在 2021/6/24 下午8:30, David Woodhouse 写道:

From: David Woodhouse<redacted>

When the underlying socket isn't configured with a virtio_net_hdr, the
existing code in vhost_net_build_xdp() would attempt to validate
uninitialised data, by copying zero bytes (sock_hlen) into the local
copy of the header and then trying to validate that.

Fixing it is somewhat non-trivial because the tun device might put a
struct tun_pi*before*  the virtio_net_hdr, which makes it hard to find.
So just stop messing with someone else's data in vhost_net_build_xdp(),
and let tap and tun validate it for themselves, as they do in the
non-XDP case anyway.

Thinking in another way. All XDP stuffs for vhost is prepared for TAP. 
XDP is not expected to work for TUN.

So we can simply let's vhost doesn't go with XDP path is the underlayer 
socket is TUN.

Thanks

This means that the 'gso' member of struct tun_xdp_hdr can die, leaving
only 'int buflen'.

The socket header of sock_hlen is still copied separately from the
data payload because there may be a gap between them to ensure suitable
alignment of the latter.

Fixes: 0a0be13b8fe2 ("vhost_net: batch submitting XDP buffers to underlayer sockets")
Signed-off-by: David Woodhouse<redacted>
---
  drivers/net/tap.c      | 25 ++++++++++++++++++++++---
  drivers/net/tun.c      | 21 ++++++++++++++++++---
  drivers/vhost/net.c    | 30 +++++++++---------------------
  include/linux/if_tun.h |  1 -
  4 files changed, 49 insertions(+), 28 deletions(-)