[PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs_rename function.

[PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs_rename function.

[Liu Ye]

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.

Signed-off-by: Liu Ye <liuye@kylinos.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

Re: [PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs_rename function.

[Muchun Song]

> On Mar 5, 2025, at 10:01, Liu Ye <liuye@kylinos.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:

Reviewed-by: Muchun Song <muchun.song@linux.dev>

Thanks.

> 
> Signed-off-by: Liu Ye <liuye@kylinos.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
> 

Re: [PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs_rename function.

[Qi Zheng]

On 3/5/25 11:17 AM, Muchun Song wrote:
> 
> 
>> On Mar 5, 2025, at 10:01, Liu Ye <liuye@kylinos.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@linux.dev>
> 
> Thanks.
> 
>>
>> Signed-off-by: Liu Ye <liuye@kylinos.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
>>
> 

Re: [PATCH] mm/shrinker_debug: Fix possible memory leak in shrinker_debugfs_rename function.

[Muchun Song]

> On Mar 5, 2025, at 14:10, liuye <liuye@kylinos.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@kylinos.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@bytedance.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@linux.dev> 
>>> 
>>> Thanks.
> Thanks.
>>> 
>>>> 
>>>> Signed-off-by: Liu Ye <liuye@kylinos.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 
>>>> 
>>> 
>>