Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753186AbbLLWSI (ORCPT ); Sat, 12 Dec 2015 17:18:08 -0500 Received: from mail-pa0-f52.google.com ([209.85.220.52]:36216 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751506AbbLLWQr (ORCPT ); Sat, 12 Dec 2015 17:16:47 -0500 From: Peter Hurley To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-kernel@vger.kernel.org, Peter Hurley Subject: [PATCH 4/6] tty: Fix ioctl(FIOASYNC) on hungup file Date: Sat, 12 Dec 2015 14:16:37 -0800 Message-Id: <1449958599-5533-5-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.6.3 In-Reply-To: <1449958599-5533-1-git-send-email-peter@hurleysoftware.com> References: <1449958599-5533-1-git-send-email-peter@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1591 Lines: 49 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 e9b7591..19cec0e 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2250,10 +2250,11 @@ 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; -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/