* [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4]
@ 2020-03-09 12:17 David Howells
2020-03-09 12:17 ` [RFC PATCH 01/17] uapi: General notification queue definitions " David Howells
` (16 more replies)
0 siblings, 17 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: Casey Schaufler, Stephen Smalley, linux-security-module,
dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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) Mount topology events, such as mounting, unmounting, mount expiry,
mount reconfiguration.
(3) Superblock events, such as R/W<->R/O changes, quota overrun and I/O
errors (not complete yet).
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.
WHY
===
(1) Key/keyring notifications.
If you have your kerberos tickets in a file/directory, your gnome
desktop will monitor that using something like fanotify and tell you
if your credentials cache changes.
We also have the ability to cache your kerberos tickets in the
session, user or persistent keyring so that it isn't left around on
disk across a reboot or logout. Keyrings, however, cannot currently
be monitored asynchronously, so the desktop has to poll for it - not
so good on a laptop.
This source will allow the desktop to avoid the need to poll. Here's
a pull request for usage by gnome-online-accounts:
https://gitlab.gnome.org/GNOME/gnome-online-accounts/merge_requests/47
(2) Mount notifications.
This one is wanted to avoid repeated trawling of /proc/mounts or
similar to work out changes to the mount object attributes and mount
topology. I'm told that the proc file holding the namespace_sem is a
point of contention, especially as the process of generating the text
descriptions of the mounts/superblocks can be quite involved.
Whilst you can use poll() on /proc/mounts, it doesn't give you any
clues as to what changed. The notification generated here directly
indicates the mounts involved in any particular event and gives an
idea of what the change was.
This is combined with a new fsinfo() system call that allows, amongst
other things, the ability to retrieve in one go an { id,
change_counter } tuple from all the children of a specified mount,
allowing buffer overruns to be dealt with quickly.
This is of use to systemd to improve efficiency:
https://lore.kernel.org/linux-fsdevel/20200227151421.3u74ijhqt6ekbiss@ws.net.home/
And it's not just Red Hat that's potentially interested in this:
https://lore.kernel.org/linux-fsdevel/293c9bd3-f530-d75e-c353-ddeabac27cf6@6wind.com/
(3) Superblock notifications.
This one is provided to allow systemd or the desktop to more easily
detect events such as I/O errors and EDQUOT/ENOSPC. This would be of
interest to Postgres:
https://lore.kernel.org/linux-fsdevel/20200211005626.7yqjf5rbs3vbwagd@alap3.anarazel.de/
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_mount(AT_FDCWD, "/", 0, fd, 0x02);
watch_sb(AT_FDCWD, "/mnt", 0, fd, 0x03);
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
(*) A test program is provided (samples/watch_queue/watch_test) that can
be used to monitor for keyrings, mount and superblock events.
Information on the notifications is simply logged to stdout.
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 #4:
(*) Dropped USB and device notifications for the moment as there's some
dispute over whether another avenue should be used for USB
notifications.
(*) Include mount and superblock event sources in the patchset.
- These now increment event counters that fsinfo() will be able to
retrieve (separate patch set).
ver #3:
(*) Rebase to after latest upstream pipe patches.
(*) Fix a missing ref get in add_watch_to_object().
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 (17):
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
watch_queue: Add a key/keyring notification facility
Add sample notification program
pipe: Allow buffers to be marked read-whole-or-error for notifications
pipe: Add notification lossage handling
selinux: Implement the watch_key security hook
smack: Implement the watch_key and post_notification hooks
watch_queue: Add security hooks to rule on setting mount and sb watches
watch_queue: Implement mount topology and attribute change notifications
watch_queue: sample: Display mount tree change notifications
watch_queue: Introduce a non-repeating system-unique superblock ID
watch_queue: Add superblock notifications
watch_queue: sample: Display superblock notifications
Documentation/security/keys/core.rst | 58 ++
Documentation/userspace-api/ioctl/ioctl-number.rst | 1
Documentation/watch_queue.rst | 354 +++++++++++
arch/alpha/kernel/syscalls/syscall.tbl | 2
arch/arm/tools/syscall.tbl | 2
arch/arm64/include/asm/unistd.h | 2
arch/ia64/kernel/syscalls/syscall.tbl | 2
arch/m68k/kernel/syscalls/syscall.tbl | 2
arch/microblaze/kernel/syscalls/syscall.tbl | 2
arch/mips/kernel/syscalls/syscall_n32.tbl | 2
arch/mips/kernel/syscalls/syscall_n64.tbl | 2
arch/mips/kernel/syscalls/syscall_o32.tbl | 2
arch/parisc/kernel/syscalls/syscall.tbl | 2
arch/powerpc/kernel/syscalls/syscall.tbl | 2
arch/s390/kernel/syscalls/syscall.tbl | 2
arch/sh/kernel/syscalls/syscall.tbl | 2
arch/sparc/kernel/syscalls/syscall.tbl | 2
arch/x86/entry/syscalls/syscall_32.tbl | 2
arch/x86/entry/syscalls/syscall_64.tbl | 2
arch/xtensa/kernel/syscalls/syscall.tbl | 2
fs/Kconfig | 21 +
fs/Makefile | 1
fs/internal.h | 1
fs/mount.h | 35 +
fs/mount_notify.c | 186 ++++++
fs/namespace.c | 22 +
fs/pipe.c | 242 +++++--
fs/splice.c | 12
fs/super.c | 156 +++++
include/linux/dcache.h | 1
include/linux/fs.h | 84 +++
include/linux/key.h | 3
include/linux/lsm_audit.h | 1
include/linux/lsm_hooks.h | 62 ++
include/linux/pipe_fs_i.h | 27 +
include/linux/security.h | 47 +
include/linux/syscalls.h | 4
include/linux/watch_queue.h | 127 ++++
include/uapi/asm-generic/unistd.h | 6
include/uapi/linux/keyctl.h | 2
include/uapi/linux/watch_queue.h | 163 +++++
init/Kconfig | 12
kernel/Makefile | 1
kernel/sys_ni.c | 6
kernel/watch_queue.c | 659 ++++++++++++++++++++
samples/Kconfig | 6
samples/Makefile | 1
samples/watch_queue/Makefile | 7
samples/watch_queue/watch_test.c | 260 ++++++++
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 | 37 +
security/selinux/hooks.c | 14
security/smack/smack_lsm.c | 83 ++-
60 files changed, 2837 insertions(+), 107 deletions(-)
create mode 100644 Documentation/watch_queue.rst
create mode 100644 fs/mount_notify.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] 18+ messages in thread
* [RFC PATCH 01/17] uapi: General notification queue definitions [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
@ 2020-03-09 12:17 ` David Howells
2020-03-09 12:17 ` [RFC PATCH 02/17] security: Add hooks to rule on setting a watch " David Howells
` (15 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 02/17] security: Add hooks to rule on setting a watch [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
2020-03-09 12:17 ` [RFC PATCH 01/17] uapi: General notification queue definitions " David Howells
@ 2020-03-09 12:17 ` David Howells
2020-03-09 12:17 ` [RFC PATCH 03/17] security: Add a hook for the point of notification insertion " David Howells
` (14 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: Casey Schaufler, Stephen Smalley, linux-security-module,
dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 20d8cf194fb7..79d7c73676d7 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,
@@ -1985,6 +2003,12 @@ 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 64b19f050343..7a36064a64ea 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1276,6 +1276,23 @@ 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 565bc9b67276..22877f47cf62 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1988,6 +1988,20 @@ 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 03/17] security: Add a hook for the point of notification insertion [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
2020-03-09 12:17 ` [RFC PATCH 01/17] uapi: General notification queue definitions " David Howells
2020-03-09 12:17 ` [RFC PATCH 02/17] security: Add hooks to rule on setting a watch " David Howells
@ 2020-03-09 12:17 ` David Howells
2020-03-09 12:17 ` [RFC PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE " David Howells
` (13 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: Casey Schaufler, Stephen Smalley, linux-security-module,
dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 | 14 ++++++++++++++
security/security.c | 9 +++++++++
3 files changed, 37 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 79d7c73676d7..16530255dc11 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,
@@ -2009,6 +2020,9 @@ 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 7a36064a64ea..910a1efa9a79 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
@@ -1292,6 +1294,18 @@ 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
diff --git a/security/security.c b/security/security.c
index 22877f47cf62..db7b574c9c70 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1988,6 +1988,15 @@ 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (2 preceding siblings ...)
2020-03-09 12:17 ` [RFC PATCH 03/17] security: Add a hook for the point of notification insertion " David Howells
@ 2020-03-09 12:17 ` David Howells
2020-03-09 12:17 ` [RFC PATCH 05/17] pipe: Add general notification queue support " David Howells
` (12 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 05/17] pipe: Add general notification queue support [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (3 preceding siblings ...)
2020-03-09 12:17 ` [RFC PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE " David Howells
@ 2020-03-09 12:17 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 06/17] watch_queue: Add a key/keyring notification facility " David Howells
` (11 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:17 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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/userspace-api/ioctl/ioctl-number.rst | 1
Documentation/watch_queue.rst | 354 +++++++++++
fs/pipe.c | 206 ++++--
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 | 657 ++++++++++++++++++++
10 files changed, 1333 insertions(+), 76 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/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 2e91370dc159..cdf8551d70d7 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -201,6 +201,7 @@ 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 5a34d6c22d4c..36eedf8cb143 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>
@@ -459,6 +460,13 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
goto out;
}
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue) {
+ ret = -EXDEV;
+ goto out;
+ }
+#endif
+
/*
* Only wake up if the pipe started out empty, since
* otherwise there should be no readers waiting.
