Message-ID: <1381251080.2081.243.camel@joe-AO722>
Subject: Re: [PATCH] core: Catch overflows in do_div() function
From: Joe Perches <joe@perches.com>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Anatol Pomozov <anatol.pomozov@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, rdunlap@infradead.org
Date: Tue, 08 Oct 2013 09:51:20 -0700
In-Reply-To: <CAFLxGvzrEQGE8+QAFCQL=z2hwe578pBdWOu4B+DkJDjxkM0=hw@mail.gmail.com>
References: <CAOMFOmXfw2DkesOYip9VFDdUQgVN48qbJfuertPaSCz5aGdaeA@mail.gmail.com>
	 <1381248622-27809-1-git-send-email-anatol.pomozov@gmail.com>
	 <1381249090.2081.240.camel@joe-AO722>
	 <CAFLxGvzrEQGE8+QAFCQL=z2hwe578pBdWOu4B+DkJDjxkM0=hw@mail.gmail.com>
Content-Type: text/plain; charset="ISO-8859-1"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1087
Lines: 26

On Tue, 2013-10-08 at 18:45 +0200, Richard Weinberger wrote:
> On Tue, Oct 8, 2013 at 6:18 PM, Joe Perches <joe@perches.com> wrote:
> > On Tue, 2013-10-08 at 09:10 -0700, Anatol Pomozov wrote:
> >> If second parameter passed to this function was 64 then it silently
> >> truncates to 32 bits. Catch such situation.
> > []
> >> diff --git a/include/asm-generic/div64.h b/include/asm-generic/div64.h
> > []
> >> @@ -25,6 +26,7 @@
> >>  # define do_div(n,base) ({                                   \
> >>       uint32_t __base = (base);                               \
> >>       uint32_t __rem;                                         \
> >> +     BUG_ON(sizeof(base) > 4 && base >= (1UL<<32));          \
> >
> > I think this would be better as a BUILD_BUG_ON
> 
> No. BUILD_BUG_ON works only for constants.

Add __builtin_constant_p(base).


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/