linux-kernel - Re: [PATCH] usb: gadget: f_uac2: fixup feedback endpoint stop

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Message-ID: <87a6l39us6.fsf@kernel.org>
Date:   Fri, 27 Aug 2021 11:05:38 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Pavel Hofman <pavel.hofman@...tera.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jack Pham <jackp@...eaurora.org>, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Ferry Toth <ftoth@...londelft.nl>
Subject: Re: [PATCH] usb: gadget: f_uac2: fixup feedback endpoint stop


Hi,

Jerome Brunet <jbrunet@...libre.com> writes:

> When the uac2 function is stopped, there seems to be an issue reported on
> some platforms (Intel Merrifield at least)
>
> BUG: kernel NULL pointer dereference, address: 0000000000000008
> ...
> RIP: 0010:dwc3_gadget_del_and_unmap_request+0x19/0xe0
> ...
> Call Trace:
>  dwc3_remove_requests.constprop.0+0x12f/0x170
>  __dwc3_gadget_ep_disable+0x7a/0x160
>  dwc3_gadget_ep_disable+0x3d/0xd0
>  usb_ep_disable+0x1c/0x70
>  u_audio_stop_capture+0x79/0x120 [u_audio]
>  afunc_set_alt+0x73/0x80 [usb_f_uac2]
>  composite_setup+0x224/0x1b90 [libcomposite]
>
> The issue happens only when the gadget is using the sync type "async", not
> "adaptive". This indicates that problem is coming from the feedback
> endpoint, which is only used with async synchronization mode.
>
> The problem is that request is freed regardless of usb_ep_dequeue(), which
> ends up badly if the request is not actually dequeued yet.
>
> Update the feedback endpoint free function to release the endpoint the same
> way it is done for the data endpoint, which takes care of the problem.
>
> Reported-by: Ferry Toth <ftoth@...londelft.nl>
> Tested-by: Ferry Toth <ftoth@...londelft.nl>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
>  Hi Felipe,
>
>  This solves the issue reported here [0] and makes revert [1]
>  unnecessary.

awesome work! Thanks

Acked-by: Felipe Balbi <balbi@...nel.org>

-- 
balbi