linux-kernel - Re: [PATCH v3 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs

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Message-ID: <20250320054010.914-1-rakie.kim@sk.com>
Date: Thu, 20 Mar 2025 14:40:01 +0900
From: Rakie Kim <rakie.kim@...com>
To: Rakie Kim <rakie.kim@...com>
Cc: akpm@...ux-foundation.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-cxl@...r.kernel.org,
	joshua.hahnjy@...il.com,
	dan.j.williams@...el.com,
	ying.huang@...ux.alibaba.com,
	david@...hat.com,
	Jonathan.Cameron@...wei.com,
	kernel_team@...ynix.com,
	honggyu.kim@...com,
	yunjeong.mun@...com,
	gourry@...rry.net
Subject: Re: [PATCH v3 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs

On Thu, 20 Mar 2025 13:17:46 +0900 Rakie Kim <rakie.kim@...com> wrote:

Hi Gregory

I initially planned to separate this patch from the hotplug-related patch
series as an independent update. However, after reviewing the code following
Jonathan's suggestion to consolidate `kobject` and `node_attrs` into a single
struct, I realized that most of the intended functionality for Patch 2 was
already incorporated.

As a result, Patch 1 now only contains the `kobject_put` fix, while the
struct consolidation work has been included in Patch 2. Given the current
design, it seems more natural to keep Patch 1 and Patch 2 together as part
of the same patch series rather than separating them.

Rakie

> Memory leaks occurred when removing sysfs attributes for weighted
> interleave. Improper kobject deallocation led to unreleased memory
> when initialization failed or when nodes were removed.
> 
> This patch resolves the issue by replacing unnecessary `kfree()`
> calls with `kobject_put()`, ensuring proper cleanup and preventing
> memory leaks.
> 
> By correctly using `kobject_put()`, the release function now
> properly deallocates memory without causing resource leaks,
> thereby improving system stability.
> 
> Fixes: dce41f5ae253 ("mm/mempolicy: implement the sysfs-based weighted_interleave interface")
> Signed-off-by: Rakie Kim <rakie.kim@...com>
> ---
>  mm/mempolicy.c | 61 +++++++++++++++++++++++++-------------------------
>  1 file changed, 31 insertions(+), 30 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index bbaadbeeb291..5950d5d5b85e 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -3448,7 +3448,9 @@ static void sysfs_wi_release(struct kobject *wi_kobj)
>  
>  	for (i = 0; i < nr_node_ids; i++)
>  		sysfs_wi_node_release(node_attrs[i], wi_kobj);
> -	kobject_put(wi_kobj);
> +
> +	kfree(node_attrs);
> +	kfree(wi_kobj);
>  }
>  
>  static const struct kobj_type wi_ktype = {
> @@ -3494,15 +3496,22 @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
>  	struct kobject *wi_kobj;
>  	int nid, err;
>  
> -	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
> -	if (!wi_kobj)
> +	node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
> +			     GFP_KERNEL);
> +	if (!node_attrs)
>  		return -ENOMEM;
>  
> +	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
> +	if (!wi_kobj) {
> +		err = -ENOMEM;
> +		goto node_out;
> +	}
> +
>  	err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
>  				   "weighted_interleave");
>  	if (err) {
> -		kfree(wi_kobj);
> -		return err;
> +		kobject_put(wi_kobj);
> +		goto err_out;
>  	}
>  
>  	for_each_node_state(nid, N_POSSIBLE) {
> @@ -3512,9 +3521,17 @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
>  			break;
>  		}
>  	}
> -	if (err)
> +	if (err) {
>  		kobject_put(wi_kobj);
> +		goto err_out;
> +	}
> +
>  	return 0;
> +
> +node_out:
> +	kfree(node_attrs);
> +err_out:
> +	return err;
>  }
>  
>  static void mempolicy_kobj_release(struct kobject *kobj)
> @@ -3528,7 +3545,6 @@ static void mempolicy_kobj_release(struct kobject *kobj)
>  	mutex_unlock(&iw_table_lock);
>  	synchronize_rcu();
>  	kfree(old);
> -	kfree(node_attrs);
>  	kfree(kobj);
>  }
>  
> @@ -3542,37 +3558,22 @@ static int __init mempolicy_sysfs_init(void)
>  	static struct kobject *mempolicy_kobj;
>  
>  	mempolicy_kobj = kzalloc(sizeof(*mempolicy_kobj), GFP_KERNEL);
> -	if (!mempolicy_kobj) {
> -		err = -ENOMEM;
> -		goto err_out;
> -	}
> -
> -	node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
> -			     GFP_KERNEL);
> -	if (!node_attrs) {
> -		err = -ENOMEM;
> -		goto mempol_out;
> -	}
> +	if (!mempolicy_kobj)
> +		return -ENOMEM;
>  
>  	err = kobject_init_and_add(mempolicy_kobj, &mempolicy_ktype, mm_kobj,
>  				   "mempolicy");
>  	if (err)
> -		goto node_out;
> +		goto err_out;
>  
>  	err = add_weighted_interleave_group(mempolicy_kobj);
> -	if (err) {
> -		pr_err("mempolicy sysfs structure failed to initialize\n");
> -		kobject_put(mempolicy_kobj);
> -		return err;
> -	}
> +	if (err)
> +		goto err_out;
> +
> +	return 0;
>  
> -	return err;
> -node_out:
> -	kfree(node_attrs);
> -mempol_out:
> -	kfree(mempolicy_kobj);
>  err_out:
> -	pr_err("failed to add mempolicy kobject to the system\n");
> +	kobject_put(mempolicy_kobj);
>  	return err;
>  }
>  
> 
> base-commit: 4701f33a10702d5fc577c32434eb62adde0a1ae1
> -- 
> 2.34.1
>