TTY: do not update atime/mtime on read/write
authorJiri Slaby <jslaby@suse.cz>
Fri, 15 Feb 2013 14:25:05 +0000 (15:25 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 15 Feb 2013 18:52:36 +0000 (10:52 -0800)
commitb0de59b5733d18b0d1974a060860a8b5c1b36a2e
treeb304fafe3dcbb26212d95438fe2d98184752b9fc
parentcb8081cb6bfbdb867d17cafaaf3509ee31140f7f
TTY: do not update atime/mtime on read/write

On http://vladz.devzero.fr/013_ptmx-timing.php, we can see how to find
out length of a password using timestamps of /dev/ptmx. It is
documented in "Timing Analysis of Keystrokes and Timing Attacks on
SSH". To avoid that problem, do not update time when reading
from/writing to a TTY.

I am afraid of regressions as this is a behavior we have since 0.97
and apps may expect the time to be current, e.g. for monitoring
whether there was a change on the TTY. Now, there is no change. So
this would better have a lot of testing before it goes upstream.

References: CVE-2013-0160

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: stable <stable@vger.kernel.org> # after 3.9 is out
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/tty_io.c