From: Eric Dumazet Date: Tue, 16 Jun 2015 14:59:11 +0000 (-0700) Subject: packet: read num_members once in packet_rcv_fanout() X-Git-Tag: v4.2~362^2~2^2~14 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f98f4514d07871da7a113dd9e3e330743fd70ae4;p=platform%2Fkernel%2Flinux-amlogic.git packet: read num_members once in packet_rcv_fanout() 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 --- diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index b5989c6..131545a 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1353,7 +1353,7 @@ 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 = READ_ONCE(f->num_members); struct packet_sock *po; unsigned int idx;