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SubjectRe: [PATCH] doc: missing value 2 for randomize-va-space

[ added Ingo to CC ]

On Fri, 3 Jul 2009, Horst Schirmeier wrote:

> On Fri, 03 Jul 2009, Jiri Kosina wrote:
> > > There a few legacy applications out there (such as some ancient
> >
> > ... would you please fix this typo/grammo as well? (There a few ...)
> >
> > > versions of libc.so.5 from 1996) that assume that brk area starts
> >
> > Also, the text itself doesn't seem to be super-clear ... namely, it
> > describes what CONFIG_COMPAT_BRK is about, but doesn't really clarify how
> > exactly does this correlate with randomize_va_space == 2. Would you mind
> > also fixing this bit?
>
> I hope I didn't misread the sources :-) Opinions?
>
> ---
>
> The documentation for /proc/sys/kernel/* does not mention the possible
> value 2 for randomize-va-space yet. While being there, doing some
> reformatting, fixing grammar problems and clarifying the correlations
> between randomize-va-space, kernel parameter "norandmaps" and the
> CONFIG_COMPAT_BRK option.
>
> Signed-off-by: Horst Schirmeier <horst@schirmeier.com>

Acked-by: Jiri Kosina <jkosina@suse.cz>

Ingo, will you take this through your tree?

>
> ---
> Documentation/sysctl/kernel.txt | 30 +++++++++++++++++-------------
> 1 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index 322a00b..dd8322f 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -303,25 +303,29 @@ This option can be used to select the type of process address
> space randomization that is used in the system, for architectures
> that support this feature.
>
> -0 - Turn the process address space randomization off by default.
> +0 - Turn the process address space randomization off. This is the
> + default for architectures that do not support this feature anyways,
> + and kernels that are booted with the "norandmaps" parameter.
>
> 1 - Make the addresses of mmap base, stack and VDSO page randomized.
> This, among other things, implies that shared libraries will be
> - loaded to random addresses. Also for PIE-linked binaries, the location
> - of code start is randomized.
> + loaded to random addresses. Also for PIE-linked binaries, the
> + location of code start is randomized. This is the default if the
> + CONFIG_COMPAT_BRK option is enabled.
>
> - With heap randomization, the situation is a little bit more
> - complicated.
> - There a few legacy applications out there (such as some ancient
> +2 - Additionally enable heap randomization. This is the default if
> + CONFIG_COMPAT_BRK is disabled.
> +
> + There are a few legacy applications out there (such as some ancient
> versions of libc.so.5 from 1996) that assume that brk area starts
> - just after the end of the code+bss. These applications break when
> - start of the brk area is randomized. There are however no known
> + 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 choose full randomization. However there is
> - a CONFIG_COMPAT_BRK option for systems with ancient and/or broken
> - binaries, that makes heap non-randomized, but keeps all other
> - parts of process address space randomized if randomize_va_space
> - sysctl is turned on.
> + systems it is safe to choose full randomization.
> +
> + Systems with ancient and/or broken binaries should be configured
> + with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
> + address space randomization.
>
> ==============================================================
>
>
> --
> PGP-Key 0xD40E0E7A
>

Thanks,

--
Jiri Kosina
SUSE Labs


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