Re: [PATCH v2] ftrace: Fix use-after-free for dynamic ftrace_ops

[Steven Rostedt]

On Thu, 3 Nov 2022 11:10:10 +0800
Li Huafei <lihuafei1@xxxxxxxxxx> wrote:

> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3028,18 +3028,8 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
>  		command |= FTRACE_UPDATE_TRACE_FUNC;
>  	}
>  
> -	if (!command || !ftrace_enabled) {
> -		/*
> -		 * If these are dynamic or per_cpu ops, they still
> -		 * need their data freed. Since, function tracing is
> -		 * not currently active, we can just free them
> -		 * without synchronizing all CPUs.
> -		 */
> -		if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
> -			goto free_ops;
> -
> -		return 0;
> -	}
> +	if (!command || !ftrace_enabled)
> +		goto out;
>  

Hi Li,

I think you misunderstood me. What I was suggesting was to get rid of
the ftrace_enabled check. The DYNAMIC part is most definitely needed.

	if (!command) {
		if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
			goto out;
		return 0;
	}

-- Steve