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

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Date:	Mon, 02 Apr 2012 20:19:59 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"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>
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

Oleg Nesterov wrote:
> On 04/02, Konstantin Khlebnikov wrote:
>>
>> In this patch I leave mm->exe_file lockless.
>> After exec/fork we can change it only for current task and only if mm->mm_users == 1.
>>
>> something like this:
>>
>> task_lock(current);
>
> OK, this protects against the race with get_task_mm()
>
>> if (atomic_read(&current->mm->mm_users) == 1)
>
> this means PR_SET_MM_EXE_FILE can fail simply because someone did
> get_task_mm(). Or the caller is multithreaded.

This is sad, seems like we should keep mm->exe_file protection by mm->mmap_sem.
So, I'll rework this patch...

>
>> 	set_mm_exe_file(current->mm, new_file);
>
> No, fput() can sleep.

Yep

>
> Oleg.
>
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