@@ -628,22 +636,37 @@ static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
int count, head, tail, mask;
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);
- default:
- return -ENOIOCTLCMD;
+ return put_user(count, (int __user *)arg);
+
+#ifdef CONFIG_WATCH_QUEUE
+ case IOC_WATCH_QUEUE_SET_SIZE: {
+ int ret;
+ __pipe_lock(pipe);
+ ret = watch_queue_set_size(pipe, arg);
+ __pipe_unlock(pipe);
+ return ret;
+ }
+
+ case IOC_WATCH_QUEUE_SET_FILTER:
+ return watch_queue_set_filter(
+ pipe, (struct watch_notification_filter __user *)arg);
+#endif
+
+ default:
+ return -ENOIOCTLCMD;
}
}
@@ -753,27 +776,27 @@ 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);
}
@@ -795,12 +818,12 @@ 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),
@@ -812,6 +835,7 @@ 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;
@@ -829,7 +853,14 @@ void free_pipe_info(struct pipe_inode_info *pipe)
{
int i;
- (void) account_pipe_buffers(pipe->user, pipe->ring_size, 0);
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue) {
+ watch_queue_clear(pipe->watch_queue);
+ put_watch_queue(pipe->watch_queue);
+ }
+#endif
+
+ (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;
@@ -905,6 +936,17 @@ int create_pipe_files(struct file **res, int flags)
if (!inode)
return -ENFILE;
+ if (flags & O_NOTIFICATION_PIPE) {
+#ifdef CONFIG_WATCH_QUEUE
+ if (watch_queue_init(inode->i_pipe) < 0) {
+ iput(inode);
+ return -ENOMEM;
+ }
+#else
+ return -ENOPKG;
+#endif
+ }
+
f = alloc_file_pseudo(inode, pipe_mnt, "",
O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
&pipefifo_fops);
@@ -935,7 +977,7 @@ 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);
@@ -1183,42 +1225,12 @@ 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.
@@ -1230,17 +1242,13 @@ 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
@@ -1268,15 +1276,67 @@ 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;
wake_up_interruptible_all(&pipe->rd_wait);
wake_up_interruptible_all(&pipe->wr_wait);
+ 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.
+ */
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+{
+ unsigned long user_bufs;
+ unsigned int nr_slots, size;
+ long ret = 0;
+
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ return -EBUSY;
+#endif
+
+ 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;
}
@@ -1285,9 +1345,17 @@ 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;
+#ifdef CONFIG_WATCH_QUEUE
+ if (for_splice && pipe->watch_queue)
+ return NULL;
+#endif
+ return pipe;
}
long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -1295,7 +1363,7 @@ 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 d671936d0aad..6e6ea30c72b4 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)
@@ -1278,7 +1278,7 @@ 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,
@@ -1313,7 +1313,7 @@ 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;
@@ -1766,8 +1766,8 @@ 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 d5765039652a..8cd14d72dfd1 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
@@ -44,6 +45,7 @@ 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;
@@ -52,6 +54,7 @@ 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;
@@ -62,6 +65,9 @@ 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
};
/*
@@ -236,9 +242,20 @@ 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..5e08db2adc31
--- /dev/null
+++ b/include/linux/watch_queue.h
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/* User-mappable watch queue
+ *
+ * Copyright (C) 2020 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 cfee56c151f1..92229457dc7f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -339,6 +339,18 @@ 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 4cb4130ced32..41e7e3ae07ec 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -115,6 +115,7 @@ 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_SYSCTL_KUNIT_TEST) += sysctl-test.o
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
new file mode 100644
index 000000000000..c103e34f8705
--- /dev/null
+++ b/kernel/watch_queue.c
@@ -0,0 +1,657 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Watch queue and general notification mechanism, built on pipes
+ *
+ * Copyright (C) 2020 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->rd_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->rd_wait.lock);
+ BUG();
+ }
+ wake_up_interruptible_sync_poll_locked(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
+ done = true;
+
+out:
+ spin_unlock_irq(&pipe->rd_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);
+ wfilter = rcu_replace_pointer(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);
+ kref_get(&watch->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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 06/17] watch_queue: Add a key/keyring notification facility [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (4 preceding siblings ...)
2020-03-09 12:17 ` [RFC PATCH 05/17] pipe: Add general notification queue support " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 07/17] Add sample notification program " David Howells
` (10 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 d9b0b859018b..0154721b20b2 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 47c041563d41..d4dc5ea208af 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -116,3 +116,12 @@ 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 b975f8f11124..6ee9d8f6a4a5 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -156,6 +156,9 @@ 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 ba3e2da14cef..2a230c665162 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 718bf7217420..59b19268dca4 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -444,6 +444,7 @@ 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;
@@ -453,7 +454,7 @@ 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 */
@@ -601,6 +602,7 @@ 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);
@@ -611,7 +613,7 @@ 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)
@@ -764,9 +766,11 @@ 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);
@@ -1023,9 +1027,11 @@ 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);
@@ -1057,15 +1063,17 @@ 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);
@@ -1087,8 +1095,10 @@ 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 07/17] Add sample notification program [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (5 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 06/17] watch_queue: Add a key/keyring notification facility " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
` (9 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 | 6 +
samples/Makefile | 1
samples/watch_queue/Makefile | 7 +
samples/watch_queue/watch_test.c | 183 ++++++++++++++++++++++++++++++++++++++
4 files changed, 197 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 9d236c346de5..5c31971a5745 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -190,5 +190,11 @@ config SAMPLE_INTEL_MEI
help
Build a sample program to work with mei device.
+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 f8f847b4f61f..8617edf7f19a 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -24,3 +24,4 @@ obj-$(CONFIG_VIDEO_PCI_SKELETON) += v4l/
obj-y += vfio-mdev/
subdir-$(CONFIG_SAMPLE_VFS) += vfs
obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/
+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..9bf60abf5c7e
--- /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) 2020 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (6 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 07/17] Add sample notification program " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 09/17] pipe: Add notification lossage handling " David Howells
` (8 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 36eedf8cb143..c98452868dde 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -320,8 +320,14 @@ 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 8cd14d72dfd1..fee90981ba40 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 c103e34f8705..ad64ea300f6d 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 9bf60abf5c7e..924e13a49c37 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 09/17] pipe: Add notification lossage handling [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (7 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 10/17] selinux: Implement the watch_key security hook " David Howells
` (7 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, 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 c98452868dde..238601a7ab24 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -314,6 +314,30 @@ 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;
@@ -355,6 +379,10 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (!buf->len) {
pipe_buf_release(pipe, buf);
spin_lock_irq(&pipe->rd_wait.lock);
+#ifdef CONFIG_WATCH_QUEUE
+ if (buf->flags & PIPE_BUF_FLAG_LOSS)
+ pipe->note_loss = true;
+#endif
tail++;
pipe->tail = tail;
spin_unlock_irq(&pipe->rd_wait.lock);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index fee90981ba40..50a4cfee36e2 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
@@ -55,6 +59,9 @@ 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 ad64ea300f6d..9a9699c06709 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 924e13a49c37..0eaff5dc04c3 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 10/17] selinux: Implement the watch_key security hook [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (8 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 09/17] pipe: Add notification lossage handling " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:18 ` [RFC PATCH 11/17] smack: Implement the watch_key and post_notification hooks " David Howells
` (6 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: Stephen Smalley, dhowells, dhowells, casey, sds, nicolas.dichtel,
raven, christian, andres, jlayton, dray, kzak, keyrings,
linux-api, linux-fsdevel, 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 4b6991e178d3..95be16d3f47a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6563,6 +6563,17 @@ 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
@@ -7078,6 +7089,9 @@ 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 11/17] smack: Implement the watch_key and post_notification hooks [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (9 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 10/17] selinux: Implement the watch_key security hook " David Howells
@ 2020-03-09 12:18 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches " David Howells
` (5 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:18 UTC (permalink / raw)
To: torvalds, viro
Cc: Casey Schaufler, dhowells, dhowells, casey, sds, nicolas.dichtel,
raven, christian, andres, jlayton, dray, kzak, keyrings,
linux-api, linux-fsdevel, 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 | 83 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 83 insertions(+), 1 deletion(-)
diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 99d629fd9944..28f23b341c1c 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -75,6 +75,7 @@ struct common_audit_data {
#define LSM_AUDIT_DATA_IBPKEY 13
#define LSM_AUDIT_DATA_IBENDPORT 14
#define LSM_AUDIT_DATA_LOCKDOWN 15
+#define LSM_AUDIT_DATA_NOTIFICATION 16
union {
struct path path;
struct dentry *dentry;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8c61d175e195..2862fc383473 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -41,6 +41,7 @@
#include <linux/parser.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
+#include <linux/watch_queue.h>
#include "smack.h"
#define TRANS_TRUE "TRUE"
@@ -4265,7 +4266,7 @@ 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
@@ -4311,8 +4312,81 @@ 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
*
@@ -4701,8 +4775,15 @@ 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 related [flat|nested] 18+ messages in thread
* [RFC PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (10 preceding siblings ...)
