linux-kernel - Re: [PATCH v3] usb: gadget: forbid queuing request to a disabled ep

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Message-ID: <87bn9pdrkq.fsf@saruman.tx.rr.com>
Date:	Thu, 17 Dec 2015 09:26:29 -0600
From:	Felipe Balbi <balbi@...com>
To:	<changbin.du@...el.com>
CC:	<gregkh@...uxfoundation.org>, <John.Youn@...opsys.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lkp@...org>, <fengguang.wu@...el.com>,
	"Du, Changbin" <changbin.du@...el.com>
Subject: Re: [PATCH v3] usb: gadget: forbid queuing request to a disabled ep


Hi,

changbin.du@...el.com writes:
> From: "Du, Changbin" <changbin.du@...el.com>
>
> Queue a request to disabled ep  doesn't make sense, and induce caller
> make mistakes.
>
> Here is a example for the android mtp gadget function driver. A mem
> corruption can happen on below senario.
> 1) On disconnect, mtp driver disable its EPs,
> 2) During send_file_work and receive_file_work, mtp queues a request
>    to ep. (The mtp driver need improve its synchronization logic!)
> 3) mtp_function_unbind is invoked and all mtp requests are freed.
> 4) when udc process the request queued on step 2, will cause kernel
>    NULL pointer dereference exception.
>
> Signed-off-by: Du, Changbin <changbin.du@...el.com>
> ---
> change from v2: igonre ep0 as it always enabled during usb session.
> change from v1: add WARN_ON_ONCE message.
> ---
>  include/linux/usb/gadget.h | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 3d583a1..0c5d9ea 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -402,6 +402,9 @@ static inline void usb_ep_free_request(struct usb_ep *ep,
>  static inline int usb_ep_queue(struct usb_ep *ep,
>  			       struct usb_request *req, gfp_t gfp_flags)
>  {
> +	if (WARN_ON_ONCE(!ep->enabled && !ep->address))

this will only trigger for a disabled ep0. Are you testing any of your
patches at all ?

-- 
balbi

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