media: usbvision: fix a potential NULL pointer dereference

In case usb_alloc_coherent fails, the fix returns -ENOMEM to
avoid a potential NULL pointer dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/usbvision/usbvision-core.c

@@ -2302,6 +2302,9 @@ int usbvision_init_isoc(struct usb_usbvision *usbvision)
 					   sb_size,
 					   GFP_KERNEL,
 					   &urb->transfer_dma);
+		if (!usbvision->sbuf[buf_idx].data)
+			return -ENOMEM;
+
 		urb->dev = dev;
 		urb->context = usbvision;
 		urb->pipe = usb_rcvisocpipe(dev, usbvision->video_endp);