linux-kernel - Re: [PATCH] comedi: integer overflow in do_insnlist

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Message-ID: <20111123215111.GD3258@mwanda>
Date:	Thu, 24 Nov 2011 00:51:11 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Ian Abbott <abbotti@....co.uk>, Xi Wang <xi.wang@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Mori Hess <fmhess@...rs.sourceforge.net>,
	"security@...nel.org" <security@...nel.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Ian Abbott <ian.abbott@....co.uk>,
	Franky Lin <frankyl@...adcom.com>,
	Greg Dietsche <Gregory.Dietsche@....edu>,
	Mark Pearson <markpearson_de@...oo.de>
Subject: Re: [PATCH] comedi: integer overflow in do_insnlist_ioctl()

On Wed, Nov 23, 2011 at 10:41:07PM +0100, Lars-Peter Clausen wrote:
> >     if (insnlist.n_insns <= ULONG_MAX / sizeof(struct comedi_insn))
> >         insns =
> >             kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns,
> >                 GFP_KERNEL);
> >     if (!insns)
> >         ...
> > 
> > (note that insns is initialized to NULL).
> > 
> 
> Just use kcalloc, it will do the right thing for you.
> 

I think the reason why I didn't do that in my original patch is that
kcalloc() has a memset(..., 0, ...) in it so it's a slow down.  But
this isn't performance critical code so that would work.

regards,
dan carpenter

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