e5f..83e4e8784b88 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -435,3 +435,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 # 435 reserved for clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 09b0cd7dab0a..9a70a3be3b7b 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -441,3 +441,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 435	common	clone3				sys_clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index e7c5ab38e403..b39527fc32c9 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -374,3 +374,4 @@
 433	n32	fspick				sys_fspick
 434	n32	pidfd_open			sys_pidfd_open
 435	n32	clone3				__sys_clone3
+436	n32	watch_devices			sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 13cd66581f3b..a7f0c5e71768 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -350,3 +350,4 @@
 433	n64	fspick				sys_fspick
 434	n64	pidfd_open			sys_pidfd_open
 435	n64	clone3				__sys_clone3
+436	n64	watch_devices			sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 353539ea4140..6f378288598c 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -423,3 +423,4 @@
 433	o32	fspick				sys_fspick
 434	o32	pidfd_open			sys_pidfd_open
 435	o32	clone3				__sys_clone3
+436	o32	watch_devices			sys_watch_devices
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 285ff516150c..b64bbafa5919 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -433,3 +433,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 435	common	clone3				sys_clone3_wrapper
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 43f736ed47f2..0a503239ab5c 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -517,3 +517,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 435	nospu	clone3				ppc_clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 3054e9c035a3..19b43c0d928a 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -438,3 +438,4 @@
 433  common	fspick			sys_fspick			sys_fspick
 434  common	pidfd_open		sys_pidfd_open			sys_pidfd_open
 435  common	clone3			sys_clone3			sys_clone3
+436  common	watch_devices		sys_watch_devices		sys_watch_devices
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index b5ed26c4c005..b454e07c9372 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -438,3 +438,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 # 435 reserved for clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 8c8cc7537fb2..8ef43c27457e 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -481,3 +481,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 # 435 reserved for clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 3fe02546aed3..9b225c0d5240 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -440,3 +440,4 @@
 433	i386	fspick			sys_fspick			__ia32_sys_fspick
 434	i386	pidfd_open		sys_pidfd_open			__ia32_sys_pidfd_open
 435	i386	clone3			sys_clone3			__ia32_sys_clone3
+436	i386	watch_devices		sys_watch_devices		__ia32_sys_watch_devices
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index c29976eca4a8..29293d103829 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -357,6 +357,7 @@
 433	common	fspick			__x64_sys_fspick
 434	common	pidfd_open		__x64_sys_pidfd_open
 435	common	clone3			__x64_sys_clone3/ptregs
+436	common	watch_devices		__x64_sys_watch_devices
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 25f4de729a6d..243fa18b8d1e 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -406,3 +406,4 @@
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
 435	common	clone3				sys_clone3
+436	common	watch_devices			sys_watch_devices
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 28b92e3cc570..e37d37684132 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -1,6 +1,15 @@
 # SPDX-License-Identifier: GPL-2.0
 menu "Generic Driver Options"
 
+config DEVICE_NOTIFICATIONS
+	bool "Provide device event notifications"
+	depends on WATCH_QUEUE
+	help
+	  This option provides support for getting hardware event notifications
+	  on devices, buses and interfaces.  This makes use of the
+	  /dev/watch_queue misc device to handle the notification buffer.
+	  device_notify(2) is used to set/remove watches.
+
 config UEVENT_HELPER
 	bool "Support for uevent helper"
 	help
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 157452080f3d..4db2e8f1a1f4 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -7,6 +7,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 			   attribute_container.o transport_class.o \
 			   topology.o container.o property.o cacheinfo.o \
 			   devcon.o swnode.o
+obj-$(CONFIG_DEVICE_NOTIFICATIONS) += watch.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-y			+= power/
 obj-$(CONFIG_ISA_BUS_API)	+= isa.o
diff --git a/drivers/base/watch.c b/drivers/base/watch.c
new file mode 100644
index 000000000000..725aaa24275b
--- /dev/null
+++ b/drivers/base/watch.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Event notifications.
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/device.h>
+#include <linux/watch_queue.h>
+#include <linux/syscalls.h>
+#include <linux/init_task.h>
+#include <linux/security.h>
+
+/*
+ * Global queue for watching for device layer events.
+ */
+static struct watch_list device_watchers = {
+	.watchers	= HLIST_HEAD_INIT,
+	.lock		= __SPIN_LOCK_UNLOCKED(&device_watchers.lock),
+};
+
+static DEFINE_SPINLOCK(device_watchers_lock);
+
+/**
+ * post_device_notification - Post notification of a device event
+ * @n - The notification to post
+ * @id - The device ID
+ *
+ * Note that there's only a global queue to which all events are posted.  Might
+ * want to provide per-dev queues also.
+ */
+void post_device_notification(struct watch_notification *n, u64 id)
+{
+	post_watch_notification(&device_watchers, n, &init_cred, id);
+}
+EXPORT_SYMBOL(post_device_notification);
+
+/**
+ * sys_watch_devices - Watch for device events.
+ * @watch_fd: The watch queue to send notifications to.
+ * @watch_id: The watch ID to be placed in the notification (-1 to remove watch)
+ * @flags: Flags (reserved for future)
+ */
+SYSCALL_DEFINE3(watch_devices, int, watch_fd, int, watch_id, unsigned int, flags)
+{
+	struct watch_queue *wqueue;
+	struct watch *watch = NULL;
+	long ret = -ENOMEM;
+
+	if (watch_id < -1 || watch_id > 0xff || flags)
+		return -EINVAL;
+
+	wqueue = get_watch_queue(watch_fd);
+	if (IS_ERR(wqueue)) {
+		ret = PTR_ERR(wqueue);
+		goto err;
+	}
+
+	if (watch_id >= 0) {
+		watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+		if (!watch)
+			goto err_wqueue;
+
+		init_watch(watch, wqueue);
+		watch->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+		ret = security_watch_devices();
+		if (ret < 0)
+			goto err_watch;
+
+		spin_lock(&device_watchers_lock);
+		ret = add_watch_to_object(watch, &device_watchers);
+		spin_unlock(&device_watchers_lock);
+		if (ret == 0)
+			watch = NULL;
+	} else {
+		spin_lock(&device_watchers_lock);
+		ret = remove_watch_from_object(&device_watchers, wqueue, 0,
+					       false);
+		spin_unlock(&device_watchers_lock);
+	}
+
+err_watch:
+	kfree(watch);
+err_wqueue:
+	put_watch_queue(wqueue);
+err:
+	return ret;
+}
diff --git a/include/linux/device.h b/include/linux/device.h
index 297239a08bb7..f30e80185825 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -43,6 +43,7 @@ struct iommu_group;
 struct iommu_fwspec;
 struct dev_pin_info;
 struct iommu_param;
+struct watch_notification;
 
 struct bus_attribute {
 	struct attribute	attr;
@@ -1654,6 +1655,12 @@ struct device_link *device_link_add(struct device *consumer,
 void device_link_del(struct device_link *link);
 void device_link_remove(void *consumer, struct device *supplier);
 
