[PATCH 2/2] ext4: Testing lock class and subclass got the same name pointer

[botta633]

Checking if the lockdep_map->name will change when setting the subclass.
It shouldn't change so that the lock class and subclass will have the same name


Reported-by: <syzbot+7f4a6f7f7051474e40ad@xxxxxxxxxxxxxxxxxxxxxxxxx>
Fixes: fd5e3f5fe27
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: botta633 <bottaawesome633@xxxxxxxxx>
---
 lib/locking-selftest.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 6f6a5fc85b42..1d7885205f36 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -2710,12 +2710,24 @@ static void local_lock_3B(void)
 
 }
 
+static void class_subclass_X1_name(void)
+{
+	const char *name_before_subclass = rwsem_X1.dep_map.name;
+	const char *name_after_subclass;
+
+	WARN_ON(!rwsem_X1.dep_map.name);
+	lockdep_set_subclass(&rwsem_X1, 1);
+	WARN_ON(name_before_subclass != name_after_subclass);
+}
+
 static void local_lock_tests(void)
 {
 	printk("  --------------------------------------------------------------------------\n");
 	printk("  | local_lock tests |\n");
 	printk("  ---------------------\n");
 
+	init_class_X(&lock_X1, &rwlock_X1, &mutex_X1, &rwsem_X1);
+
 	print_testname("local_lock inversion  2");
 	dotest(local_lock_2, SUCCESS, LOCKTYPE_LL);
 	pr_cont("\n");
@@ -2727,6 +2739,10 @@ static void local_lock_tests(void)
 	print_testname("local_lock inversion 3B");
 	dotest(local_lock_3B, FAILURE, LOCKTYPE_LL);
 	pr_cont("\n");
+
+	print_testname("Class and subclass");
+	dotest(class_subclass_X1_name, SUCCESS, LOCKTYPE_RWSEM);
+	pr_cont("\n");
 }
 
 static void hardirq_deadlock_softirq_not_deadlock(void)
-- 
2.45.2