[patch] staging: speakup: safely close tty

[Okash Khawaja <okash.khawaja@gmail.com>]

Speakup opens tty using tty_open_by_driver. When closing, it calls
tty_ldisc_release but doesn't close and remove the tty itself. As a
result, that tty cannot then be opened from user space. This patch calls
tty_release_struct which ensures that tty is safely removed and freed
up. It also calls tty_ldisc_release, so speakup doesn't need to call it.

This patch also unregisters N_SPEAKUP. It is registered when a speakup
module is loaded.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>

---
 drivers/staging/speakup/spk_ttyio.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -300,7 +300,9 @@ void spk_ttyio_release(void)
 
 	tty_ldisc_flush(speakup_tty);
 	tty_unlock(speakup_tty);
-	tty_ldisc_release(speakup_tty);
+	tty_release_struct(speakup_tty, speakup_tty->index);
+	if (tty_unregister_ldisc(N_SPEAKUP))
+		pr_warn("speakup: failed to unregister line discipline N_SPEAKUP\n");
 }
 EXPORT_SYMBOL_GPL(spk_ttyio_release);