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>
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