clockevents: Prevent shift out of bounds

Andrey reported that on a kernel with UBSan enabled he found:

     UBSan: Undefined behaviour in ../kernel/time/clockevents.c:75:34

     I guess it should be 1ULL here instead of 1U:
            (!ismax || evt->mult <= (1U << evt->shift)))

That's indeed the correct solution because shift might be 32.

Reported-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 9c94c19..5544990 100644 (file)
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -72,7 +72,7 @@ static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
         * Also omit the add if it would overflow the u64 boundary.
         */
        if ((~0ULL - clc > rnd) &&
-           (!ismax || evt->mult <= (1U << evt->shift)))
+           (!ismax || evt->mult <= (1ULL << evt->shift)))
                clc += rnd;
 
        do_div(clc, evt->mult);