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

[Zhang, Chen]

> -----Original Message-----
> From: Jason Wang <jasowang@redhat.com>
> Sent: Tuesday, August 9, 2022 4:43 PM
> 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 V3] net/colo.c: Fix the pointer issue reported by 
> Coverity.
> 
> On Tue, Aug 9, 2022 at 4:29 PM Zhang, Chen <chen.zhang@intel.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Jason Wang <jasowang@redhat.com>
> > > Sent: Tuesday, August 9, 2022 4:12 PM
> > > 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 V3] net/colo.c: Fix the pointer issue reported by
> Coverity.
> > >
> > > 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?
> >
> > No, I just try to avoid overflow with a maliciously over-large
> > vnet_hdr_len value as Peter's comments.
> > If enabled the RSS, how to get the maximum of vnet_hdr size?
> 
> With hash_report the maximum is sizeof(virtio_net_hdr_v1_hash). But it might
> be extended in the future.
> 
> We can probably start from it.

Thanks, I will change here to " if ((pkt->vnet_hdr_len > 
sizeof(virtio_net_hdr_v1_hash)) ||" in next version.

Thanks
Chen

> 
> Thanks
> 
> >
> > Thanks
> > Chen
> >
> > >
> > > 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
> > > >
> >