[PATCH 3.18 099/121] virtio_net: check return value of skb_to_sgvec always

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Jason A. Donenfeld <Jason@xxxxxxxxx>

commit e2fcad58fd230f635a74e4e983c6f4ea893642d2 upstream.

Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Reviewed-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[natechancellor: backport to 3.18]
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -854,7 +854,7 @@ static int xmit_skb(struct send_queue *s
 	struct skb_vnet_hdr *hdr;
 	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 	struct virtnet_info *vi = sq->vq->vdev->priv;
-	unsigned num_sg;
+	int num_sg;
 	unsigned hdr_len;
 	bool can_push;
 
@@ -906,11 +906,16 @@ static int xmit_skb(struct send_queue *s
 	if (can_push) {
 		__skb_push(skb, hdr_len);
 		num_sg = skb_to_sgvec(skb, sq->sg, 0, skb->len);
+		if (unlikely(num_sg < 0))
+			return num_sg;
 		/* Pull header back to avoid skew in tx bytes calculations. */
 		__skb_pull(skb, hdr_len);
 	} else {
 		sg_set_buf(sq->sg, hdr, hdr_len);
-		num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1;
+		num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len);
+		if (unlikely(num_sg < 0))
+			return num_sg;
+		num_sg++;
 	}
 	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
 }