linux-kernel - Re: sys

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Message-ID: <20120924185119.GI16532@moon>
Date:	Mon, 24 Sep 2012 22:51:19 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
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

On Mon, Sep 24, 2012 at 11:29:09AM -0700, Eric W. Biederman wrote:
> >  
> > +#ifdef CONFIG_MMU
> >  	if (addr >= TASK_SIZE || addr < mmap_min_addr)
> > +#else
> > +	if (addr >= TASK_SIZE)
> > +#endif
> 
> 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.
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