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clockevents: Prevent shift out of bounds

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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>
This commit is contained in:
Thomas Gleixner 2014-10-20 15:07:50 +04:00
parent 6891c4509c
commit 10632008b9
1 changed files with 1 additions and 1 deletions
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2
kernel/time/clockevents.c
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@ -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. * Also omit the add if it would overflow the u64 boundary.
*/ */
if ((~0ULL - clc > rnd) && if ((~0ULL - clc > rnd) &&
(!ismax || evt->mult <= (1U << evt->shift))) (!ismax || evt->mult <= (1ULL << evt->shift)))
clc += rnd; clc += rnd;
do_div(clc, evt->mult); do_div(clc, evt->mult);