linux-kernel - Re: [PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs

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Message-ID: <a2b3609c-9907-4ee6-a0df-6b4c84100d33@bytedance.com>
Date: Wed, 5 Mar 2025 11:26:43 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Muchun Song <muchun.song@...ux.dev>, Liu Ye <liuye@...inos.cn>
Cc: akpm@...ux-foundation.org, david@...morbit.com, roman.gushchin@...ux.dev,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/shrinker_debug: Fix possible memory leak in
 shrinker_debugfs_rename function.



On 3/5/25 11:17 AM, Muchun Song wrote:
> 
> 
>> On Mar 5, 2025, at 10:01, Liu Ye <liuye@...inos.cn> wrote:
>>
>> After calling debugfs_change_name function, the return value should be
>> checked and the old name restored. If debugfs_change_name fails, the new
>> name memory should be freed.
> 
> Seems it is not a big problem, no memory leak at least. The effect is that
> the shrinker->name is not consistent with the name displayed in debugfs.
> Right? But the improvement LGTM. So:

Right, so the subject needs to be changed.

Maybe:

mm: shrinker: fix name consistency issue in shrinker_debugfs_rename()

?

BTW, it seems that the callers of shrinker_debugfs_rename() did not
process the return value of the function?

> 
> Reviewed-by: Muchun Song <muchun.song@...ux.dev>
> 
> Thanks.
> 
>>
>> Signed-off-by: Liu Ye <liuye@...inos.cn>
>> ---
>> mm/shrinker_debug.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
>> index 794bd433cce0..20eaee3e97f7 100644
>> --- a/mm/shrinker_debug.c
>> +++ b/mm/shrinker_debug.c
>> @@ -214,10 +214,14 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
>> ret = debugfs_change_name(shrinker->debugfs_entry, "%s-%d",
>> shrinker->name, shrinker->debugfs_id);
>>
>> + 	if (ret) {
>> + 		shrinker->name = old;
>> + 		kfree_const(new);
>> + 	} else {
>> + 		kfree_const(old);
>> + 	}
>> 	mutex_unlock(&shrinker_mutex);
>>
>> - 	kfree_const(old);
>> -
>> 	return ret;
>> }
>> EXPORT_SYMBOL(shrinker_debugfs_rename);
>> -- 
>> 2.25.1
>>
>