[PATCH] tty: vt: add a bounds checking in vt_do_kdgkb_ioctl()

[Hangyu Hua]

As array_index_nospec's comments indicate，a bounds checking need to add
before calling array_index_nospec.

Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
---
 drivers/tty/vt/keyboard.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index be8313cdbac3..b9845455df79 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -2067,6 +2067,9 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
 	if (get_user(kb_func, &user_kdgkb->kb_func))
 		return -EFAULT;
 
+	if (kb_func >= MAX_NR_FUNC)
+		return -EFAULT;
+
 	kb_func = array_index_nospec(kb_func, MAX_NR_FUNC);
 
 	switch (cmd) {
-- 
2.34.1