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+extern void post_device_notification(struct watch_notification *n, u64 id);
+#else
+static inline void post_device_notification(struct watch_notification *n, u64 id) {}
+#endif
+
 #ifndef dev_fmt
 #define dev_fmt(fmt) fmt
 #endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index f7c561c4dcdd..565f033a61bc 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1000,6 +1000,7 @@ asmlinkage long sys_fspick(int dfd, const char __user *path, unsigned int flags)
 asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
 				       siginfo_t __user *info,
 				       unsigned int flags);
+asmlinkage long sys_watch_devices(int watch_fd, int watch_id, unsigned int flags);
 
 /*
  * Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 1fc8faa6e973..4794d3c2afd7 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -850,9 +850,11 @@ __SYSCALL(__NR_pidfd_open, sys_pidfd_open)
 #define __NR_clone3 435
 __SYSCALL(__NR_clone3, sys_clone3)
 #endif
+#define __NR_watch_devices 436
+__SYSCALL(__NR_watch_devices, sys_watch_devices)
 
 #undef __NR_syscalls
-#define __NR_syscalls 436
+#define __NR_syscalls 437
 
 /*
  * 32 bit systems traditionally used different
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 34b76895b81e..184ad68c087f 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -51,6 +51,7 @@ COND_SYSCALL_COMPAT(io_pgetevents);
 COND_SYSCALL(io_uring_setup);
 COND_SYSCALL(io_uring_enter);
 COND_SYSCALL(io_uring_register);
+COND_SYSCALL(watch_devices);
 
 /* fs/xattr.c */
 


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 11/14] block: Add block layer notifications [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (9 preceding siblings ...)
  2019-11-07 13:36 ` [RFC PATCH 10/14] Add a general, global device notification watch list " David Howells
@ 2019-11-07 13:37 ` " David Howells
  2019-11-07 13:37 ` [RFC PATCH 12/14] usb: Add USB subsystem " David Howells
                   ` (3 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:37 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add a block layer notification mechanism whereby notifications about
block-layer events such as I/O errors, can be reported to a monitoring
process asynchronously.

Firstly, an event queue needs to be created:

	pipe2(fds, O_NOTIFICATION_PIPE);
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);

then a notification can be set up to report block notifications via that
queue:

	struct watch_notification_filter filter = {
		.nr_filters = 1,
		.filters = {
			[0] = {
				.type = WATCH_TYPE_BLOCK_NOTIFY,
				.subtype_filter[0] = UINT_MAX;
			},
		},
	};
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
	watch_devices(fds[1], 12);

After that, records will be placed into the queue when, for example, errors
occur on a block device.  Records are of the following format:

	struct block_notification {
		struct watch_notification watch;
		__u64	dev;
		__u64	sector;
	} *n;

Where:

	n->watch.type will be WATCH_TYPE_BLOCK_NOTIFY

	n->watch.subtype will be the type of notification, such as
	NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM.

	n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
	record.

	n->watch.info & WATCH_INFO_ID will be the second argument to
	watch_devices(), shifted.

	n->dev will be the device numbers munged together.

	n->sector will indicate the affected sector (if appropriate for the
	event).

Note that it is permissible for event records to be of variable length -
or, at least, the length may be dependent on the subtype.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/watch_queue.rst    |    4 +++-
 block/Kconfig                    |    9 +++++++++
 block/blk-core.c                 |   29 ++++++++++++++++++++++++++++
 include/linux/blkdev.h           |   15 ++++++++++++++
 include/uapi/linux/watch_queue.h |   30 ++++++++++++++++++++++++++++-
 samples/watch_queue/watch_test.c |   40 +++++++++++++++++++++++++++++++++++++-
 6 files changed, 124 insertions(+), 3 deletions(-)

diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index ed592700be0e..f2299f631ae8 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -8,7 +8,9 @@ opened by userspace.  This can be used in conjunction with::
 
   * Key/keyring notifications
 
-  * General device event notifications
+  * General device event notifications, including::
+
+    * Block layer event notifications
 
 
 The notifications buffers can be enabled by:
diff --git a/block/Kconfig b/block/Kconfig
index 41c0917ce622..0906227a9431 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -177,6 +177,15 @@ config BLK_SED_OPAL
 	Enabling this option enables users to setup/unlock/lock
 	Locking ranges for SED devices using the Opal protocol.
 
+config BLK_NOTIFICATIONS
+	bool "Block layer event notifications"
+	depends on DEVICE_NOTIFICATIONS
+	help
+	  This option provides support for getting block layer event
+	  notifications.  This makes use of the /dev/watch_queue misc device to
+	  handle the notification buffer and provides the device_notify() system
+	  call to enable/disable watches.
+
 menu "Partition Types"
 
 source "block/partitions/Kconfig"
diff --git a/block/blk-core.c b/block/blk-core.c
index d5e668ec751b..08e9b12ff5a5 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -184,6 +184,22 @@ static const struct {
 	[BLK_STS_IOERR]		= { -EIO,	"I/O" },
 };
 
