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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D567AC7EE23 for ; Thu, 8 Jun 2023 10:17:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235796AbjFHKR2 (ORCPT ); Thu, 8 Jun 2023 06:17:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233473AbjFHKRZ (ORCPT ); Thu, 8 Jun 2023 06:17:25 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F363D2706 for ; Thu, 8 Jun 2023 03:16:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1686219399; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xYCw3I4nWr1p+lEe4qR80qwR+LhJGCUxY2FlsUOhHns=; b=TaS/yqanJbPbe4mRWobdIxOEiyhnO80LNH3IS6mPXJj3x/d0thz6MYDTuENKjYV9QqxcCB CUdztk4YdI0x2XGe5ehjbCrGc6WvUqo4FML4YhSrFPJOls8il9GtZe7dTTOWkLwoEX1RYf HchJzq/u12PkXj2tjvCr2nYNEb4C/wU= Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-298-V9RVtU4UNqGI7yO4LVyt7A-1; Thu, 08 Jun 2023 06:16:38 -0400 X-MC-Unique: V9RVtU4UNqGI7yO4LVyt7A-1 Received: by mail-ed1-f69.google.com with SMTP id 4fb4d7f45d1cf-5149e1bd242so443639a12.3 for ; Thu, 08 Jun 2023 03:16:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686219397; x=1688811397; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xYCw3I4nWr1p+lEe4qR80qwR+LhJGCUxY2FlsUOhHns=; b=Tb1dGHhwlhd901zUmAt4z09qk9/Qr2w42jxFy76fH8W8zl9+QI9IpPdRFkvkdQfi0b eZuTkyaOprx5xyJJ/kqG1Vfn1m7cGHG5Q30js2KbgAGQWX8QJoaKH0fasUXhLsdTgY32 opdnjnMPOD42W+oMzpgnpFl0VR+Xj+gUKl3TGDx1I7a2fzg7HkXGzkIwpcMMOro1XYkQ y5OblwVMEjwXZswbU5ghacjqn2IFCdC+V3au4I+kNd1B9nHtinIwVk26Huh/8mK+ah4d UybIi46SfNs3xMu6zzDEsSFGAFLG/TaWOODyLBruqYNyQSF0K6cowiH28XqSbD/+y0+E yo0g== X-Gm-Message-State: AC+VfDwnaaFvsOrlalpcPjzkh4JdZ0hQ38XCXW5h4giFoh3C/hYVFLMv oFb3pkx7xnxnf8xVwOuMbhqoFXlK7K2ymY4qVrawSj5R/sFory4iWrPWGnyjvRj35+pve06kiu3 0SGMxOCoTJz3mDu5mseVhPBGu X-Received: by 2002:a17:906:4fcd:b0:978:9ad7:e736 with SMTP id i13-20020a1709064fcd00b009789ad7e736mr1906687ejw.39.1686219396857; Thu, 08 Jun 2023 03:16:36 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6FwyrOWXKjHsDINcg4QuGkxMlJ+8bPC1MM3qHtDfay7aIVDCD3WI28XJhe+u0atwcZ/NErNA== X-Received: by 2002:a17:906:4fcd:b0:978:9ad7:e736 with SMTP id i13-20020a1709064fcd00b009789ad7e736mr1906661ejw.39.1686219396526; Thu, 08 Jun 2023 03:16:36 -0700 (PDT) Received: from localhost.localdomain ([46.33.96.32]) by smtp.gmail.com with ESMTPSA id e20-20020a170906249400b00977da0f14ffsm506558ejb.171.2023.06.08.03.16.35 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 08 Jun 2023 03:16:35 -0700 (PDT) From: Michal Sekletar To: jirislaby@kernel.org Cc: arozansk@redhat.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, msekleta@redhat.com, shuah@kernel.org Subject: [PATCH v2 1/2] tty: tty_io: update timestamps on all device nodes Date: Thu, 8 Jun 2023 12:16:15 +0200 Message-Id: <20230608101616.44152-1-msekleta@redhat.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org User space applications watch for timestamp changes on character device files in order to determine idle time of a given terminal session. For example, "w" program uses this information to populate the IDLE column of its output [1]. Similarly, systemd-logind has optional feature where it uses atime of the tty character device to determine if there was activity on the terminal associated with the logind's session object. If there was no activity for a configured period of time then logind will terminate such session [2]. Now, usually (e.g. bash running on the terminal) the use of the terminal will update timestamps (atime and mtime) on the corresponding terminal character device. However, if access to the terminal, e.g. /dev/pts/0, is performed through magic character device /dev/tty then such access obviously changes the state of the terminal, however timestamps on the device that correspond to the terminal (/dev/pts/0) are not updated. This patch makes sure that we update timestamps on *all* character devices that correspond to the given tty, because outside observers (w, systemd-logind) are maybe checking these timestamps. Obviously, they can not check timestamps on /dev/tty as that has per-process meaning. [1] https://gitlab.com/procps-ng/procps/-/blob/v4.0.0/w.c#L286 [2] https://github.com/systemd/systemd/blob/v252/NEWS#L477 Signed-off-by: Michal Sekletar --- v1 -> v2: Minor style tweaks based on code review comments drivers/tty/tty_io.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index c84be40fb..a505d2c49 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -101,6 +101,7 @@ #include #include #include +#include #include #include @@ -811,18 +812,26 @@ void start_tty(struct tty_struct *tty) } EXPORT_SYMBOL(start_tty); -static void tty_update_time(struct timespec64 *time) +static void tty_update_time(struct tty_struct *tty, bool mtime) { time64_t sec = ktime_get_real_seconds(); + struct tty_file_private *priv; - /* - * We only care if the two values differ in anything other than the - * lower three bits (i.e every 8 seconds). If so, then we can update - * the time of the tty device, otherwise it could be construded as a - * security leak to let userspace know the exact timing of the tty. - */ - if ((sec ^ time->tv_sec) & ~7) - time->tv_sec = sec; + spin_lock(&tty->files_lock); + list_for_each_entry(priv, &tty->tty_files, list) { + struct inode *inode = file_inode(priv->file); + struct timespec64 *time = mtime ? &inode->i_mtime : &inode->i_atime; + + /* + * We only care if the two values differ in anything other than the + * lower three bits (i.e every 8 seconds). If so, then we can update + * the time of the tty device, otherwise it could be construded as a + * security leak to let userspace know the exact timing of the tty. + */ + if ((sec ^ time->tv_sec) & ~7) + time->tv_sec = sec; + } + spin_unlock(&tty->files_lock); } /* @@ -928,7 +937,7 @@ static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to) tty_ldisc_deref(ld); if (i > 0) - tty_update_time(&inode->i_atime); + tty_update_time(tty, false); return i; } @@ -1036,7 +1045,7 @@ static inline ssize_t do_tty_write( cond_resched(); } if (written) { - tty_update_time(&file_inode(file)->i_mtime); + tty_update_time(tty, true); ret = written; } out: -- 2.39.1