4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Willem de Bruijn <willemb@xxxxxxxxxx>
[ Upstream commit 4971613c1639d8e5f102c4e797c3bf8f83a5a69e ]
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@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/packet/af_packet.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3069,13 +3069,15 @@ static int packet_do_bind(struct sock *s
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) {