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From:   Andy Lutomirski <luto@kernel.org>
Date:   Sat, 12 Oct 2019 16:12:49 -0700
Message-ID: <CALCETrWF61dmSpMEYvqa2FHWL8Zj6GJtevFTfymV20CCjiqRcg@mail.gmail.com>
Subject: Re: [PATCH 6/7] Allow users to require UFFD_SECURE
To:     Daniel Colascione <dancol@google.com>
Cc:     Linux API <linux-api@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, lokeshgidra@google.com,
        Nick Kralevich <nnk@google.com>, nosh@google.com,
        Tim Murray <timmurray@google.com>
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On Sat, Oct 12, 2019 at 12:16 PM Daniel Colascione <dancol@google.com> wrote:
>
> This change adds 2 as an allowable value for
> unprivileged_userfaultfd. (Previously, this sysctl could be either 0
> or 1.) When unprivileged_userfaultfd is 2, users with CAP_SYS_PTRACE
> may create userfaultfd with or without UFFD_SECURE, but users without
> CAP_SYS_PTRACE must pass UFFD_SECURE to userfaultfd in order for the
> system call to succeed, effectively forcing them to opt into
> additional security checks.

This patch can go away entirely if you make UFFD_SECURE automatic.