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From 579bb2000dbcd8a415660e76d31f521d87ac1302 Mon Sep 17 00:00:00 2001
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From: "Michael S. Tsirkin" <mst@redhat.com>
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Date: Thu, 3 Apr 2014 19:52:17 +0300
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Subject: [PATCH] virtio-scsi: fix buffer overrun on invalid state load
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2013-4542
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hw/scsi/scsi-bus.c invokes load_request.
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virtio_scsi_load_request does:
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qemu_get_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));
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this probably can make elem invalid, for example,
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make in_num or out_num huge, then:
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virtio_scsi_parse_req(s, vs->cmd_vqs[n], req);
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will do:
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if (req->elem.out_num > 1) {
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qemu_sgl_init_external(req, &req->elem.out_sg[1],
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&req->elem.out_addr[1],
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req->elem.out_num - 1);
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} else {
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qemu_sgl_init_external(req, &req->elem.in_sg[1],
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&req->elem.in_addr[1],
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req->elem.in_num - 1);
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}
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and this will access out of array bounds.
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Note: this adds security checks within assert calls since
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SCSIBusInfo's load_request cannot fail.
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For now simply disable builds with NDEBUG - there seems
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to be little value in supporting these.
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Cc: Andreas Färber <afaerber@suse.de>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit 3c3ce981423e0d6c18af82ee62f1850c2cda5976)
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---
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hw/scsi/virtio-scsi.c | 9 +++++++++
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1 file changed, 9 insertions(+)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index b0d7517..1752193 100644
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--- a/hw/scsi/virtio-scsi.c
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+++ b/hw/scsi/virtio-scsi.c
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@@ -147,6 +147,15 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq)
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qemu_get_be32s(f, &n);
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assert(n < vs->conf.num_queues);
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qemu_get_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));
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+ /* TODO: add a way for SCSIBusInfo's load_request to fail,
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+ * and fail migration instead of asserting here.
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+ * When we do, we might be able to re-enable NDEBUG below.
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+ */
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+#ifdef NDEBUG
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+#error building with NDEBUG is not supported
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+#endif
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+ assert(req->elem.in_num <= ARRAY_SIZE(req->elem.in_sg));
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+ assert(req->elem.out_num <= ARRAY_SIZE(req->elem.out_sg));
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virtio_scsi_parse_req(s, vs->cmd_vqs[n], req);
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scsi_req_ref(sreq);
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