From 125c50411b6df22afee8bb353b524f96b2ea71e8 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Fri, 27 Feb 2015 18:40:31 +0100 Subject: [PATCH] tty: fix up atime/mtime mess, take four 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: Greg Kroah-Hartman --- 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 d35afccdb6c9..2967b6eb4c70 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -992,8 +992,8 @@ 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; } -- 2.20.1