This is a note to let you know that I've just added the patch titled
tty: fix up atime/mtime mess, take four
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-fix-up-atime-mtime-mess-take-four.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f0bf0bd07943bfde8f5ac39a32664810a379c7d3 Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@xxxxxxx>
Date: Fri, 27 Feb 2015 18:40:31 +0100
Subject: tty: fix up atime/mtime mess, take four
From: Jiri Slaby <jslaby@xxxxxxx>
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 <jslaby@xxxxxxx>
Reported-by: John Paul Perry <john_paul.perry@xxxxxxxxxxxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_io.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1028,8 +1028,8 @@ 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;
}
Patches currently in stable-queue which might be from jslaby@xxxxxxx are
queue-3.19/tty-fix-up-atime-mtime-mess-take-four.patch
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