linux-kernel - Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation for 32-bit systems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1519665265.31245.6.camel@synopsys.com>
Date:   Mon, 26 Feb 2018 17:14:26 +0000
From:   Evgeniy Didin <Evgeniy.Didin@...opsys.com>
To:     "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "Evgeniy.Didin@...opsys.com" <Evgeniy.Didin@...opsys.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Alexey.Brodkin@...opsys.com" <Alexey.Brodkin@...opsys.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "Vineet.Gupta1@...opsys.com" <Vineet.Gupta1@...opsys.com>,
        "Eugeniy.Paltsev@...opsys.com" <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>
Subject: Re: [PATCH 2/2 v3] mmc: dw_mmc: Fix the CTO overflow calculation
 for 32-bit systems

On Mon, 2018-02-26 at 18:53 +0200, Andy Shevchenko wrote:
> On Mon, Feb 26, 2018 at 5:14 PM, Evgeniy Didin
> <Evgeniy.Didin@...opsys.com> wrote:
> > On Mon, 2018-02-26 at 16:39 +0200, Andy Shevchenko wrote:
> > > On Mon, Feb 26, 2018 at 4:34 PM, Evgeniy Didin
> > > <Evgeniy.Didin@...opsys.com> wrote:
> > > > In commit 4c2357f57dd5 ("mmc: dw_mmc: Fix the CTO timeout calculation")
> > > > have been made changes which can cause multiply overflow for 32-bit systems.
> > > > The value of cto_ms is lower the drto_ms, but nevertheless overflow can occur.
> > > > Lets cast this multiply to u64 type which prevents overflow.
> > > > -       cto_ms = DIV_ROUND_UP(MSEC_PER_SEC * cto_clks * cto_div, host->bus_hz);
> > > > +
> > > > +       cto_ms = DIV_ROUND_UP((u64)MSEC_PER_SEC * cto_clks * cto_div, host->bus_hz);
> > > 
> > > IIRC, someone commented on this or similar, i.e.
> > > 
> > > DIV_ROUND_UP_ULL() ?
> > 
> > Switch DIV_ROUND_UP macro to DIV_ROUND_UP_ULL is not reasonable
> > because overflow happens on multiply and DIV_ROUND_UP_ULL helps
> > with sum overflow.
> 
> Did you try to compile your code for 32-bit target?
Yes, we have compiled code for 32-bit system. 
I am wondering why are you asking that?

--
Best regards,
Evgeniy Didin