virtio-net: correctly check num_buf during err path

[ 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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 925d15ea35cb92f11d07ebd61d6a0650b6d53f78..c5a1d221c49b012d77e2c88cb0f640de583671db 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -777,7 +777,7 @@ err_xdp:
        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",