[3.11.y.z extended stable] Patch "af_packet: block BH in prb_shutdown_retire_blk_timer()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    af_packet: block BH in prb_shutdown_retire_blk_timer()

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 24991e0cc88fea92bf1e50449aa2f9b5f08d6673 Mon Sep 17 00:00:00 2001
From: Veaceslav Falico <vfalico at redhat.com>
Date: Fri, 29 Nov 2013 09:53:23 +0100
Subject: af_packet: block BH in prb_shutdown_retire_blk_timer()

commit ec6f809ff6f19fafba3212f6aff0dda71dfac8e8 upstream.

Currently we're using plain spin_lock() in prb_shutdown_retire_blk_timer(),
however the timer might fire right in the middle and thus try to re-aquire
the same spinlock, leaving us in a endless loop.

To fix that, use the spin_lock_bh() to block it.

Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
CC: "David S. Miller" <davem at davemloft.net>
CC: Daniel Borkmann <dborkman at redhat.com>
CC: Willem de Bruijn <willemb at google.com>
CC: Phil Sutter <phil at nwl.cc>
CC: Eric Dumazet <edumazet at google.com>
Reported-by: Jan Stancek <jstancek at redhat.com>
Tested-by: Jan Stancek <jstancek at redhat.com>
Signed-off-by: Veaceslav Falico <vfalico at redhat.com>
Acked-by: Daniel Borkmann <dborkman at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/packet/af_packet.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e7fdbd8..151e8ae 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -439,9 +439,9 @@ static void prb_shutdown_retire_blk_timer(struct packet_sock *po,

 	pkc = tx_ring ? &po->tx_ring.prb_bdqc : &po->rx_ring.prb_bdqc;

-	spin_lock(&rb_queue->lock);
+	spin_lock_bh(&rb_queue->lock);
 	pkc->delete_blk_timer = 1;
-	spin_unlock(&rb_queue->lock);
+	spin_unlock_bh(&rb_queue->lock);

 	prb_del_retire_blk_timer(pkc);
 }
--
1.8.3.2