linux-kernel - Re: Oops in sound/usb/pcm.c:match_endpoint

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Message-ID: <alpine.LNX.2.00.1301102038560.1321@xoschi>
Date:	Thu, 10 Jan 2013 20:45:02 +0100 (CET)
From:	Eldad Zack <eldad@...refinery.com>
To:	Takashi Iwai <tiwai@...e.de>
cc:	Jens Axboe <axboe@...nel.dk>, perex@...ex.cz,
	alsa-devel@...a-project.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Oops in sound/usb/pcm.c:match_endpoint_audioformats() in current
 -git


On Thu, 10 Jan 2013, Takashi Iwai wrote:

> At Thu, 10 Jan 2013 13:49:22 +0100,
> Jens Axboe wrote:
> > 
> > Here it is, it's from the one introducing the audioformat lookup.
> > Confirmed that 3.8-rc3 with this backed out works fine, too. So should
> > be fairly confident in that result.

> From: Takashi Iwai <tiwai@...e.de>
> Subject: [PATCH] ALSA: usb-audio: Fix NULL dereference by access to
>  non-existing substream
> 
> The commit [0d9741c0: ALSA: usb-audio: sync ep init fix for
> audioformat mismatch] introduced the correction of parameters to be
> set for sync EP.  But since the new code assumes that the sync EP is
> always paired with the data EP of another direction, it triggers Oops
> when a device only with a single direction is used.

Yes - sorry, I didn't consider this at all.

> This patch adds a proper check of sync EP type and the presence of the
> paired substream for avoiding the crash.
> 
> Reported-by: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
>  sound/usb/pcm.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> index c659310..21c0001 100644
> --- a/sound/usb/pcm.c
> +++ b/sound/usb/pcm.c
> @@ -511,6 +511,17 @@ static int configure_sync_endpoint(struct snd_usb_substream *subs)
>  	struct snd_usb_substream *sync_subs =
>  		&subs->stream->substream[subs->direction ^ 1];
>  
> +	if (subs->sync_endpoint->type != SND_USB_ENDPOINT_TYPE_DATA ||
> +	    !subs->stream) {
> +		ret = snd_usb_endpoint_set_params(subs->sync_endpoint,
> +						  subs->pcm_format,
> +						  subs->channels,
> +						  subs->period_bytes,
> +						  subs->cur_rate,
> +						  subs->cur_audiofmt,
> +						  NULL);
> +	}
> +

I think you want to return here, no?



Jens, could you please send me the device's descriptors (lsusb -v)?
I'd like to take a closer look at this.

Cheers,
Eldad

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