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

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Message-ID: <50EF23E8.1070202@kernel.dk>
Date:	Thu, 10 Jan 2013 21:26:16 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Takashi Iwai <tiwai@...e.de>
CC:	Eldad Zack <eldad@...refinery.com>, 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 2013-01-10 21:19, Takashi Iwai wrote:
> At Thu, 10 Jan 2013 20:45:02 +0100 (CET),
> Eldad Zack wrote:
>>
>>
>> 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?
> 
> Ah, yes, good catch.  It was dropped during rebasing and rewriting.
> Below is the revised patch.

Thanks, I'll give it a go and report back.

-- 
Jens Axboe

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