This is a note to let you know that I've just added the patch titled
audit: Fix use after free in audit_remove_watch_rule()
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
audit-fix-use-after-free-in-audit_remove_watch_rule.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d76036ab47eafa6ce52b69482e91ca3ba337d6d6 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 15 Aug 2017 13:00:36 +0200
Subject: audit: Fix use after free in audit_remove_watch_rule()
From: Jan Kara <jack@xxxxxxx>
commit d76036ab47eafa6ce52b69482e91ca3ba337d6d6 upstream.
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.
Reported-by: Tony Jones <tonyj@xxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Tested-by: Tony Jones <tonyj@xxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/audit_watch.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -457,13 +457,15 @@ void audit_remove_watch_rule(struct audi
list_del(&krule->rlist);
if (list_empty(&watch->rules)) {
+ /*
+ * 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)) {
- audit_get_parent(parent);
+ if (list_empty(&parent->watches))
fsnotify_destroy_mark(&parent->mark, audit_watch_group);
- audit_put_parent(parent);
- }
+ audit_put_parent(parent);
}
}
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-4.9/audit-fix-use-after-free-in-audit_remove_watch_rule.patch