linux-kernel - Re: [PATCH v2] loongarch: Support RANDOMIZE_KSTACK

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Message-ID: <202407190858.3097E9AF98@keescook>
Date: Fri, 19 Jul 2024 09:01:23 -0700
From: Kees Cook <kees@...nel.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: chenhuacai@...nel.org, kernel@...0n.name, gustavoars@...nel.org,
	arnd@...db.de, maobibo@...ngson.cn, loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] loongarch: Support RANDOMIZE_KSTACK_OFFSET

On Fri, Jul 19, 2024 at 11:14:27AM +0800, Jinjie Ruan wrote:
> Add support of kernel stack offset randomization while handling syscall,
> the offset is defaultly limited by KSTACK_OFFSET_MAX().
> 
> In order to avoid trigger stack canaries (due to __builtin_alloca) and
> slowing down the entry path, use __no_stack_protector attribute to
> disable stack protector for do_syscall() at function level.
> 
> With this patch, the REPORT_STACK test show that:
> 	`loongarch64 bits of stack entropy: 7`

I suspect this will report the correct "6" after now that this commit
has landed:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=872bb37f6829d4f7f3ed5afe2786add3d4384b4b

> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> Suggested-by: Huacai Chen <chenhuacai@...nel.org>

Thanks for adding this and getting it tested!

Reviewed-by: Kees Cook <kees@...nel.org>

-- 
Kees Cook