linux-kernel - RE: [PATCH 1/1] tty: fix up atime/mtime mess, take four

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Message-ID: <4FC69820B05DEF40B2BA46A25025C092C2F22D97@US70UWXCHMBA01.zam.alcatel-lucent.com>
Date:	Fri, 27 Feb 2015 21:27:04 +0000
From:	"Perry, John Paul G (John Paul)** CTR **" 
	<john_paul.perry@...atel-lucent.com>
To:	Greg KH <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.cz>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: RE: [PATCH 1/1] tty: fix up atime/mtime mess, take four

Thanks everyone!

John Paul

-----Original Message-----
From: Greg KH [mailto:gregkh@...uxfoundation.org] 
Sent: Friday, February 27, 2015 11:23 AM
To: Jiri Slaby
Cc: linux-kernel@...r.kernel.org; Perry, John Paul G (John Paul)** CTR **; stable@...r.kernel.org; Linus Torvalds
Subject: Re: [PATCH 1/1] tty: fix up atime/mtime mess, take four

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@...e.cz>
> Reported-by: John Paul Perry <john_paul.perry@...atel-lucent.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: <stable@...r.kernel.org> # all, as b0b885657 was backported
> Cc: Linus Torvalds <torvalds@...ux-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
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