linux-kernel - Re: [RFC PATCH v9 0/3] Add introspect_access(2) (was O

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Date:   Mon, 14 Sep 2020 18:43:17 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Arnd Bergmann <arnd@...db.de>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        linux-api@...r.kernel.org
Cc:     James Morris <jmorris@...ei.org>,
        Matthew Wilcox <willy@...radead.org>,
        Mimi Zohar <zohar@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        Aleksa Sarai <cyphar@...har.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christian Heimes <christian@...hon.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Deven Bowers <deven.desai@...ux.microsoft.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Eric Chiang <ericchiang@...gle.com>,
        Florian Weimer <fweimer@...hat.com>, Jan Kara <jack@...e.cz>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Philippe Trébuchet 
        <philippe.trebuchet@....gouv.fr>,
        Scott Shell <scottsh@...rosoft.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        Steve Dower <steve.dower@...hon.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Thibaut Sautereau <thibaut.sautereau@...p-os.org>,
        Vincent Strubel <vincent.strubel@....gouv.fr>,
        kernel-hardening@...ts.openwall.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH v9 0/3] Add introspect_access(2) (was O_MAYEXEC)

Arnd and Michael,

What do you think of "should_faccessat" or "entrusted_faccessat" for
this new system call?


On 12/09/2020 02:28, James Morris wrote:
> On Thu, 10 Sep 2020, Matthew Wilcox wrote:
> 
>> On Thu, Sep 10, 2020 at 08:38:21PM +0200, Mickaël Salaün wrote:
>>> There is also the use case of noexec mounts and file permissions. From
>>> user space point of view, it doesn't matter which kernel component is in
>>> charge of defining the policy. The syscall should then not be tied with
>>> a verification/integrity/signature/appraisal vocabulary, but simply an
>>> access control one.
>>
>> permission()?
>>
> 
> The caller is not asking the kernel to grant permission, it's asking 
> "SHOULD I access this file?"
> 
> The caller doesn't know, for example, if the script file it's about to 
> execute has been signed, or if it's from a noexec mount. It's asking the 
> kernel, which does know. (Note that this could also be extended to reading 
> configuration files).
> 
> How about: should_faccessat ?
> 

Sounds good to me.