+#ifdef CONFIG_BLK_NOTIFICATIONS
+static const
+enum block_notification_type blk_notifications[ARRAY_SIZE(blk_errors)] = {
+	[BLK_STS_TIMEOUT]	= NOTIFY_BLOCK_ERROR_TIMEOUT,
+	[BLK_STS_NOSPC]		= NOTIFY_BLOCK_ERROR_NO_SPACE,
+	[BLK_STS_TRANSPORT]	= NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT,
+	[BLK_STS_TARGET]	= NOTIFY_BLOCK_ERROR_CRITICAL_TARGET,
+	[BLK_STS_NEXUS]		= NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS,
+	[BLK_STS_MEDIUM]	= NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM,
+	[BLK_STS_PROTECTION]	= NOTIFY_BLOCK_ERROR_PROTECTION,
+	[BLK_STS_RESOURCE]	= NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE,
+	[BLK_STS_DEV_RESOURCE]	= NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE,
+	[BLK_STS_IOERR]		= NOTIFY_BLOCK_ERROR_IO,
+};
+#endif
+
 blk_status_t errno_to_blk_status(int errno)
 {
 	int i;
@@ -224,6 +240,19 @@ static void print_req_error(struct request *req, blk_status_t status,
 		req->cmd_flags & ~REQ_OP_MASK,
 		req->nr_phys_segments,
 		IOPRIO_PRIO_CLASS(req->ioprio));
+
+#ifdef CONFIG_BLK_NOTIFICATIONS
+	if (blk_notifications[idx]) {
+		struct block_notification n = {
+			.watch.type	= WATCH_TYPE_BLOCK_NOTIFY,
+			.watch.subtype	= blk_notifications[idx],
+			.watch.info	= watch_sizeof(n),
+			.dev		= req->rq_disk ? disk_devt(req->rq_disk) : 0,
+			.sector		= blk_rq_pos(req),
+		};
+		post_block_notification(&n);
+	}
+#endif
 }
 
 static void req_bio_endio(struct request *rq, struct bio *bio,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f3ea78b0c91c..477472c11815 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -27,6 +27,7 @@
 #include <linux/percpu-refcount.h>
 #include <linux/scatterlist.h>
 #include <linux/blkzoned.h>
+#include <linux/watch_queue.h>
 
 struct module;
 struct scsi_ioctl_command;
@@ -1773,6 +1774,20 @@ static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
 }
 #endif /* CONFIG_BLK_DEV_ZONED */
 
+#ifdef CONFIG_BLK_NOTIFICATIONS
+static inline void post_block_notification(struct block_notification *n)
+{
+	u64 id = 0; /* Might want to allow dev# here. */
+
+	post_device_notification(&n->watch, id);
+}
+#else
+static inline void post_block_notification(struct block_notification *n)
+{
+}
+#endif
+
+
 #else /* CONFIG_BLOCK */
 
 struct block_device;
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index c3d8320b5d3a..557771413242 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -14,7 +14,8 @@
 enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */
 	WATCH_TYPE_KEY_NOTIFY	= 1,	/* Key change event notification */
-	WATCH_TYPE__NR		= 2
+	WATCH_TYPE_BLOCK_NOTIFY	= 2,	/* Block layer event notification */
+	WATCH_TYPE__NR		= 3
 };
 
 enum watch_meta_notification_subtype {
@@ -101,4 +102,31 @@ struct key_notification {
 	__u32	aux;		/* Per-type auxiliary data */
 };
 
+/*
+ * Type of block layer notification.
+ */
+enum block_notification_type {
+	NOTIFY_BLOCK_ERROR_TIMEOUT		= 1, /* Timeout error */
+	NOTIFY_BLOCK_ERROR_NO_SPACE		= 2, /* Critical space allocation error */
+	NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT = 3, /* Recoverable transport error */
+	NOTIFY_BLOCK_ERROR_CRITICAL_TARGET	= 4, /* Critical target error */
+	NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS	= 5, /* Critical nexus error */
+	NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM	= 6, /* Critical medium error */
+	NOTIFY_BLOCK_ERROR_PROTECTION		= 7, /* Protection error */
+	NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE	= 8, /* Kernel resource error */
+	NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE	= 9, /* Device resource error */
+	NOTIFY_BLOCK_ERROR_IO			= 10, /* Other I/O error */
+};
+
+/*
+ * Block layer notification record.
+ * - watch.type = WATCH_TYPE_BLOCK_NOTIFY
+ * - watch.subtype = enum block_notification_type
+ */
+struct block_notification {
+	struct watch_notification watch; /* WATCH_TYPE_BLOCK_NOTIFY */
+	__u64	dev;			/* Device number */
+	__u64	sector;			/* Affected sector */
+};
+
 #endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 58e826109ecc..55879531a7d5 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -58,6 +58,32 @@ static void saw_key_change(struct watch_notification *n, size_t len)
 	       k->key_id, n->subtype, key_subtypes[n->subtype], k->aux);
 }
 
+static const char *block_subtypes[256] = {
+	[NOTIFY_BLOCK_ERROR_TIMEOUT]			= "timeout",
+	[NOTIFY_BLOCK_ERROR_NO_SPACE]			= "critical space allocation",
+	[NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT]	= "recoverable transport",
+	[NOTIFY_BLOCK_ERROR_CRITICAL_TARGET]		= "critical target",
+	[NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS]		= "critical nexus",
+	[NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM]		= "critical medium",
+	[NOTIFY_BLOCK_ERROR_PROTECTION]			= "protection",
+	[NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE]		= "kernel resource",
+	[NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE]		= "device resource",
+	[NOTIFY_BLOCK_ERROR_IO]				= "I/O",
+};
+
+static void saw_block_change(struct watch_notification *n, size_t len)
+{
+	struct block_notification *b = (struct block_notification *)n;
+
+	if (len < sizeof(struct block_notification))
+		return;
+
+	printf("BLOCK %08llx e=%u[%s] s=%llx\n",
+	       (unsigned long long)b->dev,
+	       n->subtype, block_subtypes[n->subtype],
+	       (unsigned long long)b->sector);
+}
+
 /*
  * Consume and display events.
  */
@@ -131,6 +157,9 @@ static void consumer(int fd)
 			case WATCH_TYPE_KEY_NOTIFY:
 				saw_key_change(&n.n, len);
 				break;
+			case WATCH_TYPE_BLOCK_NOTIFY:
+				saw_block_change(&n.n, len);
+				break;
 			default:
 				printf("other type\n");
 				break;
@@ -142,12 +171,16 @@ static void consumer(int fd)
 }
 
 static struct watch_notification_filter filter = {
-	.nr_filters	= 1,
+	.nr_filters	= 2,
 	.filters = {
 		[0]	= {
 			.type			= WATCH_TYPE_KEY_NOTIFY,
 			.subtype_filter[0]	= UINT_MAX,
 		},
+		[1]	= {
+			.type			= WATCH_TYPE_BLOCK_NOTIFY,
+			.subtype_filter[0]	= UINT_MAX,
+		},
 	},
 };
 
