[Qemu-devel] [PATCH 22/23] virtio-scsi: fix buffer overrun on invalid state load

[Michael S. Tsirkin]

CVE-2013-4542

hw/scsi/scsi-bus.c invokes load_request.

 virtio_scsi_load_request does:
    qemu_get_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));

this probably can make elem invalid, for example,
make in_num or out_num huge, then:

    virtio_scsi_parse_req(s, vs->cmd_vqs[n], req);

will do:

    if (req->elem.out_num > 1) {
        qemu_sgl_init_external(req, &req->elem.out_sg[1],
                               &req->elem.out_addr[1],
                               req->elem.out_num - 1);
    } else {
        qemu_sgl_init_external(req, &req->elem.in_sg[1],
                               &req->elem.in_addr[1],
                               req->elem.in_num - 1);
    }

and this will access out of array bounds.
suggested patch:

Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
 hw/scsi/virtio-scsi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 26d95a1..51cc929 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -147,6 +147,8 @@ static void *virtio_scsi_load_request(QEMUFile *f, 
SCSIRequest *sreq)
     qemu_get_be32s(f, &n);
     assert(n < vs->conf.num_queues);
     qemu_get_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));
+    assert(req->elem.in_num <= ARRAY_SIZE(req->elem.in_sg));
+    assert(req->elem.out_num <= ARRAY_SIZE(req->elem.out_sg));
     virtio_scsi_parse_req(s, vs->cmd_vqs[n], req);
 
     scsi_req_ref(sreq);
-- 
MST