usb-storage: fix NULL pointer dereference.

When a usb packet is canceled we need to check whenever we actually have
a scsi request in flight before we try to cancel it.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/hw/usb-msd.c b/hw/usb-msd.c
index e92434cc942446310234b0251c44cf8667ec685e..08d2d2ac774807334cc939384f3c3bbdc0da38e6 100644 (file)
--- a/hw/usb-msd.c
+++ b/hw/usb-msd.c
@@ -325,7 +325,10 @@ static int usb_msd_handle_control(USBDevice *dev, USBPacket *p,
 static void usb_msd_cancel_io(USBDevice *dev, USBPacket *p)
 {
     MSDState *s = DO_UPCAST(MSDState, dev, dev);
-    scsi_req_cancel(s->req);
+
+    if (s->req) {
+        scsi_req_cancel(s->req);
+    }
 }
 
 static int usb_msd_handle_data(USBDevice *dev, USBPacket *p)