linux-kernel - Re: [PATCH stable 4.9] posix-timers: Sanitize overrun handling

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Message-ID: <alpine.DEB.2.21.1811080747450.1666@nanos.tec.linutronix.de>
Date:   Thu, 8 Nov 2018 07:48:16 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
cc:     linux-kernel@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
        stable@...r.kernel.org, gregkh@...uxfoundation.org,
        Peter Zijlstra <peterz@...radead.org>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH stable 4.9] posix-timers: Sanitize overrun handling

Florian,

On Wed, 7 Nov 2018, Florian Fainelli wrote:
> On 11/1/18 1:02 PM, Florian Fainelli wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > [ Upstream commit 78c9c4dfbf8c04883941445a195276bb4bb92c76 ]
> > 
> > The posix timer overrun handling is broken because the forwarding functions
> > can return a huge number of overruns which does not fit in an int. As a
> > consequence timer_getoverrun(2) and siginfo::si_overrun can turn into
> > random number generators.
> > 
> > The k_clock::timer_forward() callbacks return a 64 bit value now. Make
> > k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal
> > accounting is correct. 3Remove the temporary (int) casts.
> > 
> > Add a helper function which clamps the overrun value returned to user space
> > via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value
> > between 0 and INT_MAX. INT_MAX is an indicator for user space that the
> > overrun value has been clamped.
> > 
> > Reported-by: Team OWL337 <icytxw@...il.com>
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Acked-by: John Stultz <john.stultz@...aro.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Michael Kerrisk <mtk.manpages@...il.com>
> > Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de
> > [florian: Make patch apply to v4.9.135]
> > Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> > ---
> > Thomas, can you review for correctness? Thanks!
> 
> Thomas, John, does that look like a reasonable backport for 4.9?

Looks correct.

Thanks,

	tglx