virtio-net: fix leaking page for gso packet during mergeable XDP

BugLink: http://bugs.launchpad.net/bugs/1789666
[ Upstream commit 3d62b2a0db505bbf9ed0755f254e45d775f9807f ]

We need to drop refcnt to xdp_page if we see a gso packet. Otherwise
it will be leaked. Fixing this by moving the check of gso packet above
the linearizing logic. While at it, remove useless comment as well.

Cc: John Fastabend <john.fastabend@gmail.com>
Fixes: 72979a6c3590 ("virtio_net: xdp, add slowpath case for non contiguous buffers")
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index dc675af103d98e92cb6e7a86503ccc87cb861a29..27a94aa4ed09154448857c7c4222a349bc1784a6 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -665,6 +665,13 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                void *data;
                u32 act;
 
+               /* Transient failure which in theory could occur if
+                * in-flight packets from before XDP was enabled reach
+                * the receive path after XDP is loaded.
+                */
+               if (unlikely(hdr->hdr.gso_type))
+                       goto err_xdp;
+
                /* This happens when rx buffer size is underestimated */
                if (unlikely(num_buf > 1 ||
                             headroom < virtnet_get_headroom(vi))) {
@@ -680,14 +687,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                        xdp_page = page;
                }
 
-               /* Transient failure which in theory could occur if
-                * in-flight packets from before XDP was enabled reach
-                * the receive path after XDP is loaded. In practice I
-                * was not able to create this condition.
-                */
-               if (unlikely(hdr->hdr.gso_type))
-                       goto err_xdp;
-
                /* Allow consuming headroom but reserve enough space to push
                 * the descriptor on if we get an XDP_TX return code.
                 */