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From: Mimi Zohar <zohar@linux.ibm.com>
To: Stefan Berger <stefanb@linux.ibm.com>,
	jejb@linux.ibm.com,
	Christian Brauner <christian.brauner@ubuntu.com>
Cc: linux-integrity@vger.kernel.org, serge@hallyn.com,
	containers@lists.linux.dev, dmitry.kasatkin@gmail.com,
	ebiederm@xmission.com, krzysztof.struczynski@huawei.com,
	roberto.sassu@huawei.com, mpeters@redhat.com, lhinds@redhat.com,
	lsturman@redhat.com, puiterwi@redhat.com, jamjoom@us.ibm.com,
	linux-kernel@vger.kernel.org, paul@paul-moore.com,
	rgb@redhat.com, linux-security-module@vger.kernel.org,
	jmorris@namei.org
Subject: Re: [PATCH v5 15/16] ima: Move dentries into ima_namespace
Date: Fri, 10 Dec 2021 10:48:33 -0500	[thread overview]
Message-ID: <70e68bb6fd8e70b32fa2404768a6240791546496.camel@linux.ibm.com> (raw)
In-Reply-To: <9806a2ba-8b45-3bb8-22c5-797ab2affaac@linux.ibm.com>

On Fri, 2021-12-10 at 10:32 -0500, Stefan Berger wrote:
> On 12/10/21 10:26, Mimi Zohar wrote:
> > On Fri, 2021-12-10 at 09:26 -0500, James Bottomley wrote:
> >> On Fri, 2021-12-10 at 09:17 -0500, Stefan Berger wrote:
> >>> On 12/10/21 08:02, Mimi Zohar wrote:
> >>>> On Fri, 2021-12-10 at 07:40 -0500, Stefan Berger wrote:
> >>>>> On 12/10/21 07:09, Mimi Zohar wrote:
> >>>>>> On Fri, 2021-12-10 at 12:49 +0100, Christian Brauner wrote:
> >>>>>>>> There's still the problem that if you write the policy,
> >>>>>>>> making the file disappear then unmount and remount
> >>>>>>>> securityfs it will come back.  My guess for fixing this is
> >>>>>>>> that we only stash the policy file reference,
> >>>>>>>> create it if NULL but then set the pointer to PTR_ERR(-
> >>>>>>>> EINVAL) or something and refuse to create it for that
> >>>>>>>> value.
> >>>>>>> Some sort of indicator that gets stashed in struct ima_ns
> >>>>>>> that the file does not get recreated on consecutive mounts.
> >>>>>>> That shouldn't be hard to fix.
> >>>>>> The policy file disappearing is for backwards compatibility,
> >>>>>> prior to being able to extend the custom policy.  For embedded
> >>>>>> usecases, allowing the policy to be written exactly once might
> >>>>>> makes sense.  Do we really want/need to continue to support
> >>>>>> removing the policy in namespaces?
> >>>>> I don't have an answer but should the behavior for the same
> >>>>> #define in this case be different for host and namespaces? Or
> >>>>> should we just 'select IMA_WRITE_POLICY and IMA_READ_POLICY' when
> >>>>> IMA_NS is selected?
> >>>> The latter option sounds good.  Being able to analyze the namespace
> >>>> policy is really important.
> >>> Ok, I will adjust the Kconfig for this then. This then warrants the
> >>> question whether to move the dentry into the ima_namespace. The
> >>> current code looks like this.
> >>>
> >>> #if !defined(CONFIG_IMA_WRITE_POLICY) &&
> >>> !defined(CONFIG_IMA_READ_POLICY)
> >>>           securityfs_remove(ns->policy_dentry);
> >>>           ns->policy_dentry = NULL;
> >>>           ns->policy_dentry_removed = true;
> >>> #elif defined(CONFIG_IMA_WRITE_POLICY)
> >>>
> >>> With IMA_NS selecting IMA_WRITE_POLICY and IMA_READ_POLICY the above
> >>> wouldn't be necessary anymore but I find it 'cleaner' to still have
> >>> the dentry isolated rather than it being a global static as it was
> >>> before...
> >> This is really, really why you don't want the semantics inside the
> >> namespace to differ from those outside, because it creates confusion
> >> for the people reading the code, especially with magically forced
> >> config options like this.  I'd strongly suggest you either keep the
> >> semantic in the namespace or eliminate it entirely.
> >>
> >> If you really, really have to make the namespace behave differently,
> >> then use global variables and put a big comment on that code saying it
> >> can never be reached once CONFIG_IMA_NS is enabled.
> > The problem seems to be with removing the securityfs policy file.
> > Instead of removing it, just make it inacessible for the "if
> > !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)"
> > case.
> 
> So we would then leave it up to the one building the kernel to select 
> the proper compile time options (suggested ones being IMA_WRITE_POLICY 
> and IMA_READ_POLICY being enabled?) and behavior of host and IMA 
> namespace is then the same per those options? Removing the file didn't 
> seem the problem to me but more like whether the host should ever behave 
> differently from the namespace.

