linux-kernel - Re: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.21.1907282013310.1791@nanos.tec.linutronix.de>
Date:   Sun, 28 Jul 2019 20:14:27 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Arnd Bergmann <arnd@...db.de>
cc:     Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Paul Bolle <pebolle@...cali.nl>
Subject: Re: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace
 on i386

On Sun, 28 Jul 2019, Arnd Bergmann wrote:

> On Sun, Jul 28, 2019 at 12:30 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> > On Sun, 28 Jul 2019, Arnd Bergmann wrote:
> > > On Sat, Jul 27, 2019 at 7:53 PM Andy Lutomirski <luto@...nel.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 :)