commit e422777fdd4746de1109575c51e65038d4c5c1be upstream.

When a mark gets a new event bit, fanotify and inotify may avoid
recalculating the object mask if the cached aggregate already contains that
bit. This is racy with a recalculation triggered by a concurrent update to
another mark on the same connector.

The concurrent scan can read the mark before the new bit is added, while
the updater reads the old aggregate before that scan publishes its result.
The updater then skips recalculation and the scan publishes a mask without
the bit, leaving the object mask stale after both updates complete.

This can be reproduced with two fanotify groups watching the same inode:
one thread removes FAN_MODIFY from one existing mark while another thread
adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
writes can fail to produce FAN_MODIFY for the group whose mark now contains
the bit. This was reproduced on an unmodified v6.12.95 kernel. The
equivalent inotify interleaving loses IN_MODIFY events.

For normal fanotify additions, recalculate whenever the raw mark mask
changes. The normal mask is not cleared asynchronously, so an unchanged
addition cannot introduce missing interest. Always recalculate ignore-mask
updates because FS_MODIFY handling may clear the ignore mask without taking
mark->lock, making snapshot comparisons unreliable.

Always recalculate after updating an existing inotify watch. Its replace
path temporarily sets mark->mask to zero, so a concurrent scan can observe
zero even when the old and final masks are equal. Assigning the replacement
mask directly would avoid the transient zero, but existing-watch updates
are infrequent, so unconditional recalculation is simpler.

Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit d7f1cf5be33ef0175a4e8ed8687aeb98fb00a851 upstream.

fsnotify_pre_content() builds its file_range on the triggering task's
stack. fanotify_alloc_perm_event() saves a pointer to range.pos in the
heap-allocated permission event so copy_range_info_to_user() can report
the offset later.

The event reader can set the event state to FAN_EVENT_REPORTED and then
sleep while preparing the file descriptor. If a signal interrupts the
triggering task at that point, fanotify_get_response() changes the state
to FAN_EVENT_CANCELED and returns. This unwinds the file_range stack
frame while the reader still owns the event. The reader then dereferences
pevent->ppos and copies the stale stack value to userspace.

KASAN reported:

  BUG: KASAN: use-after-free in fanotify_read+0x293e/0x2970
  Read of size 8 at addr ffff88811434fc50 by task fanotify_inotif/95
  Call Trace:
   fanotify_read+0x293e/0x2970
   vfs_read+0x177/0xa20
   ksys_read+0xf7/0x1c0
   do_syscall_64+0xf9/0x540
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

Store the range position directly in the permission event and use
FANOTIFY_NO_RANGE when range information is unavailable. The event remains
alive until the reader finishes, so the reported offset no longer depends
on the triggering task's stack.

Fixes: 870499bc1d4d ("fanotify: report file range info with pre-content events")
Cc: stable@vger.kernel.org
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
Link: https://patch.msgid.link/20260730134316.2085087-1-nicoyip.dev@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull fsnotify updates from Jan Kara:

 - fanotify improvements for pidfd reporting

 - small cleanup in fanotify_error_event_equal

* tag 'fsnotify_for_v7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: allow reporting pidfds for reaped tasks
  fanotify: report thread pidfds for FAN_REPORT_TID
  fanotify: simplify fanotify_error_event_equal

Pull vfs directory delegations from Christian Brauner:
 "This contains the VFS prerequisites for supporting directory
  delegations in nfsd via CB_NOTIFY callbacks.

  The filelock core gains support for ignoring delegation breaks for
  directory change events together with an inode_lease_ignore_mask()
  helper, and fsnotify gains fsnotify_modify_mark_mask() and a
  FSNOTIFY_EVENT_RENAME data type.

  With this in place nfsd can request delegations on directories and set
  up inotify watches to trigger sending CB_NOTIFY events to clients
  instead of having every directory change break the delegation.

  New tracepoints are added to fsnotify() and to the start of
  break_lease(), and trace_break_lease_block() is passed the currently
  blocking lease instead of the new one.

  A follow-up fix moves the LEASE_BREAK_* flags out of
  #ifdef CONFIG_FILE_LOCKING to fix the build for CONFIG_FILE_LOCKING=n
  configurations"

* tag 'vfs-7.2-rc1.directory.delegations' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  filelock: move LEASE_BREAK_* flags out of #ifdef CONFIG_FILE_LOCKING
  fsnotify: add FSNOTIFY_EVENT_RENAME data type
  fsnotify: add fsnotify_modify_mark_mask()
  fsnotify: new tracepoint in fsnotify()
  filelock: add an inode_lease_ignore_mask helper
  filelock: add a tracepoint to start of break_lease()
  filelock: add support for ignoring deleg breaks for dir change events
  filelock: pass current blocking lease to trace_break_lease_block() rather than "new_fl"

Fanotify used to refuse to report pidfds for reaped tasks by applying a
pid_has_task() check before calling pidfd_prepare(). This prevented
userspace from obtaining information about the task.

Register the event pid with pidfs when creating the fanotify event if
pidfd reporting was requested, so pidfd_prepare() can later create a
pidfd for the reaped task.

Suggested-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/linux-fsdevel/20260528-schmuckvoll-heilen-garen-be77b4208671@brauner/
Signed-off-by: AnonymeMeow <anonymemeow@gmail.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Link: https://patch.msgid.link/20260607003343.425939-3-anonymemeow@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>

The FAN_REPORT_PIDFD and FAN_REPORT_TID flags used to be mutually
exclusive because by the time the pidfd support was introduced to
fanotify, pidfds could only be created for thread group leaders. Now
that the pidfd API supports thread-specific pidfds via PIDFD_THREAD,
this restriction can be lifted.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: AnonymeMeow <anonymemeow@gmail.com>
Link: https://patch.msgid.link/20260607003343.425939-2-anonymemeow@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>

Return the result of calling fanotify_fsid_equal() directly to simplify
the code.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20260527142233.1256340-3-thorsten.blum@linux.dev
Signed-off-by: Jan Kara <jack@suse.cz>

nfsd needs to be able to modify the mask on an existing mark when new
directory delegations are set or unset. Add an exported function that
allows the caller to set and clear bits in the mark->mask, and does
the recalculation if something changed.

Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260428-dir-deleg-v3-6-5a0780ba9def@kernel.org
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Add a tracepoint so we can see exactly how this is being called.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260428-dir-deleg-v3-5-5a0780ba9def@kernel.org
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Pull fsnotify fixes from Jan Kara:
 "Three fixes for fsnotify / fanotify"

* tag 'fsnotify_for_v7.1-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fsnotify: fix inode reference leak in fsnotify_recalc_mask()
  fanotify: Fix spelling mistake "enforecement" -> "enforcement"
  fanotify: fix false positive on permission events