linux-kernel - Re: [PATCH] time: fix a assignment error in ntp module

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Message-ID: <alpine.DEB.2.21.1906171705280.1854@nanos.tec.linutronix.de>
Date:   Mon, 17 Jun 2019 17:06:35 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Miroslav Lichvar <mlichvar@...hat.com>
cc:     维康石 <swkhack@...il.com>,
        John Stultz <john.stultz@...aro.org>, sboyd@...nel.org,
        LKML <linux-kernel@...r.kernel.org>, swkhack@...com
Subject: Re: [PATCH] time: fix a assignment error in ntp module

Miroslav,

On Mon, 17 Jun 2019, Miroslav Lichvar wrote:

> On Mon, Jun 17, 2019 at 02:14:57PM +0200, Thomas Gleixner wrote:
> > On Mon, 17 Jun 2019, 维康石 wrote:
> > > Yes,the  >UINT_MAX value can be passed by
> > > syscall adjtimex->do_adjtimex->__do_adjtimex->process_adjtimex_modes by the
> > > proper arugments.
> > 
> > So there is clearly some sanity check missing, but surely not that
> > type cast.
> 
> As the offset is saved in an int (and returned via adjtimex() in the
> tai field), should be the maximum INT_MAX?

Right.

> We probably also want to avoid overflow in the offset on a leap second
> and the CLOCK_TAI clock itself, so maybe it would make sense to
> specify a much smaller maximum like 1000000?
> 
> Even 1000 should be good enough for near future. Negative values are
> not allowed anyway. If the Earth's rotation changed significantly
> (e.g. hitting a very large asteroid), there probably wouldn't be
> anyone left to care about TAI. 

Hehehe. I leave it to you to find a sane limit taking all the possible
events into account :)

Thanks,

	tglx