2020-03-09 12:18 ` [RFC PATCH 11/17] smack: Implement the watch_key and post_notification hooks " David Howells
@ 2020-03-09 12:19 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications " David Howells
` (4 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: Casey Schaufler, Stephen Smalley, linux-security-module,
dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
Add security hooks that will allow an LSM to rule on whether or not a watch
may be set on a mount or on a superblock. 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 | 16 ++++++++++++++++
security/security.c | 14 ++++++++++++++
3 files changed, 54 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 16530255dc11..c4451ac197ae 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1427,6 +1427,18 @@
* Check to see if a process is allowed to watch for event notifications
* from devices (as a global set).
*
+ * @watch_mount:
+ * Check to see if a process is allowed to watch for mount topology change
+ * notifications on a mount subtree.
+ * @watch: The watch object
+ * @path: The root of the subtree to watch.
+ *
+ * @watch_sb:
+ * Check to see if a process is allowed to watch for event notifications
+ * from a superblock.
+ * @watch: The watch object
+ * @sb: The superblock to watch.
+ *
* @post_notification:
* Check to see if a watch notification can be posted to a particular
* queue.
@@ -1722,6 +1734,12 @@ union security_list_options {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int (*watch_devices)(void);
#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ int (*watch_mount)(struct watch *watch, struct path *path);
+#endif
+#ifdef CONFIG_SB_NOTIFICATIONS
+ int (*watch_sb)(struct watch *watch, struct super_block *sb);
+#endif
#ifdef CONFIG_WATCH_QUEUE
int (*post_notification)(const struct cred *w_cred,
const struct cred *cred,
@@ -2020,6 +2038,12 @@ struct security_hook_heads {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
struct hlist_head watch_devices;
#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ struct hlist_head watch_mount;
+#endif
+#ifdef CONFIG_SB_NOTIFICATIONS
+ struct hlist_head watch_sb;
+#endif
#ifdef CONFIG_WATCH_QUEUE
struct hlist_head post_notification;
#endif /* CONFIG_WATCH_QUEUE */
diff --git a/include/linux/security.h b/include/linux/security.h
index 910a1efa9a79..2ca2569bc12c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1306,6 +1306,22 @@ static inline int security_post_notification(const struct cred *w_cred,
return 0;
}
#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_MOUNT_NOTIFICATIONS)
+int security_watch_mount(struct watch *watch, struct path *path);
+#else
+static inline int security_watch_mount(struct watch *watch, struct path *path)
+{
+ return 0;
+}
+#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_SB_NOTIFICATIONS)
+int security_watch_sb(struct watch *watch, struct super_block *sb);
+#else
+static inline int security_watch_sb(struct watch *watch, struct super_block *sb)
+{
+ return 0;
+}
+#endif
#ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/security.c b/security/security.c
index db7b574c9c70..5c0463444a90 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2004,6 +2004,20 @@ int security_watch_key(struct key *key)
}
#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+int security_watch_mount(struct watch *watch, struct path *path)
+{
+ return call_int_hook(watch_mount, 0, watch, path);
+}
+#endif
+
+#ifdef CONFIG_SB_NOTIFICATIONS
+int security_watch_sb(struct watch *watch, struct super_block *sb)
+{
+ return call_int_hook(watch_sb, 0, watch, sb);
+}
+#endif
+
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int security_watch_devices(void)
{
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [RFC PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (11 preceding siblings ...)
2020-03-09 12:19 ` [RFC PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches " David Howells
@ 2020-03-09 12:19 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 14/17] watch_queue: sample: Display mount tree " David Howells
` (3 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
Add a mount notification facility whereby notifications about changes in
mount topology and configuration can be received. Note that this only
covers vfsmount topology changes and not superblock events. A separate
facility will be added for that.
Every mount is given a change counter than counts the number of topological
rearrangements in which it is involved and the number of attribute changes
it undergoes. This allows notification loss to be dealt with. Later
patches will provide a way to quickly retrieve this value, along with
information about topology and parameters for the superblock.
Firstly, a watch 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_MOUNT_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
watch_mount(AT_FDCWD, "/", 0, fds[1], 0x02);
In this case, it would let me monitor the mount topology subtree rooted at
"/" for events. Mount notifications propagate up the tree towards the
root, so a watch will catch all of the events happening in the subtree
rooted at the watch.
After setting the watch, records will be placed into the queue when, for
example, as superblock switches between read-write and read-only. Records
are of the following format:
struct mount_notification {
struct watch_notification watch;
__u32 triggered_on;
__u32 changed_mount;
} *n;
Where:
n->watch.type will be WATCH_TYPE_MOUNT_NOTIFY.
n->watch.subtype will indicate the type of event, such as
NOTIFY_MOUNT_NEW_MOUNT.
n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
record.
n->watch.info & WATCH_INFO_ID will be the fifth argument to
watch_mount(), shifted.
n->watch.info & NOTIFY_MOUNT_IN_SUBTREE if true indicates that the
notifcation was generated in the mount subtree rooted at the watch,
and not actually in the watch itself.
n->watch.info & NOTIFY_MOUNT_IS_RECURSIVE if true indicates that
the notifcation was generated by an event (eg. SETATTR) that was
applied recursively. The notification is only generated for the
object that initially triggered it.
n->watch.info & NOTIFY_MOUNT_IS_NOW_RO will be used for
NOTIFY_MOUNT_READONLY, being set if the superblock becomes R/O, and
being cleared otherwise, and for NOTIFY_MOUNT_NEW_MOUNT, being set
if the new mount is a submount (e.g. an automount).
n->watch.info & NOTIFY_MOUNT_IS_SUBMOUNT if true indicates that the
NOTIFY_MOUNT_NEW_MOUNT notification is in response to a mount
performed by the kernel (e.g. an automount).
n->triggered_on indicates the ID of the mount on which the watch
was installed.
n->changed_mount indicates the ID of the mount that was affected.
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>
---
arch/alpha/kernel/syscalls/syscall.tbl | 1
arch/arm/tools/syscall.tbl | 1
arch/arm64/include/asm/unistd.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
fs/Kconfig | 9 +
fs/Makefile | 1
fs/mount.h | 35 +++++
fs/mount_notify.c | 186 +++++++++++++++++++++++++++
fs/namespace.c | 22 +++
include/linux/dcache.h | 1
include/linux/syscalls.h | 2
include/uapi/asm-generic/unistd.h | 4 -
include/uapi/linux/watch_queue.h | 32 +++++
kernel/sys_ni.c | 3
27 files changed, 310 insertions(+), 3 deletions(-)
create mode 100644 fs/mount_notify.c
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 36d42da7466a..b869428033ef 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -477,3 +477,4 @@
# 545 reserved for clone3
547 common openat2 sys_openat2
548 common pidfd_getfd sys_pidfd_getfd
+549 common watch_mount sys_watch_mount
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 4d1cf74a2caa..9c389da9efcc 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -451,3 +451,4 @@
435 common clone3 sys_clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 1dd22da1c3a9..75f04a1023be 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 439
+#define __NR_compat_syscalls 440
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index 042911e670b8..6817f865cc71 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -358,3 +358,4 @@
# 435 reserved for clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index f4f49fcb76d0..fbf85da75ecb 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -437,3 +437,4 @@
435 common clone3 __sys_clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 4c67b11f9c9e..b05b192da1e2 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -443,3 +443,4 @@
435 common clone3 sys_clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 1f9e8ad636cc..0f85d2a033f9 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -376,3 +376,4 @@
435 n32 clone3 __sys_clone3
437 n32 openat2 sys_openat2
438 n32 pidfd_getfd sys_pidfd_getfd
+439 n32 watch_mount sys_watch_mount
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index c0b9d802dbf6..905cf9ac0792 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -352,3 +352,4 @@
435 n64 clone3 __sys_clone3
437 n64 openat2 sys_openat2
438 n64 pidfd_getfd sys_pidfd_getfd
+439 n64 watch_mount sys_watch_mount
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index ac586774c980..834b26b08d74 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -425,3 +425,4 @@
435 o32 clone3 __sys_clone3
437 o32 openat2 sys_openat2
438 o32 pidfd_getfd sys_pidfd_getfd
+439 o32 watch_mount sys_watch_mount
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 52a15f5cd130..badd3449db43 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -435,3 +435,4 @@
435 common clone3 sys_clone3_wrapper
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 35b61bfc1b1a..b404361bc929 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -519,3 +519,4 @@
435 nospu clone3 ppc_clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index bd7bd3581a0f..33071de24511 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -440,3 +440,4 @@
435 common clone3 sys_clone3 sys_clone3
437 common openat2 sys_openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount sys_watch_mount
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index c7a30fcd135f..682c125122f4 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -440,3 +440,4 @@
# 435 reserved for clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index f13615ecdecc..febf3cd675e3 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -483,3 +483,4 @@
# 435 reserved for clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index c17cb77eb150..085bcc5afdf1 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -442,3 +442,4 @@
435 i386 clone3 sys_clone3 __ia32_sys_clone3
437 i386 openat2 sys_openat2 __ia32_sys_openat2
438 i386 pidfd_getfd sys_pidfd_getfd __ia32_sys_pidfd_getfd
+439 i386 watch_mount sys_watch_mount __ia32_sys_watch_mount
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 44d510bc9b78..9cfb6b2eb319 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -359,6 +359,7 @@
435 common clone3 __x64_sys_clone3/ptregs
437 common openat2 __x64_sys_openat2
438 common pidfd_getfd __x64_sys_pidfd_getfd
+439 common watch_mount __x64_sys_watch_mount
#
# 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 85a9ab1bc04d..1a066a43a58b 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -408,3 +408,4 @@
435 common clone3 sys_clone3
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
+439 common watch_mount sys_watch_mount
diff --git a/fs/Kconfig b/fs/Kconfig
index 708ba336e689..d7039137d538 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -117,6 +117,15 @@ source "fs/verity/Kconfig"
source "fs/notify/Kconfig"
+config MOUNT_NOTIFICATIONS
+ bool "Mount topology change notifications"
+ select WATCH_QUEUE
+ help
+ This option provides support for getting change notifications on the
+ mount tree topology. This makes use of the /dev/watch_queue misc
+ device to handle the notification buffer and provides the
+ mount_notify() system call to enable/disable watchpoints.
