Re: [PATCH 1/1] tty: fix up atime/mtime mess, take four

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Feb 27, 2015 at 06:40:31PM +0100, Jiri Slaby wrote:
> This problem was taken care of three times already in
> * b0de59b5733d18b0d1974a060860a8b5c1b36a2e (TTY: do not update
>   atime/mtime on read/write),
> * 37b7f3c76595e23257f61bd80b223de8658617ee (TTY: fix atime/mtime
>   regression), and
> * b0b885657b6c8ef63a46bc9299b2a7715d19acde (tty: fix up atime/mtime
>   mess, take three)
> 
> But it still misses one point. As John Paul correctly points out, we
> do not care about setting date. If somebody ever changes wall
> time backwards (by mistake for example), tty timestamps are never
> updated until the original wall time passes.
> 
> So check the absolute difference of times and if it large than "8
> seconds or so", always update the time. That means we will update
> immediatelly when changing time. Ergo, CAP_SYS_TIME can foul the
> check, but it was always that way.
> 
> Thanks John for serving me this so nicely debugged.
> 
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> Reported-by: John Paul Perry <john_paul.perry@alcatel-lucent.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: <stable@vger.kernel.org> # all, as b0b885657 was backported
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>  drivers/tty/tty_io.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Thanks, I'll queue this up and get it to Linus soon.

greg k-h