From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: [PATCH] n_tty: Protect minimum_to_wake reset for concurrent readers Date: Thu, 7 Nov 2013 14:01:57 -0500 Message-ID: <1383850917-24416-1-git-send-email-peter@hurleysoftware.com> Return-path: Received: from mailout02.c08.mtsvc.net ([205.186.168.190]:43900 "EHLO mailout02.c08.mtsvc.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405Ab3KGTWY (ORCPT ); Thu, 7 Nov 2013 14:22:24 -0500 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Peter Hurley With multiple, concurrent readers (each waiting to acquire the atomic_read_lock mutex), a departing reader may mistakenly reset minimum_to_wake after a new reader has already set a new value. Protect the minimum_to_wake reset with the atomic_read_lock critical section. Signed-off-by: Peter Hurley --- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index ce11cd5..bf9650d 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2253,12 +2253,12 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, n_tty_set_room(tty); up_read(&tty->termios_rwsem); - mutex_unlock(&ldata->atomic_read_lock); remove_wait_queue(&tty->read_wait, &wait); - if (!waitqueue_active(&tty->read_wait)) ldata->minimum_to_wake = minimum; + mutex_unlock(&ldata->atomic_read_lock); + __set_current_state(TASK_RUNNING); if (b - buf) retval = b - buf; -- 1.8.1.2