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Date: Thu, 15 Jan 2015 17:15:43 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Calvin Owens <calvinowens@fb.com>,
        Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>,
        Alexey Dobriyan <adobriyan@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
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        Peter Feiner <pfeiner@google.com>,
        Grant Likely <grant.likely@secretlab.ca>,
        linux-kernel <linux-kernel@vger.kernel.org>, <kernel-team@fb.com>
Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files
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On Thu, 15 Jan 2015 00:51:50 +0100 Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> > There are still several flags unused in vma.vm_flags btw.
> >
> > I'm not sure that we can repurpose vm_pgoff (or vm_private_data) for
> > this: a badly behaved thread could make its sp point at a random vma
> > then trick the kernel into scribbling on that vma's vm_proff?
> 
> Well, we could still check vm_file for being NULL before writing to
> vm_pgoff/vm_stack_tid. 

Yes, I guess that would work.  We'd need to check that nobody else
is already playing similar games with vm_pgoff.