[PATCH] kasan/quarantine: fix NULL pointer dereference bug

[js1304]

From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

If we move an item on qlist's tail, we need to update qlist's tail
properly. curr->next can be NULL since it is singly linked list
so it is invalid for tail. curr is scheduled to be moved so
using prev would be correct.

Unfortunately, I got this bug sometime ago and lose oops message.
But, the bug looks trivial and no need to attach oops.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 mm/kasan/quarantine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 4973505..9a132fd 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -255,7 +255,7 @@ static void qlist_move_cache(struct qlist_head *from,
 			} else
 				prev->next = curr->next;
 			if (unlikely(from->tail == qlink))
-				from->tail = curr->next;
+				from->tail = prev;
 			from->bytes -= cache->size;
 			qlist_put(to, qlink, cache->size);
 		} else {
-- 
1.9.1