From 7eee92bf2e54235ab90f90d4b97b9256f51b076d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 16 Jun 2015 07:59:11 -0700 Subject: [PATCH] packet: read num_members once in packet_rcv_fanout() [ 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(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 81b4b816f131..62df51d99993 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1217,7 +1217,7 @@ 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; -- 2.34.1