Commit 35eb7258 authored Jun 20, 2017 by Thomas Gleixner

itimer: Make timeval to nsec conversion range limited



The expiry time of a itimer is supplied through sys_setitimer() via a
struct timeval. The timeval is validated for correctness.

In the actual set timer implementation the timeval 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 timeval_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. 

Reported-by: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170620154113.505981643@linutronix.de

parent d15bc69a

kernel/time/itimer.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -152,8 +152,12 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
		u64 oval, nval, ointerval, ninterval;
		struct cpu_itimer *it = &tsk->signal->it[clock_id];

		nval = timeval_to_ns(&value->it_value);
		ninterval = timeval_to_ns(&value->it_interval);
		/*
		* Use the to_ktime conversion because that clamps the maximum
		* value to KTIME_MAX and avoid multiplication overflows.
		*/
		nval = ktime_to_ns(timeval_to_ktime(value->it_value));
		ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));

		spin_lock_irq(&tsk->sighand->siglock);

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