Commit 95e32b4e authored by Eric Dumazet's avatar Eric Dumazet Committed by Luis Henriques

packet: read num_members once in packet_rcv_fanout()

commit f98f4514 upstream.

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 95ec3eb4 ("packet: Add 'cpu' fanout policy.")

Fixes: dc99f600 ("packet: Add fanout support.")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[ luis: backported to 3.16: used davem's backport to 3.14 ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 1a47fb7d
...@@ -1346,7 +1346,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev, ...@@ -1346,7 +1346,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev) struct packet_type *pt, struct net_device *orig_dev)
{ {
struct packet_fanout *f = pt->af_packet_priv; 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; struct packet_sock *po;
unsigned int idx; unsigned int idx;
......
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