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posix-timers: Sanitize overrun handling

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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@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de
This commit is contained in:
Thomas Gleixner 2018-06-26 15:21:32 +02:00
parent 6fec64e1c9
commit 78c9c4dfbf
3 changed files with 23 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/linux/posix-timers.h
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@ -95,8 +95,8 @@ struct k_itimer {
clockid_t it_clock;
timer_t it_id;
int it_active;
int it_overrun;
int it_overrun_last;
s64 it_overrun;
s64 it_overrun_last;
int it_requeue_pending;
int it_sigev_notify;
ktime_t it_interval;