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

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Message-Id: <451E5C9A-F7FB-41DD-B760-25E4883B0861@linux.dev>
Date: Wed, 5 Mar 2025 14:46:02 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: liuye <liuye@...inos.cn>
Cc: Qi Zheng <zhengqi.arch@...edance.com>,
 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 Mar 5, 2025, at 14:10, liuye <liuye@...inos.cn> wrote:
> 
> 
> 在 2025/3/5 11:26, Qi Zheng 写道:
>> 
>> 
>> 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()
>> 
>> ?
>  I will send a new patch using this subject later.

Please update the commit message as well to include the effect.

> And add  Reviewed-by：Qi Zheng <zhengqi.arch@...edance.com> ？
> 
>> 
>> BTW, it seems that the callers of shrinker_debugfs_rename() did not 
>> process the return value of the function?
> 
> Yes,  At the same time, I also found that many positions using 
> debugfs_change_name did not determine the return value.
> 
>> 
>>> 
>>> Reviewed-by: Muchun Song <muchun.song@...ux.dev> 
>>> 
>>> Thanks.
> 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 
>>>> 
>>> 
>>