linux-kernel - Re: [RFC] Limit mappings to ten per page per process

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

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