Extend the test module with a new test case (test1) that intentionally
overflows a local u64 buffer to corrupt the stack canary.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/test.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/test.c b/mm/kstackwatch/test.c
index 80fec9cf3243..012692c97a50 100644
--- a/mm/kstackwatch/test.c
+++ b/mm/kstackwatch/test.c
@@ -32,6 +32,20 @@ static void test_watch_fire(void)
 	pr_info("exit of %s\n", __func__);
 }
 
+static void test_canary_overflow(void)
+{
+	u64 buffer[BUFFER_SIZE];
+
+	pr_info("entry of %s\n", __func__);
+
+	/* intentionally overflow */
+	for (int i = BUFFER_SIZE; i < BUFFER_SIZE + 10; i++)
+		buffer[i] = 0xdeadbeefdeadbeef;
+	barrier_data(buffer);
+
+	pr_info("exit of %s\n", __func__);
+}
+
 static ssize_t test_dbgfs_write(struct file *file, const char __user *buffer,
 				size_t count, loff_t *pos)
 {
@@ -54,6 +68,9 @@ static ssize_t test_dbgfs_write(struct file *file, const char __user *buffer,
 		case 0:
 			test_watch_fire();
 			break;
+		case 1:
+			test_canary_overflow();
+			break;
 		default:
 			pr_err("Unknown test number %d\n", test_num);
 			return -EINVAL;
@@ -74,7 +91,8 @@ static ssize_t test_dbgfs_read(struct file *file, char __user *buffer,
 		"============ usage ===============\n"
 		"Usage:\n"
 		"echo test{i} > /sys/kernel/debug/kstackwatch/test\n"
-		" test0 - test watch fire\n";
+		" test0 - test watch fire\n"
+		" test1 - test canary overflow\n";
 
 	return simple_read_from_buffer(buffer, count, ppos, usage,
 				       strlen(usage));
-- 
2.43.0