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From:   Jann Horn <jannh@google.com>
Date:   Fri, 30 Oct 2020 04:07:44 +0100
Message-ID: <CAG48ez1FQVkt78129WozBwFbVhAPyAr9oJAHFHAbbNxEBr9h1g@mail.gmail.com>
Subject: Re: [PATCH v22 08/12] landlock: Add syscall implementations
To:     =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>,
        Kees Cook <keescook@chromium.org>
Cc:     James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@amacapital.net>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Jeff Dike <jdike@addtoit.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Shuah Khan <shuah@kernel.org>,
        Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@linux.microsoft.com>
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On Thu, Oct 29, 2020 at 12:30 PM Micka=C3=ABl Sala=C3=BCn <mic@digikod.net>=
 wrote:
> On 29/10/2020 02:06, Jann Horn wrote:
> > On Tue, Oct 27, 2020 at 9:04 PM Micka=C3=ABl Sala=C3=BCn <mic@digikod.n=
et> wrote:
> >> These 3 system calls are designed to be used by unprivileged processes
> >> to sandbox themselves:
[...]
> >> +       /*
> >> +        * Similar checks as for seccomp(2), except that an -EPERM may=
 be
> >> +        * returned.
> >> +        */
> >> +       if (!task_no_new_privs(current)) {
> >> +               err =3D security_capable(current_cred(), current_user_=
ns(),
> >> +                               CAP_SYS_ADMIN, CAP_OPT_NOAUDIT);
> >
> > I think this should be ns_capable_noaudit(current_user_ns(), CAP_SYS_AD=
MIN)?
>
> Right. The main difference is that ns_capable*() set PF_SUPERPRIV in
> current->flags. I guess seccomp should use ns_capable_noaudit() as well?

Yeah. That seccomp code is from commit e2cfabdfd0756, with commit date
in April 2012, while ns_capable_noaudit() was introduced in commit
98f368e9e263, with commit date in June 2016; the seccomp code predates
the availability of that API.

Do you want to send a patch to Kees for that, or should I?