Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932731AbbG1JtR (ORCPT ); Tue, 28 Jul 2015 05:49:17 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:33693 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754843AbbG1Jps (ORCPT ); Tue, 28 Jul 2015 05:45:48 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" , Jiri Slaby Subject: [PATCH 3.12 081/124] packet: read num_members once in packet_rcv_fanout() Date: Tue, 28 Jul 2015 11:43:35 +0200 Message-Id: X-Mailer: git-send-email 2.4.6 In-Reply-To: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> References: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1648 Lines: 46 From: Eric Dumazet 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit f98f4514d07871da7a113dd9e3e330743fd70ae4 ] We need to tell compiler it must not read f->num_members multiple times. Otherwise testing if num is not zero is flaky, and we could attempt an invalid divide by 0 in fanout_demux_cpu() Note bug was present in packet_rcv_fanout_hash() and packet_rcv_fanout_lb() but final 3.1 had a simple location after commit 95ec3eb417115fb ("packet: Add 'cpu' fanout policy.") Fixes: dc99f600698dc ("packet: Add fanout support.") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- net/packet/af_packet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index a84612585fc8..e844c6152570 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1224,7 +1224,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { struct packet_fanout *f = pt->af_packet_priv; - unsigned int num = f->num_members; + unsigned int num = ACCESS_ONCE(f->num_members); struct packet_sock *po; unsigned int idx; -- 2.4.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/