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

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

From: Veaceslav Falico <vfal...@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" <da...@davemloft.net>
CC: Daniel Borkmann <dbork...@redhat.com>
CC: Willem de Bruijn <will...@google.com>
CC: Phil Sutter <p...@nwl.cc>
CC: Eric Dumazet <eduma...@google.com>
Reported-by: Jan Stancek <jstan...@redhat.com>
Tested-by: Jan Stancek <jstan...@redhat.com>
Signed-off-by: Veaceslav Falico <vfal...@redhat.com>
Acked-by: Daniel Borkmann <dbork...@redhat.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/packet/af_packet.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -504,9 +504,9 @@ static void prb_shutdown_retire_blk_time
 
        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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