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

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/
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250219135040.3a9fbe00@gandalf.local.home
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6b0c25761ccb1e5ef002f0f388019310d7de2655..de25c0505b6b3411d692c0649a8dd652253ad9c4 100644 (file)
--- 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);
 }