+
source "fs/quota/Kconfig"
source "fs/autofs/Kconfig"
diff --git a/fs/Makefile b/fs/Makefile
index 505e51166973..4477757780d0 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -22,6 +22,7 @@ obj-y += no-block.o
endif
obj-$(CONFIG_PROC_FS) += proc_namespace.o
+obj-$(CONFIG_MOUNT_NOTIFICATIONS) += mount_notify.o
obj-y += notify/
obj-$(CONFIG_EPOLL) += eventpoll.o
diff --git a/fs/mount.h b/fs/mount.h
index 711a4093e475..381f842f3a27 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -4,6 +4,7 @@
#include <linux/poll.h>
#include <linux/ns_common.h>
#include <linux/fs_pin.h>
+#include <linux/watch_queue.h>
struct mnt_namespace {
atomic_t count;
@@ -72,6 +73,12 @@ struct mount {
int mnt_expiry_mark; /* true if marked for expiry */
struct hlist_head mnt_pins;
struct hlist_head mnt_stuck_children;
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ atomic_t mnt_topology_changes; /* Number of topology changes applied */
+ atomic_t mnt_attr_changes; /* Number of attribute changes applied */
+ atomic_t mnt_subtree_notifications; /* Number of notifications in subtree */
+ struct watch_list *mnt_watchers; /* Watches on dentries within this mount */
+#endif
} __randomize_layout;
#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
@@ -153,3 +160,31 @@ static inline bool is_anon_ns(struct mnt_namespace *ns)
{
return ns->seq == 0;
}
+
+extern void post_mount_notification(struct mount *changed,
+ struct mount_notification *notify);
+
+static inline void notify_mount(struct mount *changed,
+ struct mount *aux,
+ enum mount_notification_subtype subtype,
+ u32 info_flags)
+{
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ if (aux)
+ atomic_inc(&changed->mnt_topology_changes);
+ else
+ atomic_inc(&changed->mnt_attr_changes);
+
+ {
+ struct mount_notification n = {
+ .watch.type = WATCH_TYPE_MOUNT_NOTIFY,
+ .watch.subtype = subtype,
+ .watch.info = info_flags | watch_sizeof(n),
+ .triggered_on = changed->mnt_id,
+ .changed_mount = aux ? aux->mnt_id : 0,
+ };
+
+ post_mount_notification(changed, &n);
+ }
+#endif
+}
diff --git a/fs/mount_notify.c b/fs/mount_notify.c
new file mode 100644
index 000000000000..d946765afcc4
--- /dev/null
+++ b/fs/mount_notify.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Provide mount topology/attribute change notifications.
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/syscalls.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include "mount.h"
+
+/*
+ * Post mount notifications to all watches going rootwards along the tree.
+ *
+ * Must be called with the mount_lock held.
+ */
+void post_mount_notification(struct mount *changed,
+ struct mount_notification *notify)
+{
+ const struct cred *cred = current_cred();
+ struct path cursor;
+ struct mount *mnt;
+ unsigned seq;
+
+ seq = 0;
+ rcu_read_lock();
+restart:
+ cursor.mnt = &changed->mnt;
+ cursor.dentry = changed->mnt.mnt_root;
+ mnt = real_mount(cursor.mnt);
+ notify->watch.info &= ~NOTIFY_MOUNT_IN_SUBTREE;
+
+ read_seqbegin_or_lock(&rename_lock, &seq);
+ for (;;) {
+ if (mnt->mnt_watchers &&
+ !hlist_empty(&mnt->mnt_watchers->watchers)) {
+ if (cursor.dentry->d_flags & DCACHE_MOUNT_WATCH)
+ post_watch_notification(mnt->mnt_watchers,
+ ¬ify->watch, cred,
+ (unsigned long)cursor.dentry);
+ } else {
+ cursor.dentry = mnt->mnt.mnt_root;
+ }
+ notify->watch.info |= NOTIFY_MOUNT_IN_SUBTREE;
+
+ if (cursor.dentry == cursor.mnt->mnt_root ||
+ IS_ROOT(cursor.dentry)) {
+ struct mount *parent = READ_ONCE(mnt->mnt_parent);
+
+ /* Escaped? */
+ if (cursor.dentry != cursor.mnt->mnt_root)
+ break;
+
+ /* Global root? */
+ if (mnt == parent)
+ break;
+
+ cursor.dentry = READ_ONCE(mnt->mnt_mountpoint);
+ mnt = parent;
+ cursor.mnt = &mnt->mnt;
+ atomic_inc(&mnt->mnt_subtree_notifications);
+ } else {
+ cursor.dentry = cursor.dentry->d_parent;
+ }
+ }
+
+ if (need_seqretry(&rename_lock, seq)) {
+ seq = 1;
+ goto restart;
+ }
+
+ done_seqretry(&rename_lock, seq);
+ rcu_read_unlock();
+}
+
+static void release_mount_watch(struct watch *watch)
+{
+ struct dentry *dentry = (struct dentry *)(unsigned long)watch->id;
+
+ dput(dentry);
+}
+
+/**
+ * sys_watch_mount - Watch for mount topology/attribute changes
+ * @dfd: Base directory to pathwalk from or fd referring to mount.
+ * @filename: Path to mount to place the watch upon
+ * @at_flags: Pathwalk control flags
+ * @watch_fd: The watch queue to send notifications to.
+ * @watch_id: The watch ID to be placed in the notification (-1 to remove watch)
+ */
+SYSCALL_DEFINE5(watch_mount,
+ int, dfd,
+ const char __user *, filename,
+ unsigned int, at_flags,
+ int, watch_fd,
+ int, watch_id)
+{
+ struct watch_queue *wqueue;
+ struct watch_list *wlist = NULL;
+ struct watch *watch = NULL;
+ struct mount *m;
+ struct path path;
+ unsigned int lookup_flags =
+ LOOKUP_DIRECTORY | LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
+ int ret;
+
+ if (watch_id < -1 || watch_id > 0xff)
+ return -EINVAL;
+ if ((at_flags & ~(AT_NO_AUTOMOUNT | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+ if (at_flags & AT_NO_AUTOMOUNT)
+ lookup_flags &= ~LOOKUP_AUTOMOUNT;
+ if (at_flags & AT_EMPTY_PATH)
+ lookup_flags |= LOOKUP_EMPTY;
+
+ ret = user_path_at(dfd, filename, lookup_flags, &path);
+ if (ret)
+ return ret;
+
+ ret = inode_permission(path.dentry->d_inode, MAY_EXEC);
+ if (ret)
+ goto err_path;
+
+ wqueue = get_watch_queue(watch_fd);
+ if (IS_ERR(wqueue))
+ goto err_path;
+
+ m = real_mount(path.mnt);
+
+ if (watch_id >= 0) {
+ ret = -ENOMEM;
+ if (!READ_ONCE(m->mnt_watchers)) {
+ wlist = kzalloc(sizeof(*wlist), GFP_KERNEL);
+ if (!wlist)
+ goto err_wqueue;
+ init_watch_list(wlist, release_mount_watch);
+ }
+
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (!watch)
+ goto err_wlist;
+
+ init_watch(watch, wqueue);
+ watch->id = (unsigned long)path.dentry;
+ watch->info_id = (u32)watch_id << 24;
+
+ ret = security_watch_mount(watch, &path);
+ if (ret < 0)
+ goto err_watch;
+
+ down_write(&m->mnt.mnt_sb->s_umount);
+ if (!m->mnt_watchers) {
+ m->mnt_watchers = wlist;
+ wlist = NULL;
+ }
+
+ ret = add_watch_to_object(watch, m->mnt_watchers);
+ if (ret == 0) {
+ spin_lock(&path.dentry->d_lock);
+ path.dentry->d_flags |= DCACHE_MOUNT_WATCH;
+ spin_unlock(&path.dentry->d_lock);
+ dget(path.dentry);
+ watch = NULL;
+ }
+ up_write(&m->mnt.mnt_sb->s_umount);
+ } else {
+ down_write(&m->mnt.mnt_sb->s_umount);
+ ret = remove_watch_from_object(m->mnt_watchers, wqueue,
+ (unsigned long)path.dentry,
+ false);
+ up_write(&m->mnt.mnt_sb->s_umount);
+ }
+
+err_watch:
+ kfree(watch);
+err_wlist:
+ kfree(wlist);
+err_wqueue:
+ put_watch_queue(wqueue);
+err_path:
+ path_put(&path);
+ return ret;
+}
diff --git a/fs/namespace.c b/fs/namespace.c
index 85b5f7bea82e..54d237251941 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -498,6 +498,9 @@ static int mnt_make_readonly(struct mount *mnt)
smp_wmb();
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
unlock_mount_hash();
+ if (ret == 0)
+ notify_mount(mnt, NULL, NOTIFY_MOUNT_READONLY,
+ NOTIFY_MOUNT_IS_NOW_RO);
return ret;
}
@@ -506,6 +509,7 @@ static int __mnt_unmake_readonly(struct mount *mnt)
lock_mount_hash();
mnt->mnt.mnt_flags &= ~MNT_READONLY;
unlock_mount_hash();
+ notify_mount(mnt, NULL, NOTIFY_MOUNT_READONLY, 0);
return 0;
}
@@ -819,6 +823,7 @@ static struct mountpoint *unhash_mnt(struct mount *mnt)
*/
static void umount_mnt(struct mount *mnt)
{
+ notify_mount(mnt->mnt_parent, mnt, NOTIFY_MOUNT_UNMOUNT, 0);
put_mountpoint(unhash_mnt(mnt));
}
@@ -1159,6 +1164,11 @@ static void mntput_no_expire(struct mount *mnt)
mnt->mnt.mnt_flags |= MNT_DOOMED;
rcu_read_unlock();
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ if (mnt->mnt_watchers)
+ remove_watch_list(mnt->mnt_watchers, mnt->mnt_id);
+#endif
+
list_del(&mnt->mnt_instance);
if (unlikely(!list_empty(&mnt->mnt_mounts))) {
@@ -1453,6 +1463,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
p = list_first_entry(&tmp_list, struct mount, mnt_list);
list_del_init(&p->mnt_expire);
list_del_init(&p->mnt_list);
+
ns = p->mnt_ns;
if (ns) {
ns->mounts--;
@@ -2079,7 +2090,10 @@ static int attach_recursive_mnt(struct mount *source_mnt,
}
if (moving) {
unhash_mnt(source_mnt);
+ notify_mount(source_mnt->mnt_parent, source_mnt,
+ NOTIFY_MOUNT_MOVE_FROM, 0);
attach_mnt(source_mnt, dest_mnt, dest_mp);
+ notify_mount(dest_mnt, source_mnt, NOTIFY_MOUNT_MOVE_TO, 0);
touch_mnt_namespace(source_mnt->mnt_ns);
} else {
if (source_mnt->mnt_ns) {
@@ -2088,6 +2102,11 @@ static int attach_recursive_mnt(struct mount *source_mnt,
}
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
commit_tree(source_mnt);
+ notify_mount(dest_mnt, source_mnt, NOTIFY_MOUNT_NEW_MOUNT,
+ (source_mnt->mnt.mnt_sb->s_flags & SB_RDONLY ?
