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

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Message-ID: <20181108154625.GC8097@sasha-vm>
Date:   Thu, 8 Nov 2018 10:46:25 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        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

On Thu, Nov 08, 2018 at 07:48:16AM +0100, Thomas Gleixner wrote:
>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.

Queued for 4.9, thanks all.

--
Thanks,
Sasha