Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753330AbaJPU5J (ORCPT ); Thu, 16 Oct 2014 16:57:09 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:37138 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752784AbaJPUyk (ORCPT ); Thu, 16 Oct 2014 16:54:40 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Jiri Slaby , One Thousand Gnomes , Peter Hurley Subject: [PATCH -next 02/10] serial: core: Flush ldisc after dropping port mutex in uart_close() Date: Thu, 16 Oct 2014 16:54:19 -0400 Message-Id: <1413492867-20679-3-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.1.1 In-Reply-To: <1413492867-20679-1-git-send-email-peter@hurleysoftware.com> References: <1413492867-20679-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The tty buffers (and any line discipline buffers) must be flushed after the UART hardware has shutdown; otherwise, a racing open on the same tty may receive data from the previous session, which is a security hazard. However, holding the port mutex while flushing the line discipline buffers creates a lock inversion if the set_termios() handler takes the port mutex (as it does in the followup patch, 'serial: Fix locking for uart driver set_termios method'. Flush the ldisc buffers after dropping the port mutex; the tty lock is still held which prevents a concurrent open() from advancing while flushing. Since no new rx data is possible after uart_shutdown() until a new open reinitializes the port, the later flush has no impact on what data is being discarded. Signed-off-by: Peter Hurley --- drivers/tty/serial/serial_core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index ce0e762..6203c6c 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1360,9 +1360,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp) mutex_lock(&port->mutex); uart_shutdown(tty, state); - - tty_ldisc_flush(tty); - tty_port_tty_set(port, NULL); tty->closing = 0; spin_lock_irqsave(&port->lock, flags); @@ -1389,6 +1386,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp) wake_up_interruptible(&port->close_wait); mutex_unlock(&port->mutex); + + tty_ldisc_flush(tty); } static void uart_wait_until_sent(struct tty_struct *tty, int timeout) -- 2.1.1 -- 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/