virtio-net: fix incorrect flags recording in big mode

[ Upstream commit 0eff2eaa5322b5b141ff5d5ded26fac4a52b5f7b ]

The purpose of commit 703eec1b2422 ("virtio_net: fixing XDP for fully
checksummed packets handling") is to record the flags in advance, as
their value may be overwritten in the XDP case. However, the flags
recorded under big mode are incorrect, because in big mode, the passed
buf does not point to the rx buffer, but rather to the page of the
submitted buffer. This commit fixes this issue.

For the small mode, the commit c11a49d58ad2 ("virtio_net: Fix mismatched
buf address when unmapping for small packets") fixed it.

Tested-by: Alyssa Ross <hi@alyssa.is>
Fixes: 703eec1b2422 ("virtio_net: fixing XDP for fully checksummed packets handling")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20251111090828.23186-1-xuanzhuo@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 259e3a35dce935a1068e86b7a2e881c984dc01a6..97c49f33122c1184c623559979276f613d8ced8a 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2455,22 +2455,28 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
                return;
        }
 
-       /* 1. Save the flags early, as the XDP program might overwrite them.
+       /* About the flags below:
+        * 1. Save the flags early, as the XDP program might overwrite them.
         * These flags ensure packets marked as VIRTIO_NET_HDR_F_DATA_VALID
         * stay valid after XDP processing.
         * 2. XDP doesn't work with partially checksummed packets (refer to
         * virtnet_xdp_set()), so packets marked as
         * VIRTIO_NET_HDR_F_NEEDS_CSUM get dropped during XDP processing.
         */
-       flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
 
-       if (vi->mergeable_rx_bufs)
+       if (vi->mergeable_rx_bufs) {
+               flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
                skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit,
                                        stats);
-       else if (vi->big_packets)
+       } else if (vi->big_packets) {
+               void *p = page_address((struct page *)buf);
+
+               flags = ((struct virtio_net_common_hdr *)p)->hdr.flags;
                skb = receive_big(dev, vi, rq, buf, len, stats);
-       else
+       } else {
+               flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
                skb = receive_small(dev, vi, rq, buf, ctx, len, xdp_xmit, stats);
+       }
 
        if (unlikely(!skb))
                return;