| From e1d7ba8735551ed79c7a0463a042353574b96da3 Mon Sep 17 00:00:00 2001 |
| From: Wang YanQing <udknight@gmail.com> |
| Date: Tue, 23 Jun 2015 18:38:54 +0800 |
| Subject: time: Always make sure wall_to_monotonic isn't positive |
| |
| From: Wang YanQing <udknight@gmail.com> |
| |
| commit e1d7ba8735551ed79c7a0463a042353574b96da3 upstream. |
| |
| Two issues were found on an IMX6 development board without an |
| enabled RTC device(resulting in the boot time and monotonic |
| time being initialized to 0). |
| |
| Issue 1:exportfs -a generate: |
| "exportfs: /opt/nfs/arm does not support NFS export" |
| Issue 2:cat /proc/stat: |
| "btime 4294967236" |
| |
| The same issues can be reproduced on x86 after running the |
| following code: |
| int main(void) |
| { |
| struct timeval val; |
| int ret; |
| |
| val.tv_sec = 0; |
| val.tv_usec = 0; |
| ret = settimeofday(&val, NULL); |
| return 0; |
| } |
| |
| Two issues are different symptoms of same problem: |
| The reason is a positive wall_to_monotonic pushes boot time back |
| to the time before Epoch, and getboottime will return negative |
| value. |
| |
| In symptom 1: |
| negative boot time cause get_expiry() to overflow time_t |
| when input expire time is 2147483647, then cache_flush() |
| always clears entries just added in ip_map_parse. |
| In symptom 2: |
| show_stat() uses "unsigned long" to print negative btime |
| value returned by getboottime. |
| |
| This patch fix the problem by prohibiting time from being set to a value which |
| would cause a negative boot time. As a result one can't set the CLOCK_REALTIME |
| time prior to (1970 + system uptime). |
| |
| Cc: Prarit Bhargava <prarit@redhat.com> |
| Cc: Richard Cochran <richardcochran@gmail.com> |
| Cc: Ingo Molnar <mingo@kernel.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Signed-off-by: Wang YanQing <udknight@gmail.com> |
| [jstultz: reworded commit message] |
| [msfjarvis: Backport to 3.18 as we are missing the do_settimeofday64 |
| function the upstream commit patches, so we apply the changes to |
| do_settimeofday] |
| Signed-off-by: John Stultz <john.stultz@linaro.org> |
| Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| kernel/time/timekeeping.c | 13 ++++++++++--- |
| 1 file changed, 10 insertions(+), 3 deletions(-) |
| |
| --- a/kernel/time/timekeeping.c |
| +++ b/kernel/time/timekeeping.c |
| @@ -712,6 +712,7 @@ int do_settimeofday(const struct timespe |
| struct timekeeper *tk = &tk_core.timekeeper; |
| struct timespec64 ts_delta, xt, tmp; |
| unsigned long flags; |
| + int ret = 0; |
| |
| if (!timespec_valid_strict(tv)) |
| return -EINVAL; |
| @@ -725,11 +726,16 @@ int do_settimeofday(const struct timespe |
| ts_delta.tv_sec = tv->tv_sec - xt.tv_sec; |
| ts_delta.tv_nsec = tv->tv_nsec - xt.tv_nsec; |
| |
| + if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { |
| + ret = -EINVAL; |
| + goto out; |
| + } |
| + |
| tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta)); |
| |
| tmp = timespec_to_timespec64(*tv); |
| tk_set_xtime(tk, &tmp); |
| - |
| +out: |
| timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET); |
| |
| write_seqcount_end(&tk_core.seq); |
| @@ -738,7 +744,7 @@ int do_settimeofday(const struct timespe |
| /* signal hrtimers about time change */ |
| clock_was_set(); |
| |
| - return 0; |
| + return ret; |
| } |
| EXPORT_SYMBOL(do_settimeofday); |
| |
| @@ -767,7 +773,8 @@ int timekeeping_inject_offset(struct tim |
| |
| /* Make sure the proposed value is valid */ |
| tmp = timespec64_add(tk_xtime(tk), ts64); |
| - if (!timespec64_valid_strict(&tmp)) { |
| + if (timespec64_compare(&tk->wall_to_monotonic, &ts64) > 0 || |
| + !timespec64_valid_strict(&tmp)) { |
| ret = -EINVAL; |
| goto error; |
| } |