rcutorture: Fix cleanup path for invalid torture_type strings

[ Upstream commit b813afae7ab6a5e91b4e16cc567331d9c2ae1f04 ]

If the specified rcutorture.torture_type is not in the rcu_torture_init()
function's torture_ops[] array, rcutorture prints some console messages
and then invokes rcu_torture_cleanup() to set state so that a future
torture test can run.  However, rcu_torture_cleanup() also attempts to
end the test that didn't actually start, and in doing so relies on the
value of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case
and inserts a check near the beginning of rcu_torture_cleanup(),
thus avoiding relying on an irrelevant cur_ops value.
Reported-by: Nkernel test robot <rong.a.chen@intel.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>

kernel/rcu/rcutorture.c

@@ -1826,6 +1826,10 @@ rcu_torture_cleanup(void)
 			cur_ops->cb_barrier();
 		return;
 	}
+	if (!cur_ops) {
+		torture_cleanup_end();
+		return;
+	}
 
 	rcu_torture_barrier_cleanup();
 	torture_stop_kthread(rcu_torture_stall, stall_task);
@@ -1964,6 +1968,7 @@ rcu_torture_init(void)
 			pr_cont(" %s", torture_ops[i]->name);
 		pr_cont("\n");
 		firsterr = -EINVAL;
+		cur_ops = NULL;
 		goto unwind;
 	}
 	if (cur_ops->fqs == NULL && fqs_duration != 0) {