From: Michal Hocko <mhocko@kernel.org>
To: Ilya Smith <blackzert@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>,
rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com,
vgupta@synopsys.com, linux@armlinux.org.uk, tony.luck@intel.com,
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Helge Deller <deller@gmx.de>,
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Andrew Morton <akpm@linux-foundation.org>,
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Kees Cook <keescook@chromium.org>,
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"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>,
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Andrea Arcangeli <aarcange@redhat.com>,
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sparclinux@vger.kernel.org, Linux-MM <linux-mm@kvack.org>
Subject: Re: [RFC PATCH v2 0/2] Randomization of address chosen by mmap.
Date: Mon, 26 Mar 2018 10:46:50 +0200 [thread overview]
Message-ID: <20180326084650.GC5652@dhcp22.suse.cz> (raw)
In-Reply-To: <651E0DB6-4507-4DA1-AD46-9C26ED9792A8@gmail.com>
On Fri 23-03-18 20:55:49, Ilya Smith wrote:
>
> > On 23 Mar 2018, at 15:48, Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Thu, Mar 22, 2018 at 07:36:36PM +0300, Ilya Smith wrote:
> >> Current implementation doesn't randomize address returned by mmap.
> >> All the entropy ends with choosing mmap_base_addr at the process
> >> creation. After that mmap build very predictable layout of address
> >> space. It allows to bypass ASLR in many cases. This patch make
> >> randomization of address on any mmap call.
> >
> > Why should this be done in the kernel rather than libc? libc is perfectly
> > capable of specifying random numbers in the first argument of mmap.
> Well, there is following reasons:
> 1. It should be done in any libc implementation, what is not possible IMO;
Is this really so helpful?
> 2. User mode is not that layer which should be responsible for choosing
> random address or handling entropy;
Why?
> 3. Memory fragmentation is unpredictable in this case
>
> Off course user mode could use random ‘hint’ address, but kernel may
> discard this address if it is occupied for example and allocate just before
> closest vma. So this solution doesn’t give that much security like
> randomization address inside kernel.
The userspace can use the new MAP_FIXED_NOREPLACE to probe for the
address range atomically and chose a different range on failure.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-03-26 8:47 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-22 16:36 [RFC PATCH v2 0/2] Randomization of address chosen by mmap Ilya Smith
2018-03-22 16:36 ` [RFC PATCH v2 1/2] " Ilya Smith
2018-03-22 20:53 ` Andrew Morton
2018-03-23 17:43 ` Ilya Smith
2018-03-22 16:36 ` [RFC PATCH v2 2/2] Architecture defined limit on memory region random shift Ilya Smith
2018-03-22 20:54 ` Andrew Morton
2018-03-23 17:48 ` Ilya Smith
2018-03-23 17:49 ` Ilya Smith
2018-03-22 20:57 ` [RFC PATCH v2 0/2] Randomization of address chosen by mmap Andrew Morton
2018-03-23 17:25 ` Ilya Smith
2018-03-23 12:48 ` Matthew Wilcox
2018-03-23 17:55 ` Ilya Smith
2018-03-26 8:46 ` Michal Hocko [this message]
2018-03-26 19:45 ` Ilya Smith
2018-03-27 7:24 ` Michal Hocko
2018-03-27 13:51 ` Ilya Smith
2018-03-27 14:38 ` Michal Hocko
2018-03-28 18:47 ` Ilya Smith
2018-03-27 22:16 ` Theodore Y. Ts'o
2018-03-27 23:58 ` Rich Felker
2018-03-28 18:48 ` Ilya Smith
2018-03-27 22:53 ` Kees Cook
2018-03-27 23:49 ` Matthew Wilcox
2018-03-27 23:57 ` Kees Cook
2018-03-28 0:00 ` Rich Felker
2018-03-28 21:07 ` Luck, Tony
2018-04-03 0:11 ` Ilya Smith
2018-03-28 21:07 ` Ilya Smith
2018-03-23 18:00 ` Rich Felker
2018-03-23 19:06 ` Matthew Wilcox
2018-03-23 19:16 ` Rich Felker
2018-03-23 19:29 ` Matthew Wilcox
2018-03-23 19:35 ` Rich Felker
2018-03-28 4:50 ` Rob Landley
2018-03-30 7:55 ` Pavel Machek
2018-03-30 9:07 ` Ilya Smith
2018-03-30 9:57 ` Pavel Machek
2018-03-30 11:10 ` Ilya Smith
2018-03-30 13:33 ` Rich Felker
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