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virtio-scsi: fix buffer overrun on invalid state load 

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.

Note: this adds security checks within assert calls since
SCSIBusInfo's load_request cannot fail.
For now simply disable builds with NDEBUG - there seems
to be little value in supporting these.

Cc: Andreas Färber <afaerber@suse.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2014-04-03 19:52:17 +03:00 committed by Juan Quintela
parent 52f91c3723
commit 3c3ce98142
1 changed files with 9 additions and 0 deletions
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9
hw/scsi/virtio-scsi.c
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@ -147,6 +147,15 @@ 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));
/* TODO: add a way for SCSIBusInfo's load_request to fail,
* and fail migration instead of asserting here.
* When we do, we might be able to re-enable NDEBUG below.
*/
#ifdef NDEBUG
#error building with NDEBUG is not supported
#endif
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);