On Thu, Oct 15, 2026 at 02:55:23PM +0200, Johannes Berg wrote:
> 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 <[email protected]>
> > > > ---
> > > > 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
header_check = vp->verify_header(
mmsg_vector->msg_hdr.msg_iov->iov_base,
skb,
vp
);
if (header_check < 0) {
/* Overlay header failed to verify - discard.
* We can actually keep this skb and reuse it,
* but that will make the prep logic too
* complex.
*/
dev_kfree_skb_irq(skb);
vp->estats.rx_encaps_errors++;
(*skbuff_vector) = NULL;
mmsg_vector++;
skbuff_vector++;
continue;
}
if (header_check > 0) {
vp->estats.rx_csum_offload_good++;
skb->ip_summed = CHECKSUM_UNNECESSARY;
}
so any negative is fine, but if we return 1 then it will force to
CHECKSUM_UNNECESSARY
which I am not sure is what was intended?
--
MST