@@ -181,6 +214,11 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
+	if (syscall(__NR_watch_devices, fd, 0x04, 0) == -1) {
+		perror("watch_devices");
+		exit(1);
+	}
+
 	consumer(fd);
 	exit(0);
 }


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 12/14] usb: Add USB subsystem notifications [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (10 preceding siblings ...)
  2019-11-07 13:37 ` [RFC PATCH 11/14] block: Add block layer notifications " David Howells
@ 2019-11-07 13:37 ` " David Howells
  2019-11-07 13:37 ` [RFC PATCH 13/14] selinux: Implement the watch_key security hook " David Howells
                   ` (2 subsequent siblings)
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:37 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Add a USB subsystem notification mechanism whereby notifications about
hardware events such as device connection, disconnection, reset and I/O
errors, can be reported to a monitoring process asynchronously.

Firstly, an event queue needs to be created:

	pipe2(fds, O_NOTIFICATION_PIPE);
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);

then a notification can be set up to report USB notifications via that
queue:

	struct watch_notification_filter filter = {
		.nr_filters = 1,
		.filters = {
			[0] = {
				.type = WATCH_TYPE_USB_NOTIFY,
				.subtype_filter[0] = UINT_MAX;
			},
		},
	};
	ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
	notify_devices(fds[1], 12);

After that, messages will be placed into the queue when events occur on a
USB device or bus.  Messages are of the following format:

	struct usb_notification {
		struct watch_notification watch;
		__u32	error;
		__u32	reserved;
		__u8	name_len;
		__u8	name[0];
	} *n;

Where:

	n->watch.type will be WATCH_TYPE_USB_NOTIFY

	n->watch.subtype will be the type of notification, such as
	NOTIFY_USB_DEVICE_ADD.

	n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
	message.

	n->watch.info & WATCH_INFO_ID will be the second argument to
	device_notify(), shifted.

	n->error and n->reserved are intended to convey information such as
	error codes, but are currently not used

	n->name_len and n->name convey the USB device name as an
	unterminated string.  This may be truncated - it is currently
	limited to a maximum 63 chars.

Note that it is permissible for messages to be of variable length - or, at
least, the length may be dependent on the subtype.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: linux-usb@vger.kernel.org
---

 Documentation/watch_queue.rst    |    9 +++++++
 drivers/usb/core/Kconfig         |    9 +++++++
 drivers/usb/core/devio.c         |   47 ++++++++++++++++++++++++++++++++++++++
 drivers/usb/core/hub.c           |    4 +++
 include/linux/usb.h              |   18 +++++++++++++++
 include/uapi/linux/watch_queue.h |   28 ++++++++++++++++++++++-
 samples/watch_queue/watch_test.c |   29 +++++++++++++++++++++++
 7 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index f2299f631ae8..5321a9cb1ab2 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -12,6 +12,8 @@ opened by userspace.  This can be used in conjunction with::
 
     * Block layer event notifications
 
+    * USB subsystem event notifications
+
 
 The notifications buffers can be enabled by:
 
@@ -262,6 +264,13 @@ Any particular buffer can be fed from multiple sources.  Sources include:
     or temporary link loss.  Watches of this type are set on the global device
     watch list.
 
+  * WATCH_TYPE_USB_NOTIFY
+
+    Notifications of this type indicate USB subsystem events, such as
+    attachment, removal, reset and I/O errors.  Separate events are generated
+    for buses and devices.  Watchpoints of this type are set on the global
+    device watch list.
+
 
 Event Filtering
 ===============
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index ecaacc8ed311..57e7b649e48b 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -102,3 +102,12 @@ config USB_AUTOSUSPEND_DELAY
 	  The default value Linux has always had is 2 seconds.  Change
 	  this value if you want a different delay and cannot modify
 	  the command line or module parameter.
+
+config USB_NOTIFICATIONS
+	bool "Provide USB hardware event notifications"
+	depends on USB && DEVICE_NOTIFICATIONS
+	help
+	  This option provides support for getting hardware event notifications
+	  on USB devices and interfaces.  This makes use of the
+	  /dev/watch_queue misc device to handle the notification buffer.
+	  device_notify(2) is used to set/remove watches.
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 3f899552f6e3..693a5657dba3 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -41,6 +41,7 @@
 #include <linux/dma-mapping.h>
 #include <asm/byteorder.h>
 #include <linux/moduleparam.h>
+#include <linux/watch_queue.h>
 
 #include "usb.h"
 
@@ -2748,13 +2749,59 @@ static void usbdev_remove(struct usb_device *udev)
 	mutex_unlock(&usbfs_mutex);
 }
 
+#ifdef CONFIG_USB_NOTIFICATIONS
+static noinline void post_usb_notification(const char *devname,
+					   enum usb_notification_type subtype,
+					   u32 error)
+{
+	unsigned int name_len, n_len;
+	u64 id = 0; /* We can put a device ID here for separate dev watches */
+
+	struct {
+		struct usb_notification n;
+		char more_name[USB_NOTIFICATION_MAX_NAME_LEN -
+			       (sizeof(struct usb_notification) -
+				offsetof(struct usb_notification, name))];
+	} n;
+
+	name_len = strlen(devname);
+	name_len = min_t(size_t, name_len, USB_NOTIFICATION_MAX_NAME_LEN);
+	n_len = offsetof(struct usb_notification, name) + name_len;
+
+	memset(&n, 0, sizeof(n));
+	memcpy(n.n.name, devname, n_len);
+
+	n.n.watch.type		= WATCH_TYPE_USB_NOTIFY;
+	n.n.watch.subtype	= subtype;
+	n.n.watch.info		= n_len;
+	n.n.error		= error;
+	n.n.name_len		= name_len;
+
+	post_device_notification(&n.n.watch, id);
+}
+
+void post_usb_device_notification(const struct usb_device *udev,
+				  enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(dev_name(&udev->dev), subtype, error);
+}
+
+void post_usb_bus_notification(const struct usb_bus *ubus,
+			       enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(ubus->bus_name, subtype, error);
+}
+#endif
+
 static int usbdev_notify(struct notifier_block *self,
 			       unsigned long action, void *dev)
 {
 	switch (action) {
 	case USB_DEVICE_ADD:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_ADD, 0);
 		break;
 	case USB_DEVICE_REMOVE:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_REMOVE, 0);
 		usbdev_remove(dev);
 		break;
 	}
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 236313f41f4a..e8ebacc15a32 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -29,6 +29,7 @@
 #include <linux/random.h>
 #include <linux/pm_qos.h>
 #include <linux/kobject.h>
+#include <linux/watch_queue.h>
 
