From: Wang YanQing <[email protected]>
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 <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Wang YanQing <[email protected]>
[jstultz: reworded commit message]
Signed-off-by: John Stultz <[email protected]>
---
kernel/time/timekeeping.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index bca3667..4cdb771 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -911,6 +911,7 @@ int do_settimeofday64(const struct timespec64 *ts)
struct timekeeper *tk = &tk_core.timekeeper;
struct timespec64 ts_delta, xt;
unsigned long flags;
+ int ret = 0;
if (!timespec64_valid_strict(ts))
return -EINVAL;
@@ -924,10 +925,15 @@ int do_settimeofday64(const struct timespec64 *ts)
ts_delta.tv_sec = ts->tv_sec - xt.tv_sec;
ts_delta.tv_nsec = ts->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));
tk_set_xtime(tk, ts);
-
+out:
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
write_seqcount_end(&tk_core.seq);
@@ -936,7 +942,7 @@ int do_settimeofday64(const struct timespec64 *ts)
/* signal hrtimers about time change */
clock_was_set();
- return 0;
+ return ret;
}
EXPORT_SYMBOL(do_settimeofday64);
@@ -965,7 +971,8 @@ int timekeeping_inject_offset(struct timespec *ts)
/* 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;
}
--
1.9.1
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