From: "Michael S. Tsirkin" <mst@redhat.com>

Date: Mon, 28 Apr 2014 16:08:21 +0300

Subject: [PATCH] virtio-net: out-of-bounds buffer write on load

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>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit 98f93ddd84800f207889491e0b5d851386b459cf)

---

 hw/net/virtio-net.c | 15 +++++++++++----

 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c

index 5907e96..8064092 100644

--- a/hw/net/virtio-net.c

+++ b/hw/net/virtio-net.c

@@ -1334,10 +1334,17 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)

         if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) {

             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);

+        } else {

+            int64_t i;

+

+            /* Overflow detected - can happen if source has a larger MAC table.

+             * We simply set overflow flag so there's no need to maintain the

+             * table of addresses, discard them all.

+             * Note: 64 bit math to avoid integer overflow.

+             */

+            for (i = 0; i < (int64_t)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;

         }