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Subject[PATCH 3.18 33/67] time: Always make sure wall_to_monotonic isnt positive
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

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;
}

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