+ NOTIFY_MOUNT_IS_NOW_RO : 0) |
+ (source_mnt->mnt.mnt_sb->s_flags & SB_SUBMOUNT ?
+ NOTIFY_MOUNT_IS_SUBMOUNT : 0));
}
hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
@@ -2464,6 +2483,8 @@ static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
mnt->mnt.mnt_flags = mnt_flags;
touch_mnt_namespace(mnt->mnt_ns);
unlock_mount_hash();
+ notify_mount(mnt, NULL, NOTIFY_MOUNT_SETATTR,
+ (mnt_flags & SB_RDONLY ? NOTIFY_MOUNT_IS_NOW_RO : 0));
}
static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
@@ -2899,6 +2920,7 @@ void mark_mounts_for_expiry(struct list_head *mounts)
propagate_mount_busy(mnt, 1))
continue;
list_move(&mnt->mnt_expire, &graveyard);
+ notify_mount(mnt, NULL, NOTIFY_MOUNT_EXPIRY, 0);
}
while (!list_empty(&graveyard)) {
mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c1488cc84fd9..7b194d778155 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -217,6 +217,7 @@ struct dentry_operations {
#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
#define DCACHE_DENTRY_CURSOR 0x20000000
#define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */
+#define DCACHE_MOUNT_WATCH 0x80000000 /* There's a mount watch here */
extern seqlock_t rename_lock;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 1815065d52f3..1fd43af3b22d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1003,6 +1003,8 @@ asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
siginfo_t __user *info,
unsigned int flags);
asmlinkage long sys_pidfd_getfd(int pidfd, int fd, unsigned int flags);
+asmlinkage long sys_watch_mount(int dfd, const char __user *path,
+ unsigned int at_flags, int watch_fd, int watch_id);
/*
* Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 3a3201e4618e..6b5748287883 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -855,9 +855,11 @@ __SYSCALL(__NR_clone3, sys_clone3)
__SYSCALL(__NR_openat2, sys_openat2)
#define __NR_pidfd_getfd 438
__SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd)
+#define __NR_watch_mount 439
+__SYSCALL(__NR_watch_mount, sys_watch_mount)
#undef __NR_syscalls
-#define __NR_syscalls 439
+#define __NR_syscalls 440
/*
* 32 bit systems traditionally used different
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index c3d8320b5d3a..b0f35cf51394 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_MOUNT_NOTIFY = 2, /* Mount topology change notification */
+ WATCH_TYPE___NR = 3
};
enum watch_meta_notification_subtype {
@@ -101,4 +102,33 @@ struct key_notification {
__u32 aux; /* Per-type auxiliary data */
};
+/*
+ * Type of mount topology change notification.
+ */
+enum mount_notification_subtype {
+ NOTIFY_MOUNT_NEW_MOUNT = 0, /* New mount added */
+ NOTIFY_MOUNT_UNMOUNT = 1, /* Mount removed manually */
+ NOTIFY_MOUNT_EXPIRY = 2, /* Automount expired */
+ NOTIFY_MOUNT_READONLY = 3, /* Mount R/O state changed */
+ NOTIFY_MOUNT_SETATTR = 4, /* Mount attributes changed */
+ NOTIFY_MOUNT_MOVE_FROM = 5, /* Mount moved from here */
+ NOTIFY_MOUNT_MOVE_TO = 6, /* Mount moved to here (compare op_id) */
+};
+
+#define NOTIFY_MOUNT_IN_SUBTREE WATCH_INFO_FLAG_0 /* Event not actually at watched dentry */
+#define NOTIFY_MOUNT_IS_RECURSIVE WATCH_INFO_FLAG_1 /* Change applied recursively */
+#define NOTIFY_MOUNT_IS_NOW_RO WATCH_INFO_FLAG_2 /* Mount changed to R/O */
+#define NOTIFY_MOUNT_IS_SUBMOUNT WATCH_INFO_FLAG_3 /* New mount is submount */
+
+/*
+ * Mount topology/configuration change notification record.
+ * - watch.type = WATCH_TYPE_MOUNT_NOTIFY
+ * - watch.subtype = enum mount_notification_subtype
+ */
+struct mount_notification {
+ struct watch_notification watch; /* WATCH_TYPE_MOUNT_NOTIFY */
+ __u32 triggered_on; /* The mount that the notify was on */
+ __u32 changed_mount; /* The mount that got changed */
+};
+
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 3b69a560a7ac..3e1c5c9d2efe 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -85,6 +85,9 @@ COND_SYSCALL(ioprio_get);
/* fs/locks.c */
COND_SYSCALL(flock);
+/* fs/mount_notify.c */
+COND_SYSCALL(watch_mount);
+
/* fs/namei.c */
/* fs/namespace.c */
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [RFC PATCH 14/17] watch_queue: sample: Display mount tree change notifications [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (12 preceding siblings ...)
2020-03-09 12:19 ` [RFC PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications " David Howells
@ 2020-03-09 12:19 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID " David Howells
` (2 subsequent siblings)
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
This is run like:
./watch_test
and watches "/" for changes to the mount topology and the attributes of
individual mount objects.
# mount -t tmpfs none /mnt
# mount -o remount,ro /mnt
# mount -o remount,rw /mnt
producing:
# ./watch_test
read() = 16
NOTIFY[000]: ty=000002 sy=00 i=02000010
MOUNT 00000060 change=0[new_mount] aux=416
read() = 16
NOTIFY[000]: ty=000002 sy=04 i=02010010
MOUNT 000001a0 change=4[setattr] aux=0
read() = 16
NOTIFY[000]: ty=000002 sy=04 i=02010010
MOUNT 000001a0 change=4[setattr] aux=0
Signed-off-by: David Howells <dhowells@redhat.com>
---
samples/watch_queue/watch_test.c | 39 +++++++++++++++++++++++++++++++++++++-
1 file changed, 38 insertions(+), 1 deletion(-)
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 0eaff5dc04c3..49d185150506 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -26,6 +26,9 @@
#ifndef __NR_watch_devices
#define __NR_watch_devices -1
#endif
+#ifndef __NR_watch_mount
+#define __NR_watch_mount -1
+#endif
#define BUF_SIZE 256
@@ -58,6 +61,27 @@ 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 *mount_subtypes[256] = {
+ [NOTIFY_MOUNT_NEW_MOUNT] = "new_mount",
+ [NOTIFY_MOUNT_UNMOUNT] = "unmount",
+ [NOTIFY_MOUNT_EXPIRY] = "expiry",
+ [NOTIFY_MOUNT_READONLY] = "readonly",
+ [NOTIFY_MOUNT_SETATTR] = "setattr",
+ [NOTIFY_MOUNT_MOVE_FROM] = "move_from",
+ [NOTIFY_MOUNT_MOVE_TO] = "move_to",
+};
+
+static void saw_mount_change(struct watch_notification *n, size_t len)
+{
+ struct mount_notification *m = (struct mount_notification *)n;
+
+ if (len != sizeof(struct mount_notification))
+ return;
+
+ printf("MOUNT %08x change=%u[%s] aux=%u\n",
+ m->triggered_on, n->subtype, mount_subtypes[n->subtype], m->changed_mount);
+}
+
/*
* Consume and display events.
