Re: [PATCH] mm/slub: fix kobject leak in sysfs_slab_add error path

[Hongling Zeng <zhongling0719@126.com>]

在 2026年07月13日 14:27, Harry Yoo 写道:
>
> On 7/13/26 3:14 PM, Hongling Zeng wrote:
>> 在 2026年07月13日 14:07, Harry Yoo 写道:
>>> On 7/13/26 2:58 PM, Hongling Zeng wrote:
>>>> When kobject_init_and_add() fails in sysfs_slab_add(), the kobject
>>>> is not properly cleaned up, causing a memory leak.
>>>>
>>>> According to the kobject API documentation, when kobject_init_and_add()
>>>> returns an error, the caller must call kobject_put() to properly clean
>>>> up the memory associated with the object. The current code only frees
>>>> the 'name' string but forgets to release the kobject reference.
>>> This was intentional, please see commit 2420baa8e046 ("mm/slab: Allow
>>> cache creation to proceed even if sysfs registration fails").
>>    Thank you for the clarification. I see now that this was an intentional
>>    design choice to allow cache creation to proceed even when sysfs
>>    registration fails.
>>
>>>> Fix this by calling kobject_put() before jumping to the error label.
>>>>
>>>> Fixes: 54b6a731025f ("slub: fix leak of 'name' in sysfs_slab_add")
>>>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
>>>> ---
>>> Uh, there was a similar attempt recently...
>>>
>>> https://lore.kernel.org/linux-mm/
>>> gimwkjjpvwu2sg5625b3eeatw2vhv7rs6enm3vepdduhcefbf5@xen5iec7sn3z
>>>
>>> Sounds like we need a comment saying it is intentional!
>>>
>>   Good idea. Would a patch adding a comment like this be useful?
>>
>>            err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s",
>> name);
>>    +       /*
>>    +        * Note: Intentionally not calling kobject_put() on error.
>>    +        *
>>    +        * The kobject release callback (slab_kmem_cache_release) would
>>    +        * free the entire kmem_cache structure. However, sysfs
>>    +        * registration failures are treated as non-fatal - the cache
>>    +        * continues to be used. See commit 2420baa8e046 ("mm/slab: Allow
>>    +        * cache creation to proceed even if sysfs registration fails").
>>    +        */
> Could we make it bit more concise please?
>
> Something like
>
> "Intentionally skip kobject_put(). See commit 2420baa8e046 ("mm/slab:
> Allow cache creation to proceed even if sysfs registration fails")"
>
>>            if (err)
>>                    goto out;
>>   
   Thank you for the suggestion. Here's the simplified version:

   [PATCH v1] mm/slub: add comment explaining intentional kobject handling
   in sysfs_slab_add

   Please review.

   Thanks!

   Best regards,
   Hongling Zeng