From 5f936e19cc0ef97dbe3a56e9498922ad5ba1edef Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 2 Jul 2018 09:34:29 +0200 Subject: alarmtimer: Prevent overflow for relative nanosleep Air Icy reported: UBSAN: Undefined behaviour in kernel/time/alarmtimer.c:811:7 signed integer overflow: 1529859276030040771 + 9223372036854775807 cannot be represented in type 'long long int' Call Trace: alarm_timer_nsleep+0x44c/0x510 kernel/time/alarmtimer.c:811 __do_sys_clock_nanosleep kernel/time/posix-timers.c:1235 [inline] __se_sys_clock_nanosleep kernel/time/posix-timers.c:1213 [inline] __x64_sys_clock_nanosleep+0x326/0x4e0 kernel/time/posix-timers.c:1213 do_syscall_64+0xb8/0x3a0 arch/x86/entry/common.c:290 alarm_timer_nsleep() uses ktime_add() to add the current time and the relative expiry value. ktime_add() has no sanity checks so the addition can overflow when the relative timeout is large enough. Use ktime_add_safe() which has the necessary sanity checks in place and limits the result to the valid range. Fixes: 9a7adcf5c6de ("timers: Posix interface for alarm-timers") Reported-by: Team OWL337 Signed-off-by: Thomas Gleixner Cc: John Stultz Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1807020926360.1595@nanos.tec.linutronix.de --- kernel/time/alarmtimer.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 78a3cc5..fa5de5e 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -808,7 +808,8 @@ static int alarm_timer_nsleep(const clockid_t which_clock, int flags, /* Convert (if necessary) to absolute time */ if (flags != TIMER_ABSTIME) { ktime_t now = alarm_bases[type].gettime(); - exp = ktime_add(now, exp); + + exp = ktime_add_safe(now, exp); } ret = alarmtimer_do_nsleep(&alarm, exp, type); -- cgit v1.1