[PATCH 4.4 012/137] staging/speakup: Use tty_ldisc_ref() for paste kworker

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Hurley <redacted>

commit f4f9edcf9b5289ed96113e79fa65a7bf27ecb096 upstream.

As the function documentation for tty_ldisc_ref_wait() notes, it is
only callable from a tty file_operations routine; otherwise there
is no guarantee the ref won't be NULL.

The key difference with the VT's paste_selection() is that is an ioctl,
where __speakup_paste_selection() is completely async kworker, kicked
off from interrupt context.

Fixes: 28a821c30688 ("Staging: speakup: Update __speakup_paste_selection()
       tty (ab)usage to match vt")
Signed-off-by: Peter Hurley <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/staging/speakup/selection.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/staging/speakup/selection.c
+++ b/drivers/staging/speakup/selection.c

@@ -142,7 +142,9 @@ static void __speakup_paste_selection(st
 	struct tty_ldisc *ld;
 	DECLARE_WAITQUEUE(wait, current);
 
-	ld = tty_ldisc_ref_wait(tty);
+	ld = tty_ldisc_ref(tty);
+	if (!ld)
+		goto tty_unref;
 	tty_buffer_lock_exclusive(&vc->port);
 
 	add_wait_queue(&vc->paste_wait, &wait);

@@ -162,6 +164,7 @@ static void __speakup_paste_selection(st
 
 	tty_buffer_unlock_exclusive(&vc->port);
 	tty_ldisc_deref(ld);
+tty_unref:
 	tty_kref_put(tty);
 }