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authorDavid Engraf <david.engraf@sysgo.com>2013-03-19 13:29:55 +0100
committerJohn Stultz <john.stultz@linaro.org>2013-04-08 13:21:20 -0700
commit51fd36f3fad8447c487137ae26b9d0b3ce77bb25 (patch)
tree737cecc049ec3b4682ffc3b4d4bc44d1cebe7f61 /kernel/hrtimer.c
parent8f294b5a139ee4b75e890ad5b443c93d1e558a8b (diff)
downloadlinux-51fd36f3fad8447c487137ae26b9d0b3ce77bb25.tar.gz
hrtimer: Fix ktime_add_ns() overflow on 32bit architectures
One can trigger an overflow when using ktime_add_ns() on a 32bit architecture not supporting CONFIG_KTIME_SCALAR. When passing a very high value for u64 nsec, e.g. 7881299347898368000 the do_div() function converts this value to seconds (7881299347) which is still to high to pass to the ktime_set() function as long. The result in is a negative value. The problem on my system occurs in the tick-sched.c, tick_nohz_stop_sched_tick() when time_delta is set to timekeeping_max_deferment(). The check for time_delta < KTIME_MAX is valid, thus ktime_add_ns() is called with a too large value resulting in a negative expire value. This leads to an endless loop in the ticker code: time_delta: 7881299347898368000 expires = ktime_add_ns(last_update, time_delta) expires: negative value This fix caps the value to KTIME_MAX. This error doesn't occurs on 64bit or architectures supporting CONFIG_KTIME_SCALAR (e.g. ARM, x86-32). Cc: stable@vger.kernel.org Signed-off-by: David Engraf <david.engraf@sysgo.com> [jstultz: Minor tweaks to commit message & header] Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel/hrtimer.c')
-rw-r--r--kernel/hrtimer.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 071e093c448..c0875ae0de1 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -286,6 +286,10 @@ ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
} else {
unsigned long rem = do_div(nsec, NSEC_PER_SEC);
+ /* Make sure nsec fits into long */
+ if (unlikely(nsec > KTIME_SEC_MAX))
+ return (ktime_t){ .tv64 = KTIME_MAX };
+
tmp = ktime_set((long)nsec, rem);
}