tracing: React to error return from traceprobe_parse_event_name()

The function traceprobe_parse_event_name() may set the first two function
arguments to a non-null value and still return -EINVAL to indicate an
unsuccessful completion of the function. Hence, it is not sufficient to
just check the result of the two function arguments for being not null,
but the return value also needs to be checked.

Commit 95c104c378dc ("tracing: Auto generate event name when creating a
group of events") changed the error-return-value checking of the second
traceprobe_parse_event_name() invocation in __trace_eprobe_create() and
removed checking the return value to jump to the error handling case.

Reinstate using the return value in the error-return-value checking.

Link: https://lkml.kernel.org/r/[e-mail]

Fixes: 95c104c378dc ("tracing: Auto generate event name when creating a group of events")
Acked-by: Linyu Yuan <[e-mail]>
Signed-off-by: Lukas Bulwahn <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

kernel/trace/trace_eprobe.c

···
 	trace_probe_log_set_index(1);
 	sys_event = argv[1];
 	ret = traceprobe_parse_event_name(&sys_event, &sys_name, buf2, 0);
-	if (!sys_event || !sys_name) {
+	if (ret || !sys_event || !sys_name) {
 		trace_probe_log_err(0, NO_EVENT_INFO);
 		goto parse_error;
 	}