From 8f716035da0ad35d5a65668eb3c10aad6c439d7b Mon Sep 17 00:00:00 2001
From: Willem de Bruijn <willemb@google.com>
Date: Thu, 10 Aug 2017 12:41:58 -0400
Subject: [PATCH] packet: fix tp_reserve race in packet_set_ring

commit c27927e372f0785f3303e8fad94b85945e2c97b7 upstream.

Updates to tp_reserve can race with reads of the field in
packet_set_ring. Avoid this by holding the socket lock during
updates in setsockopt PACKET_RESERVE.

This bug was discovered by syzkaller.

Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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