Patch "packet: in packet_do_bind, test fanout with bind_lock held" has been added to the 3.18-stable tree

Patch "packet: in packet_do_bind, test fanout with bind_lock held" has been added to the 3.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    packet: in packet_do_bind, test fanout with bind_lock held

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     packet-in-packet_do_bind-test-fanout-with-bind_lock-held.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Oct 19 14:44:13 CEST 2017
From: Willem de Bruijn <willemb@google.com>
Date: Tue, 26 Sep 2017 12:19:37 -0400
Subject: packet: in packet_do_bind, test fanout with bind_lock held

From: Willem de Bruijn <willemb@google.com>


[ 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@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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
@@ -2662,13 +2662,15 @@ 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) {


Patches currently in stable-queue which might be from willemb@google.com are

queue-3.18/packet-in-packet_do_bind-test-fanout-with-bind_lock-held.patch
queue-3.18/packet-hold-bind-lock-when-rebinding-to-fanout-hook.patch