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From: Ilya Smith <blackzert@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: 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,
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Subject: Re: [RFC PATCH v2 0/2] Randomization of address chosen by mmap.
Date: Fri, 23 Mar 2018 20:55:49 +0300	[thread overview]
Message-ID: <651E0DB6-4507-4DA1-AD46-9C26ED9792A8@gmail.com> (raw)
In-Reply-To: <20180323124806.GA5624@bombadil.infradead.org>


> 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;
2. User mode is not that layer which should be responsible for choosing
random address or handling entropy;
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.

  reply	other threads:[~2018-03-23 17:55 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 [this message]
2018-03-26  8:46     ` Michal Hocko
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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