linux-kernel - [PATCH 3.10 03/54] staging/speakup: Use tty_ldisc

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Date:	Tue, 23 Feb 2016 19:33:20 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH 3.10 03/54] staging/speakup: Use tty_ldisc_ref() for paste kworker

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

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

From: Peter Hurley <peter@...leysoftware.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@...leysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);
 }