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

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Message-Id: <1467359628-8493-1-git-send-email-iamjoonsoo.kim@lge.com>
Date:	Fri,  1 Jul 2016 16:53:48 +0900
From:	js1304@...il.com
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH] kasan/quarantine: fix NULL pointer dereference bug

From: Joonsoo Kim <iamjoonsoo.kim@....com>

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@....com>
---
 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