From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22D0EC43387 for ; Fri, 11 Jan 2019 16:04:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF67420872 for ; Fri, 11 Jan 2019 16:04:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547222654; bh=UO4PE3ZAvQ1/nX/GNxzpeyTOpPgAp8zdNHfuWRA7fCE=; h=Subject:To:From:Date:List-ID:From; b=FluLPdKLRIH7+1sRK5iYW6EDDPBflHJXBgDsXgkYtNI3mgX/OchKFtzoaoIF5Wffd C5TBpfpJbVjGK4yse52fC4vSMc33BOFqISZGj01fijB3nniOvc/JMNMwJFickeaSrg G5/GBFdZX0W2nkk8+S1RXCDg3vgCsMXmAoXm2EDA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730166AbfAKQEN (ORCPT ); Fri, 11 Jan 2019 11:04:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:48172 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729359AbfAKQEN (ORCPT ); Fri, 11 Jan 2019 11:04:13 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D55820675; Fri, 11 Jan 2019 16:04:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547222652; bh=UO4PE3ZAvQ1/nX/GNxzpeyTOpPgAp8zdNHfuWRA7fCE=; h=Subject:To:From:Date:From; b=uWtfbU6mZ7vGkDIXn4CcB6Wc3mBI9sUK2nB54p+k4J69y04+q44igM3es5JkkEgOZ adEWZLYMCAdQw1n3GFA1fVbJvhv7voGxlPJhSeTDHqDhaAALoqXDmjG+0gQ+7n+raZ 0pXZARWwovLE407vZLhDWhxsltJEy2fPZ3uVLmQ0= Subject: patch "tty: Don't hold ldisc lock in tty_reopen() if ldisc present" added to tty-linus To: dima@arista.com, gregkh@linuxfoundation.org, jslaby@suse.com, lukas@mntmn.com, stable@vger.kernel.org From: Date: Fri, 11 Jan 2019 17:04:10 +0100 Message-ID: <1547222650597@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled tty: Don't hold ldisc lock in tty_reopen() if ldisc present to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From d3736d82e8169768218ee0ef68718875918091a0 Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Wed, 9 Jan 2019 01:17:40 +0000 Subject: tty: Don't hold ldisc lock in tty_reopen() if ldisc present Try to get reference for ldisc during tty_reopen(). If ldisc present, we don't need to do tty_ldisc_reinit() and lock the write side for line discipline semaphore. Effectively, it optimizes fast-path for tty_reopen(), but more importantly it won't interrupt ongoing IO on the tty as no ldisc change is needed. Fixes user-visible issue when tty_reopen() interrupted login process for user with a long password, observed and reported by Lukas. Fixes: c96cf923a98d ("tty: Don't block on IO when ldisc change is pending") Fixes: 83d817f41070 ("tty: Hold tty_ldisc_lock() during tty_reopen()") Cc: Jiri Slaby Reported-by: Lukas F. Hartmann Tested-by: Lukas F. Hartmann Cc: stable Signed-off-by: Dmitry Safonov Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index bfe9ad85b362..23c6fd238422 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1256,7 +1256,8 @@ static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct * static int tty_reopen(struct tty_struct *tty) { struct tty_driver *driver = tty->driver; - int retval; + struct tty_ldisc *ld; + int retval = 0; if (driver->type == TTY_DRIVER_TYPE_PTY && driver->subtype == PTY_TYPE_MASTER) @@ -1268,13 +1269,18 @@ static int tty_reopen(struct tty_struct *tty) if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN)) return -EBUSY; - retval = tty_ldisc_lock(tty, 5 * HZ); - if (retval) - return retval; + ld = tty_ldisc_ref_wait(tty); + if (ld) { + tty_ldisc_deref(ld); + } else { + retval = tty_ldisc_lock(tty, 5 * HZ); + if (retval) + return retval; - if (!tty->ldisc) - retval = tty_ldisc_reinit(tty, tty->termios.c_line); - tty_ldisc_unlock(tty); + if (!tty->ldisc) + retval = tty_ldisc_reinit(tty, tty->termios.c_line); + tty_ldisc_unlock(tty); + } if (retval == 0) tty->count++; -- 2.20.1