linux-kernel - [PATCH 3.16 171/366] xen-netfront: avoid crashing on resume after a failure in talk_to

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Date:   Sun, 11 Nov 2018 19:49:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>
Subject: [PATCH 3.16 171/366] xen-netfront: avoid crashing on resume after
 a failure in talk_to_netback()

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

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

From: Vitaly Kuznetsov <vkuznets@...hat.com>

commit d86b5672b1adb98b4cdd6fbf0224bbfb03db6e2e upstream.

Unavoidable crashes in netfront_resume() and netback_changed() after a
previous fail in talk_to_netback() (e.g. when we fail to read MAC from
xenstore) were discovered. The failure path in talk_to_netback() does
unregister/free for netdev but we don't reset drvdata and we try accessing
it after resume.

Fix the bug by removing the whole xen device completely with
device_unregister(), this guarantees we won't have any calls into netfront
after a failure.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/xen-netfront.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1980,8 +1980,7 @@ abort_transaction_no_dev_fatal:
 	xennet_disconnect_backend(info);
 	xennet_destroy_queues(info);
  out:
-	unregister_netdev(info->netdev);
-	xennet_free_netdev(info->netdev);
+	device_unregister(&dev->dev);
 	return err;
 }