linux-kernel - Re: mm: NULL ptr deref handling mmaping of special mappings

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Message-ID: <CALCETrXQOPBOBOgE_snjdmJM7zi34Ei8-MUA-U-YVrwubz4sOQ@mail.gmail.com>
Date:	Wed, 14 May 2014 14:33:54 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Jones <davej@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: mm: NULL ptr deref handling mmaping of special mappings

On Wed, May 14, 2014 at 2:31 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Wed, 14 May 2014 17:11:00 -0400 Sasha Levin <sasha.levin@...cle.com> wrote:
>
>> > In my linux-next all that code got deleted by Andy's "x86, vdso:
>> > Reimplement vdso.so preparation in build-time C" anyway.  What kernel
>> > were you looking at?
>>
>> Deleted? It appears in today's -next. arch/x86/vdso/vma.c:124 .
>>
>> I don't see Andy's patch removing that code either.
>
> ah, OK, it got moved from arch/x86/vdso/vdso32-setup.c into
> arch/x86/vdso/vma.c.
>
> Maybe you managed to take a fault against the symbol area between the
> _install_special_mapping() and the remap_pfn_range() call, but mmap_sem
> should prevent that.
>
> Or the remap_pfn_range() call never happened.  Should map_vdso() be
> running _install_special_mapping() at all if
> image->sym_vvar_page==NULL?

I'm confused: are we talking about 3.15-rcsomething or linux-next?
That code changed.

Would this all make more sense if there were just a single vma in
here?  cc: Pavel and Cyrill, who might have to deal with this stuff in
CRIU

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC
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