linux-kernel - Re: [PATCH v3 19/25] commoncap: handle fsid mappings with vfs caps

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Message-ID: <CAG48ez2ikuZQTctjR0RAXYUFrSsJdyn98cKGn5hGEhYjzWfO8g@mail.gmail.com>
Date:   Wed, 19 Feb 2020 16:53:47 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Stéphane Graber <stgraber@...ntu.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Stephen Barber <smbarber@...omium.org>,
        Seth Forshee <seth.forshee@...onical.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Phil Estes <estesp@...il.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v3 19/25] commoncap: handle fsid mappings with vfs caps

On Tue, Feb 18, 2020 at 3:35 PM Christian Brauner
<christian.brauner@...ntu.com> wrote:
> Switch vfs cap helpers to lookup fsids in the fsid mappings. If no fsid
> mappings are setup the behavior is unchanged, i.e. fsids are looked up in the
> id mappings.
[...]
> diff --git a/security/commoncap.c b/security/commoncap.c
[...]
> @@ -328,7 +328,7 @@ static bool rootid_owns_currentns(kuid_t kroot)
>                 return false;
>
>         for (ns = current_user_ns(); ; ns = ns->parent) {
> -               if (from_kuid(ns, kroot) == 0)
> +               if (from_kfsuid(ns, kroot) == 0)
>                         return true;
>                 if (ns == &init_user_ns)
>                         break;

Nit: Maybe change the name of this function to something that makes it
clear that this operates in the fsuid mapping domain.