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From: Arjan van de Ven <arjan@infradead.org>
To: Samium Gromoff <_deepfire@feelingofgreen.ru>
Cc: Pavel Machek <pavel@ucw.cz>,
	Valdis.Kletnieks@vt.edu, David Wagner <daw@cs.berkeley.edu>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Undo some of the pseudo-security madness
Date: Wed, 31 Jan 2007 17:59:48 +0800	[thread overview]
Message-ID: <1170237588.2865.2.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <87mz4996wg.wl@betelheise.deep.net>


> No amount of carefulness will prevent vendors stick arbitrarily
> damaging values of stack and mmap base randomisation, severely reducing
> the usefullness of MAP_FIXED.

MAP_FIXED is useful still. The only safe way is to use addresses you got
from mmap(), eg you overmap something.
Anything else is madness, with or without randomization. The C library
for example is free, and does, allocate memory and stacks etc etc.

Same for many other libraries; in addition libraries change in size all
the time... MAP_FIXED of an address you don't KNOW is free is a bug.
Period.
(using an address previously obtained from mmap() is safest, but you
could in theory also parse /proc/self/maps, although that is racey,
since nothing guarantees that the C library didn't spawn a background
thread that allocates memory)



  parent reply	other threads:[~2007-01-31 17:19 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-21 23:23 Samium Gromoff
2007-01-21 23:34 ` David Wagner
2007-01-22  0:36   ` Kyle Moffett
2007-01-22  1:53     ` Samium Gromoff
2007-02-24  9:40       ` Florian Weimer
2007-02-24 13:33         ` Samium Gromoff
2007-02-24 13:49           ` Florian Weimer
2007-01-22 15:20 ` Valdis.Kletnieks
2007-01-22 17:39   ` Samium Gromoff
2007-01-23  8:48     ` Pavel Machek
2007-01-23 14:03       ` Samium Gromoff
2007-01-23 15:41         ` Alan
2007-01-23 20:21           ` [PATCH 0/2] Mechanism to turn of ASR on a per-ELF binary basis Samium Gromoff
2007-01-23 20:28           ` [PATCH 1/2] Define the EF_AS_NO_RANDOM e_flag bit Samium Gromoff
2007-01-23 20:50             ` Jakub Jelinek
2007-01-23 21:06               ` Samium Gromoff
2007-01-23 21:16                 ` Jakub Jelinek
2007-01-23 21:54                   ` Samium Gromoff
2007-01-23 23:21                   ` Samium Gromoff
2007-01-24 17:08                     ` Pavel Machek
2007-01-29  1:18             ` Arjan van de Ven
2007-01-23 20:31           ` [PATCH 2/2] Make the EF_AS_NO_RANDOM e_flag bit disable PF_RANDOMIZE Samium Gromoff
2007-02-24  9:51           ` [PATCH] Undo some of the pseudo-security madness Florian Weimer
2007-02-24 13:36             ` Samium Gromoff
2007-01-31  9:59         ` Arjan van de Ven [this message]
2007-02-01  8:05           ` Florian Weimer
  -- strict thread matches above, loose matches on Subject: below --
2007-01-22  0:54 Samium Gromoff
2007-01-20 14:37 Samium Gromoff
2007-01-20 16:12 ` Samium Gromoff
2007-01-20 21:58 ` David Wagner
2007-01-21  2:16 ` Arjan van de Ven
2007-01-21 21:38   ` Samium Gromoff
2007-01-21 22:09   ` Samium Gromoff
2007-01-21 22:16     ` David Wagner
2007-01-22  0:35     ` Arjan van de Ven
2007-01-22  1:15       ` Samium Gromoff
2007-01-22 17:52       ` Samium Gromoff
2007-01-23  8:44         ` Pavel Machek

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