Commit 10632008 authored Oct 20, 2014 by Thomas Gleixner

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>

parent 6891c450

kernel/time/clockevents.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);