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| author | Eric Dumazet <edumazet@google.com> | 2015-06-16 07:59:11 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-07-10 10:40:20 -0700 |
| commit | 7eee92bf2e54235ab90f90d4b97b9256f51b076d (patch) | |
| tree | a441e7bb008661633a7e9d52d0caba0378ef6f16 | |
| parent | 019b1332afd4dc4c80fa83379866d01984933694 (diff) | |
| download | lwn-7eee92bf2e54235ab90f90d4b97b9256f51b076d.tar.gz lwn-7eee92bf2e54235ab90f90d4b97b9256f51b076d.zip | |
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 <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | net/packet/af_packet.c | 2 |
1 files changed, 1 insertions, 1 deletions
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; |