tracing: Consider the NULL character when validating the event length

[ Upstream commit 0b6e2e22cb23105fcb171ab92f0f7516c69c8471 ]

strlen() returns a string length excluding the null byte. If the string
length equals to the maximum buffer length, the buffer will have no
space for the NULL terminating character.

This commit checks this condition and returns failure for it.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: dec65d79fd26 ("tracing/probe: Check event name length correctly")
Signed-off-by: Leo Yan <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

kernel/trace/trace_probe.c

@@ -256,7 +256,7 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
 	if (len == 0) {
 		trace_probe_log_err(offset, NO_EVENT_NAME);
 		return -EINVAL;
-	} else if (len > MAX_EVENT_NAME_LEN) {
+	} else if (len >= MAX_EVENT_NAME_LEN) {
 		trace_probe_log_err(offset, EVENT_TOO_LONG);
 		return -EINVAL;
 	}