[Qemu-devel] [PATCH 007/108] virtio-net: out-of-bounds buffer write on invalid state load

[Michael Roth]

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

CVE-2013-4150 QEMU 1.5.0 out-of-bounds buffer write in
virtio_net_load()@hw/net/virtio-net.c

This code is in hw/net/virtio-net.c:

    if (n->max_queues > 1) {
        if (n->max_queues != qemu_get_be16(f)) {
            error_report("virtio-net: different max_queues ");
            return -1;
        }

        n->curr_queues = qemu_get_be16(f);
        for (i = 1; i < n->curr_queues; i++) {
            n->vqs[i].tx_waiting = qemu_get_be32(f);
        }
    }

Number of vqs is max_queues, so if we get invalid input here,
for example if max_queues = 2, curr_queues = 3, we get
write beyond end of the buffer, with data that comes from
wire.

This might be used to corrupt qemu memory in hard to predict ways.
Since we have lots of function pointers around, RCE might be possible.

Signed-off-by: Michael S. Tsirkin <address@hidden>
Acked-by: Jason Wang <address@hidden>
Reviewed-by: Michael Roth <address@hidden>
Signed-off-by: Juan Quintela <address@hidden>
(cherry picked from commit eea750a5623ddac7a61982eec8f1c93481857578)
Signed-off-by: Michael Roth <address@hidden>
---
 hw/net/virtio-net.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 33bd233..0a8cb40 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1407,6 +1407,11 @@ static int virtio_net_load(QEMUFile *f, void *opaque, 
int version_id)
         }
 
         n->curr_queues = qemu_get_be16(f);
+        if (n->curr_queues > n->max_queues) {
+            error_report("virtio-net: curr_queues %x > max_queues %x",
+                         n->curr_queues, n->max_queues);
+            return -1;
+        }
         for (i = 1; i < n->curr_queues; i++) {
             n->vqs[i].tx_waiting = qemu_get_be32(f);
         }
-- 
1.9.1