linux-kernel - Re: [PATCH 6/7] mm: kill vma flag VM

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Date:	Tue, 03 Apr 2012 09:10:20 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Matt Helsley <matthltc@...ibm.com>
CC:	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eric Paris <eparis@...hat.com>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

Matt Helsley wrote:
> On Sat, Mar 31, 2012 at 10:13:24PM +0200, Oleg Nesterov wrote:
>> On 03/31, Konstantin Khlebnikov wrote:
>>>
>>> comment from v2.6.25-6245-g925d1c4 ("procfs task exe symlink"),
>>> where all this stuff was introduced:
>>>
>>>> ...
>>>> This avoids pinning the mounted filesystem.
>>>
>>> So, this logic is hooked into every file mmap/unmmap and vma split/merge just to
>>> fix some hypothetical pinning fs from umounting by mm which already unmapped all
>>> its executable files, but still alive. Does anyone know any real world example?
>>
>> This is the question to Matt.
>
> This is where I got the scenario:
>
> https://lkml.org/lkml/2007/7/12/398

Cyrill Gogcunov's patch "c/r: prctl: add ability to set new mm_struct::exe_file"
gives userspace ability to unpin vfsmount explicitly.

https://lkml.org/lkml/2012/3/16/449

>
> Cheers,
> 	-Matt Helsley
>
> PS: I seem to keep coming back to this so I hope folks don't mind if I leave
> some more references to make (re)searching this topic easier:
>
> Thread with Cyrill Gorcunov discussing c/r of symlink:
> https://lkml.org/lkml/2012/3/16/448
>
> Thread with Oleg Nesterov re: cleanups:
> https://lkml.org/lkml/2012/3/5/240
>
> Thread with Alexey Dobriyan re: cleanups:
> https://lkml.org/lkml/2009/6/4/625
>
> mainline commit 925d1c401fa6cfd0df5d2e37da8981494ccdec07
> Date:   Tue Apr 29 01:01:36 2008 -0700
>
> 	procfs task exe symlink
>

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