linux-kernel - Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

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Message-ID: <aYTH6A2rZQ4Ky-PL@smile.fi.intel.com>
Date: Thu, 5 Feb 2026 18:40:08 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Xie Yuanbin <xieyuanbin1@...wei.com>
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
	chleroy@...nel.org, kees@...nel.org, andy@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, lilinjie8@...wei.com,
	liaohua4@...wei.com
Subject: Re: [PATCH 2/2] powerpc/text-patching: Fix possible
 stringop-overread compilation error

On Thu, Feb 05, 2026 at 06:05:17PM +0800, Xie Yuanbin wrote:

First of all, when sending a series, always add a cover letter to explain
dependencies, goal, and how to route the series via the respective tree(s),
et cetera.

> For strnlen(), if the compiler detects that the maxlen argument exceeds
> the valid memory size of the input string object, a compilation error may
> occur.
> 
> For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
> __always_inline,

So, there is no issue in upstream without the mentioned change, right?

> using default ppc64_defconfig, and setting
> CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n,
> CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Then, when using gcc-15 for compilation,
> the following error will be triggered:
> ```log
>   CC      arch/powerpc/kernel/optprobes.o
> In file included from ./arch/powerpc/include/asm/kprobes.h:24,
>                  from ./include/linux/kprobes.h:31,
>                  from arch/powerpc/kernel/optprobes.c:8:
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> ```
> 
> Refer to the implementation of fortify's strnlen(). If the string length
> is a compile-time constant, do not call the strnlen() function.

I don't with the first patch this is a correct approach.
But I let others to comment, I assume Kees knows better
what's this and how it can be fixed without exporting
special macros.

-- 
With Best Regards,
Andy Shevchenko