Re: [PATCH V3] net/colo.c: Fix the pointer issue reported by Coverity.

[Jason Wang]

On Tue, Aug 9, 2022 at 11:05 AM Zhang Chen <chen.zhang@intel.com> wrote:
>
> When enable the virtio-net-pci, guest network packet will
> load the vnet_hdr. In COLO status, the primary VM's network
> packet maybe redirect to another VM, it need filter-redirect
> enable the vnet_hdr flag at the same time, COLO-proxy will
> correctly parse the original network packet. If have any
> misconfiguration here, the vnet_hdr_len is wrong for parse
> the packet, the data+offset will point to wrong place.
>
> Signed-off-by: Zhang Chen <chen.zhang@intel.com>
> ---
>  net/colo.c | 18 ++++++++++--------
>  net/colo.h |  1 +
>  2 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/net/colo.c b/net/colo.c
> index 6b0ff562ad..4f1b4a61f6 100644
> --- a/net/colo.c
> +++ b/net/colo.c
> @@ -44,21 +44,23 @@ int parse_packet_early(Packet *pkt)
>  {
>      int network_length;
>      static const uint8_t vlan[] = {0x81, 0x00};
> -    uint8_t *data = pkt->data + pkt->vnet_hdr_len;
> +    uint8_t *data = pkt->data;
>      uint16_t l3_proto;
>      ssize_t l2hdr_len;
>
> -    if (data == NULL) {
> -        trace_colo_proxy_main_vnet_info("This packet is not parsed 
> correctly, "
> +    assert(data);
> +
> +    /* Check the received vnet_hdr_len then add the offset */
> +    if ((pkt->vnet_hdr_len > sizeof(struct virtio_net_hdr)) ||

Virtio-net starts to support RSS so it means the vnet_hdr size could
be greater than virtio_net_hdr now.

Or did you actually mean "<" here?

Thanks

> +        (pkt->size < sizeof(struct eth_header) + sizeof(struct vlan_header)
> +        + pkt->vnet_hdr_len)) {
> +        trace_colo_proxy_main_vnet_info("This packet may be load wrong "
>                                          "pkt->vnet_hdr_len", 
> pkt->vnet_hdr_len);
>          return 1;
>      }
> -    l2hdr_len = eth_get_l2_hdr_length(data);
> +    data += pkt->vnet_hdr_len;
>
> -    if (pkt->size < ETH_HLEN + pkt->vnet_hdr_len) {
> -        trace_colo_proxy_main("pkt->size < ETH_HLEN");
> -        return 1;
> -    }
> +    l2hdr_len = eth_get_l2_hdr_length(data);
>
>      /*
>       * TODO: support vlan.
> diff --git a/net/colo.h b/net/colo.h
> index 8b3e8d5a83..22fc3031f7 100644
> --- a/net/colo.h
> +++ b/net/colo.h
> @@ -18,6 +18,7 @@
>  #include "qemu/jhash.h"
>  #include "qemu/timer.h"
>  #include "net/eth.h"
> +#include "standard-headers/linux/virtio_net.h"
>
>  #define HASHTABLE_MAX_SIZE 16384
>
> --
> 2.25.1
>