[PATCH] arm64: Kconfig RANDOMIZE_MODULE_REGION_FULL correction

[PATCH] arm64: Kconfig RANDOMIZE_MODULE_REGION_FULL correction

[Ross Meikleham]

In the 5.1.5 Kernel RANDOMIZE_MODULE_REGION_FULL was a 4GB window,
however this was changed to 2GB from 5.1.6  
(see /arch/arm64/kernel/kaslr.c). This updates the
config description for RANDOMIZE_MODULE_REGION_FULL in /arch/arm64/Kconfig
to reflect this.

Signed-off-by: Ross Meikleham <RossMeikleham@gmail.com>
---
 arch/arm64/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..b8fd2c590057 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1782,11 +1782,11 @@ config RANDOMIZE_BASE
 	  If unsure, say N.
 
 config RANDOMIZE_MODULE_REGION_FULL
-	bool "Randomize the module region over a 4 GB range"
+	bool "Randomize the module region over a 2 GB range"
 	depends on RANDOMIZE_BASE
 	default y
 	help
-	  Randomizes the location of the module region inside a 4 GB window
+	  Randomizes the location of the module region inside a 2 GB window
 	  covering the core kernel. This way, it is less likely for modules
 	  to leak information about the location of core kernel data structures
 	  but it does imply that function calls between modules and the core
-- 
2.18.0

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Re: [PATCH] arm64: Kconfig RANDOMIZE_MODULE_REGION_FULL correction

[Will Deacon]

Hi Ross,

[+Ard]

On Sat, Nov 07, 2020 at 02:31:19PM +0000, Ross Meikleham wrote:
> In the 5.1.5 Kernel RANDOMIZE_MODULE_REGION_FULL was a 4GB window,
> however this was changed to 2GB from 5.1.6  

5.1.5 and 5.1.6 are both stable releases, so it's not terribly useful to
talk about them here and you can't really infer much about when the change
was introduced. Please can you refer to the commit instead? I think you
want:

commit b2eed9b58811 ("arm64/kernel: kaslr: reduce module randomization range to 2 GB")

> (see /arch/arm64/kernel/kaslr.c). This updates the

(you can remove the "see ..." part as it's obvious once you refer to the
commit.

> config description for RANDOMIZE_MODULE_REGION_FULL in /arch/arm64/Kconfig
> to reflect this.

There's no need to say "This...". Documentation/process/submitting-patches.rst
has a bit about how to write commit messages, but I suggest changing this
last sentence to:

Fix the stale Kconfig entry for RANDOMIZE_MODULE_REGION_FULL.

> Signed-off-by: Ross Meikleham <RossMeikleham@gmail.com>
> ---
>  arch/arm64/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 6d232837cbee..b8fd2c590057 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1782,11 +1782,11 @@ config RANDOMIZE_BASE
>  	  If unsure, say N.
>  
>  config RANDOMIZE_MODULE_REGION_FULL
> -	bool "Randomize the module region over a 4 GB range"
> +	bool "Randomize the module region over a 2 GB range"
>  	depends on RANDOMIZE_BASE
>  	default y
>  	help
> -	  Randomizes the location of the module region inside a 4 GB window
> +	  Randomizes the location of the module region inside a 2 GB window
>  	  covering the core kernel. This way, it is less likely for modules
>  	  to leak information about the location of core kernel data structures
>  	  but it does imply that function calls between modules and the core

Patch looks fine. Please send a v2 with the commit message sorted out and I
can queue it as a fix.

Cheers,

Will

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