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Date: Fri, 1 Jun 2018 11:23:11 +1000
From: Patrick Oppenlander <patrick.oppenlander@...il.com>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] SYS_futex FUTEX_WAIT requires a valid timeout argument

On Fri., 1 Jun. 2018, 11:01 Rich Felker, <dalias@...c.org> wrote:

> On Fri, Jun 01, 2018 at 10:49:20AM +1000, patrick.oppenlander@...il.com
> wrote:
> > From: Patrick Oppenlander <patrick.oppenlander@...il.com>
> >
> > ---
> >  src/internal/pthread_impl.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
> > index fc2def63..97522bfe 100644
> > --- a/src/internal/pthread_impl.h
> > +++ b/src/internal/pthread_impl.h
> > @@ -155,8 +155,8 @@ static inline void __wake(volatile void *addr, int
> cnt, int priv)
> >  static inline void __futexwait(volatile void *addr, int val, int priv)
> >  {
> >       if (priv) priv = FUTEX_PRIVATE;
> > -     __syscall(SYS_futex, addr, FUTEX_WAIT|priv, val) != -ENOSYS ||
> > -     __syscall(SYS_futex, addr, FUTEX_WAIT, val);
> > +     __syscall(SYS_futex, addr, FUTEX_WAIT|priv, val, 0) != -ENOSYS ||
> > +     __syscall(SYS_futex, addr, FUTEX_WAIT, val, 0);
> >  }
> >
> >  void __acquire_ptc(void);
> > --
> > 2.17.0
>
> This looks correct. Did you hit things that broke because it was
> missing?
>
> Rich
>

Syscall argument validation in my nommu kernel caught it. I'm sure Linux
would catch it too.

I didn't prove that it causes observable issues in userspace.

Patrick

>

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