Re: [PATCH 3/7] USB: add direction bit to urb->transfer_flags

On Mon, 30 Jul 2007 17:06:16 -0400 (EDT), Alan Stern <[email protected]> wrote:

> --- usb-2.6.orig/drivers/usb/core/urb.c
> +++ usb-2.6/drivers/usb/core/urb.c
> @@ -309,7 +309,21 @@ int usb_submit_urb(struct urb *urb, gfp_
>  	xfertype = usb_endpoint_type(&ep->desc);
> -	is_out = usb_pipeout(urb->pipe);
> +	if (xfertype == USB_ENDPOINT_XFER_CONTROL) {
> +		struct usb_ctrlrequest *setup =
> +				(struct usb_ctrlrequest *) urb->setup_packet;
> +
> +		if (!setup)
> +			return -ENOEXEC;

I welcome this. I should be able to rip some code out of usbmon now.

The comment in usb.h says:
 *  (Note
 * that transfer_buffer and setup_packet must still be set because not all
 * host controllers use DMA, nor do virtual root hubs).

But in case of data, this happens when a driver attempts to set up DMA
with a highmem page without doing a kmap first. I think we never enforced
the above comment. And I think that I managed to oops usbmon by dereferencing
garbage in transfer_buffer before but I may not remember right.
But the setup packet should be mapped to be used, right? There's no
good reason for setup_packet not to be mapped, right?

-- Pete

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