Hi,
Comments inline.
BRs,
Xiao
> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.anan...@intel.com>
> Sent: Tuesday, March 16, 2021 2:53 AM
> To: David Marchand <david.march...@redhat.com>; Wang, Xiao W
> <xiao.w.w...@intel.com>
> Cc: Xia, Chenbo <chenbo....@intel.com>; Maxime Coquelin
> <maxime.coque...@redhat.com>; Liu, Yong <yong....@intel.com>; dev
> <dev@dpdk.org>; dpdk stable <sta...@dpdk.org>
> Subject: RE: [dpdk-stable] [PATCH v2] vhost: add header check in dequeue
> offload
>
>
>
> > -----Original Message-----
> > From: David Marchand <david.march...@redhat.com>
> > Sent: Monday, March 15, 2021 4:17 PM
> > To: Wang, Xiao W <xiao.w.w...@intel.com>
> > Cc: Xia, Chenbo <chenbo....@intel.com>; Maxime Coquelin
> <maxime.coque...@redhat.com>; Liu, Yong <yong....@intel.com>; dev
> > <dev@dpdk.org>; Ananyev, Konstantin <konstantin.anan...@intel.com>;
> dpdk stable <sta...@dpdk.org>
> > Subject: Re: [dpdk-stable] [PATCH v2] vhost: add header check in dequeue
> offload
> >
> > On Mon, Mar 15, 2021 at 4:52 PM Xiao Wang <xiao.w.w...@intel.com>
> wrote:
> > >
> > > When parsing the virtio net header and packet header for dequeue
> offload,
> > > we need to perform sanity check on the packet header to ensure:
> > > - No out-of-boundary memory access.
> > > - The packet header and virtio_net header are valid and aligned.
> > >
> > > Fixes: d0cf91303d73 ("vhost: add Tx offload capabilities")
> > > Cc: sta...@dpdk.org
> > >
> > > Signed-off-by: Xiao Wang <xiao.w.w...@intel.com>
> > > ---
> > > v2:
> > > Allow empty L4 payload for cksum offload.
> > > ---
> > > lib/librte_vhost/virtio_net.c | 49
> +++++++++++++++++++++++++++++++++++++------
> > > 1 file changed, 43 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> > > index 583bf379c6..53a8ff2898 100644
> > > --- a/lib/librte_vhost/virtio_net.c
> > > +++ b/lib/librte_vhost/virtio_net.c
> > > @@ -1821,44 +1821,64 @@ virtio_net_with_host_offload(struct
> virtio_net *dev)
> > > return false;
> > > }
> > >
> > > -static void
> > > -parse_ethernet(struct rte_mbuf *m, uint16_t *l4_proto, void
> **l4_hdr)
> > > +static int
> > > +parse_ethernet(struct rte_mbuf *m, uint16_t *l4_proto, void
> **l4_hdr,
> > > + uint16_t *len)
> > > {
> > > struct rte_ipv4_hdr *ipv4_hdr;
> > > struct rte_ipv6_hdr *ipv6_hdr;
> > > void *l3_hdr = NULL;
> > > struct rte_ether_hdr *eth_hdr;
> > > uint16_t ethertype;
> > > + uint16_t data_len = m->data_len;
> >
> > >
> > > eth_hdr = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
> > >
> > > + if (data_len <= sizeof(struct rte_ether_hdr))
> > > + return -EINVAL;
> >
> > On principle, the check should happen before calling rte_pktmbuf_mtod,
> > like what rte_pktmbuf_read does.
Yes, I agree. Will fix it in v3.
> >
> > Looking at the rest of the patch, does this helper function only
> > handle mono segment mbufs?
> > My reading of copy_desc_to_mbuf() was that it could generate multi
> > segments mbufs...
copy_desc_to_mbuf() could generate multi seg mbufs, and the whole packet would
be copied into these multi-mbufs when packet size is larger than mbuf's
capacity.
Anyway, one mbuf's capacity is big enough for holding the L2/L3/L4 header.
> >
> >
> > [snip]
> >
> > > case RTE_ETHER_TYPE_IPV4:
> > > + if (data_len <= sizeof(struct rte_ipv4_hdr))
> > > + return -EINVAL;
> > > ipv4_hdr = l3_hdr;
> > > *l4_proto = ipv4_hdr->next_proto_id;
> > > m->l3_len = rte_ipv4_hdr_len(ipv4_hdr);
> > > + if (data_len <= m->l3_len) {
> > > + m->l3_len = 0;
> > > + return -EINVAL;
> > > + }
> >
> > ... so here, comparing l3 length to only the first segment length
> > (data_len) would be invalid.
> >
> > If this helper must deal with multi segments, why not use
> rte_pktmbuf_read?
> > This function returns access to mbuf data after checking offset and
> > length are contiguous, else copy the needed data in a passed buffer.
>
> From my understanding, yes multi-seg is allowed, but an expectation
> Is that at least packet header (l2/l3/l4?) will always reside in first
> segment.
Yeah, I think so.
Thanks for all the comments,
-Xiao
>
> >
> >
> > > *l4_hdr = (char *)l3_hdr + m->l3_len;
> > > m->ol_flags |= PKT_TX_IPV4;
> > > + data_len -= m->l3_len;
> > > break;
> >
> >
> > --
> > David Marchand
