[PATCH] tty: vt: keyboard: do not copy an extra-byte in copy_to_user

Ajay Garg
2021-11-06T09:21:00Z

Both (statically-allocated) "user_kdgkb->kb_string" and
(dynamically-allocated) "kbs" are of length "len", so we must
not copy more than "len" bytes.

Signed-off-by: Ajay Garg <ajaygargnsit@gmail.com>
---
drivers/tty/vt/keyboard.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index c7fbbcdcc346..dfef7de8a057 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -2070,7 +2070,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
len = strlcpy(kbs, func_table[kb_func] ? : "", len);
spin_unlock_irqrestore(&func_buf_lock, flags);

- ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ?
+ ret = copy_to_user(user_kdgkb->kb_string, kbs, len) ?
-EFAULT : 0;

break;
--
2.30.2