1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 18085a20df23..b4f37c65b95c 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2740,18 +2740,21 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
  *      @tty; tty
  *      @arg: user buffer for result
  *
- *      Copies the kernel idea of the window size into the user buffer. No
- *      locking is done.
+ *      Copies the kernel idea of the window size into the user buffer.
  *
- *      FIXME: Returning random values racing a window size set is wrong
- *      should lock here against that
+ *      Locking: tty->termios_sem is taken to ensure the winsize data
+ *              is consistent.
  */
 
 static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
 {
-        if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
-                return -EFAULT;
-        return 0;
+        int err;
+
+        down(&tty->termios_sem);
+        err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
+        up(&tty->termios_sem);
+
+        return err ? -EFAULT: 0;
 }
 
 /**