[PATCH] fsnotify: don't put user context if it was never assigned

[Sasha Levin]

On some failure paths we may attempt to free user context even
if it wasn't assigned yet. This will cause a NULL ptr deref
and a kernel BUG.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 fs/notify/inotify/inotify_fsnotify.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index 43ab1e1..9c8187e 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -165,8 +165,10 @@ static void inotify_free_group_priv(struct fsnotify_group *group)
 	/* ideally the idr is empty and we won't hit the BUG in the callback */
 	idr_for_each(&group->inotify_data.idr, idr_callback, group);
 	idr_destroy(&group->inotify_data.idr);
-	atomic_dec(&group->inotify_data.user->inotify_devs);
-	free_uid(group->inotify_data.user);
+	if (group->inotify_data.user) {
+		atomic_dec(&group->inotify_data.user->inotify_devs);
+		free_uid(group->inotify_data.user);
+	}
 }
 
 static void inotify_free_event(struct fsnotify_event *fsn_event)
-- 
1.7.10.4

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