Re: [PATCH net-next v2 2/7] um: vector: honor virtio net hdr conversion failures

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2026-10-15 at 08:52 -0400, Michael S. Tsirkin wrote:
> On Thu, Oct 15, 2026 at 02:47:01PM +0200, Johannes Berg wrote:
> > On Thu, 2026-10-15 at 08:41 -0400, Michael S. Tsirkin wrote:
> > > virtio_net_hdr_to_skb() refuses packets whose checksum metadata
> > > it cannot make sense of, but the vector raw transport ignored
> > > its return value: rejected packets went on into the stack with
> > > their metadata unvalidated.
> > > 
> > > Propagate the failure.
> > > 
> > > Assisted-by: LLM
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > >  arch/um/drivers/vector_transports.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/um/drivers/vector_transports.c b/arch/um/drivers/vector_transports.c
> > > index e1fb2a76fdff..8b7548458663 100644
> > > --- a/arch/um/drivers/vector_transports.c
> > > +++ b/arch/um/drivers/vector_transports.c
> > > @@ -210,7 +210,9 @@ static int raw_verify_header(
> > >  		return 1;
> > >  
> > >  	skb_set_network_header(skb, ETH_HLEN);
> > > -	virtio_net_hdr_to_skb(skb, vheader, virtio_legacy_is_little_endian());
> > > +	if (virtio_net_hdr_to_skb(skb, vheader,
> > > +			virtio_legacy_is_little_endian()) < 0)
> > > +		return -1;
> > >  	return 0;
> > > 
> > 
> > Seems it'd be simpler to just
> > 
> > 	return virtio_net_hdr_to_skb(...);
> > 
> > As far as I can tell, the function only returns -EINVAL or 0 (never a
> > positive value), and the caller only cares about negative (error) or
> > positive (no checksum needed), so that'd be equivalent?
> > 
> > johannes
> 
> if raw_verify_header can safely return any errno - i did not want to
> audit it.

You already used an LLM and still didn't want to? ;-)

I checked briefly (by hand) and it seems fine, it's assigned to the
function pointer, which only has two callers on the _kern.c side.

johannes