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| author | David Engraf <david.engraf@sysgo.com> | 2013-03-19 13:29:55 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-05-07 20:33:10 -0700 |
| commit | f931d5e4bf1902ae2a4829db0e6f3c789fd7d092 (patch) | |
| tree | 11a16f38534e057cebabe49c7eb1af48f35ddad1 | |
| parent | bee59d68d7cc802c9ee4e7ecda01ba4c906dbd73 (diff) | |
hrtimer: Fix ktime_add_ns() overflow on 32bit architectures
commit 51fd36f3fad8447c487137ae26b9d0b3ce77bb25 upstream.
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).
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/hrtimer.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 14be27feda4..2fff8e174f4 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -276,6 +276,10 @@ 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); } |