 #include <linux/uaccess.h>
 #include <asm/byteorder.h>
@@ -4605,6 +4606,9 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 				(udev->config) ? "reset" : "new", speed,
 				devnum, driver_name);
 
+	if (udev->config)
+		post_usb_device_notification(udev, NOTIFY_USB_DEVICE_RESET, 0);
+
 	/* Set up TT records, if needed  */
 	if (hdev->tt) {
 		udev->tt = hdev->tt;
diff --git a/include/linux/usb.h b/include/linux/usb.h
index e656e7b4b1e4..93fa0666f95a 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -26,6 +26,7 @@
 struct usb_device;
 struct usb_driver;
 struct wusb_dev;
+enum usb_notification_type;
 
 /*-------------------------------------------------------------------------*/
 
@@ -2015,6 +2016,23 @@ extern void usb_led_activity(enum usb_led_event ev);
 static inline void usb_led_activity(enum usb_led_event ev) {}
 #endif
 
+/*
+ * Notification functions.
+ */
+#ifdef CONFIG_USB_NOTIFICATIONS
+extern void post_usb_device_notification(const struct usb_device *udev,
+					 enum usb_notification_type subtype,
+					 u32 error);
+extern void post_usb_bus_notification(const struct usb_bus *ubus,
+				      enum usb_notification_type subtype,
+				      u32 error);
+#else
+static inline void post_usb_device_notification(const struct usb_device *udev,
+						unsigned int subtype, u32 error) {}
+static inline void post_usb_bus_notification(const struct usb_bus *ubus,
+					     unsigned int subtype, u32 error) {}
+#endif
+
 #endif  /* __KERNEL__ */
 
 #endif
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 557771413242..ad1ae229674a 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -15,7 +15,8 @@ enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */
 	WATCH_TYPE_KEY_NOTIFY	= 1,	/* Key change event notification */
 	WATCH_TYPE_BLOCK_NOTIFY	= 2,	/* Block layer event notification */
-	WATCH_TYPE__NR		= 3
+	WATCH_TYPE_USB_NOTIFY	= 3,	/* USB subsystem event notification */
+	WATCH_TYPE__NR		= 4
 };
 
 enum watch_meta_notification_subtype {
@@ -129,4 +130,29 @@ struct block_notification {
 	__u64	sector;			/* Affected sector */
 };
 
+/*
+ * Type of USB layer notification.
+ */
+enum usb_notification_type {
+	NOTIFY_USB_DEVICE_ADD		= 0, /* USB device added */
+	NOTIFY_USB_DEVICE_REMOVE	= 1, /* USB device removed */
+	NOTIFY_USB_DEVICE_RESET		= 2, /* USB device reset */
+	NOTIFY_USB_DEVICE_ERROR		= 3, /* USB device error */
+};
+
+/*
+ * USB subsystem notification record.
+ * - watch.type = WATCH_TYPE_USB_NOTIFY
+ * - watch.subtype = enum usb_notification_type
+ */
+struct usb_notification {
+	struct watch_notification watch; /* WATCH_TYPE_USB_NOTIFY */
+	__u32	error;
+	__u32	reserved;
+	__u8	name_len;		/* Length of device name */
+	__u8	name[0];		/* Device name (padded to __u64, truncated at 63 chars) */
+};
+
+#define USB_NOTIFICATION_MAX_NAME_LEN 63
+
 #endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 55879531a7d5..37461295e825 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -84,6 +84,26 @@ static void saw_block_change(struct watch_notification *n, size_t len)
 	       (unsigned long long)b->sector);
 }
 
+static const char *usb_subtypes[256] = {
+	[NOTIFY_USB_DEVICE_ADD]		= "dev-add",
+	[NOTIFY_USB_DEVICE_REMOVE]	= "dev-remove",
+	[NOTIFY_USB_DEVICE_RESET]	= "dev-reset",
+	[NOTIFY_USB_DEVICE_ERROR]	= "dev-error",
+};
+
+static void saw_usb_event(struct watch_notification *n, size_t len)
+{
+	struct usb_notification *u = (struct usb_notification *)n;
+
+	if (len < sizeof(struct usb_notification))
+		return;
+
+	printf("USB %*.*s %s e=%x r=%x\n",
+	       u->name_len, u->name_len, u->name,
+	       usb_subtypes[n->subtype],
+	       u->error, u->reserved);
+}
+
 /*
  * Consume and display events.
  */
@@ -160,6 +180,9 @@ static void consumer(int fd)
 			case WATCH_TYPE_BLOCK_NOTIFY:
 				saw_block_change(&n.n, len);
 				break;
+			case WATCH_TYPE_USB_NOTIFY:
+				saw_usb_event(&n.n, len);
+				break;
 			default:
 				printf("other type\n");
 				break;
@@ -171,7 +194,7 @@ static void consumer(int fd)
 }
 
 static struct watch_notification_filter filter = {
-	.nr_filters	= 2,
+	.nr_filters	= 3,
 	.filters = {
 		[0]	= {
 			.type			= WATCH_TYPE_KEY_NOTIFY,
@@ -181,6 +204,10 @@ static struct watch_notification_filter filter = {
 			.type			= WATCH_TYPE_BLOCK_NOTIFY,
 			.subtype_filter[0]	= UINT_MAX,
 		},
+		[2]	= {
+			.type			= WATCH_TYPE_USB_NOTIFY,
+			.subtype_filter[0]	= UINT_MAX,
+		},
 	},
 };
 


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 13/14] selinux: Implement the watch_key security hook [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (11 preceding siblings ...)
  2019-11-07 13:37 ` [RFC PATCH 12/14] usb: Add USB subsystem " David Howells
@ 2019-11-07 13:37 ` " David Howells
  2019-11-07 13:37 ` [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks " David Howells
  2019-11-07 17:16 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:37 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Implement the watch_key security hook to make sure that a key grants the
caller View permission in order to set a watch on a key.

