linux-kernel - [PATCH -tip] timekeeping: fix getboottime() sets invalid value

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Message-ID: <4A937FDE.4050506@ct.jp.nec.com>
Date:	Tue, 25 Aug 2009 15:08:30 +0900
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Ingo Molnar <mingo@...e.hu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	John Stultz <johnstul@...ibm.com>,
	Daniel Walker <dwalker@...o99.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH -tip] timekeeping: fix getboottime() sets invalid value

From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>

Don't use timespec_add_safe() with wall_to_monotonic, because wall_to_monotonic
has negative values which will cause overflow in timespec_add_safe().
That makes btime in /proc/stat invalid.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
---
 kernel/time/timekeeping.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 03cbeb3..fb0f46f 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -826,9 +826,11 @@ void update_wall_time(void)
  */
 void getboottime(struct timespec *ts)
 {
-	struct timespec boottime;
+	struct timespec boottime = {
+		.tv_sec = wall_to_monotonic.tv_sec + total_sleep_time.tv_sec,
+		.tv_nsec = wall_to_monotonic.tv_nsec + total_sleep_time.tv_nsec
+	};
 
-	boottime = timespec_add_safe(wall_to_monotonic, total_sleep_time);
 	set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
 }
 
-- 
1.6.3.3

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