linux-kernel - Re: [PATCH] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate

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Message-ID: <s5h39bqmiuo.wl%tiwai@suse.de>
Date:	Sun, 08 Jan 2012 14:20:15 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Xi Wang <xi.wang@...il.com>
Cc:	Jaroslav Kysela <perex@...ex.cz>,
	Clemens Ladisch <clemens@...isch.de>,
	Daniel Mack <zonque@...il.com>,
	Wolfgang Breyha <wbreyha@....net>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: usb-audio: fix possible hang and overflow in parse_uac2_sample_rate_range()

At Sun, 8 Jan 2012 07:45:09 -0500,
Xi Wang wrote:
> 
> On Jan 8, 2012, at 4:09 AM, Takashi Iwai wrote:
> > As of now, I have little time to evaluate, so I might have missed
> > something, but I wonder whether 
> > 
> > 		/* avoid overflow */
> > 		if (nr_rates == KMALLOC_MAX_SIZE / sizeof(int))
> > 			break;
> > 
> > is the best way to check.  This looks ugly to me.
> > If we need to limit the number of rates, better to define some proper
> > numbers as the upper limit.  And then, it should warn, not only
> > breaking loop.
> 
> Thanks for looking into this.  Yeah, I agree using something like
> MAX_NR_RATES is better.  Is 65535 okay or do we need a larger limit?

It's way too higher than any realistic situation ;)
I guess 1000 or such should suffice.


thanks,

Takashi
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