Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934249AbbGHH6G (ORCPT ); Wed, 8 Jul 2015 03:58:06 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43169 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933908AbbGHHgv (ORCPT ); Wed, 8 Jul 2015 03:36:51 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" Subject: [PATCH 4.1 07/56] packet: read num_members once in packet_rcv_fanout() Date: Wed, 8 Jul 2015 00:34:56 -0700 Message-Id: <20150708073238.168007921@linuxfoundation.org> X-Mailer: git-send-email 2.4.5 In-Reply-To: <20150708073237.780280770@linuxfoundation.org> References: <20150708073237.780280770@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1528 Lines: 43 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ 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: Greg Kroah-Hartman --- net/packet/af_packet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1353,7 +1353,7 @@ static int packet_rcv_fanout(struct sk_b 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 = READ_ONCE(f->num_members); struct packet_sock *po; unsigned int idx; -- 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/