Messages in this thread Patch in this message | | | Date | Tue, 20 Jun 2017 17:37:36 +0200 | From | Thomas Gleixner <> | Subject | [patch 2/2] posix-cpu-timers: Make timespec to nsec conversion safe |
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The expiry time of a posix cpu timer is supplied through sys_timer_set() via a struct timespec. The timespec is validated for correctness.
In the actual set timer implementation the timespec is converted to a scalar nanoseconds value. If the tv_sec part of the time spec is large enough the conversion to nanoseconds (sec * NSEC_PER_SEC) overflows 64bit.
Mitigate that by using the timespec_to_ktime() conversion function, which checks the tv_sec part for a potential mult overflow and clamps the result to KTIME_MAX, which is about 292 years.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/time/posix-cpu-timers.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -572,7 +572,11 @@ static int posix_cpu_timer_set(struct k_ WARN_ON_ONCE(p == NULL); - new_expires = timespec64_to_ns(&new->it_value); + /* + * Use the to_ktime conversion because that clamps the maximum + * value to KTIME_MAX and avoid multiplication overflows. + */ + new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value)); /* * Protect against sighand release/switch in exit/exec and p->cpu_timers
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