linux-kernel - Re: [PATCH] perf/x86: Replace strncpy() with memcpy() for vendor string

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Message-ID: <20250704102007.6354ce9f@pumpkin>
Date: Fri, 4 Jul 2025 10:20:07 +0100
From: David Laight <david.laight.linux@...il.com>
To: Usman Akinyemi <usmanakinyemi202@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
 namhyung@...nel.org, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com,
 adrian.hunter@...el.com, kan.liang@...ux.intel.com, james.clark@...aro.org,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH] perf/x86: Replace strncpy() with memcpy() for vendor
 string

On Thu, 19 Jun 2025 03:28:43 +0530
Usman Akinyemi <usmanakinyemi202@...il.com> wrote:

> strncpy() is unsafe for fixed-size binary data as
> it may not NUL-terminate and is deprecated for such
> usage. Since we're copying raw CPUID register values,
> memcpy() is the correct and safe choice.
> 
> Signed-off-by: Usman Akinyemi <usmanakinyemi202@...il.com>
> ---
>  tools/perf/arch/x86/util/header.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/arch/x86/util/header.c b/tools/perf/arch/x86/util/header.c
> index 412977f8aa83..43ba55627817 100644
> --- a/tools/perf/arch/x86/util/header.c
> +++ b/tools/perf/arch/x86/util/header.c
> @@ -16,9 +16,9 @@ void get_cpuid_0(char *vendor, unsigned int *lvl)
>  	unsigned int b, c, d;
>  
>  	cpuid(0, 0, lvl, &b, &c, &d);
> -	strncpy(&vendor[0], (char *)(&b), 4);
> -	strncpy(&vendor[4], (char *)(&d), 4);
> -	strncpy(&vendor[8], (char *)(&c), 4);
> +	memcpy(&vendor[0], (char *)(&b), 4);
> +	memcpy(&vendor[4], (char *)(&d), 4);
> +	memcpy(&vendor[8], (char *)(&c), 4);

Why not:
	cpuid(0, 0, lvl, (void *)vendor, (void *)(vendor + 8), (void *)(vendor + 4));


>  	vendor[12] = '\0';
>  }
>