Re: [ 02/42] TTY: do not update atime/mtime on read/write

Greg Kroah-Hartman
2013-04-30T01:37:44Z

On Mon, Apr 29, 2013 at 05:36:40PM -0700, Simon Kirby wrote:
> On Mon, Apr 29, 2013 at 05:21:17PM -0700, Greg Kroah-Hartman wrote:
>
> > On Mon, Apr 29, 2013 at 05:14:45PM -0700, Simon Kirby wrote:
> > > On Mon, Apr 29, 2013 at 12:01:44PM -0700, Greg Kroah-Hartman wrote:
> > >
> > > > 3.8-stable review patch. If anyone has any objections, please let me know.
> > >
> > > I object. This breaks functionality I use every day (seeing who else is
> > > working on stuff with "w").
> > >
> > > Furthermore, the patch does not actually fix the hole referenced (see
> > > ptmx-keystroke-latency.c on http://vladz.devzero.fr/013_ptmx-timing.php).
> > > I can still reproduce the timing capture even with this patch applied
> > > (in 3.9-rc8).
> >
> > How? There are no keystrokes being reported to other users, or did we
> > miss something with this patch?
>
> wget http://vladz.devzero.fr/svn/codes/PoC/ptmx-keystroke-latency.c
> gcc -O ptmx-keystroke-latency ptmx-keystroke-latency.c
> ./ptmx-keystroke-latency
>
> Log in to another tty, as another user. See keystroke timing. 3.9-rc8.
>
> Seems like it was missed. Meanwhile, idle times in "w" do not update.

Ah, it's using inotify on the /dev/ptmx device. Jiri, your change
really doesn't affect that at all :(

Simon, you mention a grsec change somewhere that addresses this issue.
Any hints on where that would be?

thanks,

greg k-h