Re: [PATCH 1/2] linux: clock_settime: Remove check for nanoseconds validity

[Paul Eggert <eggert@cs.ucla.edu>]

On 11/27/19 9:04 AM, Lukasz Majewski wrote:

>> a/sysdeps/unix/sysv/linux/clock_settime.c +++
>> b/sysdeps/unix/sysv/linux/clock_settime.c @@ -25,13 +25,6 @@
>>   int
>>   __clock_settime64 (clockid_t clock_id, const struct __timespec64
>> *tp) {
>> -  /* Make sure the time cvalue is OK.  */
>> -  if (! valid_nanoseconds (tp->tv_nsec))
>> -    {
>> -      __set_errno (EINVAL);
>> -      return -1;
>> -    }
>> -
> I'm just wondering if this patch is OK, as with other patches, which
> convert time to use 64 bit syscalls we do rely on Linux kernel to
> check the nanoseconds (and return proper error).

Suppose tp->tv_sec == 1 && tp->tv_nsec == -1 && !defined 
__ASSUME_TIME64_SYSCALLS && !defined __NR_clock_settime64. Then the 
current code will fail with errno == EINVAL, but with the proposed patch 
the code will succeed and set the time to 1 second after the Epoch.

Code should always check for valid nanoseconds before calling 
valid_timespec64_to_timespec with possibly-invalid input. In this 
function, the check can be done at about the same time as the 
in_time_t_range check; that'd be better than what the current code does.