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 my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus 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 hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From f0bf0bd07943bfde8f5ac39a32664810a379c7d3 Mon Sep 17 00:00:00 2001
From: Jiri Slaby <[email protected]>
Date: Fri, 27 Feb 2015 18:40:31 +0100
Subject: tty: fix up atime/mtime mess, take four
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 <[email protected]>
Reported-by: John Paul Perry <[email protected]>
Cc: <[email protected]> # all, as b0b885657 was backported
Acked-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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 51f066aa375e..2bb4dfc02873 100644
--- 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;
}
--
2.3.1
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