[PATCH V2] net/colo.c: Fix the pointer issuse reported by Coverity.

Zhang Chen posted 1 patch 6 days, 13 hours ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20220805093813.119839-1-chen.zhang@intel.com
Maintainers: Zhang Chen <chen.zhang@intel.com>, Li Zhijian <lizhijian@fujitsu.com>, Jason Wang <jasowang@redhat.com>
net/colo.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
[PATCH V2] net/colo.c: Fix the pointer issuse reported by Coverity.
Posted by Zhang Chen 6 days, 13 hours ago
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 | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/colo.c b/net/colo.c
index 6b0ff562ad..524afa3d9b 100644
--- a/net/colo.c
+++ b/net/colo.c
@@ -44,21 +44,22 @@ 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->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.
-- 
2.25.1
Re: [PATCH V2] net/colo.c: Fix the pointer issuse reported by Coverity.
Posted by Peter Maydell 6 days, 13 hours ago
On Fri, 5 Aug 2022 at 10:53, 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 | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/net/colo.c b/net/colo.c
> index 6b0ff562ad..524afa3d9b 100644
> --- a/net/colo.c
> +++ b/net/colo.c
> @@ -44,21 +44,22 @@ 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->size < sizeof(struct eth_header) + sizeof(struct vlan_header)
> +        + pkt->vnet_hdr_len) {

I think this expression needs more care to avoid overflow
with a maliciously over-large vnet_hdr_len value.

Casting pkt->vnet_hdr_len to int64_t would be one way to do that;
there may be better approaches.

thanks
-- PMM
RE: [PATCH V2] net/colo.c: Fix the pointer issuse reported by Coverity.
Posted by Zhang, Chen 2 days, 20 hours ago

> -----Original Message-----
> From: Peter Maydell <peter.maydell@linaro.org>
> Sent: Friday, August 5, 2022 5:57 PM
> To: Zhang, Chen <chen.zhang@intel.com>
> Cc: Jason Wang <jasowang@redhat.com>; Li Zhijian <lizhijian@fujitsu.com>;
> qemu-dev <qemu-devel@nongnu.org>
> Subject: Re: [PATCH V2] net/colo.c: Fix the pointer issuse reported by
> Coverity.
> 
> On Fri, 5 Aug 2022 at 10:53, 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 | 17 +++++++++--------
> >  1 file changed, 9 insertions(+), 8 deletions(-)
> >
> > diff --git a/net/colo.c b/net/colo.c
> > index 6b0ff562ad..524afa3d9b 100644
> > --- a/net/colo.c
> > +++ b/net/colo.c
> > @@ -44,21 +44,22 @@ 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->size < sizeof(struct eth_header) + sizeof(struct vlan_header)
> > +        + pkt->vnet_hdr_len) {
> 
> I think this expression needs more care to avoid overflow with a maliciously
> over-large vnet_hdr_len value.
> 
> Casting pkt->vnet_hdr_len to int64_t would be one way to do that; there
> may be better approaches.

Yes, you are right. And I found better to use this check to avoid overflow:
"pkt->vnet_hdr_len < sizeof(struct virtio_net_hdr)"
I will fix it in next version.

Thanks
Chen


> 
> thanks
> -- PMM