Subject: [PATCH 1/1] xen-netfront: update num_queues to real created

From: Joe Jin <[email-masked]>
Date: Thu, 15 Oct 2015 10:34:15 +0800

Sometimes xennet_create_queues() may failed to created all requested
queues, we need to update num_queues to real created to avoid NULL
pointer dereference.

Signed-off-by: Joe Jin <[email-masked]>
Cc: Wei Liu <[email-masked]>
Cc: Ian Campbell <[email-masked]>
Cc: David S. Miller <[email-masked]>
---
 drivers/net/xen-netfront.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index f821a97..d580aec 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1746,7 +1746,7 @@ static int xennet_create_queues(struct netfront_info *info,
 		dev_err(&info->netdev->dev, "no queues\n");
 		return -EINVAL;
 	}
-	return 0;
+	return num_queues;
 }
 
 /* Common code used when first setting up, and when resuming. */
@@ -1788,9 +1788,12 @@ static int talk_to_netback(struct xenbus_device *dev,
 	if (info->queues)
 		xennet_destroy_queues(info);
 
-	err = xennet_create_queues(info, num_queues);
-	if (err < 0)
+	/* Update queues number to real created */
+	num_queues = xennet_create_queues(info, num_queues);
+	if (num_queues < 0) {
+		err = num_queues;
 		goto destroy_ring;
+	}
 
 	/* Create shared ring, alloc event channel -- for each queue */
 	for (i = 0; i < num_queues; ++i) {
-- 
1.7.1