RE: [PATCH] net/colo.c: Fix the pointer issuse reported by Coverity.

[Zhang, Chen]

> -----Original Message-----
> From: Jason Wang <jasowang@redhat.com>
> Sent: Friday, August 5, 2022 11:46 AM
> To: Zhang, Chen <chen.zhang@intel.com>
> Cc: Peter Maydell <peter.maydell@linaro.org>; Li Zhijian
> <lizhijian@fujitsu.com>; qemu-dev <qemu-devel@nongnu.org>
> Subject: Re: [PATCH] net/colo.c: Fix the pointer issuse reported by Coverity.
> 
> On Tue, Aug 2, 2022 at 4:24 PM 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 | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/net/colo.c b/net/colo.c
> > index 6b0ff562ad..dfb15b4c14 100644
> > --- a/net/colo.c
> > +++ b/net/colo.c
> > @@ -44,21 +44,25 @@ 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) {
> 
> I wonder under which case we can see data == NULL?
> 
> AFAIK, data is either dup via packet_new() or assigned to a pointer to the buf
> in packet_new_nocopy().

Yes, you are right. I just checked it for hint of bugs.
Do you think no need to do it?

Thanks
Chen

> 
> Thanks
> 
> > -        trace_colo_proxy_main_vnet_info("This packet is not parsed 
> > correctly,
> "
> > -                                        "pkt->vnet_hdr_len", 
> > pkt->vnet_hdr_len);
> > +        trace_colo_proxy_main("COLO-proxy got NULL data packet ");
> >          return 1;
> >      }
> > -    l2hdr_len = eth_get_l2_hdr_length(data);
> >
> > -    if (pkt->size < ETH_HLEN + pkt->vnet_hdr_len) {
> > -        trace_colo_proxy_main("pkt->size < ETH_HLEN");
> > +    /* Check the received vnet_hdr_len then add the offset */
> > +    if (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;
> >      }
> > +    data += pkt->vnet_hdr_len;
> > +
> > +    l2hdr_len = eth_get_l2_hdr_length(data);
> >
> >      /*
> >       * TODO: support vlan.
> > --
> > 2.25.1
> >