From: Enrico Zanda <[email protected]>
When vhost owns the virtio-net header, i.e. when
VHOST_NET_F_VIRTIO_NET_HDR is negotiated, sock_hlen is 0,
meaning that no header will be forwarded to the TAP device.
In the current vhost_net_build_xdp() implementation,
when sock_hlen == 0, the gso pointer can point at the start of the
Ethernet frame instead of a virtio-net header.
This results in a wrong interpretation of the destination MAC address
bytes as struct virtio_net_hdr fields.
This can, for some MAC addresses, trigger -EINVAL and return early
before the TX descriptor is completed, which can stall vhost-net TX.
Before 97b2409f28e0, the gso pointer was set to the zeroed padding area,
using it as a synthetic virtio-net header. Restore that behavior.
Fixes: 97b2409f28e0 ("vhost-net: reduce one userspace copy when building XDP
buff")
Signed-off-by: Enrico Zanda <[email protected]>
---
drivers/vhost/net.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 77b59f49bddb..3e72b9c6af0c 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -731,10 +731,12 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue
*nvq,
goto err;
}
- gso = buf + pad - sock_hlen;
-
- if (!sock_hlen)
+ if (!sock_hlen) {
memset(buf, 0, pad);
+ gso = buf;
+ } else {
+ gso = buf + pad - sock_hlen;
+ }
if ((gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
vhost16_to_cpu(vq, gso->csum_start) +
--
2.43.0
