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From: Justin Stitt <justinstitt@google.com>
Date: Thu, 16 May 2024 16:55:19 -0700
Message-ID: <CAFhGd8rTHPiKG+XOkkUihj9r8k1=n3zgitpM9X2aQf6zhp9psQ@mail.gmail.com>
Subject: Re: [PATCH] ntp: remove accidental integer wrap-around
To: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <jstultz@google.com>, Stephen Boyd <sboyd@kernel.org>, 
	Nathan Chancellor <nathan@kernel.org>, Bill Wendling <morbo@google.com>, linux-kernel@vger.kernel.org, 
	llvm@lists.linux.dev, linux-hardening@vger.kernel.org
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On Thu, May 16, 2024 at 4:40=E2=80=AFPM Justin Stitt <justinstitt@google.co=
m> wrote:
> Isn't this usually supplied from the user and can be some pretty
> random stuff? Are you suggesting we update
> timekeeping_validate_timex() to include a check to limit the maxerror
> field to (NTP_PHASE_LIMIT-(MAXFREQ / NSEC_PER_USEC))? It seems like we
> should handle the overflow case where it happens: in
> second_overflow().

Or, I suppose we could add a check to timekeeping_validate_timex() like:

if (txc->modes & ADJ_MAXERROR) {
    if (txc->maxerror < 0 || txc->maxerror > NTP_PHASE_LIMIT)
        return -EINVAL;
}


> Thanks
> Justin