Subject: [PATCH 37/43] virtio-net: correctly check num_buf during err path

From: Jason Wang <[email-masked]>
Date: Tue, 22 May 2018 11:44:30 +0800

[ Upstream commit 850e088d5bbb333342fd4def08d0a4035f2b7126 ]

If we successfully linearize the packet, num_buf will be set to zero
which may confuse error handling path which assumes num_buf is at
least 1 and this can lead the code tries to pop the descriptor of next
buffer. Fixing this by checking num_buf against 1 before decreasing.

Fixes: 4941d472bf95 ("virtio-net: do not reset during XDP set")
Signed-off-by: Jason Wang <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/virtio_net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 62f2bee34a4b..64e7a32098be 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -874,7 +874,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	rcu_read_unlock();
 err_skb:
 	put_page(page);
-	while (--num_buf) {
+	while (num_buf-- > 1) {
 		buf = virtqueue_get_buf(rq->vq, &len);
 		if (unlikely(!buf)) {
 			pr_debug("%s: rx error: %d buffers missing\n",
-- 
2.17.1