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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,
	fenghua.yu@intel.com, ralf@linux-mips.org, jejb@parisc-linux.org,
	Helge Deller <deller@gmx.de>,
	benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net,
	tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, nyc@holomorphy.com, viro@zeniv.linux.org.uk,
	arnd@arndb.de, gregkh@linuxfoundation.org,
	deepa.kernel@gmail.com, Hugh Dickins <hughd@google.com>,
	kstewart@linuxfoundation.org, pombredanne@nexb.com,
	Andrew Morton <akpm@linux-foundation.org>,
	steve.capper@arm.com, punit.agrawal@arm.com,
	aneesh.kumar@linux.vnet.ibm.com, npiggin@gmail.com,
	Kees Cook <keescook@chromium.org>,
	bhsharma@redhat.com, riel@redhat.com, nitin.m.gupta@oracle.com,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>,
	ross.zwisler@linux.intel.com, Jerome Glisse <jglisse@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Oleg Nesterov <oleg@redhat.com>,
	linux-alpha@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
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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

  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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