Re: [PATCH] cgroup: fix potential null pointer risk

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Tue, May 17, 2022 at 03:31:06PM +0800, Shida Zhang wrote:
> We previously assumed 'parent' could be null,
> so null pointer judgment should be added.
> 
> Signed-off-by: Shida Zhang <zhangshida-UOlijcLmZ/InDS1+zs4M5A@public.gmane.org>
> ---
>  kernel/cgroup/cgroup.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index adb820e98f24..7f230b0ab644 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -5701,7 +5701,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
>  	}
>  	spin_unlock_irq(&css_set_lock);
>  
> -	cgroup1_check_for_release(parent);
> +	if (parent)
> +		cgroup1_check_for_release(parent);

The function is never called for a root cgroup. The parent check up above in
the same function is superflous. So, maybe remove that?

Thanks.

-- 
tejun