[PATCH 3.2 168/185] af_packet: block BH in prb_shutdown_retire_blk_timer()

[Ben Hutchings]

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Veaceslav Falico <vfalico@xxxxxxxxxx>

[ 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@xxxxxxxxxxxxx>
CC: Daniel Borkmann <dborkman@xxxxxxxxxx>
CC: Willem de Bruijn <willemb@xxxxxxxxxx>
CC: Phil Sutter <phil@xxxxxx>
CC: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Jan Stancek <jstancek@xxxxxxxxxx>
Tested-by: Jan Stancek <jstancek@xxxxxxxxxx>
Signed-off-by: Veaceslav Falico <vfalico@xxxxxxxxxx>
Acked-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 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 7616c58..4f19bf2 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -505,9 +505,9 @@ 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);
 }

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