Commit 0a8f11f8 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
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tracing: Do not take trace_event_sem in print_event_fields() 

On some paths in print_event_fields() it takes the trace_event_sem for
read, even though it should always be held when the function is called.

Remove the taking of that mutex and add a lockdep_assert_held_read() to
make sure the trace_event_sem is held when print_event_fields() is called.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250501224128.0b1f0571@batman.local.home


Fixes: 80a76994 ("tracing: Add "fields" option to show raw trace event fields")
Reported-by: default avatar <syzbot+441582c1592938fccf09@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/6813ff5e.050a0220.14dd7d.001b.GAE@google.com/


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 1be8e54a

kernel/trace/trace_output.c

+2 −2
Original line number Diff line number Diff line
@@ -1042,11 +1042,12 @@ enum print_line_t print_event_fields(struct trace_iterator *iter, 
	struct trace_event_call *call;

	struct list_head *head;



	lockdep_assert_held_read(&trace_event_sem);



	/* ftrace defined events have separate call structures */

	if (event->type <= __TRACE_LAST_TYPE) {

		bool found = false;



		down_read(&trace_event_sem);

		list_for_each_entry(call, &ftrace_events, list) {

			if (call->event.type == event->type) {

				found = true;
@@ -1056,7 +1057,6 @@ enum print_line_t print_event_fields(struct trace_iterator *iter, 
			if (call->event.type > __TRACE_LAST_TYPE)

				break;

		}

		up_read(&trace_event_sem);

		if (!found) {

			trace_seq_printf(&iter->seq, "UNKNOWN TYPE %d\n", event->type);

			goto out;