linux-kernel - Re: [PATCH v8 2/3] Teach SELinux about anonymous inodes

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Date:   Mon, 31 Aug 2020 14:05:43 -0400
From:   Stephen Smalley <stephen.smalley.work@...il.com>
To:     Lokesh Gidra <lokeshgidra@...gle.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        James Morris <jmorris@...ei.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Daniel Colascione <dancol@...col.org>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        KP Singh <kpsingh@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Thomas Cedeno <thomascedeno@...gle.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Matthew Garrett <matthewgarrett@...gle.com>,
        Aaron Goidel <acgoide@...ho.nsa.gov>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        YueHaibing <yuehaibing@...wei.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Adrian Reber <areber@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        SElinux list <selinux@...r.kernel.org>, kaleshsingh@...gle.com,
        calin@...gle.com, surenb@...gle.com,
        Nick Kralevich <nnk@...gle.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        kernel-team@...roid.com, Daniel Colascione <dancol@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v8 2/3] Teach SELinux about anonymous inodes

On Thu, Aug 27, 2020 at 2:35 AM Lokesh Gidra <lokeshgidra@...gle.com> wrote:
>
> From: Daniel Colascione <dancol@...gle.com>
>
> This change uses the anon_inodes and LSM infrastructure introduced in
> the previous patch to give SELinux the ability to control
> anonymous-inode files that are created using the new anon_inode_getfd_secure()
> function.
>
> A SELinux policy author detects and controls these anonymous inodes by
> adding a name-based type_transition rule that assigns a new security
> type to anonymous-inode files created in some domain. The name used
> for the name-based transition is the name associated with the
> anonymous inode for file listings --- e.g., "[userfaultfd]" or
> "[perf_event]".
>
> Example:
>
> type uffd_t;
> type_transition sysadm_t sysadm_t : anon_inode uffd_t "[userfaultfd]";
> allow sysadm_t uffd_t:anon_inode { create };
>
> (The next patch in this series is necessary for making userfaultfd
> support this new interface.  The example above is just
> for exposition.)
>
> Signed-off-by: Daniel Colascione <dancol@...gle.com>
> Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> Acked-by: Stephen Smalley <stephen.smalley.work@...il.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> ---
>  security/selinux/hooks.c            | 53 +++++++++++++++++++++++++++++
>  security/selinux/include/classmap.h |  2 ++
>  2 files changed, 55 insertions(+)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a340986aa92e..b83f56e5ef40 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2926,6 +2926,58 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
>         return 0;
>  }
>
> +static int selinux_inode_init_security_anon(struct inode *inode,
> +                                           const struct qstr *name,
> +                                           const struct inode *context_inode)
> +{
> +       const struct task_security_struct *tsec = selinux_cred(current_cred());
> +       struct common_audit_data ad;
> +       struct inode_security_struct *isec;
> +       int rc;
> +
> +       if (unlikely(!selinux_state.initialized))

This should use selinux_initialized(&selinux_state) instead.