Re: [PATCH v5 2/3] x86/cpu: Check if feature string is non-zero

[Sohil Mehta]

On 2/12/2026 7:35 AM, Maciej Wieczor-Retman wrote:

>  
> +const char *x86_cap_name(unsigned int bit)
> +{
> +	unsigned int word = bit >> 5;
> +	static char undef_buf[16];
> +	const char *name = NULL;
> +
> +	if (likely(word < NCAPINTS))
> +		name = x86_cap_flags[bit];
> +	else if (likely(word < NCAPINTS + NBUGINTS))
> +		name = x86_bug_flags[bit - 32 * NCAPINTS];
> +
> +	if (name)
> +		return name;
> +
> +	snprintf(undef_buf, sizeof(undef_buf), "%u:%u", word, bit & 31);
> +	return undef_buf;
> +}
> +

Isn't it unsafe to return undef_buf because the pointer is local to this
function even though it is marked static?

For example, the consecutive calls below would overwrite the value
stored at that address.

>  			pr_warn_once("x86 CPU feature dependency check failure: CPU%d has '%s' enabled but '%s' disabled. Kernel might be fine, but no guarantees.\n",
>  				     smp_processor_id(),
> -				     x86_feature_name(d->feature, feature_buf),
> -				     x86_feature_name(d->depends, depends_buf));
> +				     x86_cap_name(d->feature),
> +				     x86_cap_name(d->depends));
>  		}
>  	}
>  }