[PATCH v3 6/7] hw/scsi/virtio-scsi: harden virtio_scsi_load_request() against invalid stream

[Laurent Vivier <lvivier@redhat.com>]

virtio_scsi_load_request() uses assert() and exit(1) for conditions
that can be triggered by a crafted migration stream: an out-of-range
queue index, a malformed SCSI request, or a command mode mismatch.

Replace these with proper error returns so the migration fails
gracefully instead of aborting the destination QEMU process.

Cc: qemu-stable@nongnu.org
Fixes: 5db1764cc1f6 ("virtio-scsi: add migration support")
Fixes: d2ad7dd46e72 ("virtio-scsi: add multiqueue capability")
Fixes: 36b15c79aa1b ("virtio-scsi: start preparing for any_layout")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---

Notes:
    v2: add error_setg() calls with descriptive error messages for
        all three error paths

 hw/scsi/virtio-scsi.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 10eee3a4cff8..8814b246048f 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -272,7 +272,12 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq,
     uint32_t n;
 
     qemu_get_be32s(f, &n);
-    assert(n < vs->conf.num_queues);
+    if (n >= vs->conf.num_queues) {
+        error_setg(errp, "Invalid queues number %u > %u", n,
+                   vs->conf.num_queues);
+        return NULL;
+    }
+
     req = qemu_get_virtqueue_element(vdev, f,
                                      sizeof(VirtIOSCSIReq) + vs->cdb_size);
     if (!req) {
@@ -283,14 +288,20 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq,
 
     if (virtio_scsi_parse_req(req, sizeof(VirtIOSCSICmdReq) + vs->cdb_size,
                               sizeof(VirtIOSCSICmdResp) + vs->sense_size) < 0) {
-        error_report("invalid SCSI request migration data");
-        exit(1);
+        error_setg(errp, "invalid SCSI request migration data");
+        virtio_scsi_free_req(req);
+        return NULL;
     }
 
     scsi_req_ref(sreq);
     req->sreq = sreq;
-    if (req->sreq->cmd.mode != SCSI_XFER_NONE) {
-        assert(req->sreq->cmd.mode == req->mode);
+    if (req->sreq->cmd.mode != SCSI_XFER_NONE &&
+        req->sreq->cmd.mode != req->mode) {
+        error_setg(errp, "Invalid SCSI request mode %u",
+                   req->sreq->cmd.mode);
+        scsi_req_unref(sreq);
+        virtio_scsi_free_req(req);
+        return NULL;
     }
     return req;
 }
-- 
2.54.0