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Subject: Re: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <20190723091820.GZ3402@hirez.programming.kicks-ass.net>
Date:   Tue, 23 Jul 2019 07:04:46 -0700
Cc:     Andy Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
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Message-Id: <17F255F9-5084-4E30-9AD6-80A4F49BD0D8@amacapital.net>
References: <20190719170343.GA13680@linux.intel.com> <19EF7AC8-609A-4E86-B45E-98DFE965DAAB@amacapital.net> <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> <20190723091820.GZ3402@hirez.programming.kicks-ass.net>
To:     Peter Zijlstra <peterz@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Jul 23, 2019, at 2:18 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>=20
>> On Mon, Jul 22, 2019 at 04:47:36PM -0700, Andy Lutomirski wrote:
>>=20
>> I don't love this whole concept, but I also don't have a better idea.
>=20
> Are we really talking about changing the kernel because BPF is expecting
> things? That is, did we just elevate everything BPF can observe to ABI?
>=20

No, this isn=E2=80=99t about internals in the kernel mode sense. It=E2=80=99=
s about the smallish number of cases where the kernel causes user code to do=
 a specific syscall and the user has a policy that doesn=E2=80=99t allow tha=
t syscall.  This is visible to user code via seccomp and ptrace.

Yes, it=E2=80=99s obnoxious.  Do you have any suggestions?=