From: Matthew Wilcox <willy@infradead.org>
To: "Tobin C. Harding" <me@tobin.cc>
Cc: linux-mm@kvack.org, kernel-hardening@lists.openwall.com,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [RFC] Warn the user when they could overflow mapcount
Date: Wed, 7 Feb 2018 20:06:55 -0800 [thread overview]
Message-ID: <20180208040655.GD14918@bombadil.infradead.org> (raw)
In-Reply-To: <20180208031804.GD3304@eros>
On Thu, Feb 08, 2018 at 02:18:04PM +1100, Tobin C. Harding wrote:
> > +++ b/Documentation/sysctl/vm.txt
> > @@ -379,7 +379,8 @@ While most applications need less than a thousand maps, certain
> > programs, particularly malloc debuggers, may consume lots of them,
> > e.g., up to one or two maps per allocation.
> >
> > -The default value is 65536.
> > +The default value is 65530. Increasing this value without decreasing
> > +pid_max may allow a hostile user to corrupt kernel memory.
>
> Just checking - did you mean the final '0' on this value?
That's what my laptop emits ...
mm/mmap.c:int max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
include/linux/mm.h:#define DEFAULT_MAX_MAP_COUNT (USHRT_MAX - MAPCOUNT_ELF_CORE_MARGIN)
include/linux/mm.h:#define MAPCOUNT_ELF_CORE_MARGIN (5)
should be the same value for everybody.
next prev parent reply other threads:[~2018-02-08 4:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-08 2:11 [RFC] Warn the user when they could overflow mapcount Matthew Wilcox
2018-02-08 2:56 ` Jann Horn
2018-02-08 4:04 ` Matthew Wilcox
2018-02-08 17:58 ` valdis.kletnieks
2018-02-08 18:05 ` Daniel Micay
2018-02-08 18:56 ` Matthew Wilcox
2018-02-08 19:33 ` Daniel Micay
2018-02-08 19:42 ` Matthew Wilcox
2018-02-08 19:48 ` Daniel Micay
2018-02-08 20:21 ` Matthew Wilcox
2018-02-08 21:37 ` [RFC] Limit mappings to ten per page per process Matthew Wilcox
2018-02-09 4:26 ` Kirill A. Shutemov
2018-02-14 13:51 ` Matthew Wilcox
2018-02-14 14:05 ` Kirill A. Shutemov
2018-02-09 1:47 ` [RFC] Warn the user when they could overflow mapcount Daniel Micay
2018-02-08 3:18 ` Tobin C. Harding
2018-02-08 4:06 ` Matthew Wilcox [this message]
2018-03-02 21:26 ` [RFC] Handle mapcount overflows Matthew Wilcox
2018-03-02 22:03 ` Matthew Wilcox
2019-05-01 14:41 ` Jann Horn
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