linux-kernel - Re: [PATCH v2] sched/topology: Convert kzalloc() to kcalloc() in topology.c

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Message-ID: <a65ca1f7-dcb8-46f7-9b55-7e7fbaaa4afe@linux.ibm.com>
Date: Thu, 18 Dec 2025 10:00:51 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Fushuai Wang <fushuai.wang@...ux.dev>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        vschneid@...hat.com, linux-kernel@...r.kernel.org,
        wangfushuai@...du.com, Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH v2] sched/topology: Convert kzalloc() to kcalloc() in
 topology.c

Hi Fushuai,

On 18/12/25 08:27, Fushuai Wang wrote:
> The kzalloc() doesn't check for overflows in size multiplication,
> so use kcalloc() instead.
> 
> Signed-off-by: Fushuai Wang <wangfushuai@...du.com>
> ---
> v1->v2: remove useless parenthesis
> 
>  kernel/sched/topology.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index cf643a5ddedd..d228abe45c12 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -2055,7 +2055,7 @@ void sched_init_numa(int offline_node)
>  
>  	sched_domains_numa_levels = 0;
>  
> -	masks = kzalloc(sizeof(void *) * nr_levels, GFP_KERNEL);
> +	masks = kcalloc(nr_levels, sizeof(void *), GFP_KERNEL);
>  	if (!masks)
>  		return;
>  
> @@ -2064,7 +2064,7 @@ void sched_init_numa(int offline_node)
>  	 * CPUs of nodes that are that many hops away from us.
>  	 */
>  	for (i = 0; i < nr_levels; i++) {
> -		masks[i] = kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
> +		masks[i] = kcalloc(nr_node_ids, sizeof(void *), GFP_KERNEL);
>  		if (!masks[i])
>  			return;
>  
> @@ -2096,7 +2096,7 @@ void sched_init_numa(int offline_node)
>  	/* Compute default topology size */
>  	for (i = 0; sched_domain_topology[i].mask; i++);
>  
> -	tl = kzalloc((i + nr_levels + 1) *
> +	tl = kcalloc(i + nr_levels + 1,
>  			sizeof(struct sched_domain_topology_level), GFP_KERNEL);
>  	if (!tl)
>  		return;

Practically, overflow seems highly unlikely here given the maximum values of
nr_levels and nr_node_ids.

However, since the code path is used only once during the boot initialization,
it shouldn't hurt to have this change.

Hence,
Reviewed-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>

Thanks,
Vineeth