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

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

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

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@gandalf.local.home/

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 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

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

[Masami Hiramatsu]

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

> From: Steven Rostedt <rostedt@goodmis.org>
> 
> 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@gandalf.local.home/
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

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@kernel.org>