Messages in this thread Patch in this message | | | From | Yu Liao <> | Subject | [PATCH v2] timekeeping: Make sure wall_to_monotonic isn't positive | Date | Mon, 13 Dec 2021 21:57:27 +0800 |
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After commit e1d7ba873555 ("time: Always make sure wall_to_monotonic isn't positive"), we can still change wall_to_monotonic to positive by running the following code: int main(void) { struct timespec time;
clock_gettime(CLOCK_MONOTONIC, &time); time.tv_nsec = 0; clock_settime(CLOCK_REALTIME, &time); return 0; }
The reason is that the parameters of timespec64_compare() may be unnormalized, and timespec64_compare() simply compare tv_sec, for example: wall_to_monotonic = {tv_sec = -10, tv_nsec = 900000000} ts_delta = {tv_sec = -9, tv_nsec = -900000000}
timespec64_compare() result is wall_to_monotonic < ts_delta, but actually wall_to_monotonic > ts_delta. After normalized, the result of timespec64_compare() is correct: wall_to_monotonic = {tv_sec = -10, tv_nsec = 900000000} ts_delta = {tv_sec = -10, tv_nsec = 100000000}
Use timespec64_sub() to ensure ts_delta normalized, and the code looks more concise.
Signed-off-by: Yu Liao <liaoyu15@huawei.com> --- kernel/time/timekeeping.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index b348749a9fc6..dcdcb85121e4 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1306,8 +1306,7 @@ int do_settimeofday64(const struct timespec64 *ts) timekeeping_forward_now(tk); xt = tk_xtime(tk); - ts_delta.tv_sec = ts->tv_sec - xt.tv_sec; - ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec; + ts_delta = timespec64_sub(*ts, xt); if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { ret = -EINVAL; -- 2.25.1
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