linux-kernel - [PATCH 4.18 121/150] virtio_net: avoid using netif_tx

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Date:   Fri,  2 Nov 2018 19:34:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ake Koomsin <ake@...l.co.jp>,
        Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.18 121/150] virtio_net: avoid using netif_tx_disable() for serializing tx routine

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

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

From: Ake Koomsin <ake@...l.co.jp>

[ Upstream commit 05c998b738fdd3e5d6a257bcacc8f34b6284d795 ]

Commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
introduces netif_tx_disable() after netif_device_detach() in order to
avoid use-after-free of tx queues. However, there are two issues.

1) Its operation is redundant with netif_device_detach() in case the
   interface is running.
2) In case of the interface is not running before suspending and
   resuming, the tx does not get resumed by netif_device_attach().
   This results in losing network connectivity.

It is better to use netif_tx_lock_bh()/netif_tx_unlock_bh() instead for
serializing tx routine during reset. This also preserves the symmetry
of netif_device_detach() and netif_device_attach().

Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
Signed-off-by: Ake Koomsin <ake@...l.co.jp>
Acked-by: Jason Wang <jasowang@...hat.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/virtio_net.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2162,8 +2162,9 @@ static void virtnet_freeze_down(struct v
 	/* Make sure no work handler is accessing the device */
 	flush_work(&vi->config_work);

+	netif_tx_lock_bh(vi->dev);
 	netif_device_detach(vi->dev);
-	netif_tx_disable(vi->dev);
+	netif_tx_unlock_bh(vi->dev);
 	cancel_delayed_work_sync(&vi->refill);

 	if (netif_running(vi->dev)) {
@@ -2199,7 +2200,9 @@ static int virtnet_restore_up(struct vir
 		}
 	}

+	netif_tx_lock_bh(vi->dev);
 	netif_device_attach(vi->dev);
+	netif_tx_unlock_bh(vi->dev);
 	return err;
 }