lkml.org 
[lkml]   [2013]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[ 02/42] TTY: do not update atime/mtime on read/write
    Date
    3.8-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiri Slaby <jslaby@suse.cz>

    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>

    ---
    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
    @@ -977,8 +977,7 @@ 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;
    }

    @@ -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;



    \
     
     \ /
      Last update: 2013-04-29 22:21    [W:4.187 / U:0.656 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site