From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756845AbcAJFqO (ORCPT ); Sun, 10 Jan 2016 00:46:14 -0500 Received: from mail-pa0-f52.google.com ([209.85.220.52]:34359 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752368AbcAJFpY (ORCPT ); Sun, 10 Jan 2016 00:45:24 -0500 From: Peter Hurley To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-kernel@vger.kernel.org, Peter Hurley Subject: [PATCH v2 4/7] tty: Fix ioctl(FIOASYNC) on hungup file Date: Sat, 9 Jan 2016 21:45:11 -0800 Message-Id: <1452404714-9295-5-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1452404714-9295-1-git-send-email-peter@hurleysoftware.com> References: <1449958599-5533-1-git-send-email-peter@hurleysoftware.com> <1452404714-9295-1-git-send-email-peter@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A small race window exists which allows signal-driven async i/o to be enabled for the tty when the file ptr has already been hungup and signal-driven i/o has been disabled: CPU 0 CPU 1 ----- ------ ioctl_fioasync(on) filp->f_op->fasync(on) __tty_hangup() tty_fasync(on) tty_lock() tty_lock() ... . filp->f_op = &hung_up_tty_fops; (waiting) __tty_fasync(off) . tty_unlock() /* gets tty lock */ /* enables FASYNC */ Check the tty has not been hungup while holding tty_lock. Signed-off-by: Peter Hurley --- drivers/tty/tty_io.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 05b0a9c..7113bfa 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2260,10 +2260,11 @@ out: static int tty_fasync(int fd, struct file *filp, int on) { struct tty_struct *tty = file_tty(filp); - int retval; + int retval = -ENOTTY; tty_lock(tty); - retval = __tty_fasync(fd, filp, on); + if (!tty_hung_up_p(filp)) + retval = __tty_fasync(fd, filp, on); tty_unlock(tty); return retval; -- 2.7.0