This is a note to let you know that I've just added the patch titled
TTY: do not update atime/mtime on read/write
to the 3.4-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-do-not-update-atime-mtime-on-read-write.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b0de59b5733d18b0d1974a060860a8b5c1b36a2e Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@xxxxxxx>
Date: Fri, 15 Feb 2013 15:25:05 +0100
Subject: TTY: do not update atime/mtime on read/write
From: Jiri Slaby <jslaby@xxxxxxx>
commit b0de59b5733d18b0d1974a060860a8b5c1b36a2e upstream.
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@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_io.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -974,8 +974,7 @@ static ssize_t tty_read(struct file *fil
else
i = -EIO;
tty_ldisc_deref(ld);
- if (i > 0)
- inode->i_atime = current_fs_time(inode->i_sb);
+
return i;
}
@@ -1076,11 +1075,8 @@ static inline ssize_t do_tty_write(
break;
cond_resched();
}
- if (written) {
- struct inode *inode = file->f_path.dentry->d_inode;
- inode->i_mtime = current_fs_time(inode->i_sb);
+ if (written)
ret = written;
- }
out:
tty_write_unlock(tty);
return ret;
Patches currently in stable-queue which might be from jslaby@xxxxxxx are
queue-3.4/tty-fix-atime-mtime-regression.patch
queue-3.4/tty-do-not-update-atime-mtime-on-read-write.patch
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