linux-kernel - Re: [PATCH -next] arm64/ptrace: Fix stack-out-of-bounds read in regs_get_kernel_stack

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Message-ID: <20250612163331.GA13384@willie-the-truck>
Date: Thu, 12 Jun 2025 17:33:32 +0100
From: Will Deacon <will@...nel.org>
To: Tengda Wu <wutengda@...weicloud.com>
Cc: Oleg Nesterov <oleg@...hat.com>,
	Catalin Marinas <catalin.marinas@....com>,
	"David A . Long" <dave.long@...aro.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] arm64/ptrace: Fix stack-out-of-bounds read in
 regs_get_kernel_stack_nth()

On Wed, Jun 04, 2025 at 12:55:33AM +0000, Tengda Wu wrote:
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index f79b0d5f71ac..fe3f7e554d14 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -141,7 +141,7 @@ unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
>  
>  	addr += n;
>  	if (regs_within_kernel_stack(regs, (unsigned long)addr))
> -		return *addr;
> +		return READ_ONCE_NOCHECK(addr);

I think this should be '*addr', but that makes me wonder wtf s390 is
doing...

Will