Re: [PATCH 2/2] cgroup: Fix reference count leak when cft->open is NULL

[Michal Koutný]

On Fri, Jul 18, 2025 at 07:54:09PM +0800, Zijiang Huang <huangzjsmile@xxxxxxxxx> wrote:
> @@ -4134,8 +4134,10 @@ static int cgroup_file_open(struct kernfs_open_file *of)
>  	get_cgroup_ns(ctx->ns);
>  	of->priv = ctx;
>  
> -	if (!cft->open)
> +	if (!cft->open) {
> +		get_cgroup_ns(ctx->ns);
>  		return 0;
> +	}
>  
>  	ret = cft->open(of);
>  	if (ret) {

1) You wanted to call put_cgroup_ns() instead of get_cgroup_ns()
2) The refernce needs to be kept during the whole lifetime of
   cgroup_file_ctx, this return path still leads to a valid ctx, so it's
   released in cgroup_file_release().

Or could you decribe more how could a release be missed?

Thanks,
Michal

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