Re: [PATCH] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 7/11/26 4:46 PM, Hongling Zeng wrote:
> When kobject_init_and_add() fails, the kobject API requires calling
> kobject_put() to properly clean up the memory, not direct kfree().
> 
> According to the kobject API documentation, kobject_init_and_add()
> calls kobject_init() internally. If the subsequent kobject_add()
> fails, the kobject has still been initialized and must be cleaned up
> via the reference count mechanism (kobject_put), not direct kfree().
> 
> Direct kfree() leaves the kobject's internal state (including the
> reference count and kset membership) uncleaned, which can cause:
>   - Memory leaks of kobject internal structures
>   - Potential use-after-free if there are pending references
>   - Inconsistent state with the rest of the error handling code
> 
> This fix matches the pattern used elsewhere in the kernel and in the
> same function (err_put label) which correctly uses kobject_put().
> 
> Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface")
> Cc: stable@vger.kernel.org

I don't think this need to CC stable.

> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> ---

A related fix was already sent before[1]. As noted in the previous 
comments, just change it to 'goto err_put'.

[1] 
https://lore.kernel.org/all/20260412175428.2613383-1-lgs201920130244@gmail.com/

>   mm/huge_memory.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 2bccb0a53a0a..7aeb17d60ac7 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -819,7 +819,7 @@ static struct thpsize *thpsize_create(int order, struct kobject *parent)
>   	ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent,
>   				   "hugepages-%lukB", size);
>   	if (ret) {
> -		kfree(thpsize);
> +		kobject_put(&thpsize->kobj);
>   		goto err;
>   	}
>