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[02/23] virtio-net: out-of-bounds buffer write on load

Message ID 1386087086-3691-3-git-send-email-mst@redhat.com
State New
Headers show

Commit Message

Michael S. Tsirkin Dec. 3, 2013, 4:28 p.m. UTC 
CVE-2013-4149 QEMU 1.3.0 out-of-bounds buffer write in
virtio_net_load()@hw/net/virtio-net.c

>         } else if (n->mac_table.in_use) {
>             uint8_t *buf = g_malloc0(n->mac_table.in_use);

We are allocating buffer of size n->mac_table.in_use

>             qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);

and read to the n->mac_table.in_use size buffer n->mac_table.in_use *
ETH_ALEN bytes, corrupting memory.

If adversary controls state then memory written there is controlled
by adversary.

Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/net/virtio-net.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

Peter Maydell Dec. 3, 2013, 7:25 p.m. UTC | #1 
On 3 December 2013 16:28, Michael S. Tsirkin <mst@redhat.com> wrote:
> CVE-2013-4149 QEMU 1.3.0 out-of-bounds buffer write in
> virtio_net_load()@hw/net/virtio-net.c
>
>>         } else if (n->mac_table.in_use) {
>>             uint8_t *buf = g_malloc0(n->mac_table.in_use);
>
> We are allocating buffer of size n->mac_table.in_use
>
>>             qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);
>
> and read to the n->mac_table.in_use size buffer n->mac_table.in_use *
> ETH_ALEN bytes, corrupting memory.
>
> If adversary controls state then memory written there is controlled
> by adversary.
>
> Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  hw/net/virtio-net.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index b75c753..2b92640 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1337,9 +1337,11 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
>              qemu_get_buffer(f, n->mac_table.macs,
>                              n->mac_table.in_use * ETH_ALEN);
>          } else if (n->mac_table.in_use) {
> -            uint8_t *buf = g_malloc0(n->mac_table.in_use);
> -            qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);
> -            g_free(buf);
> +            int i;
> +
> +            for (i = 0; i < n->mac_table.in_use * ETH_ALEN; ++i) {
> +                qemu_get_byte(f);
> +            }
>              n->mac_table.multi_overflow = n->mac_table.uni_overflow = 1;
>              n->mac_table.in_use = 0;
>          }

This code could use a comment specifically saying that we just
throw away the incoming table data.

NB: if you accept my suggestion of leaving in_use as a signed
value, watch out that signed arithmetic overflow is undefined
behavior.

thanks
-- PMM
diff mbox

Patch

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index b75c753..2b92640 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1337,9 +1337,11 @@  static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
             qemu_get_buffer(f, n->mac_table.macs,
                             n->mac_table.in_use * ETH_ALEN);
         } else if (n->mac_table.in_use) {
-            uint8_t *buf = g_malloc0(n->mac_table.in_use);
-            qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);
-            g_free(buf);
+            int i;
+
+            for (i = 0; i < n->mac_table.in_use * ETH_ALEN; ++i) {
+                qemu_get_byte(f);
+            }
             n->mac_table.multi_overflow = n->mac_table.uni_overflow = 1;
             n->mac_table.in_use = 0;
         }