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authorJohn Stultz <john.stultz@linaro.org>2012-08-21 20:30:48 -0400
committerThomas Gleixner <tglx@linutronix.de>2012-08-22 10:42:13 +0200
commit6ea565a9be32a3c8d1092017686f183b6d8c4514 (patch)
tree2db67e9659f91f11997998ba9845f4c7cb0d89ab
parent85dc8f05c93c8105987de9d7e7cebf15a72ff4ec (diff)
downloadlinaro-lsk-6ea565a9be32a3c8d1092017686f183b6d8c4514.tar.gz
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 <schwab@linux-m68k.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Link: http://lkml.kernel.org/r/1345595449-34965-4-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--kernel/time/timekeeping.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 1dbf80ec769..a5a9389c4c3 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;
/*