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

[Jason Wang]

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

>
> 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
> > >
>