From: Matthew Wilcox <willy@infradead.org>
To: Daniel Colascione <dancol@google.com>
Cc: dave.hansen@intel.com, linux-mm@kvack.org,
Tim Murray <timmurray@google.com>,
Minchan Kim <minchan@kernel.org>
Subject: Re: Why do we let munmap fail?
Date: Mon, 21 May 2018 17:22:39 -0700 [thread overview]
Message-ID: <20180522002239.GA4860@bombadil.infradead.org> (raw)
In-Reply-To: <CAKOZuesScfm_5=2FYurY3ojdhQtcwPWY+=hayJ5cG7pQU1LP9g@mail.gmail.com>
On Mon, May 21, 2018 at 05:00:47PM -0700, Daniel Colascione wrote:
> On Mon, May 21, 2018 at 4:32 PM Dave Hansen <dave.hansen@intel.com> wrote:
> > I think there's still a potential dead-end here. "Deallocation" does
> > not always free resources.
>
> Sure, but the general principle applies: reserve resources when you *can*
> fail so that you don't fail where you can't fail.
Umm. OK. But you want an mmap of 4TB to succeed, right? That implies
preallocating one billion * sizeof(*vma). That's, what, dozens of
gigabytes right there?
I'm sympathetic to wanting to keep both vma-merging and
unmap-anything-i-mapped working, but your proposal isn't going to fix it.
You need to handle the attacker writing a program which mmaps 46 bits
of address space and then munmaps alternate pages. That program needs
to be detected and stopped.
next prev parent reply other threads:[~2018-05-22 0:22 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-21 22:07 Daniel Colascione
2018-05-21 22:12 ` Dave Hansen
2018-05-21 22:20 ` Daniel Colascione
2018-05-21 22:29 ` Dave Hansen
2018-05-21 22:35 ` Daniel Colascione
2018-05-21 22:48 ` Dave Hansen
2018-05-21 22:54 ` Daniel Colascione
2018-05-21 23:02 ` Dave Hansen
2018-05-21 23:16 ` Daniel Colascione
2018-05-21 23:32 ` Dave Hansen
2018-05-22 0:00 ` Daniel Colascione
2018-05-22 0:22 ` Matthew Wilcox [this message]
2018-05-22 0:38 ` Daniel Colascione
2018-05-22 1:19 ` Theodore Y. Ts'o
2018-05-22 1:41 ` Daniel Colascione
2018-05-22 2:09 ` Daniel Colascione
2018-05-22 2:11 ` Matthew Wilcox
2018-05-22 1:22 ` Matthew Wilcox
2018-05-22 5:34 ` Nicholas Piggin
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