tracing: probes: Fix a possible race in trace_probe_log APIs

Since the shared trace_probe_log variable can be accessed and
modified via probe event create operation of kprobe_events,
uprobe_events, and dynamic_events, it should be protected.
In the dynamic_events, all operations are serialized by
`dyn_event_ops_mutex`. But kprobe_events and uprobe_events
interfaces are not serialized.

To solve this issue, introduces dyn_event_create(), which runs
create() operation under the mutex, for kprobe_events and
uprobe_events. This also uses lockdep to check the mutex is
held when using trace_probe_log* APIs.

Link: https://lore.kernel.org/all/174684868120.551552.3068655787654268804.stgit@devnote2/

Reported-by: Paul Cacheux <paulcacheux@gmail.com>
Closes: https://lore.kernel.org/all/20250510074456.805a16872b591e2971a4d221@kernel.org/
Fixes: ab105a4fb894 ("tracing: Use tracing error_log with probe events")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 2eeecb6c95ee..424751cdf31f 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -154,9 +154,12 @@ fail:
 }
 
 static struct trace_probe_log trace_probe_log;
+extern struct mutex dyn_event_ops_mutex;
 
 void trace_probe_log_init(const char *subsystem, int argc, const char **argv)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	trace_probe_log.subsystem = subsystem;
 	trace_probe_log.argc = argc;
 	trace_probe_log.argv = argv;
@@ -165,11 +168,15 @@ void trace_probe_log_init(const char *subsystem, int argc, const char **argv)
 
 void trace_probe_log_clear(void)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	memset(&trace_probe_log, 0, sizeof(trace_probe_log));
 }
 
 void trace_probe_log_set_index(int index)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	trace_probe_log.index = index;
 }
 
@@ -178,6 +185,8 @@ void __trace_probe_log_err(int offset, int err_type)
 	char *command, *p;
 	int i, len = 0, pos = 0;
 
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	if (!trace_probe_log.argv)
 		return;