[PATCH 3.10 03/54] staging/speakup: Use tty_ldisc_ref() for paste kworker

Greg Kroah-Hartman
2016-02-24T03:54:49Z

From: Peter Hurley <peter@hurleysoftware.com>

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 <peter@hurleysoftware.com>
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
@@ -139,7 +139,9 @@ 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;

/* FIXME: this is completely unsafe */
add_wait_queue(&vc->paste_wait, &wait);
@@ -158,6 +160,7 @@ static void __speakup_paste_selection(st
current->state = TASK_RUNNING;

tty_ldisc_deref(ld);
+tty_unref:
tty_kref_put(tty);
}