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=-12.0 required=3.0 tests=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 4B49EC4360F for ; Wed, 27 Mar 2019 18:28:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E7302147C for ; Wed, 27 Mar 2019 18:28:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711300; bh=JJ0KpCIWEA8w6BSbuTFDcJK/KG2R3YFEF/23SX5ETug=; h=Subject:To:From:Date:List-ID:From; b=G+NF8ee2IEQaa/srxqMb7LRL46mSNsOcNGd5UdMDjtqRc1Kc0r7hxKIEtxTHt7KXD BV7nWUVWtE8niRvFTPOxitsNnMabUhsn2ZAAKWcO7/Pm9G6TK0RXc+LDeJjcOYXGvU ucVNoKRhIXfka7rZr8qXrYgzVOze4dJaaPCZRdmo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391880AbfC0S2S (ORCPT ); Wed, 27 Mar 2019 14:28:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:48096 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391869AbfC0S2S (ORCPT ); Wed, 27 Mar 2019 14:28:18 -0400 Received: from localhost (unknown [88.128.80.233]) (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 69ED52082F; Wed, 27 Mar 2019 18:28:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711296; bh=JJ0KpCIWEA8w6BSbuTFDcJK/KG2R3YFEF/23SX5ETug=; h=Subject:To:From:Date:From; b=z4Ch05gkZ/p4fgWbzs3g6FRENWfaySu5IK27pgHWF9y8Xs8JohRHbah3VLcx5944P 0CjPzkGUjqDjlI4skZUimHgtef88YZWvxx2+Zs7JGfzGmTrn8B1FOwxSNCNj5u1iwK 27KoISclluPJVv/MT7+YsB2sruO0XURtJG66fYkU= Subject: patch "tty: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval ==" added to tty-testing To: tomli@tomli.me, gregkh@linuxfoundation.org, nicolas.pitre@linaro.org, stable@vger.kernel.org From: Date: Thu, 28 Mar 2019 01:29:14 +0900 Message-ID: <155370415411239@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: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval == 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-testing 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 be merged to the tty-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >From 75ddbc1fb11efac87b611d48e9802f6fe2bb2163 Mon Sep 17 00:00:00 2001 From: Yifeng Li Date: Tue, 5 Mar 2019 07:02:49 +0800 Subject: tty: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval == 0 Previously, in the userspace, it was possible to use the "setterm" command from util-linux to blank the VT console by default, using the following command. According to the man page, > The force option keeps the screen blank even if a key is pressed. It was implemented by calling TIOCL_BLANKSCREEN. case BLANKSCREEN: ioctlarg = TIOCL_BLANKSCREEN; if (ioctl(STDIN_FILENO, TIOCLINUX, &ioctlarg)) warn(_("cannot force blank")); break; However, after Linux 4.12, this command ceased to work anymore, which is unexpected. By inspecting the kernel source, it shows that the issue was triggered by the side-effect from commit a4199f5eb809 ("tty: Disable default console blanking interval"). The console blanking is implemented by function do_blank_screen() in vt.c: "blank_state" will be initialized to "blank_normal_wait" in con_init() if AND ONLY IF ("blankinterval" > 0). If "blankinterval" is 0, "blank_state" will be "blank_off" (== 0), and a call to do_blank_screen() will always abort, even if a forced blanking is required from the user by calling TIOCL_BLANKSCREEN, the console won't be blanked. This behavior is unexpected from a user's point-of-view, since it's not mentioned in any documentation. The setterm man page suggests it will always work, and the kernel comments in uapi/linux/tiocl.h says > /* keep screen blank even if a key is pressed */ > #define TIOCL_BLANKSCREEN 14 To fix it, we simply remove the "blank_state != blank_off" check, as pointed out by Nicolas Pitre, this check doesn't logically make sense and it's safe to remove. Suggested-by: Nicolas Pitre Fixes: a4199f5eb809 ("tty: Disable default console blanking interval") Signed-off-by: Yifeng Li Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vt.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index d34984aa646d..721edee50234 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -4178,8 +4178,6 @@ void do_blank_screen(int entering_gfx) return; } - if (blank_state != blank_normal_wait) - return; blank_state = blank_off; /* don't blank graphics */ -- 2.21.0