virtio_net: fix memory leak inside XPD_TX with mergeable

stable inclusion
from stable-v5.10.138
commit faafa2a87f697ee537c29446097e1cc3143506fa
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60QFD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=faafa2a87f697ee537c29446097e1cc3143506fa

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

commit 7a542bee upstream.

When we call xdp_convert_buff_to_frame() to get xdpf, if it returns
NULL, we should check if xdp_page was allocated by xdp_linearize_page().
If it is newly allocated, it should be freed here alone. Just like any
other "goto err_xdp".

Fixes: 44fa2dbd ("xdp: transition into using xdp_frame for ndo_xdp_xmit")
Signed-off-by: NXuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

drivers/net/virtio_net.c

@@ -968,8 +968,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		case XDP_TX:
 			stats->xdp_tx++;
 			xdpf = xdp_convert_buff_to_frame(&xdp);
-			if (unlikely(!xdpf))
+			if (unlikely(!xdpf)) {
+				if (unlikely(xdp_page != page))
+					put_page(xdp_page);
 				goto err_xdp;
+			}
 			err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
 			if (unlikely(err < 0)) {
 				trace_xdp_exception(vi->dev, xdp_prog, act);