linux-kernel - Re: [tip:x86/mm] x86: Fix mmap random address range

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Date:	Wed, 07 Dec 2011 07:29:14 -0500
From:	Valdis.Kletnieks@...edu
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	tglx@...utronix.de, ludwig.nussel@...e.de,
	harvey.harrison@...il.com, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86: Fix mmap random address range

On Mon, 05 Dec 2011 09:52:17 PST, tip-bot for Ludwig Nussel said:
> Commit-ID:  9af0c7a6fa860698d080481f24a342ba74b68982
> Gitweb:     http://git.kernel.org/tip/9af0c7a6fa860698d080481f24a342ba74b68982
> Author:     Ludwig Nussel <ludwig.nussel@...e.de>
> AuthorDate: Tue, 15 Nov 2011 14:46:46 -0800
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Mon, 5 Dec 2011 17:07:23 +0100
>
> x86: Fix mmap random address range
>
> On x86_32 casting the unsigned int result of get_random_int() to
> long may result in a negative value.  On x86_32 the range of
> mmap_rnd() therefore was -255 to 255.  The 32bit mode on x86_64
> used 0 to 255 as intended.

Will somebody please hand me a big dose of caffeine and explain to me
how the range could have been -255 to 255?  -256 maybe, or -128 to 127,
but -255??!?

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