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authorJan Kara <jack@suse.cz>2017-08-15 13:00:36 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-24 17:12:18 -0700
commitadcfbb2d9e386517db84ac56fa3e4abd56db75b3 (patch)
treeccf3b14ac7b174821a9a21199fbf401d936bd7a0 /kernel
parent5170d210efe44e947abecd60fd0805e970add4fc (diff)
audit: Fix use after free in audit_remove_watch_rule()
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@suse.de> Signed-off-by: Jan Kara <jack@suse.cz> Tested-by: Tony Jones <tonyj@suse.de> Signed-off-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/audit_watch.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index 0d302a87f21b..690e1e3c59f7 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -457,13 +457,15 @@ void audit_remove_watch_rule(struct audit_krule *krule)
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);
}
}