Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Mon, 06 Nov 2017 23:03:02 +0000 | Subject | [PATCH 3.16 191/294] packet: in packet_do_bind, test fanout with bind_lock held |
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3.16.50-rc1 review patch. If anyone has any objections, please let me know.
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From: Willem de Bruijn <willemb@google.com>
commit 4971613c1639d8e5f102c4e797c3bf8f83a5a69e upstream.
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: Ben Hutchings <ben@decadent.org.uk> --- 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 @@ -2696,13 +2696,15 @@ 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) {
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