[PATCH 4.14 36/41] virtio-net: correctly check num_buf during err path

From: Greg Kroah-Hartman
Date: Sat Jun 09 2018 - 11:36:24 EST

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


From: Jason Wang <jasowang@xxxxxxxxxx>

[ 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 <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
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
@@ -777,7 +777,7 @@ err_xdp:
- 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",