Re: [PATCH] sound/usb: fix to release stream resources from media_snd_device_delete()

Mauro Carvalho Chehab
2016-03-19T02:57:15Z

Em Fri, 18 Mar 2016 20:50:31 -0600
Shuah Khan <shuahkh@osg.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@osg.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