hrtimer: check relative timeouts for overflow

hrtimer: check relative timeouts for overflow

Various user space callers ask for relative timeouts. While we fixed
that overflow issue in hrtimer_start(), the sites which convert
relative user space values to absolute timeouts themself were uncovered.

Instead of putting overflow checks into each place add a function
which does the sanity checking and convert all affected callers to use
it.

Thanks to Frans Pop, who reported the problem and tested the fixes.

Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Tested-by: Frans Pop <[email protected]>