For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
---

 security/selinux/hooks.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9625b99e677f..53637dccee00 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6579,6 +6579,17 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
 	*_buffer = context;
 	return rc;
 }
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+static int selinux_watch_key(struct key *key)
+{
+	struct key_security_struct *ksec = key->security;
+	u32 sid = current_sid();
+
+	return avc_has_perm(&selinux_state,
+			    sid, ksec->sid, SECCLASS_KEY, KEY_NEED_VIEW, NULL);
+}
+#endif
 #endif
 
 #ifdef CONFIG_SECURITY_INFINIBAND
@@ -7012,6 +7023,9 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(key_free, selinux_key_free),
 	LSM_HOOK_INIT(key_permission, selinux_key_permission),
 	LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	LSM_HOOK_INIT(watch_key, selinux_watch_key),
+#endif
 #endif
 
 #ifdef CONFIG_AUDIT


^ permalink raw reply	[flat|nested] 22+ messages in thread

* [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (12 preceding siblings ...)
  2019-11-07 13:37 ` [RFC PATCH 13/14] selinux: Implement the watch_key security hook " David Howells
@ 2019-11-07 13:37 ` " David Howells
  2019-11-07 17:16 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 13:37 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, dhowells, keyrings,
	linux-usb, linux-block, linux-security-module, linux-fsdevel,
	linux-api, linux-security-module, linux-kernel

Implement the watch_key security hook in Smack to make sure that a key
grants the caller Read permission in order to set a watch on a key.

Also implement the post_notification security hook to make sure that the
notification source is granted Write permission by the watch queue.

For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
---

 include/linux/lsm_audit.h  |    1 +
 security/smack/smack_lsm.c |   82 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 915330abf6e5..734d67889826 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -74,6 +74,7 @@ struct common_audit_data {
 #define LSM_AUDIT_DATA_FILE	12
 #define LSM_AUDIT_DATA_IBPKEY	13
 #define LSM_AUDIT_DATA_IBENDPORT 14
+#define LSM_AUDIT_DATA_NOTIFICATION 15
 	union 	{
 		struct path path;
 		struct dentry *dentry;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index ecea41ce919b..71b6f37d49c1 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4273,7 +4273,7 @@ static int smack_key_permission(key_ref_t key_ref,
 	if (tkp == NULL)
 		return -EACCES;
 
-	if (smack_privileged_cred(CAP_MAC_OVERRIDE, cred))
+	if (smack_privileged(CAP_MAC_OVERRIDE))
 		return 0;
 
 #ifdef CONFIG_AUDIT
@@ -4319,8 +4319,81 @@ static int smack_key_getsecurity(struct key *key, char **_buffer)
 	return length;
 }
 
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+/**
+ * smack_watch_key - Smack access to watch a key for notifications.
+ * @key: The key to be watched
+ *
+ * Return 0 if the @watch->cred has permission to read from the key object and
+ * an error otherwise.
+ */
+static int smack_watch_key(struct key *key)
+{
+	struct smk_audit_info ad;
+	struct smack_known *tkp = smk_of_current();
+	int rc;
+
+	if (key == NULL)
+		return -EINVAL;
+	/*
+	 * If the key hasn't been initialized give it access so that
+	 * it may do so.
+	 */
+	if (key->security == NULL)
+		return 0;
+	/*
+	 * This should not occur
+	 */
+	if (tkp == NULL)
+		return -EACCES;
+
+	if (smack_privileged_cred(CAP_MAC_OVERRIDE, current_cred()))
+		return 0;
+
+#ifdef CONFIG_AUDIT
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_KEY);
+	ad.a.u.key_struct.key = key->serial;
+	ad.a.u.key_struct.key_desc = key->description;
+#endif
+	rc = smk_access(tkp, key->security, MAY_READ, &ad);
+	rc = smk_bu_note("key watch", tkp, key->security, MAY_READ, rc);
+	return rc;
+}
+#endif /* CONFIG_KEY_NOTIFICATIONS */
 #endif /* CONFIG_KEYS */
 
+#ifdef CONFIG_WATCH_QUEUE
+/**
+ * smack_post_notification - Smack access to post a notification to a queue
+ * @w_cred: The credentials of the watcher.
+ * @cred: The credentials of the event source (may be NULL).
+ * @n: The notification message to be posted.
+ */
+static int smack_post_notification(const struct cred *w_cred,
+				   const struct cred *cred,
+				   struct watch_notification *n)
+{
+	struct smk_audit_info ad;
+	struct smack_known *subj, *obj;
+	int rc;
+
+	/* Always let maintenance notifications through. */
+	if (n->type == WATCH_TYPE_META)
+		return 0;
+
+	if (!cred)
+		return 0;
+	subj = smk_of_task(smack_cred(cred));
+	obj = smk_of_task(smack_cred(w_cred));
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_NOTIFICATION);
+	rc = smk_access(subj, obj, MAY_WRITE, &ad);
+	rc = smk_bu_note("notification", subj, obj, MAY_WRITE, rc);
+	return rc;
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
 /*
  * Smack Audit hooks
  *
@@ -4709,8 +4782,15 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(key_free, smack_key_free),
 	LSM_HOOK_INIT(key_permission, smack_key_permission),
 	LSM_HOOK_INIT(key_getsecurity, smack_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	LSM_HOOK_INIT(watch_key, smack_watch_key),
+#endif
 #endif /* CONFIG_KEYS */
 
+#ifdef CONFIG_WATCH_QUEUE
+	LSM_HOOK_INIT(post_notification, smack_post_notification),
+#endif
+
  /* Audit hooks */
 #ifdef CONFIG_AUDIT
 	LSM_HOOK_INIT(audit_rule_init, smack_audit_rule_init),


^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 05/14] pipe: Add general notification queue support [ver #2]
  2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
                   ` (13 preceding siblings ...)
  2019-11-07 13:37 ` [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks " David Howells
@ 2019-11-07 17:16 ` " David Howells
  14 siblings, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 17:16 UTC (permalink / raw)
  To: torvalds
  Cc: dhowells, Greg Kroah-Hartman, Casey Schaufler, Stephen Smalley,
	nicolas.dichtel, raven, Christian Brauner, keyrings, linux-usb,
	linux-block, linux-security-module, linux-fsdevel, linux-api,
	linux-kernel

Sigh.  I forgot to build it with the new config options disabled.  I've fixed
that up and pushed it to the git tree.