*/
@@ -134,6 +158,9 @@ static void consumer(int fd)
default:
printf("other type\n");
break;
+ case WATCH_TYPE_MOUNT_NOTIFY:
+ saw_mount_change(&n.n, len);
+ break;
}
p += len;
@@ -142,12 +169,17 @@ 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_MOUNT_NOTIFY,
+ // Reject move-from notifications
+ .subtype_filter[0] = UINT_MAX & ~(1 << NOTIFY_MOUNT_MOVE_FROM),
+ },
},
};
@@ -181,6 +213,11 @@ int main(int argc, char **argv)
exit(1);
}
+ if (syscall(__NR_watch_mount, AT_FDCWD, "/", 0, fd, 0x02) == -1) {
+ perror("watch_mount");
+ exit(1);
+ }
+
consumer(fd);
exit(0);
}
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [RFC PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (13 preceding siblings ...)
2020-03-09 12:19 ` [RFC PATCH 14/17] watch_queue: sample: Display mount tree " David Howells
@ 2020-03-09 12:19 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 16/17] watch_queue: Add superblock notifications " David Howells
2020-03-09 12:19 ` [RFC PATCH 17/17] watch_queue: sample: Display " David Howells
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
Introduce an (effectively) non-repeating system-unique superblock ID that
can be used to determine that two object are in the same superblock without
risking reuse of the ID in the meantime (as is possible with device IDs).
The ID is time-based to make it harder to use it as a covert communications
channel.
In future patches, this ID will be used to tag superblock notification
messages. It will also be made queryable.
Signed-off-by: David Howells <dhowells@redhat.com>
---
fs/internal.h | 1 +
fs/super.c | 24 ++++++++++++++++++++++++
include/linux/fs.h | 3 +++
3 files changed, 28 insertions(+)
diff --git a/fs/internal.h b/fs/internal.h
index f3f280b952a3..a0d90f23593c 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -109,6 +109,7 @@ extern int reconfigure_super(struct fs_context *);
extern bool trylock_super(struct super_block *sb);
extern struct super_block *user_get_super(dev_t);
extern bool mount_capable(struct fs_context *);
+extern void vfs_generate_unique_id(u64 *);
/*
* open.c
diff --git a/fs/super.c b/fs/super.c
index cd352530eca9..ececa5695fd1 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -44,6 +44,8 @@ static int thaw_super_locked(struct super_block *sb);
static LIST_HEAD(super_blocks);
static DEFINE_SPINLOCK(sb_lock);
+static u64 vfs_last_identifier;
+static u64 vfs_identifier_offset;
static char *sb_writers_name[SB_FREEZE_LEVELS] = {
"sb_writers",
@@ -273,6 +275,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
goto fail;
if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
goto fail;
+ vfs_generate_unique_id(&s->s_unique_id);
return s;
fail:
@@ -1867,3 +1870,24 @@ int thaw_super(struct super_block *sb)
return thaw_super_locked(sb);
}
EXPORT_SYMBOL(thaw_super);
+
+/*
+ * Generate a unique identifier for a superblock or mount object.
+ */
+void vfs_generate_unique_id(u64 *_id)
+{
+ u64 id = ktime_to_ns(ktime_get());
+
+ spin_lock(&sb_lock);
+
+ id += vfs_identifier_offset;
+ if (id <= vfs_last_identifier) {
+ id = vfs_last_identifier + 1;
+ vfs_identifier_offset = vfs_last_identifier - id;
+ }
+
+ vfs_last_identifier = id;
+ spin_unlock(&sb_lock);
+
+ *_id = id;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3cd4fe6b845e..9de6bfe41016 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1548,6 +1548,9 @@ struct super_block {
spinlock_t s_inode_wblist_lock;
struct list_head s_inodes_wb; /* writeback inodes */
+
+ /* Superblock event notifications */
+ u64 s_unique_id;
} __randomize_layout;
/* Helper functions so that in most cases filesystems will
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [RFC PATCH 16/17] watch_queue: Add superblock notifications [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (14 preceding siblings ...)
2020-03-09 12:19 ` [RFC PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID " David Howells
@ 2020-03-09 12:19 ` David Howells
2020-03-09 12:19 ` [RFC PATCH 17/17] watch_queue: sample: Display " David Howells
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
Add a superblock event notification facility whereby notifications about
superblock events, such as I/O errors (EIO), quota limits being hit
(EDQUOT) and running out of space (ENOSPC) can be reported to a monitoring
process asynchronously. Note that this does not cover vfsmount topology
changes. watch_mount() is used for that.
Firstly, a watch 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_SB_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
watch_sb(AT_FDCWD, "/home/dhowells", 0, fds[1], 0x03);
In this case, it would let me monitor my own homedir for events. After
setting the watch, records will be placed into the queue when, for example,
as superblock switches between read-write and read-only. Records are of
the following format:
struct superblock_notification {
struct watch_notification watch;
__u64 sb_id;
} *n;
Where:
n->watch.type will be WATCH_TYPE_SB_NOTIFY.
n->watch.subtype will indicate the type of event, such as
NOTIFY_SUPERBLOCK_READONLY.
n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
record.
n->watch.info & WATCH_INFO_ID will be the fifth argument to
watch_sb(), shifted.
n->watch.info & NOTIFY_SUPERBLOCK_IS_NOW_RO will be used for
NOTIFY_SUPERBLOCK_READONLY, being set if the superblock becomes
R/O, and being cleared otherwise.
n->sb_id will be the ID of the superblock, as can be retrieved with
the fsinfo() syscall, as part of the fsinfo_sb_notifications
attribute in the the watch_id field.
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>
---
arch/alpha/kernel/syscalls/syscall.tbl | 1
arch/arm/tools/syscall.tbl | 1
arch/arm64/include/asm/unistd.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
fs/Kconfig | 12 ++
fs/super.c | 132 +++++++++++++++++++++++++++
include/linux/fs.h | 81 +++++++++++++++++
include/linux/syscalls.h | 2
include/uapi/asm-generic/unistd.h | 4 +
include/uapi/linux/watch_queue.h | 31 ++++++
kernel/sys_ni.c | 3 +
24 files changed, 280 insertions(+), 3 deletions(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index b869428033ef..7c0115af9010 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -478,3 +478,4 @@
547 common openat2 sys_openat2
548 common pidfd_getfd sys_pidfd_getfd
549 common watch_mount sys_watch_mount
+550 common watch_sb sys_watch_sb
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 9c389da9efcc..f256f009a89f 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -452,3 +452,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 75f04a1023be..bc0f923e0e04 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 440
+#define __NR_compat_syscalls 441
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index 6817f865cc71..a4dafc659647 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -359,3 +359,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index fbf85da75ecb..893fb4151547 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -438,3 +438,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index b05b192da1e2..54aaf0d40c64 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -444,3 +444,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 0f85d2a033f9..fd34dd0efed0 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -377,3 +377,4 @@
437 n32 openat2 sys_openat2
438 n32 pidfd_getfd sys_pidfd_getfd
439 n32 watch_mount sys_watch_mount
+440 n32 watch_sb sys_watch_sb
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 905cf9ac0792..db0f4c0a0a0b 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -353,3 +353,4 @@
437 n64 openat2 sys_openat2
438 n64 pidfd_getfd sys_pidfd_getfd
439 n64 watch_mount sys_watch_mount
+440 n64 watch_sb sys_watch_sb
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 834b26b08d74..ce2e1326de8f 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -426,3 +426,4 @@
437 o32 openat2 sys_openat2
438 o32 pidfd_getfd sys_pidfd_getfd
439 o32 watch_mount sys_watch_mount
+440 o32 watch_sb sys_watch_sb
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index badd3449db43..6e4a7c08b64b 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -436,3 +436,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index b404361bc929..08943f3b8206 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -520,3 +520,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 33071de24511..b3b8529d2b74 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -441,3 +441,4 @@
437 common openat2 sys_openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb sys_watch_sb
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 682c125122f4..89307a20657c 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -441,3 +441,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index febf3cd675e3..4ff841a00450 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -484,3 +484,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 085bcc5afdf1..e2731d295f88 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -443,3 +443,4 @@
437 i386 openat2 sys_openat2 __ia32_sys_openat2
438 i386 pidfd_getfd sys_pidfd_getfd __ia32_sys_pidfd_getfd
439 i386 watch_mount sys_watch_mount __ia32_sys_watch_mount
+440 i386 watch_sb sys_watch_sb __ia32_sys_watch_sb
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 9cfb6b2eb319..f4391176102c 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -360,6 +360,7 @@
437 common openat2 __x64_sys_openat2
438 common pidfd_getfd __x64_sys_pidfd_getfd
439 common watch_mount __x64_sys_watch_mount
+440 common watch_sb __x64_sys_watch_sb
#
# 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 1a066a43a58b..8e7d731ed6cf 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -409,3 +409,4 @@
437 common openat2 sys_openat2
438 common pidfd_getfd sys_pidfd_getfd
439 common watch_mount sys_watch_mount
+440 common watch_sb sys_watch_sb
diff --git a/fs/Kconfig b/fs/Kconfig
index d7039137d538..fef1365c23a5 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -126,6 +126,18 @@ config MOUNT_NOTIFICATIONS
device to handle the notification buffer and provides the
mount_notify() system call to enable/disable watchpoints.
