From 6ea565a9be32a3c8d1092017686f183b6d8c4514 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Tue, 21 Aug 2012 20:30:48 -0400 Subject: [PATCH] time: Avoid potential shift overflow with large shift values Andreas Schwab noticed that the 1 << tk->shift could overflow if the shift value was greater than 30, since 1 would be a 32bit long on 32bit architectures. This issue was introduced by 1e75fa8be (time: Condense timekeeper.xtime into xtime_sec) Use 1ULL instead to ensure we don't overflow on the shift. Reported-by: Andreas Schwab Signed-off-by: John Stultz Cc: Prarit Bhargava Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1345595449-34965-4-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner --- kernel/time/timekeeping.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 1dbf80ec7696..a5a9389c4c30 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1184,9 +1184,9 @@ static void update_wall_time(void) * the vsyscall implementations are converted to use xtime_nsec * (shifted nanoseconds), this can be killed. */ - remainder = tk->xtime_nsec & ((1 << tk->shift) - 1); + remainder = tk->xtime_nsec & ((1ULL << tk->shift) - 1); tk->xtime_nsec -= remainder; - tk->xtime_nsec += 1 << tk->shift; + tk->xtime_nsec += 1ULL << tk->shift; tk->ntp_error += remainder << tk->ntp_error_shift; /* -- 2.20.1