Re: [PATCH] ftrace: Have ftrace_free_filter() WARN and exit if ops is active

[Google]

On Wed, 19 Feb 2025 13:50:40 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
> 
> The ftrace_free_filter() is used to reset the ops filters. But it must be
> done if the ops is not currently active (tracing). If it is, it will mess
> up the ftrace accounting of what functions are attached and what is not.
> 
> WARN and exit the ftrace_free_filter() if the ops is active when it is
> called.
> 
> Currently, it doesn't seem if anything does this, but it may in the
> future.
> 
> Link: https://lore.kernel.org/all/20250219095330.2e9f171c@xxxxxxxxxxxxxxxxxx/
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

Thanks,

> ---
>  kernel/trace/ftrace.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 189eb0a12f4b..4f6cad3b05b2 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1296,6 +1296,8 @@ static void free_ftrace_hash_rcu(struct ftrace_hash *hash)
>  void ftrace_free_filter(struct ftrace_ops *ops)
>  {
>  	ftrace_ops_init(ops);
> +	if (WARN_ON(ops->flags & FTRACE_OPS_FL_ENABLED))
> +		return;
>  	free_ftrace_hash(ops->func_hash->filter_hash);
>  	free_ftrace_hash(ops->func_hash->notrace_hash);
>  }
> -- 
> 2.47.2
> 


-- 
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>