Re: [PATCH v6] IB/mlx4: Fix refcount leak in add_port() error path

[Leon Romanovsky]

On Thu, May 14, 2026 at 07:01:39PM +0800, Guangshuo Li wrote:
> After kobject_init_and_add(), the lifetime of the embedded struct
> kobject is expected to be managed through the kobject core reference
> counting.
> 
> In add_port(), several failure paths after kobject_init_and_add() free
> struct mlx4_port directly instead of releasing the embedded kobject with
> kobject_put(). This leaves the kobject reference count unbalanced and can
> lead to incorrect lifetime handling.
> 
> Allocate the pkey and gid attribute arrays before kobject_init_and_add(),
> so failures before kobject initialization can be handled by directly
> freeing the allocated memory. Once kobject_init_and_add() has been
> called, route failures through kobject_put(), and call kobject_del()
> before kobject_put() on later failure paths after the kobject has been
> successfully added.
> 
> Fixes: c1e7e466120b ("IB/mlx4: Add iov directory in sysfs under the ib device")
> Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
> ---
> v6:
>   - drop the Cc stable tag
>   - allocate pkey and gid attribute arrays before kobject_init_and_add()
>   - keep the release callback unchanged by ensuring the attribute arrays
>     are initialized before kobject_init_and_add()
> 
> v5:
>   - split the add_port() error paths after kobject_init_and_add()
>   - call kobject_del() before kobject_put() for failures after
>     kobject_init_and_add() succeeds
> 
> v4:
>   - route all add_port() failures after kobject_init_and_add() through
>     a single kobject_put() based error path
>   - remove duplicated attribute array frees from add_port()
>   - keep mlx4_port_release() tolerant of partially initialized objects
> 
> v3:
>   - make mlx4_port_release() tolerate NULL attribute arrays
>   - drop the parent kobject reference on the kobject_init_and_add()
>     failure path before putting the embedded kobject
> 
> v2:
>   - note that the issue was identified by my static analysis tool
>   - and confirmed by manual review
> 
>  drivers/infiniband/hw/mlx4/sysfs.c | 39 ++++++++++++++++--------------
>  1 file changed, 21 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx4/sysfs.c b/drivers/infiniband/hw/mlx4/sysfs.c
> index b8fa4ecfc961..e4c822c96ee6 100644
> --- a/drivers/infiniband/hw/mlx4/sysfs.c
> +++ b/drivers/infiniband/hw/mlx4/sysfs.c
> @@ -636,12 +636,6 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
>  	p->port_num = port_num;
>  	p->slave = slave;
>  
> -	ret = kobject_init_and_add(&p->kobj, &port_type,
> -				   kobject_get(dev->dev_ports_parent[slave]),
> -				   "%d", port_num);
> -	if (ret)
> -		goto err_alloc;
> -
>  	p->pkey_group.name  = "pkey_idx";
>  	p->pkey_group.attrs =
>  		alloc_group_attrs(show_port_pkey,
> @@ -649,13 +643,9 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
>  				  dev->dev->caps.pkey_table_len[port_num]);
>  	if (!p->pkey_group.attrs) {
>  		ret = -ENOMEM;
> -		goto err_alloc;
> +		goto err_free_port;
>  	}
>  
> -	ret = sysfs_create_group(&p->kobj, &p->pkey_group);
> -	if (ret)
> -		goto err_free_pkey;
> -
>  	p->gid_group.name  = "gid_idx";
>  	p->gid_group.attrs = alloc_group_attrs(show_port_gid_idx, NULL, 1);
>  	if (!p->gid_group.attrs) {
> @@ -663,28 +653,41 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
>  		goto err_free_pkey;
>  	}
>  
> +	ret = kobject_init_and_add(&p->kobj, &port_type,
> +				   kobject_get(dev->dev_ports_parent[slave]),
> +				   "%d", port_num);
> +	if (ret)
> +		goto err_put;
> +
> +	ret = sysfs_create_group(&p->kobj, &p->pkey_group);
> +	if (ret)
> +		goto err_del;
> +
>  	ret = sysfs_create_group(&p->kobj, &p->gid_group);
>  	if (ret)
> -		goto err_free_gid;
> +		goto err_del;

You should call to sysfs_remove_group() too.

Thanks

>  
>  	ret = add_vf_smi_entries(p);
>  	if (ret)
> -		goto err_free_gid;
> +		goto err_del;
>  
>  	list_add_tail(&p->kobj.entry, &dev->pkeys.pkey_port_list[slave]);
>  	return 0;
>  
> -err_free_gid:
> -	kfree(p->gid_group.attrs[0]);
> -	kfree(p->gid_group.attrs);
> +err_del:
> +	kobject_del(&p->kobj);
> +
> +err_put:
> +	kobject_put(dev->dev_ports_parent[slave]);
> +	kobject_put(&p->kobj);
> +	return ret;
>  
>  err_free_pkey:
>  	for (i = 0; i < dev->dev->caps.pkey_table_len[port_num]; ++i)
>  		kfree(p->pkey_group.attrs[i]);
>  	kfree(p->pkey_group.attrs);
>  
> -err_alloc:
> -	kobject_put(dev->dev_ports_parent[slave]);
> +err_free_port:
>  	kfree(p);
>  	return ret;
>  }
> -- 
> 2.43.0
>