workqueue: Fix missing kfree(rescuer) in destroy_workqueue()

BugLink: https://bugs.launchpad.net/bugs/1858489

commit 8efe1223 upstream.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Qian Cai <cai@lca.pw>
Fixes: def98c84 ("workqueue: Fix spurious sanity check failures in destroy_workqueue()")
Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

kernel/workqueue.c

@@ -3975,6 +3975,7 @@ void destroy_workqueue(struct workqueue_struct *wq)
 
 		/* rescuer will empty maydays list before exiting */
 		kthread_stop(rescuer->task);
+		kfree(rescuer);
 	}
 
 	/* sanity checks */