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Message from discussion mm: kill vma flag VM_EXECUTABLE
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Cyrill Gorcunov  
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 More options Apr 2 2012, 12:03 pm
Newsgroups: fa.linux.kernel
From: Cyrill Gorcunov <gorcu...@openvz.org>
Date: Mon, 02 Apr 2012 16:03:11 UTC
Local: Mon, Apr 2 2012 12:03 pm
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE
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On Mon, Apr 02, 2012 at 04:48:21PM +0200, 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.

So it leads to the same question -- do we *really* need the PR_SET_MM_EXE_FILE
to be one-shot action? Yeah, I know, we agreed that one-shot is better than
anything else from sysadmin perspective and such, but maybe I could introduce
a special capability bit for c/r and allow a program which has such cap to modify
exe-file without checkin mm_users?

/me hides

> >       set_mm_exe_file(current->mm, new_file);

> No, fput() can sleep.

Sure, it was just "something like" as Konstantin stated, thanks anyway ;)

        Cyrill
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