[Qemu-devel] [PATCH 006/108] virtio-net: fix buffer overflow on invalid state load

[Michael Roth]

From: "Michael S. Tsirkin" <address@hidden>

CVE-2013-4148 QEMU 1.0 integer conversion in
virtio_net_load()@hw/net/virtio-net.c

Deals with loading a corrupted savevm image.

>         n->mac_table.in_use = qemu_get_be32(f);

in_use is int so it can get negative when assigned 32bit unsigned value.

>         /* MAC_TABLE_ENTRIES may be different from the saved image */
>         if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) {

passing this check ^^^

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

with good in_use value, "n->mac_table.in_use * ETH_ALEN" can get
positive and bigger than mac_table.macs. For example 0x81000000
satisfies this condition when ETH_ALEN is 6.

Fix it by making the value unsigned.
For consistency, change first_multi as well.

Note: all call sites were audited to confirm that
making them unsigned didn't cause any issues:
it turns out we actually never do math on them,
so it's easy to validate because both values are
always <= MAC_TABLE_ENTRIES.

Reviewed-by: Michael Roth <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Laszlo Ersek <address@hidden>
Signed-off-by: Juan Quintela <address@hidden>
(cherry picked from commit 71f7fe48e10a8437c9d42d859389f37157f59980)
Signed-off-by: Michael Roth <address@hidden>
---
 include/hw/virtio/virtio-net.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index df60f16..4b32440 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -176,8 +176,8 @@ typedef struct VirtIONet {
     uint8_t nobcast;
     uint8_t vhost_started;
     struct {
-        int in_use;
-        int first_multi;
+        uint32_t in_use;
+        uint32_t first_multi;
         uint8_t multi_overflow;
         uint8_t uni_overflow;
         uint8_t *macs;
-- 
1.9.1