Date: Tue, 25 Nov 2008 18:52:36 +0100 From: Tomas Hoger <thoger@...hat.com> To: oss-security@...ts.openwall.com Cc: rea-sec@...elabs.ru, "Steven M. Christey" <coley@...re.org>, Michael Sweet <mike@...ysw.com> Subject: Re: CVE request: cups - potential integer overflow in PNG image reader [was: CUPS DoS via RSS subscriptions] On Tue, 25 Nov 2008 15:38:30 +0300 Eygene Ryabinkin <rea-sec@...elabs.ru> wrote: > > Advisory: http://www.cups.org/str.php?L2974 > > Patch: http://www.cups.org/strfiles/2974/str2974.patch > > Hmm, my brains aren't in a perfect shape today, so I could be missing > some important point, but I don't understand how swapping 'xsize' and > 'ysize' can help to fix anything. IIRC, the order of multiplication > isn't guaranteed and multiplication is commutative, so 'xsize' and > 'ysize' both are equally good or bad and one can not prefer either. The bug suggests that xsize and ysize values use different upper bounds. So ysize * 3 can overflow (upper bound 2^31-1), while xsize * 3 can't (2^27-1). -- Tomas Hoger / Red Hat Security Response Team
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