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From: Casey Schaufler <casey@schaufler-ca.com>
To: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Tejun Heo <tj@kernel.org>,
	selinux@vger.kernel.org, Paul Moore <paul@paul-moore.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	Linux Security Module list 
	<linux-security-module@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	casey@schaufler-ca.com
Subject: Re: [PATCH v6 5/5] kernfs: initialize security of newly created nodes
Date: Thu, 21 Feb 2019 08:52:33 -0800	[thread overview]
Message-ID: <2de9569d-2368-1dc9-f757-0a7a0a116c16@schaufler-ca.com> (raw)
In-Reply-To: <CAFqZXNvWyBQ5g6nwD4AiePxEDXGP2DY31S0RWttqcRSa90SakA@mail.gmail.com>

On 2/21/2019 1:13 AM, Ondrej Mosnacek wrote:
> On Tue, Feb 19, 2019 at 5:43 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> .....
>> The state you're maintaining is kernfs state, not LSM
>> infrastructure state. The state should be maintained in
>> kernfs, not in the LSM infrastructure.
> But I'm not maintaining any state. I'm merely trying to answer the
> query "Is there anything that will handle this hook? Do I need to
> prepare stuff for it?", which is obviously a query about the LSM
> state. Granted, ideally we wouldn't need to do any preparatory work at
> all, but that would require exposing more of the kernfs internals
> (which brings its own issues, but maybe I'll need to look into that
> approach more...).

It sounds like you're bumping up against the limitations
of the finely honed optimized implementation of kernfs. :(
If it where still the pre-android era, when using an LSM
was rare, the check for an LSM might have made sense. Today,
with the vast majority of systems using LSMs*, optimizing for
the no LSM case is nonsensical.

---
* Android, Tizen, Fedora/RHEL, Ubuntu

> ...
> Kernfs is an important component of the kernel. So is
> the security infrastructure. I would hope you don't want
> to turn this into a contest to see which maintainer has
> the biggest clout.
> Oh, no, you misunderstood my intention. I just got a feeling that this
> thread was turning into a discussion about perceived code ugliness
> (and about which subsystem that ugliness ends up in), which is
> naturally a very subjective topic, so I wanted to know what is the
> opinion of the people that have the final decision about whether the
> code should get in or not. Anyway, I'll try to find a more elegant
> variant of the solution once again, hopefully I manage to get to
> something less controversial.

Thank you. I believe (which, of course, doesn't make it true)
that when a component goes outside the general system architecture
the way that kernfs does *even for performance reasons* that it is
responsible for the edge cases it encounters. I know that I've had
to do a good bit of that in Smack.
  


  reply	other threads:[~2019-02-21 16:52 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-14  9:50 [PATCH v6 0/5] Allow initializing the kernfs node's secctx based on its parent Ondrej Mosnacek
2019-02-14  9:50 ` [PATCH v6 1/5] selinux: try security xattr after genfs for kernfs filesystems Ondrej Mosnacek
2019-02-14 20:49   ` Stephen Smalley
2019-02-15 15:48     ` Ondrej Mosnacek
2019-02-14  9:50 ` [PATCH v6 2/5] kernfs: use simple_xattrs for security attributes Ondrej Mosnacek
2019-02-14  9:50 ` [PATCH v6 3/5] LSM: add new hook for kernfs node initialization Ondrej Mosnacek
2019-02-14  9:50 ` [PATCH v6 4/5] selinux: implement the kernfs_init_security hook Ondrej Mosnacek
2019-02-14  9:50 ` [PATCH v6 5/5] kernfs: initialize security of newly created nodes Ondrej Mosnacek
2019-02-14 15:48   ` Tejun Heo
2019-02-15 15:45     ` Ondrej Mosnacek
2019-02-15 15:50       ` Tejun Heo
2019-02-18 10:03         ` Ondrej Mosnacek
2019-02-18 21:02           ` Tejun Heo
2019-02-19  0:28           ` Casey Schaufler
2019-02-19 14:10             ` Ondrej Mosnacek
2019-02-19 14:21               ` Tejun Heo
2019-02-19 16:43               ` Casey Schaufler
2019-02-21  9:13                 ` Ondrej Mosnacek
2019-02-21 16:52                   ` Casey Schaufler [this message]
2019-02-22 12:52                     ` Ondrej Mosnacek

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