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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0FC66C04AAC for ; Mon, 20 May 2019 12:19:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D45DB20815 for ; Mon, 20 May 2019 12:19:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558354782; bh=3ZMQ0nLrVjSo833AKD5qQcw1NeLMf4w3zTiBPuBIfq8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yTEVRf3hXelXkFhwLC1SPfBVr4JqQCJYg7uH0VhzhblnpaCuUZPwsURw/zSfbsKFV bKU4nV1GvvOik1UGG46QDKpN1bDvx9+GNbnPQPNUuO3Mjc1EIaMcpyreOP/FhQ8IsX 9sAmVq+cNNq/cpnrcAEcSFkcwUb63HKtdY0bPHSQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733254AbfETMTm (ORCPT ); Mon, 20 May 2019 08:19:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:32816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732391AbfETMTi (ORCPT ); Mon, 20 May 2019 08:19:38 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 A7B0020815; Mon, 20 May 2019 12:19:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558354777; bh=3ZMQ0nLrVjSo833AKD5qQcw1NeLMf4w3zTiBPuBIfq8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KfQkx1l8CaAX/Q1FIv48av9xa4iOQsgKj77JVidmoO86Rxxxl84Xcqgcypy8YJn66 kAC4wtJFj/U4LJ/4Sl2mS0stylmcWjK5i+zqASZ0+vsB4ySWMp6BPvaCLlYy4OWu+/ 2S9+0t0q07cGg5vWUdX0+auDpH+ILqZZ9ys64zZ4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nicolas Pitre , Yifeng Li Subject: [PATCH 4.14 38/63] tty: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval == 0 Date: Mon, 20 May 2019 14:14:17 +0200 Message-Id: <20190520115235.356952418@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190520115231.137981521@linuxfoundation.org> References: <20190520115231.137981521@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yifeng Li commit 75ddbc1fb11efac87b611d48e9802f6fe2bb2163 upstream. 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(-) --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3840,8 +3840,6 @@ void do_blank_screen(int entering_gfx) return; } - if (blank_state != blank_normal_wait) - return; blank_state = blank_off; /* don't blank graphics */