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Message-ID: <67ec58c8c637_1d472949b@dwillia2-xfh.jf.intel.com.notmuch>
Date: Tue, 1 Apr 2025 14:21:12 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Rakie Kim <rakie.kim@...com>, <gourry@...rry.net>
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>, <rakie.kim@...com>
Subject: Re: [PATCH v4 1/3] mm/mempolicy: Fix memory leaks in weighted
interleave sysfs
Rakie Kim wrote:
> 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>
> Signed-off-by: Honggyu Kim <honggyu.kim@...com>
> Signed-off-by: Yunjeong Mun <yunjeong.mun@...com>
> Reviewed-by: Gregory Price <gourry@...rry.net>
> ---
> 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");
It would be nice if this could take advantage of scope-based cleanup to
avoid the new gotos. It would need a new:
DEFINE_FREE(kobject_put, struct kobject *, if (!IS_ERR_OR_NULL(_T)) kobject_put(_T))
...and a wrapper around kobject_init_and_add() to support auto cleanup:
struct kobject *kobject_init_and_add_or_errptr(struct kobject *kobj)
{
int err = kobject_init_and_add(kobj...);
if (err)
return ERR_PTR(err);
return kobj;
}
With those then you could do:
struct kobject *wi_kobj __free(kfree) = kzalloc(sizeof(struct kobject), GFP_KERNEL);
struct kobject *kobj __free(kobject_put) = kobject_init_and_add_or_errptr(no_free_ptr(wi_kobj), ...)
Otherwise, the patch does look good to me as is, but it seems like an
opportunity for further cleanups that might also help other
kobject_init_and_add() code paths.
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