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authorThomas Gleixner <tglx@linutronix.de>2017-06-20 17:37:36 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-06-20 21:33:56 +0200
commit098b0e01a91c42aaaf0425605cd126b03fcb0bcf (patch)
treed936fa77c10117b58f5a47f789745bc88b093c75
parent35eb7258c009dc478338e674a5a84d25d0929c56 (diff)
downloadlinux-098b0e01a91c42aaaf0425605cd126b03fcb0bcf.tar.bz2
posix-cpu-timers: Make timespec to nsec conversion safe
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> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Xishi Qiu <qiuxishi@huawei.com> Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/20170620154113.588276707@linutronix.de
-rw-r--r--kernel/time/posix-cpu-timers.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 9df618ee64cf..60cb24ac9ebc 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -580,7 +580,11 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
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