linux.git/fs/notify/notification.c, branch v4.12

fsnotify: clean up spinlock assertions

2016-10-08T01:46:26+00:00

Use assert_spin_locked() macro instead of hand-made BUG_ON statements.

Link: http://lkml.kernel.org/r/1474537439-18919-1-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara 
Suggested-by: Heiner Kallweit 
Reviewed-by: Jeff Layton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fanotify: fix possible false warning when freeing events

2016-10-08T01:46:26+00:00

When freeing permission events by fsnotify_destroy_event(), the warning
WARN_ON(!list_empty(&event->list)); may falsely hit.

This is because although fanotify_get_response() saw event->response
set, there is nothing to make sure the current CPU also sees the removal
of the event from the list.  Add proper locking around the WARN_ON() to
avoid the false warning.

Link: http://lkml.kernel.org/r/1473797711-14111-7-git-send-email-jack@suse.cz
Reported-by: Miklos Szeredi 
Signed-off-by: Jan Kara 
Reviewed-by: Lino Sanfilippo 
Cc: Eric Paris 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: convert notification_mutex to a spinlock

2016-10-08T01:46:26+00:00

notification_mutex is used to protect the list of pending events.  As such
there's no reason to use a sleeping lock for it.  Convert it to a
spinlock.

[jack@suse.cz: fixed version]
  Link: http://lkml.kernel.org/r/1474031567-1831-1-git-send-email-jack@suse.cz
Link: http://lkml.kernel.org/r/1473797711-14111-5-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara 
Reviewed-by: Lino Sanfilippo 
Tested-by: Guenter Roeck 
Cc: Miklos Szeredi 
Cc: Eric Paris 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: drop notification_mutex before destroying event

2016-10-08T01:46:26+00:00

fsnotify_flush_notify() and fanotify_release() destroy notification
event while holding notification_mutex.

The destruction of fanotify event includes a path_put() call which may
end up calling into a filesystem to delete an inode if we happen to be
the last holders of dentry reference which happens to be the last holder
of inode reference.

That in turn may violate lock ordering for some filesystems since
notification_mutex is also acquired e. g. during write when generating
fanotify event.

Also this is the only thing that forces notification_mutex to be a
sleeping lock.  So drop notification_mutex before destroying a
notification event.

Link: http://lkml.kernel.org/r/1473797711-14111-4-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara 
Cc: Miklos Szeredi 
Cc: Lino Sanfilippo 
Cc: Eric Paris 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fanotify: fix list corruption in fanotify_get_response()

2016-09-19T22:36:17+00:00

fanotify_get_response() calls fsnotify_remove_event() when it finds that
group is being released from fanotify_release() (bypass_perm is set).

However the event it removes need not be only in the group's notification
queue but it can have already moved to access_list (userspace read the
event before closing the fanotify instance fd) which is protected by a
different lock.  Thus when fsnotify_remove_event() races with
fanotify_release() operating on access_list, the list can get corrupted.

Fix the problem by moving all the logic removing permission events from
the lists to one place - fanotify_release().

Fixes: 5838d4442bd5 ("fanotify: fix double free of pending permission events")
Link: http://lkml.kernel.org/r/1473797711-14111-3-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara 
Reported-by: Miklos Szeredi 
Tested-by: Miklos Szeredi 
Reviewed-by: Miklos Szeredi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: add a way to stop queueing events on group shutdown

2016-09-19T22:36:17+00:00

Implement a function that can be called when a group is being shutdown
to stop queueing new events to the group.  Fanotify will use this.

Fixes: 5838d4442bd5 ("fanotify: fix double free of pending permission events")
Link: http://lkml.kernel.org/r/1473797711-14111-2-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara 
Reviewed-by: Miklos Szeredi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fanotify: fix double free of pending permission events

2014-08-07T01:01:12+00:00

Commit 85816794240b ("fanotify: Fix use after free for permission
events") introduced a double free issue for permission events which are
pending in group's notification queue while group is being destroyed.
These events are freed from fanotify_handle_event() but they are not
removed from groups notification queue and thus they get freed again
from fsnotify_flush_notify().

Fix the problem by removing permission events from notification queue
before freeing them if we skip processing access response.  Also expand
comments in fanotify_release() to explain group shutdown in detail.

Fixes: 85816794240b9659e66e4d9b0df7c6e814e5f603
Signed-off-by: Jan Kara 
Reported-by: Douglas Leeder 
Tested-by: Douglas Leeder 
Reported-by: Heinrich Schuchard 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: rename event handling functions

2014-08-07T01:01:12+00:00

Rename fsnotify_add_notify_event() to fsnotify_add_event() since the
"notify" part is duplicit.  Rename fsnotify_remove_notify_event() and
fsnotify_peek_notify_event() to fsnotify_remove_first_event() and
fsnotify_peek_first_event() respectively since "notify" part is duplicit
and they really look at the first event in the queue.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jan Kara 
Cc: Eric Paris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: Allocate overflow events with proper type

2014-02-25T10:18:06+00:00

Commit 7053aee26a35 "fsnotify: do not share events between notification
groups" used overflow event statically allocated in a group with the
size of the generic notification event. This causes problems because
some code looks at type specific parts of event structure and gets
confused by a random data it sees there and causes crashes.

Fix the problem by allocating overflow event with type corresponding to
the group type so code cannot get confused.

Signed-off-by: Jan Kara

fanotify: Handle overflow in case of permission events

2014-02-25T10:17:58+00:00

If the event queue overflows when we are handling permission event, we
will never get response from userspace. So we must avoid waiting for it.
Change fsnotify_add_notify_event() to return whether overflow has
happened so that we can detect it in fanotify_handle_event() and act
accordingly.

Signed-off-by: Jan Kara