linux-kernel - Re: [PATCH 2/2] mm, cma: use literal printf format string

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Message-ID: <697ca5a0-174f-441e-a27e-6a1652235a87@redhat.com>
Date: Mon, 24 Feb 2025 15:37:13 +0100
From: David Hildenbrand <david@...hat.com>
To: Arnd Bergmann <arnd@...nel.org>, Andrew Morton
 <akpm@...ux-foundation.org>, Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Frank van der Linden <fvdl@...gle.com>, Zi Yan <ziy@...dia.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 2/2] mm, cma: use literal printf format string

On 24.02.25 15:07, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Using a variable string as a printf format can be a security issue
> that clang warns about when extra warnings are enabled:
> 
> mm/cma.c:239:37: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
>    239 |                 snprintf(cma->name, CMA_MAX_NAME, name);
>        |                                                   ^~~~
> 
> This one does not appear to be a security issue since the string is
> not user controlled, but it's better to avoid the warning.
> Use "%s" as the format instead and just pass the name as the argument.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   mm/cma.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index ef0206c0f16d..09322b8284bd 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -236,7 +236,7 @@ static int __init cma_new_area(const char *name, phys_addr_t size,
>   	cma_area_count++;
>   
>   	if (name)
> -		snprintf(cma->name, CMA_MAX_NAME, name);
> +		snprintf(cma->name, CMA_MAX_NAME, "%s", name);
>   	else
>   		snprintf(cma->name, CMA_MAX_NAME,  "cma%d\n", cma_area_count);
>   

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb