linux-kernel - Re: [PATCH 1/2] mm/mempolicy: Fix incorrect freeing of wi

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Message-ID: <20250602165332.2746843-1-joshua.hahnjy@gmail.com>
Date: Mon,  2 Jun 2025 09:53:31 -0700
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: Joshua Hahn <joshua.hahnjy@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Gregory Price <gourry@...rry.net>,
	David Hildenbrand <david@...hat.com>,
	Zi Yan <ziy@...dia.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Rakie Kim <rakie.kim@...com>,
	Byungchul Park <byungchul@...com>,
	Ying Huang <ying.huang@...ux.alibaba.com>,
	Alistair Popple <apopple@...dia.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 1/2] mm/mempolicy: Fix incorrect freeing of wi_kobj

On Mon,  2 Jun 2025 09:23:39 -0700 Joshua Hahn <joshua.hahnjy@...il.com> wrote:

> We should not free wi_group->wi_kobj here. In the error path of
> add_weighted_interleave_group() where this snippet is called from,
> kobj_{del, put} is immediately called right after this section. Thus,
> it is not only unnecessary but also incorrect to free it here. 
> 
Fixes: e341f9c3c841 ("mm/mempolicy: Weighted Interleave Auto-tuning")
> Signed-off-by: Joshua Hahn <joshua.hahnjy@...il.com>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202506011545.Fduxqxqj-lkp@intel.com/
> ---
>  mm/mempolicy.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 72fd72e156b1..3b1dfd08338b 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -3708,15 +3708,13 @@ static void wi_state_free(void)
>  			lockdep_is_held(&wi_state_lock));
>  	if (!old_wi_state) {
>  		mutex_unlock(&wi_state_lock);
> -		goto out;
> +		return;
>  	}
>  
>  	rcu_assign_pointer(wi_state, NULL);
>  	mutex_unlock(&wi_state_lock);
>  	synchronize_rcu();
>  	kfree(old_wi_state);
> -out:
> -	kfree(&wi_group->wi_kobj);
>  }
>  
>  static struct kobj_attribute wi_auto_attr =
> -- 
> 2.47.1