Date: Mon, 6 May 2019 14:45:02 -0400 From: Mark Johnston <markj@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r347063 - head/sys/kern Message-ID: <20190506184502.GA35464@raichu> In-Reply-To: <335d828e-ac61-bc59-bac3-f80f27b951c7@FreeBSD.org> References: <201905032126.x43LQilu092655@repo.freebsd.org> <335d828e-ac61-bc59-bac3-f80f27b951c7@FreeBSD.org>
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On Mon, May 06, 2019 at 11:07:18AM -0700, John Baldwin wrote: > On 5/3/19 2:26 PM, Mark Johnston wrote: > > Author: markj > > Date: Fri May 3 21:26:44 2019 > > New Revision: 347063 > > URL: https://svnweb.freebsd.org/changeset/base/347063 > > > > Log: > > Disallow excessively small times of day in clock_settime(2). > > > > Reported by: syzkaller > > Reviewed by: cem, kib > > MFC after: 1 week > > Sponsored by: The FreeBSD Foundation > > Differential Revision: https://reviews.freebsd.org/D20151 > > > > Modified: > > head/sys/kern/kern_time.c > > > > Modified: head/sys/kern/kern_time.c > > ============================================================================== > > --- head/sys/kern/kern_time.c Fri May 3 21:13:09 2019 (r347062) > > +++ head/sys/kern/kern_time.c Fri May 3 21:26:44 2019 (r347063) > > @@ -412,7 +412,9 @@ kern_clock_settime(struct thread *td, clockid_t clock_ > > if (ats->tv_nsec < 0 || ats->tv_nsec >= 1000000000 || > > ats->tv_sec < 0) > > return (EINVAL); > > - if (!allow_insane_settime && ats->tv_sec > 8000ULL * 365 * 24 * 60 * 60) > > + if (!allow_insane_settime && > > + (ats->tv_sec > 8000ULL * 365 * 24 * 60 * 60 || > > + ats->tv_sec < utc_offset())) > > return (EINVAL); > > /* XXX Don't convert nsec->usec and back */ > > TIMESPEC_TO_TIMEVAL(&atv, ats); > > Pardon my ignorance, but I can't see why you are checking against utc_offset() > vs some small constant? None of the discussion in the review mentioned the > reason for using this particular value, and I didn't see any comparisons > against utc_offset or kernadjtz in kern_clock_setttime() or settime() that > would have underflowed or panicked. Can you give a bit more detail on why > utc_offset() is the lower bound? Thanks. I chose it because we subtract utc_offset() from the time passed in to clock_settime(); see settime_task_func(). That subtraction caused the underflow that later caused the observed panics.
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