linux-kernel - Re: [PATCH] core: Catch overflows in do

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Date:	Tue, 8 Oct 2013 18:45:21 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Anatol Pomozov <anatol.pomozov@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, rdunlap@...radead.org
Subject: Re: [PATCH] core: Catch overflows in do_div() function

On Tue, Oct 8, 2013 at 6:18 PM, Joe Perches <joe@...ches.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.

Anatol, have you tested whether your change increases the kernel size?

-- 
Thanks,
//richard
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