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

[Harry Yoo]

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@xxxxxxxxxx>
>>> ---
>>
>> 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;
>  

-- 
Cheers,
Harry / Hyeonggon

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