You proposed "select IMA_WRITE_POLICY and IMA_READ_POLICY'" when IMA_NS
is selected.  At least IMA_READ_POLICY should be enabled for
namespaces.

In addition, if removing the securityfs file after a custom policy is
loaded complicates namespacing, then don't remove it.

thanks,

Mimi


  reply	other threads:[~2021-12-10 15:49 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-08 22:18 [PATCH v5 00/16] ima: Namespace IMA with audit support in IMA-ns Stefan Berger
2021-12-08 22:18 ` [PATCH v5 01/16] ima: Add IMA namespace support Stefan Berger
2021-12-08 22:18 ` [PATCH v5 02/16] ima: Define ns_status for storing namespaced iint data Stefan Berger
2021-12-08 22:18 ` [PATCH v5 03/16] ima: Namespace audit status flags Stefan Berger
2021-12-08 22:18 ` [PATCH v5 04/16] ima: Move delayed work queue and variables into ima_namespace Stefan Berger
2021-12-09 13:11   ` Christian Brauner
2021-12-09 15:09     ` Stefan Berger
2021-12-08 22:18 ` [PATCH v5 05/16] ima: Move IMA's keys queue related " Stefan Berger
2021-12-08 22:18 ` [PATCH v5 06/16] ima: Move policy " Stefan Berger
2021-12-08 22:18 ` [PATCH v5 07/16] ima: Move ima_htable " Stefan Berger
2021-12-08 22:18 ` [PATCH v5 08/16] ima: Move measurement list related variables " Stefan Berger
2021-12-08 22:18 ` [PATCH v5 09/16] ima: Only accept AUDIT rules for IMA non-init_ima_ns namespaces for now Stefan Berger
2021-12-08 22:18 ` [PATCH v5 10/16] ima: Implement hierarchical processing of file accesses Stefan Berger
2021-12-08 22:18 ` [PATCH v5 11/16] securityfs: Only use simple_pin_fs/simple_release_fs for init_user_ns Stefan Berger
2021-12-08 22:18 ` [PATCH v5 12/16] securityfs: Extend securityfs with namespacing support Stefan Berger
2021-12-08 22:18 ` [PATCH v5 13/16] ima: Move some IMA policy and filesystem related variables into ima_namespace Stefan Berger
2021-12-09 19:11   ` Christian Brauner
2021-12-09 20:42     ` Stefan Berger
2021-12-10  0:57     ` Stefan Berger
2021-12-10 11:32       ` Christian Brauner
2021-12-10 13:57         ` Stefan Berger
2021-12-10 14:21           ` James Bottomley
2021-12-11  9:50           ` Christian Brauner
2021-12-11 10:45             ` Christian Brauner
2021-12-13 15:33             ` Stefan Berger
2021-12-13 15:50               ` Christian Brauner
2021-12-13 16:03                 ` Christian Brauner
2021-12-13 16:25                 ` Stefan Berger
2021-12-13 16:37                   ` Christian Brauner
2021-12-13 16:40                 ` Christian Brauner
2021-12-10 20:08         ` Stefan Berger
2021-12-11  8:46           ` Christian Brauner
2021-12-08 22:18 ` [PATCH v5 14/16] ima: Use mac_admin_ns_capable() to check corresponding capability Stefan Berger
2021-12-09  7:22   ` Denis Semakin
2021-12-09 13:23     ` James Bottomley
2021-12-09  8:09   ` Denis Semakin
2021-12-11 15:02     ` Serge E. Hallyn
2021-12-11 15:38       ` Stefan Berger
2021-12-11 16:00         ` James Bottomley
2021-12-08 22:18 ` [PATCH v5 15/16] ima: Move dentries into ima_namespace Stefan Berger
2021-12-09 14:34   ` Christian Brauner
2021-12-09 14:37     ` Christian Brauner
2021-12-09 14:41       ` Christian Brauner
2021-12-09 15:00         ` Stefan Berger
2021-12-09 15:47           ` Christian Brauner
2021-12-09 15:30       ` James Bottomley
2021-12-09 19:38         ` James Bottomley
2021-12-09 20:13           ` Stefan Berger
2021-12-10 11:49           ` Christian Brauner
2021-12-10 12:09             ` Mimi Zohar
2021-12-10 12:40               ` Stefan Berger
2021-12-10 13:02                 ` Mimi Zohar
2021-12-10 14:17                   ` Stefan Berger
2021-12-10 14:26                     ` James Bottomley
2021-12-10 15:26                       ` Mimi Zohar
2021-12-10 15:32                         ` Stefan Berger
2021-12-10 15:48                           ` Mimi Zohar [this message]
2021-12-10 16:40                             ` Stefan Berger
2021-12-10 12:40               ` James Bottomley
2021-12-10 12:54                 ` Mimi Zohar
2021-12-12 14:13             ` James Bottomley
2021-12-13 11:25               ` Christian Brauner
2021-12-08 22:18 ` [PATCH v5 16/16] ima: Setup securityfs for IMA namespace Stefan Berger

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