posix-cpu-timers: Make timespec to nsec conversion safe
authorThomas Gleixner <tglx@linutronix.de>
Tue, 20 Jun 2017 15:37:36 +0000 (17:37 +0200)
committerThomas Gleixner <tglx@linutronix.de>
Tue, 20 Jun 2017 19:33:56 +0000 (21:33 +0200)
commit098b0e01a91c42aaaf0425605cd126b03fcb0bcf
treed936fa77c10117b58f5a47f789745bc88b093c75
parent35eb7258c009dc478338e674a5a84d25d0929c56
posix-cpu-timers: Make timespec to nsec conversion safe

The expiry time of a posix cpu timer is supplied through sys_timer_set()
via a struct timespec. The timespec is validated for correctness.

In the actual set timer implementation the timespec is converted to a
scalar nanoseconds value. If the tv_sec part of the time spec is large
enough the conversion to nanoseconds (sec * NSEC_PER_SEC) overflows 64bit.

Mitigate that by using the timespec_to_ktime() conversion function, which
checks the tv_sec part for a potential mult overflow and clamps the result
to KTIME_MAX, which is about 292 years.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170620154113.588276707@linutronix.de
kernel/time/posix-cpu-timers.c