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