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SubjectRe: [PATCH] USB: gadget: epautoconf: fix ep maxpacket check
On Fri, 27 Sep 2013, Robert Baldyga wrote:

> This patch fixes validation of maxpacket value given in endpoint descriptor.
> Added check of maxpacket for bulk endpoints.
> Correct maxpacket value is:
>
> FULL-SPEED HIGH-SPEED
> BULK 64 512

Don't forget SuperSpeed. It requires Bulk endpoints to have maxpacket
= 1024.

> INTERRUPT 64 1024
> ISOCHRONOUS 1023 1024
>
> Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
> ---
> drivers/usb/gadget/epautoconf.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/gadget/epautoconf.c b/drivers/usb/gadget/epautoconf.c
> index a777f7b..35bde34 100644
> --- a/drivers/usb/gadget/epautoconf.c
> +++ b/drivers/usb/gadget/epautoconf.c
> @@ -136,16 +136,26 @@ ep_matches (
> * the usb spec fixes high speed bulk maxpacket at 512 bytes.
> */
> max = 0x7ff & usb_endpoint_maxp(desc);
> +
> + if (ep->maxpacket < max)
> + return 0;
> +
> switch (type) {
> + case USB_ENDPOINT_XFER_BULK:
> + /* BULK: limit 512 high/super speed */

512 high, 1024 super.

> + if (max > 512)
> + return 0;
> + /* FALLTHROUGH */
> +
> case USB_ENDPOINT_XFER_INT:
> - /* INT: limit 64 bytes full speed, 1024 high/super speed */
> + /* BULK/INT: limit 64 bytes full speed */
> if (!gadget_is_dualspeed(gadget) && max > 64)
> return 0;
> /* FALLTHROUGH */
>
> case USB_ENDPOINT_XFER_ISOC:
> - /* ISO: limit 1023 bytes full speed, 1024 high/super speed */
> - if (ep->maxpacket < max)
> + /* INT/ISO: limit 1023 bytes full speed, 1024 high/super speed */

The comment mentions INT/ISO. But this code can also run in the BULK
case.

> + if (max > 1024)
> return 0;
> if (!gadget_is_dualspeed(gadget) && max > 1023)
> return 0;

I suspect this code would become a lot clearer if all the FALLTHROUGH
logic were eliminated and each case was handled on its own.

Alan Stern



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