From: Yunjian Wang <wangyunjian@huawei.com>
Date: Mon, 4 Dec 2017 14:02:19 +0800
Subject: virtio_net: fix return value check in receive_mergeable()
Patch-mainline: v4.15-rc3
Git-commit: 03e9f8a05bce7330bcd9c5cc54c8e42d0fcbf993
References: bsc#1089271

The function virtqueue_get_buf_ctx() could return NULL, the return
value 'buf' need to be checked with NULL, not value 'ctx'.

Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/virtio_net.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -655,7 +655,7 @@ static struct sk_buff *receive_mergeable
 		int num_skb_frags;
 
 		buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
-		if (unlikely(!ctx)) {
+		if (unlikely(!buf)) {
 			pr_debug("%s: rx error: %d buffers out of %d missing\n",
 				 dev->name, num_buf,
 				 virtio16_to_cpu(vi->vdev,