Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964978AbbLGPAG (ORCPT ); Mon, 7 Dec 2015 10:00:06 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:59995 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964913AbbLGPAA (ORCPT ); Mon, 7 Dec 2015 10:00:00 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Hurley Subject: [PATCH 4.2 120/124] tty: Fix tty_send_xchar() lock order inversion Date: Mon, 7 Dec 2015 09:56:50 -0500 Message-Id: <20151207144925.758069814@linuxfoundation.org> X-Mailer: git-send-email 2.6.3 In-Reply-To: <20151207144919.656035367@linuxfoundation.org> References: <20151207144919.656035367@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2104 Lines: 72 4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley commit ee0c1a65cf95230d5eb3d9de94fd2ead9a428c67 upstream. The correct lock order is atomic_write_lock => termios_rwsem, as established by tty_write() => n_tty_write(). Fixes: c274f6ef1c666 ("tty: Hold termios_rwsem for tcflow(TCIxxx)") Reported-and-Tested-by: Dmitry Vyukov Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 4 ++++ drivers/tty/tty_ioctl.c | 4 ---- 2 files changed, 4 insertions(+), 4 deletions(-) --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1279,18 +1279,22 @@ int tty_send_xchar(struct tty_struct *tt int was_stopped = tty->stopped; if (tty->ops->send_xchar) { + down_read(&tty->termios_rwsem); tty->ops->send_xchar(tty, ch); + up_read(&tty->termios_rwsem); return 0; } if (tty_write_lock(tty, 0) < 0) return -ERESTARTSYS; + down_read(&tty->termios_rwsem); if (was_stopped) start_tty(tty); tty->ops->write(tty, &ch, 1); if (was_stopped) stop_tty(tty); + up_read(&tty->termios_rwsem); tty_write_unlock(tty); return 0; } --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -1142,16 +1142,12 @@ int n_tty_ioctl_helper(struct tty_struct spin_unlock_irq(&tty->flow_lock); break; case TCIOFF: - down_read(&tty->termios_rwsem); if (STOP_CHAR(tty) != __DISABLED_CHAR) retval = tty_send_xchar(tty, STOP_CHAR(tty)); - up_read(&tty->termios_rwsem); break; case TCION: - down_read(&tty->termios_rwsem); if (START_CHAR(tty) != __DISABLED_CHAR) retval = tty_send_xchar(tty, START_CHAR(tty)); - up_read(&tty->termios_rwsem); break; default: return -EINVAL; -- 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/