linux-kernel - Re: [PATCH v22 08/12] landlock: Add syscall implementations

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Date:   Fri, 30 Oct 2020 04:07:44 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        Kees Cook <keescook@...omium.org>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Jeff Dike <jdike@...toit.com>,
        Jonathan Corbet <corbet@....net>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Richard Weinberger <richard@....at>,
        Shuah Khan <shuah@...nel.org>,
        Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v22 08/12] landlock: Add syscall implementations

On Thu, Oct 29, 2020 at 12:30 PM Mickaël Salaün <mic@...ikod.net> wrote:
> On 29/10/2020 02:06, Jann Horn wrote:
> > On Tue, Oct 27, 2020 at 9:04 PM Mickaël Salaün <mic@...ikod.net> 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 = 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_ADMIN)?
>
> 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?