[Qemu-devel] [PATCH] virtio-scsi: fix use-after-free of VirtIOSCSIReq

[Paolo Bonzini]

scsi_req_continue can complete the request and cause the VirtIOSCSIReq
to be freed.  Fetch req->sreq just once to avoid the bug.

Reported-by: Richard Jones <address@hidden>
Tested-by: Richard Jones <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
 hw/scsi/virtio-scsi.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 203e624..6c02fe2 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -545,11 +545,12 @@ bool virtio_scsi_handle_cmd_req_prepare(VirtIOSCSI *s, 
VirtIOSCSIReq *req)
 
 void virtio_scsi_handle_cmd_req_submit(VirtIOSCSI *s, VirtIOSCSIReq *req)
 {
-    if (scsi_req_enqueue(req->sreq)) {
-        scsi_req_continue(req->sreq);
+    SCSIRequest *sreq = req->sreq;
+    if (scsi_req_enqueue(sreq)) {
+        scsi_req_continue(sreq);
     }
-    bdrv_io_unplug(req->sreq->dev->conf.bs);
-    scsi_req_unref(req->sreq);
+    bdrv_io_unplug(sreq->dev->conf.bs);
+    scsi_req_unref(sreq);
 }
 
 static void virtio_scsi_handle_cmd(VirtIODevice *vdev, VirtQueue *vq)
-- 
1.8.3.1