linux-kernel - Re: sys

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Message-ID: <87bogvup4w.fsf@xmission.com>
Date:	Mon, 24 Sep 2012 13:44:47 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	Mark Salter <msalter@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <rmk@....linux.org.uk>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Kees Cook <keescook@...omium.org>,
	linux-kernel@...r.kernel.org,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: sys_kcmp

Cyrill Gorcunov <gorcunov@...nvz.org> writes:

> On Mon, Sep 24, 2012 at 10:51:19PM +0400, Cyrill Gorcunov wrote:
>> > I expect what you want is a call to access_ok, rather than hard coding
>> > details about task layout here.  This test certainly looks wrong
>> > for a 32bit process on a 64bit kernel. If I read your test right it
>> > appears I can set values of say 0x100000000 on a 32bit process...
>> > 
>> > As for mmap_min_addr I would expect your find_vma check would make that
>> > test unnecessary, simply by not finding a vma...
>> 
>> Good point, Eric, thanks! I'm cooking a new patch now.
>
> Btw, Eric, I somehow miss one bit -- how would you set this 0x100000000
> if TASK_SIZE is a macro which does check for TIF_ADDR32 and sets limit
> acordingly? What i'm missing?

How odd.  Last time I had looked TASK_SIZE was a simple constant.

Still I wonder a little if all architectures currently run from 0 to
TASK_SIZE, for address space available.  I seem to remember there have
been some exceptions to that rule.  But I can't recall what they were.

Eric
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