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tracing: Do not take trace_event_sem in print_event_fields()

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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: 80a76994b2 ("tracing: Add "fields" option to show raw trace event fields")
Reported-by: syzbot+441582c1592938fccf09@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6813ff5e.050a0220.14dd7d.001b.GAE@google.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2025-05-01 22:41:28 -04:00 committed by Steven Rostedt (Google)
parent 1be8e54a1e
commit 0a8f11f856
1 changed files with 2 additions and 2 deletions
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4
kernel/trace/trace_output.c
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@ -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;