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Message-Id: <20080205192446.1ba1a1ca.randy.dunlap@oracle.com>
Date: Tue, 5 Feb 2008 19:24:46 -0800
From: Randy Dunlap <randy.dunlap@...cle.com>
To: Jiri Kosina <jkosina@...e.cz>
Cc: Arjan van de Ven <arjan@...radead.org>,
Ingo Molnar <mingo@...e.hu>, Pavel Machek <pavel@....cz>,
Hugh Dickins <hugh@...itas.com>,
kernel list <linux-kernel@...r.kernel.org>,
Abel Bernabeu <abel.bernabeu@...il.com>
Subject: Re: brk randomization breaks columns
On Tue, 5 Feb 2008 23:35:27 +0100 (CET) Jiri Kosina wrote:
> On Tue, 5 Feb 2008, Arjan van de Ven wrote:
>
> > the combo of a config option + sysctl sounds the right way forward then
> > ;(
>
> OK, so I propose the one below (unested yet, but should be trivial). Does
> anyone have any objections?
>
>
>
> From: Jiri Kosina <jkosina@...e.cz>
>
> ASLR: add possibility for more fine-grained tweaking
>
> Some prehistoric binaries don't like when start of brk area is located
> anywhere else than just after code+bss.
>
> This patch adds possibility to configure the default behavior of address
> space randomization. In addition to that, randomize_va_space now can have
> value of '2', which means full randomization including brk space.
>
> Also, documentation of randomize_va_space is added.
Thanks.
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
>
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index 8984a53..0373bbe 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -41,6 +41,7 @@ show up in /proc/sys/kernel:
> - pid_max
> - powersave-nap [ PPC only ]
> - printk
> +- randomize_va_space
> - real-root-dev ==> Documentation/initrd.txt
> - reboot-cmd [ SPARC only ]
> - rtsig-max
> @@ -280,6 +281,37 @@ send before ratelimiting kicks in.
>
> ==============================================================
>
> +randomize-va-space:
> +
> +This option can be used to select the type of process address
> +space randomization is used in the system, for architectures
s/is used/that is used/
> +that support this feature.
> +
> +One of the following numeric values is possible:
> +
> +0 - [none]
> + Turn the process address space randomization off by default.
> +
> +1 - [conservative]
> + Conservative address space randomization makes the addresses of
> + mmap base and VDSO page randomized. This, among other things,
> + implies that shared libraries will be loaded to random addresses.
> + Also for PIE binaries, the location of code start is randomized.
> +
> +2 - [full]
> +
> + This includes all the features that Conservative randomization
> + provides. In addition to that, also start of the brk area is
> + randomized.
> + There a few legacy applications out there (such as some ancient
> + versions of libc.so.5 from 1996), that assume that brk area starts
Drop comma ^ that the brk area
> + just after the end of the code+bss. These applications break when
> + start of the brk area is randomized. There are however no known
> + non-legacy applications that would be broken this way, so for most
> + systems it is safe to chose Full randomization.
choose
> +
> +==============================================================
> +
> reboot-cmd: (Sparc only)
>
> ??? This seems to be a way to give an argument to the Sparc
> diff --git a/init/Kconfig b/init/Kconfig
> index 87f50df..804a3a6 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -662,6 +662,46 @@ config SLOB
>
> endchoice
>
> +choice
> + prompt "Address space randomization type"
> + default RANDOMIZATION_CONSERVATIVE
> + help
> + This option allows to select the type of process address space
> + randomization that will be used by default (for those architectures
> + that support address space randomization). This option can be
> + overriden in runtime through kernel.randomize_va_space sysctl.
> +
> +config RANDOMIZATION_NONE
> + bool "NONE"
> + help
> + Turn the process address space randomization off by default.
> + Equivalent to sysctl kernel.randomize_va_space = 0.
> +
> +config RANDOMIZATION_CONSERVATIVE
> + bool "CONSERVATIVE"
> + help
> + Conservative address space randomization makes the addresses of
> + mmap base and VDSO page randomized. This, among other things,
> + implies that shared libraries will be loaded to random addresses.
> + Also for PIE binaries, the location of code start is randomized.
> + Equivalent to sysctl kernel.randomize_va_space = 1.
> +
> +config RANDOMIZATION_FULL
> + bool "FULL"
> + help
> + This includes all the features that Conservative randomization
> + provides. In addition to that, also start of the brk area is
> + randomized.
> + There a few legacy applications out there (such as some ancient
> + versions of libc.so.5 from 1996), that assume that brk area starts
Drop comma. s/that brk/that the brk/
> + just after the end of the code+bss. These applications break when
> + start of the brk area is randomized. There are however no known
> + non-legacy applications that would be broken this way, so for most
> + systems it is safe to chose Full randomization.
s/chose/choose/
> + Equivalent to sysctl kernel.randomize_va_space = 2.
> +
> +endchoice
> +
> config PROFILING
> bool "Profiling support (EXPERIMENTAL)"
> help
---
~Randy
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