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| author | Eric Dumazet <edumazet@google.com> | 2015-06-16 07:59:11 -0700 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-07-30 14:10:38 +0200 |
| commit | d8162e469f9782244d18f6a38e9ee16edf5b9646 (patch) | |
| tree | 8b1d0f6d68eaff85e5fc293f766dfae2fed796bc | |
| parent | f08abd15c340992b1dff9517e4f2d596e3bf5a63 (diff) | |
| download | lwn-d8162e469f9782244d18f6a38e9ee16edf5b9646.tar.gz lwn-d8162e469f9782244d18f6a38e9ee16edf5b9646.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: Jiri Slaby <jslaby@suse.cz>
| -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 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; |