linux-kernel - Re: [PATCH 09/30] mtd: Don't cast kmalloc() return value in drivers/mtd/maps/pmcmsp-flash.c

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Date:	Sun, 26 Aug 2007 16:37:13 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Denys Vlasenko <vda.linux@...glemail.com>
cc:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Jesper Juhl <jesper.juhl@...il.com>,
	linux-mtd@...ts.infradead.org,
	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/30] mtd: Don't cast kmalloc() return value in
 drivers/mtd/maps/pmcmsp-flash.c


On Aug 26 2007 15:28, Denys Vlasenko wrote:
>> >
>> > What exactely would using kcalloc() over kzalloc() here buy us?
>>
>> technically, nothing.
>
>The idea of calloc is that it can check for underflow in parameter.

Actually, overflow.

calloc(0xFFFF0000,  0x1000) => will return NULL
malloc(0xFFFF0000 * 0x1000) => silent 32 bit multiplication/truncation,
will allocate less than requested.

>calloc(-1, 10000000) => easy to detect
>malloc(-1 * 10000000) => malloc(-10000000) => not so trivial


	Jan
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