[patch] staging: speakup: safely close tty

From: Okash Khawaja
Date: Fri Jul 07 2017 - 15:13:15 EST

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@xxxxxxxxx>

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_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");