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Date: Fri, 16 Jan 2015 13:00:13 +0200
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Calvin Owens <calvinowens@fb.com>,
        Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>,
        Alexey Dobriyan <adobriyan@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        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, Jan 15, 2015 at 05:15:43PM -0800, Andrew Morton wrote:
> 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.

Well, we do use ->vm_pgoff in anonymous VMAs. For rmap in particular --
vma_address().

-- 
 Kirill A. Shutemov