linux-kernel - Re: [PATCH v13 1/3] fs: Add trusted_for(2) syscall implementation and related sysctl

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Date:   Thu, 7 Oct 2021 12:25:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christian Heimes <christian@...hon.org>,
        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>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        James Morris <jmorris@...ei.org>, Jan Kara <jack@...e.cz>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        "Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Paul Moore <paul@...l-moore.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>,
        Thibaut Sautereau <thibaut.sautereau@....gouv.fr>,
        Vincent Strubel <vincent.strubel@....gouv.fr>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v13 1/3] fs: Add trusted_for(2) syscall implementation
 and related sysctl

On Thu, Oct 07, 2021 at 08:23:18PM +0200, Mickaël Salaün wrote:
> From: Mickaël Salaün <mic@...ux.microsoft.com>
> 
> The trusted_for() syscall enables user space tasks to check that files
> are trusted to be executed or interpreted by user space.  This may allow
> script interpreters to check execution permission before reading
> commands from a file, or dynamic linkers to allow shared object loading.
> This may be seen as a way for a trusted task (e.g. interpreter) to check
> the trustworthiness of files (e.g. scripts) before extending its control
> flow graph with new ones originating from these files.
> [...]
>  aio-nr & aio-max-nr
> @@ -382,3 +383,52 @@ Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
>  on a 64bit one.
>  The current default value for  max_user_watches  is the 1/25 (4%) of the
>  available low memory, divided for the "watch" cost in bytes.
> +
> +
> +trust_policy
> +------------

bikeshed: can we name this "trusted_for_policy"? Both "trust" and
"policy" are very general words, but "trusted_for" (after this series)
will have a distinct meaning, so "trusted_for_policy" becomes more
specific/searchable.

With that renamed, I think it looks good! I'm looking forward to
interpreters using this. :)

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook