virtio-net: drop the multi-buffer XDP packet in zerocopy

In virtio-net, we have not yet supported multi-buffer XDP packet in
zerocopy mode when there is a binding XDP program. However, in that
case, when receiving multi-buffer XDP packet, we skip the XDP program
and return XDP_PASS. As a result, the packet is passed to normal network
stack which is an incorrect behavior (e.g. a XDP program for packet
count is installed, multi-buffer XDP packet arrives and does go through
XDP program. As a result, the packet count does not increase but the
packet is still received from network stack).This commit instead returns
XDP_ABORTED in that case.

Fixes: 99c861b ("virtio_net: xsk: rx: support recv merge mode")
Cc: stable@vger.kernel.org
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
Link: https://patch.msgid.link/20251022155630.49272-1-minhquangbui99@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: minhbq-99

drivers/net/virtio_net.c

@@ -1379,9 +1379,14 @@ static struct sk_buff *virtnet_receive_xsk_merge(struct net_device *dev, struct
 	ret = XDP_PASS;
 	rcu_read_lock();
 	prog = rcu_dereference(rq->xdp_prog);
-	/* TODO: support multi buffer. */
-	if (prog && num_buf == 1)
-		ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
+	if (prog) {
+		/* TODO: support multi buffer. */
+		if (num_buf == 1)
+			ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit,
+						  stats);
+		else
+			ret = XDP_ABORTED;
+	}
 	rcu_read_unlock();
 
 	switch (ret) {