linux-kernel - Re: [PATCH -next] x86: Prevent KASAN false positive warnings in __show

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Message-ID: <99878868-9898-46aa-ad4c-ef9aca3e390c@intel.com>
Date: Wed, 27 Aug 2025 07:36:56 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Tengda Wu <wutengda@...weicloud.com>, x86@...nel.org
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Thomas Gleixner <tglx@...utronix.de>, Alexander Potapenko
 <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 Dmitry Vyukov <dvyukov@...gle.com>, Ingo Molnar <mingo@...hat.com>,
 linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
 Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH -next] x86: Prevent KASAN false positive warnings in
 __show_regs()

On 8/18/25 06:07, Tengda Wu wrote:
> +__no_sanitize_address
>  void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
>  		 const char *log_lvl)

I'd feel a lot better about this if it didn't just disable KASAN for the
whole function. Surely there are other __show_regs() users that could
benefit from sanitizer coverage.

Can we limit the impact to just the asynchronous (unsafe) stack walkers?
If it's just for sysrq, this seems like the kind of thing we could just
a flag somewhere and have KASAN suppress the warning. Or to generically
tell KASAN that we might be doing accesses in a certain memory range
that are unsafe.

I'm also adding Peter and Josh to cc. Seems like the kind of thing they
might have an opinion on.