[PATCH v2] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[PATCH v2] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[Hongling Zeng]

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")
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com>

---
 Change in v2:
 - Use goto err_put instead of kobject_put() + goto err for consistency
 - Add suggested
---
 mm/huge_memory.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2bccb0a53a0a..589f7bf1f19d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -818,10 +818,8 @@ 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);
-		goto err;
-	}
+	if (ret)
+		goto err_put;
 
 
 	ret = sysfs_add_group(&thpsize->kobj, &any_ctrl_attr_grp);
-- 
2.25.1

Re: [PATCH v2] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[Lorenzo Stoakes (ARM)]

On Mon, Jul 13, 2026 at 01:41:54PM +0800, 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")
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

>
> ---
>  Change in v2:
>  - Use goto err_put instead of kobject_put() + goto err for consistency
>  - Add suggested
> ---
>  mm/huge_memory.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 2bccb0a53a0a..589f7bf1f19d 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -818,10 +818,8 @@ 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);
> -		goto err;
> -	}
> +	if (ret)
> +		goto err_put;
>
>
>  	ret = sysfs_add_group(&thpsize->kobj, &any_ctrl_attr_grp);
> --
> 2.25.1
>

Cheers, Lorenzo

Re: [PATCH v2] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[Zi Yan]

On Mon Jul 13, 2026 at 1:41 AM EDT, 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")
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>
> ---
>  Change in v2:
>  - Use goto err_put instead of kobject_put() + goto err for consistency
>  - Add suggested
> ---
>  mm/huge_memory.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>

LGTM.

Acked-by: Zi Yan <ziy@nvidia.com>



-- 
Best Regards,
Yan, Zi

Re: [PATCH v2] mm: huge_memory: Fix kobject cleanup in thpsize_create error

[Baolin Wang]

On 7/13/26 1:41 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")
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> 
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

By the way, I don't think my Suggested-by tag is needed, as it was just 
a simple comment (But no need to respin).