+config SB_NOTIFICATIONS
+ bool "Superblock event notifications"
+ select WATCH_QUEUE
+ help
+ This option provides support for receiving superblock event
+ notifications. This makes use of the /dev/watch_queue misc device to
+ handle the notification buffer and provides the sb_notify() system
+ call to enable/disable watches.
+
+ Events can include things like changing between R/W and R/O, EIO
+ generation, ENOSPC generation and EDQUOT generation.
+
source "fs/quota/Kconfig"
source "fs/autofs/Kconfig"
diff --git a/fs/super.c b/fs/super.c
index ececa5695fd1..a7aa16ca380c 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -37,6 +37,8 @@
#include <linux/lockdep.h>
#include <linux/user_namespace.h>
#include <linux/fs_context.h>
+#include <linux/syscalls.h>
+#include <linux/namei.h>
#include <uapi/linux/mount.h>
#include "internal.h"
@@ -333,6 +335,10 @@ void deactivate_locked_super(struct super_block *s)
{
struct file_system_type *fs = s->s_type;
if (atomic_dec_and_test(&s->s_active)) {
+#ifdef CONFIG_SB_NOTIFICATIONS
+ if (s->s_watchers)
+ remove_watch_list(s->s_watchers, s->s_unique_id);
+#endif
cleancache_invalidate_fs(s);
unregister_shrinker(&s->s_shrink);
fs->kill_sb(s);
@@ -972,6 +978,8 @@ int reconfigure_super(struct fs_context *fc)
/* Needs to be ordered wrt mnt_is_readonly() */
smp_wmb();
sb->s_readonly_remount = 0;
+ notify_sb(sb, NOTIFY_SUPERBLOCK_READONLY,
+ remount_ro ? NOTIFY_SUPERBLOCK_IS_NOW_RO : 0);
/*
* Some filesystems modify their metadata via some other path than the
@@ -1891,3 +1899,127 @@ void vfs_generate_unique_id(u64 *_id)
*_id = id;
}
+
+#ifdef CONFIG_SB_NOTIFICATIONS
+/*
+ * Post superblock notifications.
+ */
+void post_sb_notification(struct super_block *s, struct superblock_notification *n)
+{
+ post_watch_notification(s->s_watchers, &n->watch, current_cred(),
+ s->s_unique_id);
+}
+
+static void sb_release_watch(struct watch *watch)
+{
+ put_super(watch->private);
+}
+
+/**
+ * sys_watch_sb - Watch for superblock events.
+ * @dfd: Base directory to pathwalk from or fd referring to superblock.
+ * @filename: Path to superblock to place the watch upon
+ * @at_flags: Pathwalk control flags
+ * @watch_fd: The watch queue to send notifications to.
+ * @watch_id: The watch ID to be placed in the notification (-1 to remove watch)
+ */
+SYSCALL_DEFINE5(watch_sb,
+ int, dfd,
+ const char __user *, filename,
+ unsigned int, at_flags,
+ int, watch_fd,
+ int, watch_id)
+{
+ struct watch_queue *wqueue;
+ struct super_block *s;
+ struct watch_list *wlist = NULL;
+ struct watch *watch = NULL;
+ struct path path;
+ unsigned int lookup_flags =
+ LOOKUP_DIRECTORY | LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
+ bool drop_s_count = false;
+ int ret;
+
+ if (watch_id < -1 || watch_id > 0xff)
+ return -EINVAL;
+ if ((at_flags & ~(AT_NO_AUTOMOUNT | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+ if (at_flags & AT_NO_AUTOMOUNT)
+ lookup_flags &= ~LOOKUP_AUTOMOUNT;
+ if (at_flags & AT_EMPTY_PATH)
+ lookup_flags |= LOOKUP_EMPTY;
+
+ ret = user_path_at(dfd, filename, at_flags, &path);
+ if (ret)
+ return ret;
+
+ ret = inode_permission(path.dentry->d_inode, MAY_EXEC);
+ if (ret)
+ goto err_path;
+
+ wqueue = get_watch_queue(watch_fd);
+ if (IS_ERR(wqueue))
+ goto err_path;
+
+ s = path.dentry->d_sb;
+ if (watch_id >= 0) {
+ ret = -ENOMEM;
+ if (!READ_ONCE(s->s_watchers)) {
+ wlist = kzalloc(sizeof(*wlist), GFP_KERNEL);
+ if (!wlist)
+ goto err_wqueue;
+ init_watch_list(wlist, sb_release_watch);
+ }
+
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (!watch)
+ goto err_wlist;
+
+ init_watch(watch, wqueue);
+ watch->id = s->s_unique_id;
+ watch->private = s;
+ watch->info_id = (u32)watch_id << 24;
+
+ ret = security_watch_sb(watch, s);
+ if (ret < 0)
+ goto err_watch;
+
+ down_write(&s->s_umount);
+ ret = -EIO;
+ if (atomic_read(&s->s_active)) {
+ if (!s->s_watchers) {
+ s->s_watchers = wlist;
+ wlist = NULL;
+ }
+
+ spin_lock(&sb_lock);
+ s->s_count++;
+ spin_unlock(&sb_lock);
+ ret = add_watch_to_object(watch, s->s_watchers);
+ if (ret == 0)
+ watch = NULL; /* It worked */
+ else
+ drop_s_count = true;
+ }
+ up_write(&s->s_umount);
+ if (drop_s_count)
+ put_super(s);
+ } else {
+ ret = -EBADSLT;
+ down_write(&s->s_umount);
+ ret = remove_watch_from_object(s->s_watchers, wqueue,
+ s->s_unique_id, false);
+ up_write(&s->s_umount);
+ }
+
+err_watch:
+ kfree(watch);
+err_wlist:
+ kfree(wlist);
+err_wqueue:
+ put_watch_queue(wqueue);
+err_path:
+ path_put(&path);
+ return ret;
+}
+#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9de6bfe41016..9181cfcd5265 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -40,6 +40,7 @@
#include <linux/fs_types.h>
#include <linux/build_bug.h>
#include <linux/stddef.h>
+#include <linux/watch_queue.h>
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -1551,6 +1552,12 @@ struct super_block {
/* Superblock event notifications */
u64 s_unique_id;
+
+#ifdef CONFIG_SB_NOTIFICATIONS
+ struct watch_list *s_watchers;
+#endif
+ atomic_t s_change_counter; /* Count of config change notifications */
+ atomic_t s_notify_counter; /* Count of other notifications */
} __randomize_layout;
/* Helper functions so that in most cases filesystems will
@@ -3654,4 +3661,78 @@ static inline int inode_drain_writes(struct inode *inode)
return filemap_write_and_wait(inode->i_mapping);
}
+extern void post_sb_notification(struct super_block *, struct superblock_notification *);
+
+/**
+ * notify_sb: Post simple superblock notification.
+ * @s: The superblock the notification is about.
+ * @subtype: The type of notification.
+ * @info: WATCH_INFO_FLAG_* flags to be set in the record.
+ */
+static inline void notify_sb(struct super_block *s,
+ enum superblock_notification_type subtype,
+ u32 info)
+{
+#ifdef CONFIG_SB_NOTIFICATIONS
+ atomic_inc(&s->s_change_counter);
+ if (unlikely(READ_ONCE(s->s_watchers))) {
+ struct superblock_notification n = {
+ .watch.type = WATCH_TYPE_SB_NOTIFY,
+ .watch.subtype = subtype,
+ .watch.info = watch_sizeof(n) | info,
+ .sb_id = s->s_unique_id,
+ };
+
+ post_sb_notification(s, &n);
+ }
+#endif
+}
+
+/**
+ * notify_sb_error: Post superblock error notification.
+ * @s: The superblock the notification is about.
+ * @error: The error number to be recorded.
+ */
+static inline int notify_sb_error(struct super_block *s, int error)
+{
+#ifdef CONFIG_SB_NOTIFICATIONS
+ atomic_inc(&s->s_notify_counter);
+ if (unlikely(READ_ONCE(s->s_watchers))) {
+ struct superblock_error_notification n = {
+ .s.watch.type = WATCH_TYPE_SB_NOTIFY,
+ .s.watch.subtype = NOTIFY_SUPERBLOCK_ERROR,
+ .s.watch.info = watch_sizeof(n),
+ .s.sb_id = s->s_unique_id,
+ .error_number = error,
+ .error_cookie = 0,
+ };
+
+ post_sb_notification(s, &n.s);
+ }
+#endif
+ return error;
+}
+
+/**
+ * notify_sb_EDQUOT: Post superblock quota overrun notification.
+ * @s: The superblock the notification is about.
