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

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Message-ID: <163f298b-b492-fee0-b475-102ae8170419@digikod.net>
Date:   Fri, 30 Oct 2020 13:41:29 +0100
From:   Mickaël Salaün <mic@...ikod.net>
To:     Jann Horn <jannh@...gle.com>, 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 30/10/2020 04:07, Jann Horn wrote:
> 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?
> 

I found another case of this inconsistency in ptrace. I sent patches:
https://lore.kernel.org/lkml/20201030123849.770769-1-mic@digikod.net/