tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)

[pandora-kernel.git] / drivers / tty / tty_io.c

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 6ab0322..1f9ee25 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2474,6 +2474,28 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
        return ret;
 }
 
+/**
+ *     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
@@ -2684,7 +2706,7 @@ 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: