locktorture: Fix potential memory leak with rw lock test

When running locktorture module with the below commands with kmemleak enabled:

$ modprobe locktorture torture_type=rw_lock_irq
$ rmmod locktorture

The below kmemleak got caught:

root@10:~# echo scan > /sys/kernel/debug/kmemleak
[  323.197029] kmemleak: 2 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
root@10:~# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffffffc07592d500 (size 128):
  comm "modprobe", pid 368, jiffies 4294924118 (age 205.824s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 c3 7b 02 00 00 00 00 00  .........{......
    00 00 00 00 00 00 00 00 d7 9b 02 00 00 00 00 00  ................
  backtrace:
    [<ffffff80081e5a88>] create_object+0x110/0x288
    [<ffffff80086c6078>] kmemleak_alloc+0x58/0xa0
    [<ffffff80081d5acc>] __kmalloc+0x234/0x318
    [<ffffff80006fa130>] 0xffffff80006fa130
    [<ffffff8008083ae4>] do_one_initcall+0x44/0x138
    [<ffffff800817e28c>] do_init_module+0x68/0x1cc
    [<ffffff800811c848>] load_module+0x1a68/0x22e0
    [<ffffff800811d340>] SyS_finit_module+0xe0/0xf0
    [<ffffff80080836f0>] el0_svc_naked+0x24/0x28
    [<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffffffc07592d480 (size 128):
  comm "modprobe", pid 368, jiffies 4294924118 (age 205.824s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 3b 6f 01 00 00 00 00 00  ........;o......
    00 00 00 00 00 00 00 00 23 6a 01 00 00 00 00 00  ........#j......
  backtrace:
    [<ffffff80081e5a88>] create_object+0x110/0x288
    [<ffffff80086c6078>] kmemleak_alloc+0x58/0xa0
    [<ffffff80081d5acc>] __kmalloc+0x234/0x318
    [<ffffff80006fa22c>] 0xffffff80006fa22c
    [<ffffff8008083ae4>] do_one_initcall+0x44/0x138
    [<ffffff800817e28c>] do_init_module+0x68/0x1cc
    [<ffffff800811c848>] load_module+0x1a68/0x22e0
    [<ffffff800811d340>] SyS_finit_module+0xe0/0xf0
    [<ffffff80080836f0>] el0_svc_naked+0x24/0x28
    [<ffffffffffffffff>] 0xffffffffffffffff

It is because cxt.lwsa and cxt.lrsa don't get freed in module_exit, so free
them in lock_torture_cleanup() and free writer_tasks if reader_tasks is
failed at memory allocation.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

kernel/locking/locktorture.c

@@ -780,6 +780,10 @@ static void lock_torture_cleanup(void)
 	else
 		lock_torture_print_module_parms(cxt.cur_ops,
 						"End of test: SUCCESS");
+
+	kfree(cxt.lwsa);
+	kfree(cxt.lrsa);
+
 end:
 	torture_cleanup_end();
 }
@@ -924,6 +928,8 @@ static int __init lock_torture_init(void)
 				       GFP_KERNEL);
 		if (reader_tasks == NULL) {
 			VERBOSE_TOROUT_ERRSTRING("reader_tasks: Out of memory");
+			kfree(writer_tasks);
+			writer_tasks = NULL;
 			firsterr = -ENOMEM;
 			goto unwind;
 		}