+ */
+static inline int notify_sb_EQDUOT(struct super_block *s)
+{
+#ifdef CONFIG_SB_NOTIFICATIONS
+ atomic_inc(&s->s_notify_counter);
+ if (unlikely(READ_ONCE(s->s_watchers))) {
+ struct superblock_notification n = {
+ .watch.type = WATCH_TYPE_SB_NOTIFY,
+ .watch.subtype = NOTIFY_SUPERBLOCK_EDQUOT,
+ .watch.info = watch_sizeof(n),
+ .sb_id = s->s_unique_id,
+ };
+
+ post_sb_notification(s, &n);
+ }
+#endif
+ return -EDQUOT;
+}
+
#endif /* _LINUX_FS_H */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 1fd43af3b22d..c84440d57f52 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1005,6 +1005,8 @@ asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
asmlinkage long sys_pidfd_getfd(int pidfd, int fd, unsigned int flags);
asmlinkage long sys_watch_mount(int dfd, const char __user *path,
unsigned int at_flags, int watch_fd, int watch_id);
+asmlinkage long sys_watch_sb(int dfd, const char __user *path,
+ unsigned int at_flags, int watch_fd, int watch_id);
/*
* Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 6b5748287883..5bff318b7ffa 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -857,9 +857,11 @@ __SYSCALL(__NR_openat2, sys_openat2)
__SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd)
#define __NR_watch_mount 439
__SYSCALL(__NR_watch_mount, sys_watch_mount)
+#define __NR_watch_sb 440
+__SYSCALL(__NR_watch_sb, sys_watch_sb)
#undef __NR_syscalls
-#define __NR_syscalls 440
+#define __NR_syscalls 441
/*
* 32 bit systems traditionally used different
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index b0f35cf51394..e9c37b1ae68d 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_MOUNT_NOTIFY = 2, /* Mount topology change notification */
- WATCH_TYPE___NR = 3
+ WATCH_TYPE_SB_NOTIFY = 3, /* Superblock event notification */
+ WATCH_TYPE___NR = 4
};
enum watch_meta_notification_subtype {
@@ -131,4 +132,32 @@ struct mount_notification {
__u32 changed_mount; /* The mount that got changed */
};
+/*
+ * Type of superblock notification.
+ */
+enum superblock_notification_type {
+ NOTIFY_SUPERBLOCK_READONLY = 0, /* Filesystem toggled between R/O and R/W */
+ NOTIFY_SUPERBLOCK_ERROR = 1, /* Error in filesystem or blockdev */
+ NOTIFY_SUPERBLOCK_EDQUOT = 2, /* EDQUOT notification */
+ NOTIFY_SUPERBLOCK_NETWORK = 3, /* Network status change */
+};
+
+#define NOTIFY_SUPERBLOCK_IS_NOW_RO WATCH_INFO_FLAG_0 /* Superblock changed to R/O */
+
+/*
+ * Superblock notification record.
+ * - watch.type = WATCH_TYPE_MOUNT_NOTIFY
+ * - watch.subtype = enum superblock_notification_subtype
+ */
+struct superblock_notification {
+ struct watch_notification watch; /* WATCH_TYPE_SB_NOTIFY */
+ __u64 sb_id; /* 64-bit superblock ID */
+};
+
+struct superblock_error_notification {
+ struct superblock_notification s; /* subtype = notify_superblock_error */
+ __u32 error_number;
+ __u32 error_cookie;
+};
+
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 3e1c5c9d2efe..0ce01f86e5db 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -119,6 +119,9 @@ COND_SYSCALL_COMPAT(signalfd4);
/* fs/sync.c */
+/* fs/super.c */
+COND_SYSCALL(watch_sb);
+
/* fs/timerfd.c */
COND_SYSCALL(timerfd_create);
COND_SYSCALL(timerfd_settime);
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [RFC PATCH 17/17] watch_queue: sample: Display superblock notifications [ver #4]
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
` (15 preceding siblings ...)
2020-03-09 12:19 ` [RFC PATCH 16/17] watch_queue: Add superblock notifications " David Howells
@ 2020-03-09 12:19 ` David Howells
16 siblings, 0 replies; 18+ messages in thread
From: David Howells @ 2020-03-09 12:19 UTC (permalink / raw)
To: torvalds, viro
Cc: dhowells, dhowells, casey, sds, nicolas.dichtel, raven,
christian, andres, jlayton, dray, kzak, keyrings, linux-api,
linux-fsdevel, linux-security-module, linux-kernel
The notification is run as:
./watch_test
and it then watches "/mnt" for superblock notifications:
# mount -t tmpfs none /mnt
# ./watch_test &
# mount -o remount,ro /mnt
# mount -o remount,rw /mnt
producing:
# ./watch_test
NOTIFY[000]: ty=000003 sy=00 i=03010010
SUPER 157eb57ca7 change=0[readonly]
read() = 16
NOTIFY[000]: ty=000002 sy=04 i=02010010
MOUNT 000001a0 change=4[setattr] aux=0
read() = 16
NOTIFY[000]: ty=000002 sy=04 i=02010010
MOUNT 000001a0 change=4[setattr] aux=0
Signed-off-by: David Howells <dhowells@redhat.com>
---
samples/watch_queue/watch_test.c | 39 +++++++++++++++++++++++++++++++++++++-
1 file changed, 38 insertions(+), 1 deletion(-)
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 49d185150506..eea3bd8c6569 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -29,6 +29,9 @@
#ifndef __NR_watch_mount
#define __NR_watch_mount -1
#endif
+#ifndef __NR_watch_sb
+#define __NR_watch_sb -1
+#endif
#define BUF_SIZE 256
@@ -82,6 +85,24 @@ static void saw_mount_change(struct watch_notification *n, size_t len)
m->triggered_on, n->subtype, mount_subtypes[n->subtype], m->changed_mount);
}
+static const char *super_subtypes[256] = {
+ [NOTIFY_SUPERBLOCK_READONLY] = "readonly",
+ [NOTIFY_SUPERBLOCK_ERROR] = "error",
+ [NOTIFY_SUPERBLOCK_EDQUOT] = "edquot",
+ [NOTIFY_SUPERBLOCK_NETWORK] = "network",
+};
+
+static void saw_super_change(struct watch_notification *n, size_t len)
+{
+ struct superblock_notification *s = (struct superblock_notification *)n;
+
+ if (len < sizeof(struct superblock_notification))
+ return;
+
+ printf("SUPER %08llx change=%u[%s]\n",
+ s->sb_id, n->subtype, super_subtypes[n->subtype]);
+}
+
/*
* Consume and display events.
*/
@@ -161,6 +182,9 @@ static void consumer(int fd)
case WATCH_TYPE_MOUNT_NOTIFY:
saw_mount_change(&n.n, len);
break;
+ case WATCH_TYPE_SB_NOTIFY:
+ saw_super_change(&n.n, len);
+ break;
}
p += len;
@@ -169,7 +193,7 @@ static void consumer(int fd)
}
static struct watch_notification_filter filter = {
- .nr_filters = 2,
+ .nr_filters = 3,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
@@ -180,6 +204,14 @@ static struct watch_notification_filter filter = {
// Reject move-from notifications
.subtype_filter[0] = UINT_MAX & ~(1 << NOTIFY_MOUNT_MOVE_FROM),
},
+ [2] = {
+ .type = WATCH_TYPE_SB_NOTIFY,
+ // Only accept notification of changes to R/O state
+ .subtype_filter[0] = (1 << NOTIFY_SUPERBLOCK_READONLY),
+ // Only accept notifications of change-to-R/O
+ .info_mask = WATCH_INFO_FLAG_0,
+ .info_filter = WATCH_INFO_FLAG_0,
+ },
},
};
@@ -218,6 +250,11 @@ int main(int argc, char **argv)
exit(1);
}
+ if (syscall(__NR_watch_sb, AT_FDCWD, "/mnt", 0, fd, 0x03) == -1) {
+ perror("watch_sb");
+ exit(1);
+ }
+
consumer(fd);
exit(0);
}
^ permalink raw reply related [flat|nested] 18+ messages in thread
end of thread, other threads:[~2020-03-09 12:19 UTC | newest]
Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-03-09 12:17 [RFC PATCH 00/17] pipe: Keyrings, mount and superblock notifications [ver #4] David Howells
2020-03-09 12:17 ` [RFC PATCH 01/17] uapi: General notification queue definitions " David Howells
2020-03-09 12:17 ` [RFC PATCH 02/17] security: Add hooks to rule on setting a watch " David Howells
2020-03-09 12:17 ` [RFC PATCH 03/17] security: Add a hook for the point of notification insertion " David Howells
2020-03-09 12:17 ` [RFC PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE " David Howells
2020-03-09 12:17 ` [RFC PATCH 05/17] pipe: Add general notification queue support " David Howells
2020-03-09 12:18 ` [RFC PATCH 06/17] watch_queue: Add a key/keyring notification facility " David Howells
2020-03-09 12:18 ` [RFC PATCH 07/17] Add sample notification program " David Howells
2020-03-09 12:18 ` [RFC PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
2020-03-09 12:18 ` [RFC PATCH 09/17] pipe: Add notification lossage handling " David Howells
2020-03-09 12:18 ` [RFC PATCH 10/17] selinux: Implement the watch_key security hook " David Howells
2020-03-09 12:18 ` [RFC PATCH 11/17] smack: Implement the watch_key and post_notification hooks " David Howells
2020-03-09 12:19 ` [RFC PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches " David Howells
2020-03-09 12:19 ` [RFC PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications " David Howells
2020-03-09 12:19 ` [RFC PATCH 14/17] watch_queue: sample: Display mount tree " David Howells
2020-03-09 12:19 ` [RFC PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID " David Howells
2020-03-09 12:19 ` [RFC PATCH 16/17] watch_queue: Add superblock notifications " David Howells
2020-03-09 12:19 ` [RFC PATCH 17/17] watch_queue: sample: Display " David Howells
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