linux-kernel - [PATCH 3.2 143/199] xen-netfront: Delete rx_refill_timer in xennet_disconnect

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Date:   Fri, 10 Mar 2017 11:46:10 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Juergen Gross" <jgross@...e.com>,
        "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 143/199] xen-netfront: Delete rx_refill_timer in
 xennet_disconnect_backend()

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

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

From: Boris Ostrovsky <boris.ostrovsky@...cle.com>

commit 74470954857c264168d2b5a113904cf0cfd27d18 upstream.

rx_refill_timer should be deleted as soon as we disconnect from the
backend since otherwise it is possible for the timer to go off before
we get to xennet_destroy_queues(). If this happens we may dereference
queue->rx.sring which is set to NULL in xennet_disconnect_backend().

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Reviewed-by: Juergen Gross <jgross@...e.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: there's only one RX queue here, and del_timer_sync()
 was called from xennet_remove() but that's also too late]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1404,6 +1404,8 @@ static void xennet_disconnect_backend(st
 	spin_unlock_irq(&info->tx_lock);
 	spin_unlock_bh(&info->rx_lock);
 
+	del_timer_sync(&info->rx_refill_timer);
+
 	if (info->netdev->irq)
 		unbind_from_irqhandler(info->netdev->irq, info->netdev);
 	info->evtchn = info->netdev->irq = 0;
@@ -1940,8 +1942,6 @@ static int __devexit xennet_remove(struc
 
 	unregister_netdev(info->netdev);
 
-	del_timer_sync(&info->rx_refill_timer);
-
 	free_percpu(info->stats);
 
 	free_netdev(info->netdev);