David


^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2]
  2019-11-07 13:36 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
@ 2019-11-07 18:15   ` Andy Lutomirski
  2019-11-07 18:23   ` David Howells
  1 sibling, 0 replies; 22+ messages in thread
From: Andy Lutomirski @ 2019-11-07 18:15 UTC (permalink / raw)
  To: David Howells
  Cc: Linus Torvalds, Greg Kroah-Hartman, Casey Schaufler,
	Stephen Smalley, Nicolas Dichtel, raven, Christian Brauner,
	keyrings, USB list, linux-block, LSM List, Linux FS Devel,
	Linux API, LKML

On Thu, Nov 7, 2019 at 5:39 AM David Howells <dhowells@redhat.com> wrote:
>
> Allow a buffer to be marked such that read() must return the entire buffer
> in one go or return ENOBUFS.  Multiple buffers can be amalgamated into a
> single read, but a short read will occur if the next "whole" buffer won't
> fit.
>
> This is useful for watch queue notifications to make sure we don't split a
> notification across multiple reads, especially given that we need to
> fabricate an overrun record under some circumstances - and that isn't in
> the buffers.

Hmm.  I'm not totally in love with introducing a new error code like
this for read(), especially if it could affect the kind of pipe that
is bound to a file in a filesystem.  But maybe it's not a problem.

^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE [ver #2]
  2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
@ 2019-11-07 18:16   ` Andy Lutomirski
  2019-11-07 18:48   ` David Howells
  1 sibling, 0 replies; 22+ messages in thread
From: Andy Lutomirski @ 2019-11-07 18:16 UTC (permalink / raw)
  To: David Howells
  Cc: Linus Torvalds, Greg Kroah-Hartman, Casey Schaufler,
	Stephen Smalley, Nicolas Dichtel, raven, Christian Brauner,
	keyrings, USB list, linux-block, LSM List, Linux FS Devel,
	Linux API, LKML

On Thu, Nov 7, 2019 at 5:39 AM David Howells <dhowells@redhat.com> wrote:
>
> Add an O_NOTIFICATION_PIPE flag that can be passed to pipe2() to indicate
> that the pipe being created is going to be used for notifications.  This
> suppresses the use of splice(), vmsplice(), tee() and sendfile() on the
> pipe as calling iov_iter_revert() on a pipe when a kernel notification
> message has been inserted into the middle of a multi-buffer splice will be
> messy.

How messy?  And is there some way to make it impossible for this to
happen?  Adding a new flag to pipe2() to avoid messy kernel code seems
like a poor tradeoff.

^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2]
  2019-11-07 13:36 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
  2019-11-07 18:15   ` Andy Lutomirski
@ 2019-11-07 18:23   ` David Howells
  1 sibling, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 18:23 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: dhowells, Linus Torvalds, Greg Kroah-Hartman, Casey Schaufler,
	Stephen Smalley, Nicolas Dichtel, raven, Christian Brauner,
	keyrings, USB list, linux-block, LSM List, Linux FS Devel,
	Linux API, LKML

Andy Lutomirski <luto@kernel.org> wrote:

> > Allow a buffer to be marked such that read() must return the entire buffer
> > in one go or return ENOBUFS.  Multiple buffers can be amalgamated into a
> > single read, but a short read will occur if the next "whole" buffer won't
> > fit.
> >
> > This is useful for watch queue notifications to make sure we don't split a
> > notification across multiple reads, especially given that we need to
> > fabricate an overrun record under some circumstances - and that isn't in
> > the buffers.
> 
> Hmm.  I'm not totally in love with introducing a new error code like
> this for read(), especially if it could affect the kind of pipe that
> is bound to a file in a filesystem.  But maybe it's not a problem.

EMSGSIZE might be better?

David


^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE [ver #2]
  2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
  2019-11-07 18:16   ` Andy Lutomirski
@ 2019-11-07 18:48   ` David Howells
  2019-11-08  5:06     ` Andy Lutomirski
  2019-11-08  6:42     ` David Howells
  1 sibling, 2 replies; 22+ messages in thread
From: David Howells @ 2019-11-07 18:48 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: dhowells, Linus Torvalds, Greg Kroah-Hartman, Casey Schaufler,
	Stephen Smalley, Nicolas Dichtel, raven, Christian Brauner,
	keyrings, USB list, linux-block, LSM List, Linux FS Devel,
	Linux API, LKML

Andy Lutomirski <luto@kernel.org> wrote:

> > Add an O_NOTIFICATION_PIPE flag that can be passed to pipe2() to indicate
> > that the pipe being created is going to be used for notifications.  This
> > suppresses the use of splice(), vmsplice(), tee() and sendfile() on the
> > pipe as calling iov_iter_revert() on a pipe when a kernel notification
> > message has been inserted into the middle of a multi-buffer splice will be
> > messy.
>
> How messy?

Well, iov_iter_revert() on a pipe iterator simply walks backwards along the
ring discarding the last N contiguous slots (where N is normally the number of
slots that were filled by whatever operation is being reverted).

However, unless the code that transfers stuff into the pipe takes the spinlock
spinlock and disables softirqs for the duration of its ring filling, what were
N contiguous slots may now have kernel notifications interspersed - even if it
has been holding the pipe mutex.

So, now what do you do?  You have to free up just the buffers relevant to the
iterator and then you can either compact down the ring to free up the space or
you can leave null slots and let the read side clean them up, thereby
reducing the capacity of the pipe temporarily.

