This is a note to let you know that I've just added the patch titled
time: Always make sure wall_to_monotonic isn't positive
to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: time-always-make-sure-wall_to_monotonic-isn-t-positive.patch and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
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; }
Patches currently in stable-queue which might be from udknight@gmail.com are
queue-3.18/time-always-make-sure-wall_to_monotonic-isn-t-positive.patch