releases/3.18.85/time-always-make-sure-wall_to_monotonic-isn-t-positive.patch

   1 From e1d7ba8735551ed79c7a0463a042353574b96da3 Mon Sep 17 00:00:00 2001
   2 From: Wang YanQing <udknight@gmail.com>
   3 Date: Tue, 23 Jun 2015 18:38:54 +0800
   4 Subject: time: Always make sure wall_to_monotonic isn't positive
   5
   6 From: Wang YanQing <udknight@gmail.com>
   7
   8 commit e1d7ba8735551ed79c7a0463a042353574b96da3 upstream.
   9
  10 Two issues were found on an IMX6 development board without an
  11 enabled RTC device(resulting in the boot time and monotonic
  12 time being initialized to 0).
  13
  14 Issue 1:exportfs -a generate:
  15        "exportfs: /opt/nfs/arm does not support NFS export"
  16 Issue 2:cat /proc/stat:
  17        "btime 4294967236"
  18
  19 The same issues can be reproduced on x86 after running the
  20 following code:
  21         int main(void)
  22         {
  23             struct timeval val;
  24             int ret;
  25
  26             val.tv_sec = 0;
  27             val.tv_usec = 0;
  28             ret = settimeofday(&val, NULL);
  29             return 0;
  30         }
  31
  32 Two issues are different symptoms of same problem:
  33 The reason is a positive wall_to_monotonic pushes boot time back
  34 to the time before Epoch, and getboottime will return negative
  35 value.
  36
  37 In symptom 1:
  38           negative boot time cause get_expiry() to overflow time_t
  39           when input expire time is 2147483647, then cache_flush()
  40           always clears entries just added in ip_map_parse.
  41 In symptom 2:
  42           show_stat() uses "unsigned long" to print negative btime
  43           value returned by getboottime.
  44
  45 This patch fix the problem by prohibiting time from being set to a value which
  46 would cause a negative boot time. As a result one can't set the CLOCK_REALTIME
  47 time prior to (1970 + system uptime).
  48
  49 Cc: Prarit Bhargava <prarit@redhat.com>
  50 Cc: Richard Cochran <richardcochran@gmail.com>
  51 Cc: Ingo Molnar <mingo@kernel.org>
  52 Cc: Thomas Gleixner <tglx@linutronix.de>
  53 Signed-off-by: Wang YanQing <udknight@gmail.com>
  54 [jstultz: reworded commit message]
  55 [msfjarvis: Backport to 3.18 as we are missing the do_settimeofday64
  56 function the upstream commit patches, so we apply the changes to
  57 do_settimeofday]
  58 Signed-off-by: John Stultz <john.stultz@linaro.org>
  59 Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>
  60 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  61 ---
  62  kernel/time/timekeeping.c |   13 ++++++++++---
  63  1 file changed, 10 insertions(+), 3 deletions(-)
  64
  65 --- a/kernel/time/timekeeping.c
  66 +++ b/kernel/time/timekeeping.c
  67 @@ -712,6 +712,7 @@ int do_settimeofday(const struct timespe
  68         struct timekeeper *tk = &tk_core.timekeeper;
  69         struct timespec64 ts_delta, xt, tmp;
  70         unsigned long flags;
  71 +       int ret = 0;
  72
  73         if (!timespec_valid_strict(tv))
  74                 return -EINVAL;
  75 @@ -725,11 +726,16 @@ int do_settimeofday(const struct timespe
  76         ts_delta.tv_sec = tv->tv_sec - xt.tv_sec;
  77         ts_delta.tv_nsec = tv->tv_nsec - xt.tv_nsec;
  78
  79 +       if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
  80 +               ret = -EINVAL;
  81 +               goto out;
  82 +       }
  83 +
  84         tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
  85
  86         tmp = timespec_to_timespec64(*tv);
  87         tk_set_xtime(tk, &tmp);
  88 -
  89 +out:
  90         timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
  91
  92         write_seqcount_end(&tk_core.seq);
  93 @@ -738,7 +744,7 @@ int do_settimeofday(const struct timespe
  94         /* signal hrtimers about time change */
  95         clock_was_set();
  96
  97 -       return 0;
  98 +       return ret;
  99  }
 100  EXPORT_SYMBOL(do_settimeofday);
 101
 102 @@ -767,7 +773,8 @@ int timekeeping_inject_offset(struct tim
 103
 104         /* Make sure the proposed value is valid */
 105         tmp = timespec64_add(tk_xtime(tk),  ts64);
 106 -       if (!timespec64_valid_strict(&tmp)) {
 107 +       if (timespec64_compare(&tk->wall_to_monotonic, &ts64) > 0 ||
 108 +               !timespec64_valid_strict(&tmp)) {
 109                 ret = -EINVAL;
 110                 goto error;
 111         }