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

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Message-ID: <5cfae419-427a-471b-8bbe-645f56442e2c@kernel.org>
Date: Mon, 9 Feb 2026 14:41:51 +0100
From: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
To: Xie Yuanbin <xieyuanbin1@...wei.com>, andriy.shevchenko@...el.com,
 maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com, kees@...nel.org,
 andy@...nel.org
Cc: 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



Le 09/02/2026 à 14:25, Xie Yuanbin a écrit :
> On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
>> Le 06/02/2026 à 19:26, Kees Cook a écrit :
>>>
>>> Isn't it possible to do this and not need __compiletime_strlen at all?
>>>
>>> 	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));
>>
>> ppc_kallsyms_lookup_name() only has two callers and they call it with a
>> built-in string. I think we can do something a lot simpler, something
>> like (untested):
>>
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
>> #else
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
>> #endif
>>
>> Christophe
> 
> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
> the original non-dot symbol is missing.
> 
> What about this (Only the compilation test is performed):
> ```c
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
> 
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
> 
> 	return addr;
> }
> 
> #define ppc_kallsyms_lookup_name(x) ({					\
> 		unsigned long addr = 0;					\
> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
> 			addr = __ppc_kallsyms_lookup_name("." x);	\
> 		if (!addr)						\
> 			addr = __ppc_kallsyms_lookup_name(x);		\
> 		addr;							\
> 	})
> ```

Good point.

To avoid duplicating the string I'd suggest:

static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
{
	unsigned long addr = kallsyms_lookup_name(name);

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
		addr = kallsyms_lookup_name(name + 1);
	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
		addr = ppc_function_entry((void *)addr);

	return addr;
}

#ifdef CONFIG_PPC64_ELF_ABI_V1
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
#else
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
#endif