Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933772AbbFPJUm (ORCPT ); Tue, 16 Jun 2015 05:20:42 -0400 Received: from mail.kernel.org ([198.145.29.136]:55545 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756733AbbFPIob (ORCPT ); Tue, 16 Jun 2015 04:44:31 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Greg Kroah-Hartman , Zefan Li Subject: [PATCH 3.4 076/172] tty: fix up atime/mtime mess, take four Date: Tue, 16 Jun 2015 16:35:30 +0800 Message-Id: <1434443826-4929-76-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2149 Lines: 61 From: Jiri Slaby 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit f0bf0bd07943bfde8f5ac39a32664810a379c7d3 upstream. This problem was taken care of three times already in * b0de59b5733d18b0d1974a060860a8b5c1b36a2e (TTY: do not update atime/mtime on read/write), * 37b7f3c76595e23257f61bd80b223de8658617ee (TTY: fix atime/mtime regression), and * b0b885657b6c8ef63a46bc9299b2a7715d19acde (tty: fix up atime/mtime mess, take three) But it still misses one point. As John Paul correctly points out, we do not care about setting date. If somebody ever changes wall time backwards (by mistake for example), tty timestamps are never updated until the original wall time passes. So check the absolute difference of times and if it large than "8 seconds or so", always update the time. That means we will update immediatelly when changing time. Ergo, CAP_SYS_TIME can foul the check, but it was always that way. Thanks John for serving me this so nicely debugged. Signed-off-by: Jiri Slaby Reported-by: John Paul Perry Acked-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zefan Li --- drivers/tty/tty_io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index a07eb4c..5f0b4a4 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -941,8 +941,8 @@ EXPORT_SYMBOL(start_tty); /* We limit tty time update visibility to every 8 seconds or so. */ static void tty_update_time(struct timespec *time) { - unsigned long sec = get_seconds() & ~7; - if ((long)(sec - time->tv_sec) > 0) + unsigned long sec = get_seconds(); + if (abs(sec - time->tv_sec) & ~7) time->tv_sec = sec; } -- 1.9.1 -- 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/