From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyrill Gorcunov <gorcunov@openvz.org>
Subject: Re: sys_kcmp
Date: Mon, 24 Sep 2012 22:51:19 +0400
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To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Mark Salter <msalter@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Russell King <rmk@arm.linux.org.uk>, Geert Uytterhoeven <geert@linux-m68k.org>, Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org, Linux-Arch <linux-arch@vger.kernel.org>, Heiko Carstens <heiko.carstens@de.ibm.com>, "H. Peter Anvin" <hpa@zytor.com>, Pavel Emelyanov <xemul@parallels.com>

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.