Re: [dpdk-stable] [dpdk-dev] [PATCH v4] vhost: check header for legacy dequeue offload

[David Marchand <david.marchand@redhat.com>]

On Tue, Jun 15, 2021 at 9:06 AM Xiao Wang <xiao.w.wang@intel.com> wrote:
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index 8da8a86a10..351ff0a841 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -2259,44 +2259,64 @@ 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)
>  {


This function name is misleading, name could be parse_headers().
Its semantic gets more and more confusing with those l4_hdr and len pointers.

This function fills ->lX_len in the mbuf, everything is available for caller.

Caller can check that rte_pktmbuf_data_len() is >= m->l2_len +
m->l3_len + somesize.
=> no need for len.

l4_hdr can simply be deduced with rte_pktmbuf_mtod_offset(m, struct
somestruct *, m->l2_len + m->l3_len).
=> no need for l4_hdr.


>         struct rte_ipv4_hdr *ipv4_hdr;
>         struct rte_ipv6_hdr *ipv6_hdr;
>         void *l3_hdr = NULL;

No need for l3_hdr.


>         struct rte_ether_hdr *eth_hdr;
>         uint16_t ethertype;
> +       uint16_t data_len = m->data_len;

Avoid direct access to mbuf internals, we have inline helpers:
rte_pktmbuf_data_len(m).


> +
> +       if (data_len <= sizeof(struct rte_ether_hdr))

Strictly speaking, < is enough.


> +               return -EINVAL;
>
>         eth_hdr = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
>
>         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);

No need to decrement data_len if checks below are all done for absolute value.
See suggestions below.


>
>         if (ethertype == RTE_ETHER_TYPE_VLAN) {
> +               if (data_len <= sizeof(struct rte_vlan_hdr))
> +                       return -EINVAL;

if (data_len < sizeof(rte_ether_hdr) + sizeof(struct rte_vlan_hdr))


> +
>                 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);

Idem.


>         }
>
>         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;

if (data_len < m->l2_len + sizeof(struct rte_ipv4_hdr))


>                 ipv4_hdr = l3_hdr;

ipv4_hdr = rte_pktmbuf_mtod_offset(m, struct rte_ipv4_hdr *, m->l2_len);


>                 *l4_proto = ipv4_hdr->next_proto_id;
>                 m->l3_len = rte_ipv4_hdr_len(ipv4_hdr);
> +               if (data_len <= m->l3_len) {

if (data_len < m->l2_len + m->l3_len)


> +                       m->l3_len = 0;
> +                       return -EINVAL;

Returning here leaves m->l2_len set.


> +               }
>                 *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;

if (data_len < m->l2_len + sizeof(struct rte_ipv6_hdr))
Returning here leaves m->l2_len set.


>                 ipv6_hdr = l3_hdr;

ipv6_hdr = rte_pktmbuf_mtod_offset(m, struct rte_ipv6_hdr *, m->l2_len);


>                 *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;
> @@ -2304,6 +2324,9 @@ 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
> @@ -2312,21 +2335,27 @@ vhost_dequeue_offload_legacy(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, tcp_len;
> +
> +       if (parse_ethernet(m, &l4_proto, &l4_hdr, &len) < 0)
> +               return;
>
> -       parse_ethernet(m, &l4_proto, &l4_hdr);
>         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))

if (rte_pktmbuf_data_len(m) >= m->l2_len + m->l3_len + sizeof(struct
rte_tcp_hdr))
Then, if this check is wrong, we leave l2_len, l3_len + PKT_TX_IPVx
flag set in mbuf.

These two comments apply to other updates below.

>                                         m->ol_flags |= PKT_TX_TCP_CKSUM;
>                                 break;
>                         case (offsetof(struct rte_udp_hdr, dgram_cksum)):
> -                               if (l4_proto == IPPROTO_UDP)
> +                               if (l4_proto == IPPROTO_UDP &&
> +                                       len >= sizeof(struct rte_udp_hdr))
>                                         m->ol_flags |= PKT_TX_UDP_CKSUM;
>                                 break;
>                         case (offsetof(struct rte_sctp_hdr, cksum)):
> -                               if (l4_proto == IPPROTO_SCTP)
> +                               if (l4_proto == IPPROTO_SCTP &&
> +                                       len >= sizeof(struct rte_sctp_hdr))
>                                         m->ol_flags |= PKT_TX_SCTP_CKSUM;
>                                 break;
>                         default:
> @@ -2339,12 +2368,21 @@ vhost_dequeue_offload_legacy(struct virtio_net_hdr *hdr, struct rte_mbuf *m)
>                 switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
>                 case VIRTIO_NET_HDR_GSO_TCPV4:
>                 case VIRTIO_NET_HDR_GSO_TCPV6:
> +                       if (l4_proto != IPPROTO_TCP ||
> +                               len < sizeof(struct rte_tcp_hdr))
> +                               break;
>                         tcp_hdr = l4_hdr;

tcp_hdr = rte_pktmbuf_mtod_offset(m, struct rte_tcp_hdr *, m->l2_len +
m->l3_len);



> +                       tcp_len = (tcp_hdr->data_off & 0xf0) >> 2;
> +                       if (len < tcp_len)
> +                               break;
>                         m->ol_flags |= PKT_TX_TCP_SEG;
>                         m->tso_segsz = hdr->gso_size;
> -                       m->l4_len = (tcp_hdr->data_off & 0xf0) >> 2;
> +                       m->l4_len = tcp_len;
>                         break;
>                 case VIRTIO_NET_HDR_GSO_UDP:
> +                       if (l4_proto != IPPROTO_UDP ||
> +                               len < sizeof(struct rte_udp_hdr))
> +                               break;
>                         m->ol_flags |= PKT_TX_UDP_SEG;
>                         m->tso_segsz = hdr->gso_size;
>                         m->l4_len = sizeof(struct rte_udp_hdr);
> --
> 2.15.1
>


-- 
David Marchand