linux-kernel - Re: [PATCH] linux/bits.h: Add compile time sanity check of GENMASK inputs

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: <20190805195526.GA869@rikard>
Date:   Mon, 5 Aug 2019 21:55:26 +0200
From:   Rikard Falkeborn <rikard.falkeborn@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Rikard Falkeborn <rikard.falkeborn@...il.com>,
        Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Berg <johannes@...solutions.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] linux/bits.h: Add compile time sanity check of GENMASK
 inputs

On Sun, Aug 04, 2019 at 03:45:16PM +0900, Masahiro Yamada wrote:
> On Sun, Aug 4, 2019 at 3:36 AM Rikard Falkeborn
> <rikard.falkeborn@...il.com> wrote:
> >
> > On Sat, Aug 03, 2019 at 12:12:46PM +0900, Masahiro Yamada wrote:
> > > On Sat, Aug 3, 2019 at 12:03 PM Masahiro Yamada
> > > <yamada.masahiro@...ionext.com> wrote:
> > >
> > > >
> > > > BTW, v2 is already inconsistent.
> > > > If you wanted GENMASK_INPUT_CHECK() to return 'unsigned long',,
> > > > you would have to cast (low) > (high) as well:
> > > >
> > > >                (unsigned long)((low) > (high)), UL(0))))
> > > >
> > > > This is totally redundant, and weird.
> > >
> > > I take back this comment.
> > > You added (unsigned long) to the beginning of this macro.
> > > So, the type is consistent, but I believe all casts should be removed.
> >
> > Maybe you're right. BUILD_BUG_ON_ZERO returns size_t regardless of
> > inputs. I was worried that on some platform, size_t would be larger than
> > unsigned long (as far as I could see, the standard does not give any
> > guarantees), and thus all of a sudden GENMASK would be 8 bytes instead
> > of 4, but perhaps that is not a problem?
> 
> 
> How about adding (int) cast to BUILD_BUG_ON_ZERO() ?

I'll have a look.