1 files changed, 15 insertions, 14 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index eb881cfa53e0..2a1e95b0f282 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2770,12 +2770,11 @@ static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
  *      actually has driver level meaning and triggers a VC resize.
  *
  *      Locking:
- *              The console_sem is used to ensure we do not try and resize
- *      the console twice at once.
- *      FIXME: Two racing size sets may leave the console and kernel
- *              parameters disagreeing. Is this exploitable ?
- *      FIXME: Random values racing a window size get is wrong
- *      should lock here against that
+ *              Called function use the console_sem is used to ensure we do
+ *      not try and resize the console twice at once.
+ *              The tty->termios_sem is used to ensure we don't double
+ *      resize and get confused. Lock order - tty->termios.sem before
+ *      console sem
  */
 
 static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
@@ -2785,17 +2784,17 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
 
         if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
                 return -EFAULT;
+
+        down(&tty->termios_sem);
         if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
-                return 0;
+                goto done;
+
 #ifdef CONFIG_VT
         if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
-                int rc;
-
-                acquire_console_sem();
-                rc = vc_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row);
-                release_console_sem();
-                if (rc)
-                        return -ENXIO;
+                if (vc_lock_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row)) {
+                        up(&tty->termios_sem);
+                        return -ENXIO;
+                }
         }
 #endif
         if (tty->pgrp > 0)
@@ -2804,6 +2803,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
                 kill_pg(real_tty->pgrp, SIGWINCH, 1);
         tty->winsize = tmp_ws;
         real_tty->winsize = tmp_ws;
+done:
+        up(&tty->termios_sem);
         return 0;
 }