ACK: [SRU][Bionic][PATCH 1/1] posix-timers: Sanitize overrun handling

Tyler Hicks tyhicks at
Tue Nov 27 18:12:15 UTC 2018

On 2018-11-27 00:23:16, Khalid Elmously wrote:
> From: Thomas Gleixner <tglx at>
> CVE-2018-12896
> 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 at>
> Signed-off-by: Thomas Gleixner <tglx at>
> Acked-by: John Stultz <john.stultz at>
> Cc: Peter Zijlstra <peterz at>
> Cc: Michael Kerrisk <mtk.manpages at>
> Link:
> (cherry picked from commit 78c9c4dfbf8c04883941445a195276bb4bb92c76)
> Signed-off-by: Khalid Elmously <khalid.elmously at>

Acked-by: Tyler Hicks <tyhicks at>

This ack is only for the Bionic patch. Thanks!

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