On Sun, Nov 26, 2017 at 12:55:11PM +0530, Harsh Shandilya wrote:
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).
Change-Id: I19acf5df5cc34dd388de0dc633723fe73adc077e 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
kernel/time/timekeeping.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
Thanks for this, now queued up.
greg k-h