Commit-ID: 098b0e01a91c42aaaf0425605cd126b03fcb0bcf Gitweb: http://git.kernel.org/tip/098b0e01a91c42aaaf0425605cd126b03fcb0bcf Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Tue, 20 Jun 2017 17:37:36 +0200 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Tue, 20 Jun 2017 21:33:56 +0200 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@xxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx> Cc: John Stultz <john.stultz@xxxxxxxxxx> Link: http://lkml.kernel.org/r/20170620154113.588276707@xxxxxxxxxxxxx --- kernel/time/posix-cpu-timers.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 9df618e..60cb24a 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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