Either way, iov_iter_revert() gets more complex and has to hold the spinlock.

And if you don't take the spinlock whilst you're reverting, more notifications
can come in to make your life more interesting.

There's also a problem with splicing out from a notification pipe that the
messages are scribed onto preallocated buffers, but now the buffers need
refcounts and, in any case, are of limited quantity.

> And is there some way to make it impossible for this to happen?

Yes.  That's what I'm doing by declaring the pipe to be unspliceable up front.

> Adding a new flag to pipe2() to avoid messy kernel code seems
> like a poor tradeoff.

By far the easiest place to check whether a pipe can be spliced to is in
get_pipe_info().  That's checking the file anyway.  After that, you can't make
the check until the pipe is locked.

Furthermore, if it's not done upfront, the change to the pipe might happen
during a splicing operation that's residing in pipe_wait()... which drops the
pipe mutex.

David


^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE [ver #2]
  2019-11-07 18:48   ` David Howells
@ 2019-11-08  5:06     ` Andy Lutomirski
  2019-11-08  6:42     ` David Howells
  1 sibling, 0 replies; 22+ messages in thread
From: Andy Lutomirski @ 2019-11-08  5:06 UTC (permalink / raw)
  To: David Howells
  Cc: Andy Lutomirski, Linus Torvalds, Greg Kroah-Hartman,
	Casey Schaufler, Stephen Smalley, Nicolas Dichtel, raven,
	Christian Brauner, keyrings, USB list, linux-block, LSM List,
	Linux FS Devel, Linux API, LKML

On Thu, Nov 7, 2019 at 10:48 AM David Howells <dhowells@redhat.com> wrote:
>
> Andy Lutomirski <luto@kernel.org> wrote:
>
> > > Add an O_NOTIFICATION_PIPE flag that can be passed to pipe2() to indicate
> > > that the pipe being created is going to be used for notifications.  This
> > > suppresses the use of splice(), vmsplice(), tee() and sendfile() on the
> > > pipe as calling iov_iter_revert() on a pipe when a kernel notification
> > > message has been inserted into the middle of a multi-buffer splice will be
> > > messy.
> >
> > How messy?
>
> Well, iov_iter_revert() on a pipe iterator simply walks backwards along the
> ring discarding the last N contiguous slots (where N is normally the number of
> slots that were filled by whatever operation is being reverted).
>
> However, unless the code that transfers stuff into the pipe takes the spinlock
> spinlock and disables softirqs for the duration of its ring filling, what were
> N contiguous slots may now have kernel notifications interspersed - even if it
> has been holding the pipe mutex.
>
> So, now what do you do?  You have to free up just the buffers relevant to the
> iterator and then you can either compact down the ring to free up the space or
> you can leave null slots and let the read side clean them up, thereby
> reducing the capacity of the pipe temporarily.
>
> Either way, iov_iter_revert() gets more complex and has to hold the spinlock.

I feel like I'm missing something fundamental here.

I can open a normal pipe from userspace (with pipe() or pipe2()), and
I can have two threads.  One thread writes to the pipe with write().
The other thread writes with splice().  Everything works fine.  What's
special about notifications?

^ permalink raw reply	[flat|nested] 22+ messages in thread

* Re: [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE [ver #2]
  2019-11-07 18:48   ` David Howells
  2019-11-08  5:06     ` Andy Lutomirski
@ 2019-11-08  6:42     ` David Howells
  1 sibling, 0 replies; 22+ messages in thread
From: David Howells @ 2019-11-08  6:42 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: dhowells, Linus Torvalds, Greg Kroah-Hartman, Casey Schaufler,
	Stephen Smalley, Nicolas Dichtel, raven, Christian Brauner,
	keyrings, USB list, linux-block, LSM List, Linux FS Devel,
	Linux API, LKML

Andy Lutomirski <luto@kernel.org> wrote:

> I can open a normal pipe from userspace (with pipe() or pipe2()), and
> I can have two threads.  One thread writes to the pipe with write().
> The other thread writes with splice().  Everything works fine.

Yes.  Every operation you do on a pipe from userspace is serialised with the
pipe mutex - and both ends share the same pipe.

> What's special about notifications?

The post_notification() cannot take the pipe mutex.  It has to be callable
from softirq context.  Linus's idea is that when you're actually altering the
ring pointers you should hold the wake-queue spinlock, and post_notification()
holds the wake queue spinlock for the duration of the operation.

This means that post_notification() can be writing to the pipe whilst a
userspace-invoked operation is holding the pipe mutex and is also doing
something to the ring.

David


^ permalink raw reply	[flat|nested] 22+ messages in thread

end of thread, back to index

Thread overview: 22+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
2019-11-07 13:35 ` [RFC PATCH 02/14] security: Add hooks to rule on setting a watch " David Howells
2019-11-07 13:35 ` [RFC PATCH 03/14] security: Add a hook for the point of notification insertion " David Howells
2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
2019-11-07 18:16   ` Andy Lutomirski
2019-11-07 18:48   ` David Howells
2019-11-08  5:06     ` Andy Lutomirski
2019-11-08  6:42     ` David Howells
2019-11-07 13:36 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
2019-11-07 13:36 ` [RFC PATCH 06/14] keys: Add a notification facility " David Howells
2019-11-07 13:36 ` [RFC PATCH 07/14] Add sample notification program " David Howells
2019-11-07 13:36 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
2019-11-07 18:15   ` Andy Lutomirski
2019-11-07 18:23   ` David Howells
2019-11-07 13:36 ` [RFC PATCH 09/14] pipe: Add notification lossage handling " David Howells
2019-11-07 13:36 ` [RFC PATCH 10/14] Add a general, global device notification watch list " David Howells
2019-11-07 13:37 ` [RFC PATCH 11/14] block: Add block layer notifications " David Howells
2019-11-07 13:37 ` [RFC PATCH 12/14] usb: Add USB subsystem " David Howells
2019-11-07 13:37 ` [RFC PATCH 13/14] selinux: Implement the watch_key security hook " David Howells
2019-11-07 13:37 ` [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks " David Howells
2019-11-07 17:16 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells

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