Commit d76036ab authored by Jan Kara's avatar Jan Kara Committed by Paul Moore

audit: Fix use after free in audit_remove_watch_rule()

audit_remove_watch_rule() drops watch's reference to parent but then
continues to work with it. That is not safe as parent can get freed once
we drop our reference. The following is a trivial reproducer:

mount -o loop image /mnt
touch /mnt/file
auditctl -w /mnt/file -p wax
umount /mnt
auditctl -D
<crash in fsnotify_destroy_mark()>

Grab our own reference in audit_remove_watch_rule() earlier to make sure
mark does not get freed under us.

CC: stable@vger.kernel.org
Reported-by: default avatarTony Jones <tonyj@suse.de>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Tested-by: default avatarTony Jones <tonyj@suse.de>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent b0659ae5
......@@ -457,14 +457,16 @@ void audit_remove_watch_rule(struct audit_krule *krule)
list_del(&krule->rlist);
if (list_empty(&watch->rules)) {
audit_remove_watch(watch);
if (list_empty(&parent->watches)) {
/*
* audit_remove_watch() drops our reference to 'parent' which
* can get freed. Grab our own reference to be safe.
*/
audit_get_parent(parent);
audit_remove_watch(watch);
if (list_empty(&parent->watches))
fsnotify_destroy_mark(&parent->mark, audit_watch_group);
audit_put_parent(parent);
}
}
}
/* Update watch data in audit rules based on fsnotify events. */
......
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