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Date: Fri, 9 Feb 2018 07:26:09 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [RFC] Limit mappings to ten per page per process
Message-ID: <20180209042609.wi6zho24wmmdkg6i@node.shutemov.name>
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To: Matthew Wilcox <willy@infradead.org>
Cc: Daniel Micay <danielmicay@gmail.com>, Jann Horn <jannh@google.com>, linux-mm@kvack.org, Kernel Hardening <kernel-hardening@lists.openwall.com>, kernel list <linux-kernel@vger.kernel.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

On Thu, Feb 08, 2018 at 01:37:43PM -0800, Matthew Wilcox wrote:
> On Thu, Feb 08, 2018 at 12:21:00PM -0800, Matthew Wilcox wrote:
> > Now that I think about it, though, perhaps the simplest solution is not
> > to worry about checking whether _mapcount has saturated, and instead when
> > adding a new mmap, check whether this task already has it mapped 10 times.
> > If so, refuse the mapping.
> 
> That turns out to be quite easy.  Comments on this approach?

This *may* break some remap_file_pages() users.

And it may be rather costly for popular binaries. Consider libc.so.

-- 
 Kirill A. Shutemov

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