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authorWillem de Bruijn <willemb@google.com>2017-09-26 12:19:37 -0400
committerDavid S. Miller <davem@davemloft.net>2017-09-28 10:24:31 -0700
commit4971613c1639d8e5f102c4e797c3bf8f83a5a69e (patch)
treed7938c4f52b72eb98d9e0d5c229c805547a277f8 /net/packet
parent1579f678fb4397f9e439d2e373d4ade036c673b4 (diff)
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packet: in packet_do_bind, test fanout with bind_lock held
Once a socket has po->fanout set, it remains a member of the group until it is destroyed. The prot_hook must be constant and identical across sockets in the group. If fanout_add races with packet_do_bind between the test of po->fanout and taking the lock, the bind call may make type or dev inconsistent with that of the fanout group. Hold po->bind_lock when testing po->fanout to avoid this race. I had to introduce artificial delay (local_bh_enable) to actually observe the race. Fixes: dc99f600698d ("packet: Add fanout support.") Signed-off-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d288f52c53f7..a10c2836465c 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3069,13 +3069,15 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
int ret = 0;
bool unlisted = false;
- if (po->fanout)
- return -EINVAL;
-
lock_sock(sk);
spin_lock(&po->bind_lock);
rcu_read_lock();
+ if (po->fanout) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
if (name) {
dev = dev_get_by_name_rcu(sock_net(sk), name);
if (!dev) {