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

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Message-ID: <20190617132133.GA7851@localhost>
Date:   Mon, 17 Jun 2019 15:21:33 +0200
From:   Miroslav Lichvar <mlichvar@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
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

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?

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. 

-- 
Miroslav Lichvar