From mboxrd@z Thu Jan 1 00:00:00 1970 From: fruggeri@aristanetworks.com (Francesco Ruggeri) Subject: [PATCH 1/1] net: possible use after free in dst_release Date: Wed, 06 Jan 2016 00:18:48 -0800 Message-ID: <20160106081848.4532F6340189@us105.sjc.aristanetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: fruggeri@arista.com, edumazet@google.com, davem@davemloft.net, netdev@vger.kernel.org Return-path: Received: from prod-mx.aristanetworks.com ([162.210.130.12]:2817 "EHLO prod-mx.aristanetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043AbcAFI2D (ORCPT ); Wed, 6 Jan 2016 03:28:03 -0500 Sender: netdev-owner@vger.kernel.org List-ID: dst_release should not access dst->flags after decrementing __refcnt to 0. The dst_entry may be in dst_busy_list and dst_gc_task may dst_destroy it before dst_release gets a chance to access dst->flags. Signed-off-by: Francesco Ruggeri --- net/core/dst.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/dst.c b/net/core/dst.c index e6dc772..a1656e3 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -301,12 +301,13 @@ void dst_release(struct dst_entry *dst) { if (dst) { int newrefcnt; + unsigned short nocache = dst->flags & DST_NOCACHE; newrefcnt = atomic_dec_return(&dst->__refcnt); if (unlikely(newrefcnt < 0)) net_warn_ratelimited("%s: dst:%p refcnt:%d\n", __func__, dst, newrefcnt); - if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) + if (!newrefcnt && unlikely(nocache)) call_rcu(&dst->rcu_head, dst_destroy_rcu); } } -- 1.8.1.4