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Fri, 16 Oct 2026 02:43:09 -0700 (PDT) Date: Fri, 16 Oct 2026 05:43:06 -0400 From: "Michael S. Tsirkin" To: Johannes Berg Cc: linux-kernel@vger.kernel.org, Willem de Bruijn , Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, virtualization@lists.linux.dev, Rusty Russell , Max Krasnyansky , Richard Weinberger , Anton Ivanov , linux-um@lists.infradead.org Subject: Re: [PATCH net-next v2 2/7] um: vector: honor virtio net hdr conversion failures Message-ID: <20261016054142-mutt-send-email-mst@kernel.org> References: <6716834884238de0ab1ab313004044122aa2adbf.1792067836.git.mst@redhat.com> <8420ba1fe84fc7d105825026802d4ad10d44af71.camel@sipsolutions.net> <20261015085119-mutt-send-email-mst@kernel.org> <64ee40b97fc447bbf3abb80250ad0d9f3cf3c6fa.camel@sipsolutions.net> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64ee40b97fc447bbf3abb80250ad0d9f3cf3c6fa.camel@sipsolutions.net> 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 > > > > --- > > > > 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