linux-kernel - Re: [PATCH v14 1/6] LSM: Security blob abstraction

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Message-ID: <CAGXu5jJUiwjtEuCUB89NG9EQpxNytaaPT9PdPyHN_qUhwa+YUw@mail.gmail.com>
Date:	Mon, 29 Jul 2013 14:15:39 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	LKLM <linux-kernel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	SE Linux <selinux@...ho.nsa.gov>,
	James Morris <jmorris@...ei.org>,
	John Johansen <john.johansen@...onical.com>,
	Eric Paris <eparis@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [PATCH v14 1/6] LSM: Security blob abstraction

On Thu, Jul 25, 2013 at 11:32 AM, Casey Schaufler
<casey@...aufler-ca.com> wrote:
> Subject: [PATCH v14 1/6] LSM: Security blob abstraction
>
> Create an abstracted interface for security blobs.
> Instead of directly accessing security blob pointers
> Use lsm_get and lsm_set functions that hide the actual
> mechanism used to maintain the security blobs. This
> affects most uses of inode->i_security, file->f_security,
> cred->security and similar fields in keys, sockets,
> superblocks, ipc and keys.
>
> The use of a single 32 bit integer to refer to a security blob
> does not scale to the case where there may be more than one
> relevant security blob. Where it is possible to do so the use
> of secids (u32) has been replaced with a struct secids, which
> provides for multiple u32 values. There are components where
> u32 secids remain at the request of the maintainer of that
> component.

If I boot with "security=apparmor", lsm_set_blob ends up with a NULL
"bp" and Oopses the kernel. Still happens with
"security=yama,apparmor". As soon as I add smack anywhere in the list,
everything is fine. It seems like the AppArmor init needs to be
changed to:

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 78b271a..512f430 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -875,9 +875,9 @@ static int __init set_init_cxt(void)
                return -ENOMEM;

        cxt->profile = aa_get_profile(root_ns->unconfined);
-       lsm_set_cred(cred, cxt, &apparmor_ops);
-
-       return 0;
+       printk(KERN_INFO "AA: cred:%p cxt:%p &apparmor_ops:%p\n",
+               cred, cxt, &apparmor_ops);
+       return lsm_set_init_cred(cred, cxt, &apparmor_ops);
 }

 static int __init apparmor_init(void)

Or maybe it still needs lsm_set_cred, but an earlier
lsm_set_init_cred? It's not clear to me yet.

-Kees

-- 
Kees Cook
Chrome OS Security
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