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

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Message-ID: <8db10119-58d1-4684-8d1c-b6d82423c438@huaweicloud.com>
Date: Thu, 28 Aug 2025 20:04:50 +0800
From: Tengda Wu <wutengda@...weicloud.com>
To: Dave Hansen <dave.hansen@...el.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 2025/8/27 22:36, Dave Hansen wrote:
> 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.

I see what you mean. Andrey has provided several approaches — perhaps we
can make a selection from those.