Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sun, 28 Jul 2019 20:14:27 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Arnd Bergmann <arnd@arndb.de>
cc:     Andy Lutomirski <luto@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Paul Bolle <pebolle@tiscali.nl>
Subject: Re: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace
 on i386
In-Reply-To: <CAK8P3a0dC5ti8nVMK8-NmmTYeEfKPdLpVf0zrQEnq76fUvh1oA@mail.gmail.com>
Message-ID: <alpine.DEB.2.21.1907282013310.1791@nanos.tec.linutronix.de>
References: <201907221012.41504DCD@keescook> <alpine.DEB.2.21.1907222027090.1659@nanos.tec.linutronix.de> <201907221135.2C2D262D8@keescook> <CALCETrVnV8o_jqRDZua1V0s_fMYweP2J2GbwWA-cLxqb_PShog@mail.gmail.com> <201907221620.F31B9A082@keescook>
 <CALCETrWqu-S3rrg8kf6aqqkXg9Z+TFQHbUgpZEiUU+m8KRARqg@mail.gmail.com> <201907231437.DB20BEBD3@keescook> <alpine.DEB.2.21.1907240038001.27812@nanos.tec.linutronix.de> <201907231636.AD3ED717D@keescook> <alpine.DEB.2.21.1907240155080.2034@nanos.tec.linutronix.de>
 <20190726180103.GE3188@linux.intel.com> <CALCETrUe50sbMx+Pg+fQdVFVeZ_zTffNWGJUmYy53fcHNrOhrQ@mail.gmail.com> <CAK8P3a3_tki1mi4OjLJdaGLwVA7JE0wE1kczE_q7kEpr5e8sMQ@mail.gmail.com> <alpine.DEB.2.21.1907281225410.1791@nanos.tec.linutronix.de>
 <CAK8P3a0dC5ti8nVMK8-NmmTYeEfKPdLpVf0zrQEnq76fUvh1oA@mail.gmail.com>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sun, 28 Jul 2019, Arnd Bergmann wrote:

> On Sun, Jul 28, 2019 at 12:30 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Sun, 28 Jul 2019, Arnd Bergmann wrote:
> > > On Sat, Jul 27, 2019 at 7:53 PM Andy Lutomirski <luto@kernel.org> wrote:
> 
> > Which is totally irrelevant because res is NULL and that NULL pointer check
> > should simply return -EFAULT, which is what the syscall fallback returns
> > because the pointer is NULL.
> >
> > But that NULL pointer check is inconsistent anyway:
> >
> >  - 64 bit does not have it and never had
> >
> >  - the vdso is not capable of handling faults properly anyway. If the
> >    pointer is not valid, then it will segfault. So just preventing the
> >    segfault for NULL is silly.
> >
> > I'm going to just remove it.
> 
> Ah, you are right, I misread.
> 
> Anyway, if we want to keep the traditional behavior and get fewer surprises
> for users of seccomp and anything else that might observe clock_gettime
> behavior, below is how I'd do it. (not even build tested, x86-only. I'll
> send a proper patch if this is where we want to take it).

I posted a series which fixes up the mess 2 hours before you sent this mail :)