Mailing List Archive

[PATCH] time: Fix casting issue in timekeeping_forward_now
arch_gettimeoffset returns a u32 value which when shifted by tk->shift can
overflow. Cast it to u64 first.

Signed-off-by: Andreas Schwab <>
Found this by inspection, I don't know if any existing users of
ARCH_USES_GETTIMEOFFSET are affected. In other words, this is untested,
but looks pretty obvious.

Can tk->shift be bigger than 30? If so then the shifts in
update_wall_time need to be adjusted as well.


kernel/time/timekeeping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e16af19..8776d66 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -276,7 +276,7 @@ static void timekeeping_forward_now(struct timekeeper *tk)
tk->xtime_nsec += cycle_delta * tk->mult;

/* If arch requires, add in gettimeoffset() */
- tk->xtime_nsec += arch_gettimeoffset() << tk->shift;
+ tk->xtime_nsec += (u64)arch_gettimeoffset() << tk->shift;



Andreas Schwab,
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"And now for something completely different."
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