diff options
| author | Jiri Slaby <jslaby@suse.cz> | 2013-02-15 15:25:05 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-05-01 09:46:00 -0700 |
| commit | cb3ab89ba72b5bc7579c9d5194828245e2119c74 (patch) | |
| tree | b27ca89d385c8cf3730b33ff738b645cb91cf6cb | |
| parent | 85d273bc26fdd491058394e6dc487b41d02e17f3 (diff) | |
TTY: do not update atime/mtime on read/write
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@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_io.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index da9fde85075..e95ef3a4d33 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -977,8 +977,7 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count, else i = -EIO; tty_ldisc_deref(ld); - if (i > 0) - inode->i_atime = current_fs_time(inode->i_sb); + return i; } @@ -1079,11 +1078,8 @@ 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; |