linux-kernel - Re: [PATCH] sched/topology: Fix memory leak in the error path of sched_init

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Message-ID: <87ikgjt6mb.fsf@DESKTOP-5N7EMDA>
Date: Mon, 13 Oct 2025 18:53:48 +0800
From: "Huang, Ying" <ying.huang@...ux.alibaba.com>
To: Luo Gengkun <luogengkun@...weicloud.com>
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,  huang.ying.caritas@...il.com,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/topology: Fix memory leak in the error path of
 sched_init_numa

Luo Gengkun <luogengkun@...weicloud.com> writes:

> In sched_init_numa, masks are used to store memory, but the error path
> returns directly without freeing the allocated memory.
> To fix this, the freeing logic in sched_reset_numa can be extraced into a
> new function, free_masks, which can be called on the error path.

Good catch!  Thanks!

> Fixes: 0fb3978b0aac ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")
> Signed-off-by: Luo Gengkun <luogengkun@...weicloud.com>
> ---
>  kernel/sched/topology.c | 33 +++++++++++++++++++++------------
>  1 file changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 444bdfdab731..fd03bb6669f5 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1924,6 +1924,20 @@ static void init_numa_topology_type(int offline_node)
>  
>  #define NR_DISTANCE_VALUES (1 << DISTANCE_BITS)
>  
> +static void free_masks(struct cpumask ***masks, int nr_levels)

The function name appears too general.  How about __sched_free_masks()?

> +{
> +	int i, j;
> +
> +	for (i = 0; i < nr_levels && masks; i++) {
> +		if (!masks[i])
> +			continue;
> +		for_each_node(j)
> +			kfree(masks[i][j]);
> +		kfree(masks[i]);
> +	}
> +	kfree(masks);
> +}
> +
>  void sched_init_numa(int offline_node)
>  {
>  	struct sched_domain_topology_level *tl;
> @@ -2003,15 +2017,19 @@ void sched_init_numa(int offline_node)
>  	 */
>  	for (i = 0; i < nr_levels; i++) {
>  		masks[i] = kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
> -		if (!masks[i])
> +		if (!masks[i]) {
> +			free_masks(masks, nr_levels);
>  			return;
> +		}
>  
>  		for_each_cpu_node_but(j, offline_node) {
>  			struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
>  			int k;
>  
> -			if (!mask)
> +			if (!mask) {
> +				free_masks(masks, nr_levels);
>  				return;
> +			}
>  
>  			masks[i][j] = mask;
>  
> @@ -2079,18 +2097,9 @@ static void sched_reset_numa(void)
>  	masks = sched_domains_numa_masks;
>  	rcu_assign_pointer(sched_domains_numa_masks, NULL);
>  	if (distances || masks) {
> -		int i, j;
> -
>  		synchronize_rcu();
>  		kfree(distances);
> -		for (i = 0; i < nr_levels && masks; i++) {
> -			if (!masks[i])
> -				continue;
> -			for_each_node(j)
> -				kfree(masks[i][j]);
> -			kfree(masks[i]);
> -		}
> -		kfree(masks);
> +		free_masks(masks, nr_levels);
>  	}
>  	if (sched_domain_topology_saved) {
>  		kfree(sched_domain_topology);

Otherwise, the patch LGTM.  Feel free to add my

Reviewed-by: Huang Ying <ying.huang@...ux.alibaba.com>

in the future versions.

---
Best Regards,
Huang, Ying