1 files changed, 38 insertions, 6 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 892c92354745..5cec01c75691 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1463,13 +1463,13 @@ static int tty_reopen(struct tty_struct *tty)
 {
         struct tty_driver *driver = tty->driver;
 
-        if (!tty->count)
-                return -EIO;
-
         if (driver->type == TTY_DRIVER_TYPE_PTY &&
             driver->subtype == PTY_TYPE_MASTER)
                 return -EIO;
 
+        if (!tty->count)
+                return -EAGAIN;
+
         if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
                 return -EBUSY;
 
@@ -2065,7 +2065,12 @@ retry_open:
 
                 if (tty) {
                         mutex_unlock(&tty_mutex);
-                        tty_lock(tty);
+                        retval = tty_lock_interruptible(tty);
+                        if (retval) {
+                                if (retval == -EINTR)
+                                        retval = -ERESTARTSYS;
+                                goto err_unref;
+                        }
                         /* safe to drop the kref from tty_driver_lookup_tty() */
                         tty_kref_put(tty);
                         retval = tty_reopen(tty);
@@ -2083,7 +2088,11 @@ retry_open:
 
         if (IS_ERR(tty)) {
                 retval = PTR_ERR(tty);
-                goto err_file;
+                if (retval != -EAGAIN || signal_pending(current))
+                        goto err_file;
+                tty_free_file(filp);
+                schedule();
+                goto retry_open;
         }
 
         tty_add_file(tty, filp);
@@ -2152,6 +2161,7 @@ retry_open:
         return 0;
 err_unlock:
         mutex_unlock(&tty_mutex);
+err_unref:
         /* after locks to avoid deadlock */
         if (!IS_ERR_OR_NULL(driver))
                 tty_driver_kref_put(driver);
@@ -2649,6 +2659,28 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
 }
 
 /**
+ *      tiocgetd        -       get line discipline
+ *      @tty: tty device
+ *      @p: pointer to user data
+ *
+ *      Retrieves the line discipline id directly from the ldisc.
+ *
+ *      Locking: waits for ldisc reference (in case the line discipline
+ *              is changing or the tty is being hungup)
+ */
+
+static int tiocgetd(struct tty_struct *tty, int __user *p)
+{
+        struct tty_ldisc *ld;
+        int ret;
+
+        ld = tty_ldisc_ref_wait(tty);
+        ret = put_user(ld->ops->num, p);
+        tty_ldisc_deref(ld);
+        return ret;
+}
+
+/**
  *      send_break      -       performed time break
  *      @tty: device to break on
  *      @duration: timeout in mS
@@ -2874,7 +2906,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         case TIOCGSID:
                 return tiocgsid(tty, real_tty, p);
         case TIOCGETD:
-                return put_user(tty->ldisc->ops->num, (int __user *)p);
+                return tiocgetd(tty, p);
         case TIOCSETD:
                 return tiocsetd(tty, p);
         case TIOCVHANGUP: