linux-kernel - Re: [PATCH] perf: prevent overflow in size calculation

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Date:	Thu, 19 Jul 2012 19:51:40 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Namhyung Kim <namhyung@...nel.org>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf: prevent overflow in size calculation

>> +	/* Check for overflow when calculating sizeof_sym_hist */
>> +	if (size > (SIZE_MAX / sizeof(u64)))
>> +		return -1;
>
> How does it guarantee that the end result which used in zalloc below
> would not overflow?
>
>> +
>> +	sizeof_sym_hist = (sizeof(struct sym_hist) + size * sizeof(u64));
>>   	notes->src = zalloc(sizeof(*notes->src) + symbol_conf.nr_events * sizeof_sym_hist);
>>   	if (notes->src == NULL)
>>   		return -1;

Whoops. Thanks for pointing that out.
I've sent a fixed up patch (the check for sizeof_sym_hist wasn't even 
complete)

--
Cody


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