[PATCH 3.8 31/91] af_packet: block BH in prb_shutdown_retire_blk_timer()

[Kamal Mostafa]

3.8.13.15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Veaceslav Falico <vfalico at redhat.com>

[ Upstream commit ec6f809ff6f19fafba3212f6aff0dda71dfac8e8 ]

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: Kamal Mostafa <kamal 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 2d5b24a..90c1a21 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -390,9 +390,9 @@ 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