releases/4.9.131/alarmtimer-prevent-overflow-for-relative-nanosleep.patch

   1 From foo@baz Sat Sep 29 04:29:21 PDT 2018
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Mon, 2 Jul 2018 09:34:29 +0200
   4 Subject: alarmtimer: Prevent overflow for relative nanosleep
   5
   6 From: Thomas Gleixner <tglx@linutronix.de>
   7
   8 [ Upstream commit 5f936e19cc0ef97dbe3a56e9498922ad5ba1edef ]
   9
  10 Air Icy reported:
  11
  12   UBSAN: Undefined behaviour in kernel/time/alarmtimer.c:811:7
  13   signed integer overflow:
  14   1529859276030040771 + 9223372036854775807 cannot be represented in type 'long long int'
  15   Call Trace:
  16    alarm_timer_nsleep+0x44c/0x510 kernel/time/alarmtimer.c:811
  17    __do_sys_clock_nanosleep kernel/time/posix-timers.c:1235 [inline]
  18    __se_sys_clock_nanosleep kernel/time/posix-timers.c:1213 [inline]
  19    __x64_sys_clock_nanosleep+0x326/0x4e0 kernel/time/posix-timers.c:1213
  20    do_syscall_64+0xb8/0x3a0 arch/x86/entry/common.c:290
  21
  22 alarm_timer_nsleep() uses ktime_add() to add the current time and the
  23 relative expiry value. ktime_add() has no sanity checks so the addition
  24 can overflow when the relative timeout is large enough.
  25
  26 Use ktime_add_safe() which has the necessary sanity checks in place and
  27 limits the result to the valid range.
  28
  29 Fixes: 9a7adcf5c6de ("timers: Posix interface for alarm-timers")
  30 Reported-by: Team OWL337 <icytxw@gmail.com>
  31 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  32 Cc: John Stultz <john.stultz@linaro.org>
  33 Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1807020926360.1595@nanos.tec.linutronix.de
  34 Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
  35 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  36 ---
  37  kernel/time/alarmtimer.c |    3 ++-
  38  1 file changed, 2 insertions(+), 1 deletion(-)
  39
  40 --- a/kernel/time/alarmtimer.c
  41 +++ b/kernel/time/alarmtimer.c
  42 @@ -786,7 +786,8 @@ static int alarm_timer_nsleep(const cloc
  43         /* Convert (if necessary) to absolute time */
  44         if (flags != TIMER_ABSTIME) {
  45                 ktime_t now = alarm_bases[type].gettime();
  46 -               exp = ktime_add(now, exp);
  47 +
  48 +               exp = ktime_add_safe(now, exp);
  49         }
  50
  51         if (alarmtimer_do_nsleep(&alarm, exp))