linux-kernel - Re: [PATCH] sound/usb: fix to release stream resources from media_snd_device

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Message-ID: <20160318235708.1eccf0e6@recife.lan>
Date:	Fri, 18 Mar 2016 23:57:08 -0300
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Shuah Khan <shuahkh@....samsung.com>
Cc:	tiwai@...e.com, perex@...ex.cz, linux-media@...r.kernel.org,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sound/usb: fix to release stream resources from
 media_snd_device_delete()

Em Fri, 18 Mar 2016 20:50:31 -0600
Shuah Khan <shuahkh@....samsung.com> escreveu:

> Fix to release stream resources from media_snd_device_delete() before
> media device is unregistered. Without this change, stream resource free
> is attempted after the media device is unregistered which would result
> in use-after-free errors.
> 
> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
> ---
> 
> - Ran bind/unbind loop (1000 iteration) test on snd-usb-audio
>   while running mc_nextgen_test loop (1000 iterations) in parallel.
> - Ran bind/unbind and rmmod/modprobe tests on both drivers. Also
>   generated graphs when after bind/unbind, rmmod/modprobe. Graphs
>   look good.
> - Note: Please apply the following patch to fix memory leak:
>   sound/usb: Fix memory leak in media_snd_stream_delete() during unbind
>   https://lkml.org/lkml/2016/3/16/1050
> 
>  sound/usb/media.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/sound/usb/media.c b/sound/usb/media.c
> index de4a815..e35af88 100644
> --- a/sound/usb/media.c
> +++ b/sound/usb/media.c
> @@ -301,6 +301,13 @@ int media_snd_device_create(struct snd_usb_audio *chip,
>  void media_snd_device_delete(struct snd_usb_audio *chip)
>  {
>  	struct media_device *mdev = chip->media_dev;
> +	struct snd_usb_stream *stream;
> +
> +	/* release resources */
> +	list_for_each_entry(stream, &chip->pcm_list, list) {
> +		media_snd_stream_delete(&stream->substream[0]);
> +		media_snd_stream_delete(&stream->substream[1]);

I'll look on it better tomorrow, but it sounds weird to hardcode
substream[0] and [1] here... are you sure that this is valid for
*all* devices supported by snd-usb-audio?

Regards,
Mauro

> +	}
>  
>  	media_snd_mixer_delete(chip);
>  


-- 
Thanks,
Mauro