Re: [dpdk-stable] [dpdk-dev] [PATCH] vhost: add header check in dequeue offload

["Wang, Xiao W" <xiao.w.wang@intel.com>]

Hi Konstantin,

Comments inline.

BRs,
Xiao

> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> Sent: Thursday, March 11, 2021 6:38 PM
> To: Wang, Xiao W <xiao.w.wang@intel.com>; Xia, Chenbo
> <chenbo.xia@intel.com>; maxime.coquelin@redhat.com
> Cc: Liu, Yong <yong.liu@intel.com>; dev@dpdk.org; Wang, Xiao W
> <xiao.w.wang@intel.com>; stable@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] vhost: add header check in dequeue
> offload
> 
> 
> 
> >
> > 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: stable@dpdk.org
> >
> > Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> > ---
> >  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..0fba0053a3 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;
> > +
> >  	m->l2_len = sizeof(struct rte_ether_hdr);
> >  	ethertype = rte_be_to_cpu_16(eth_hdr->ether_type);
> > +	data_len -= sizeof(struct rte_ether_hdr);
> >
> >  	if (ethertype == RTE_ETHER_TYPE_VLAN) {
> > +		if (data_len <= sizeof(struct rte_vlan_hdr))
> > +			return -EINVAL;
> > +
> >  		struct rte_vlan_hdr *vlan_hdr =
> >  			(struct rte_vlan_hdr *)(eth_hdr + 1);
> >
> >  		m->l2_len += sizeof(struct rte_vlan_hdr);
> >  		ethertype = rte_be_to_cpu_16(vlan_hdr->eth_proto);
> > +		data_len -= sizeof(struct rte_vlan_hdr);
> >  	}
> >
> >  	l3_hdr = (char *)eth_hdr + m->l2_len;
> >
> >  	switch (ethertype) {
> >  	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;
> > +		}
> >  		*l4_hdr = (char *)l3_hdr + m->l3_len;
> >  		m->ol_flags |= PKT_TX_IPV4;
> > +		data_len -= m->l3_len;
> >  		break;
> >  	case RTE_ETHER_TYPE_IPV6:
> > +		if (data_len <= sizeof(struct rte_ipv6_hdr))
> > +			return -EINVAL;
> >  		ipv6_hdr = l3_hdr;
> >  		*l4_proto = ipv6_hdr->proto;
> >  		m->l3_len = sizeof(struct rte_ipv6_hdr);
> >  		*l4_hdr = (char *)l3_hdr + m->l3_len;
> >  		m->ol_flags |= PKT_TX_IPV6;
> > +		data_len -= m->l3_len;
> >  		break;
> >  	default:
> >  		m->l3_len = 0;
> > @@ -1866,6 +1886,9 @@ parse_ethernet(struct rte_mbuf *m, uint16_t
> *l4_proto, void **l4_hdr)
> >  		*l4_hdr = NULL;
> >  		break;
> >  	}
> > +
> > +	*len = data_len;
> > +	return 0;
> >  }
> >
> >  static __rte_always_inline void
> > @@ -1874,24 +1897,30 @@ vhost_dequeue_offload(struct virtio_net_hdr
> *hdr, struct rte_mbuf *m)
> >  	uint16_t l4_proto = 0;
> >  	void *l4_hdr = NULL;
> >  	struct rte_tcp_hdr *tcp_hdr = NULL;
> > +	uint16_t len = 0;
> >
> >  	if (hdr->flags == 0 && hdr->gso_type ==
> VIRTIO_NET_HDR_GSO_NONE)
> >  		return;
> >
> > -	parse_ethernet(m, &l4_proto, &l4_hdr);
> > +	if (parse_ethernet(m, &l4_proto, &l4_hdr, &len) < 0)
> > +		return;
> > +
> >  	if (hdr->flags == VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> >  		if (hdr->csum_start == (m->l2_len + m->l3_len)) {
> >  			switch (hdr->csum_offset) {
> >  			case (offsetof(struct rte_tcp_hdr, cksum)):
> > -				if (l4_proto == IPPROTO_TCP)
> > +				if (l4_proto == IPPROTO_TCP &&
> > +					len > sizeof(struct rte_tcp_hdr))
> 
> Shouldn't it be '>=' here?

You are right, there're packets with no payload. I just did an experiment where I send a tcp packet with only headers from guest using scapy and vhost side get 54 Bytes (14+20+20), there's no padding.
I would fix this issue also for udp and sctp.
Thanks for the comment.

-Xiao