linux-kernel - Re: [PATCH] arm64: kaslr: consider parange is bigger than linear_region

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Message-ID: <CAMj1kXHyZ5_+ZrcRtdx4X8LA+mzCNcXUZM_3QcEudYGbuGBq0w@mail.gmail.com>
Date: Fri, 28 Feb 2025 14:11:41 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Keun-O Park <kpark3469@...il.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	catalin.marinas@....com, will@...nel.org, Keuno Park <keun-o.park@...im.com>
Subject: Re: [PATCH] arm64: kaslr: consider parange is bigger than linear_region_size

On Fri, 28 Feb 2025 at 06:55, Keun-O Park <kpark3469@...il.com> wrote:
>
> How about adding a warning message in case of linear region
> randomization failure?
> And, there might be two options in my mind by now to consider hotplug memory.
> Either giving an option for users to override "parange" as kernel
> param or providing the legacy way((memblock_end_of_DRAM() -
> memblock_start_of_DRAM()) when CONFIG_MEMORY_HOTPLUG is off.
> Users believe KASLR will work fine by enabling CONFIG_RANDOMIZE_BASE.
> In case of linear region randomization failure, I think at least users
> need to know about this failure.
> Can you share your thoughts on this please?
>

Randomization of the linear map has always been a best effort thing,
so I don't think this is a big deal.

I wouldn't object to the new behavior being conditional on
CONFIG_MEMORY_HOTPLUG, and fallback to the old behavior otherwise. But
ultimately, it will be up to the maintainers.