Re: [PATCH 1/2] futex: adjust a futex timeout with a per-timens offset

[Andrei Vagin <avagin@gmail.com>]

On Thu, Oct 15, 2020 at 04:13:42PM +0200, Thomas Gleixner wrote:
> On Thu, Oct 15 2020 at 14:26, Dmitry Safonov wrote:
> 
> > On 10/15/20 8:29 AM, Andrei Vagin wrote:
> >> For all commands except FUTEX_WAIT, timeout is interpreted as an
> >> absolute value. This absolute value is inside the task's time namespace
> >> and has to be converted to the host's time.
> >> 
> >> Cc: <stable@vger.kernel.org>
> >> Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens offsets")
> >> Reported-by: Hans van der Laan <j.h.vanderlaan@student.utwente.nl>
> >> Signed-off-by: Andrei Vagin <avagin@gmail.com>[..]
> >> @@ -3797,6 +3798,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
> >>  		t = timespec64_to_ktime(ts);
> >>  		if (cmd == FUTEX_WAIT)
> >>  			t = ktime_add_safe(ktime_get(), t);
> >> +		else if (!(cmd & FUTEX_CLOCK_REALTIME))
> >> +			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
> >
> > Err, it probably should be
> > : else if (!(op & FUTEX_CLOCK_REALTIME))

Dmitry, thank you for catching this.

> 
> Duh, you are right. I stared at it for a while and did not spot it.
> 
> > And there's also
> > : SYSCALL_DEFINE6(futex_time32, ...)
> > which wants to be patched.
> 
> Indeed. I zapped the commits.

I sent a new version. This time, I extended the test to check
FUTEX_CLOCK_REALTIME and I compiled and run the compat version.
Everything works as it should be.

Thanks,
Andrei