Re: [PATCH v14 3/8] lib/group_cpus: Add group_mask_cpus_evenly()

[Aaron Tomlin]

On Wed, May 20, 2026 at 05:50:25PM -0400, Aaron Tomlin wrote:
> +	*nummasks = min(nr_present + nr_others, numgrps);
> +	return masks;
> +}

If a NUMA node has exactly zero online housekeeping CPUs, the grouping
algorithm processes zero for nr_present and nr_others. Erroneously, the
caller sees a non-NULL return value, assumes the mapping succeeded, and
executes a loop doing fatal: queue % nr_masks.

I suggest we must intercept, free the array, and return NULL. Therefore,
the caller falls back to safe default routing:

@@ -432,6 +432,10 @@ struct cpumask *group_mask_cpus_evenly(unsigned int numgrps,
 		return NULL;
 	}
 	*nummasks = min(nr_present + nr_others, numgrps);
+	if (*nummasks == 0) {
+		kfree(masks);
+		return NULL;
+	}
 	return masks;
 }

-- 
Aaron Tomlin