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From: Stephen Smalley <sds@tycho.nsa.gov>
To: Daniel Colascione <dancol@google.com>
Cc: Tim Murray <timmurray@google.com>,
	SElinux list <selinux@vger.kernel.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	kvm@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
	paul@paul-moore.com, Nick Kralevich <nnk@google.com>,
	Lokesh Gidra <lokeshgidra@google.com>
Subject: Re: [PATCH 2/3] Teach SELinux about anonymous inodes
Date: Fri, 14 Feb 2020 13:02:43 -0500
Message-ID: <23f725ca-5b5a-5938-fcc8-5bbbfc9ba9bc@tycho.nsa.gov> (raw)
In-Reply-To: <CAKOZuev-=7Lgu35E3tzpHQn0m_KAvvrqi+ZJr1dpqRjHERRSqg@mail.gmail.com>

On 2/14/20 12:21 PM, Daniel Colascione wrote:
> On Fri, Feb 14, 2020 at 8:38 AM Stephen Smalley <sds@tycho.nsa.gov> wrote:
>> That's assuming you are ok with having to define these type_transition
>> rules for the userfaultfd case instead of having your own separate
>> security class.  Wondering how many different anon inode names/classes
>> there are in the kernel today and how much they change over time; for a
>> small, relatively stable set, separate classes might be ok; for a large,
>> dynamic set, type transitions should scale better.
> 
> I think we can get away without a class per anonymous-inode-type. I do
> wonder whether we need a class for all anonymous inodes, though: if we
> just give them the file class and use the anon inode type name for the
> type_transition rule, isn't it possible that the type_transition rule
> might also fire for plain files with the same names in the last path
> component and the same originating sid? (Maybe I'm not understanding
> type_transition rules properly.) Using a class to encompass all
> anonymous inodes would address this problem (assuming the problem
> exists in the first place).

It shouldn't fire for non-anon inodes because on a (non-anon) file 
creation, security_transition_sid() is passed the parent directory SID 
as the second argument and we only assign task SIDs to /proc/pid 
directories, which don't support (userspace) file creation anyway.

However, in the absence of a matching type_transition rule, we'll end up 
defaulting to the task SID on the anon inode, and without a separate 
class we won't be able to distinguish it from a /proc/pid inode.  So 
that might justify a separate anoninode or similar class.

This however reminded me that for the context_inode case, we not only 
want to inherit the SID but also the sclass from the context_inode. 
That is so that anon inodes created via device node ioctls inherit the 
same SID/class pair as the device node and a single allowx rule can 
govern all ioctl commands on that device.









  reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 22:55 [PATCH v2 0/6] Harden userfaultfd Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 1/6] Add a new flags-accepting interface for anonymous inodes Daniel Colascione
2020-02-12 16:37   ` Stephen Smalley
2020-02-12 17:23     ` Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 2/6] Add a concept of a "secure" anonymous file Daniel Colascione
2020-02-12 16:49   ` Stephen Smalley
2020-02-14 22:13   ` kbuild test robot
2020-02-11 22:55 ` [PATCH v2 3/6] Teach SELinux about a new userfaultfd class Daniel Colascione
2020-02-12 17:05   ` Stephen Smalley
2020-02-12 17:19     ` Daniel Colascione
2020-02-12 18:04       ` Stephen Smalley
2020-02-12 18:59         ` Stephen Smalley
2020-02-12 19:04           ` Daniel Colascione
2020-02-12 19:11             ` Stephen Smalley
2020-02-12 19:13               ` Daniel Colascione
2020-02-12 19:17               ` Stephen Smalley
2020-02-11 22:55 ` [PATCH v2 4/6] Wire UFFD up to SELinux Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 5/6] Let userfaultfd opt out of handling kernel-mode faults Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 6/6] Add a new sysctl for limiting userfaultfd to user mode faults Daniel Colascione
2020-02-11 23:13 ` [PATCH v2 0/6] Harden userfaultfd Casey Schaufler
2020-02-11 23:27   ` Daniel Colascione
2020-02-12 16:09     ` Stephen Smalley
2020-02-21 17:56     ` James Morris
2020-02-12  7:50 ` Kees Cook
2020-02-12 16:54   ` Jann Horn
2020-02-12 17:14     ` Peter Xu
2020-02-12 19:41       ` Andrea Arcangeli
2020-02-12 20:04         ` Daniel Colascione
2020-02-12 23:41           ` Andrea Arcangeli
2020-02-12 17:12   ` Daniel Colascione
2020-02-14  3:26 ` [PATCH 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-02-14  3:26   ` [PATCH 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-02-14  3:26   ` [PATCH 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-02-14 16:39     ` Stephen Smalley
2020-02-14 17:21       ` Daniel Colascione
2020-02-14 18:02         ` Stephen Smalley [this message]
2020-02-14 18:08           ` Stephen Smalley
2020-02-14 20:24             ` Stephen Smalley
2020-02-14  3:26   ` [PATCH 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 13:53     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 13:58     ` Stephen Smalley
2020-03-26 17:59       ` Daniel Colascione
2020-03-26 17:37     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:49     ` Casey Schaufler
2020-03-26 18:14   ` [PATCH v3 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 18:14     ` [PATCH v3 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 19:00       ` Stephen Smalley
2020-03-26 18:14     ` [PATCH v3 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 19:02       ` Stephen Smalley
2020-03-26 18:14     ` [PATCH v3 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-26 20:06     ` [PATCH v4 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 20:06       ` [PATCH v4 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-27 13:40         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-27 13:41         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-01 21:39       ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-05-07 16:02           ` James Morris
2020-04-01 21:39         ` [PATCH v5 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-13 13:29         ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-22 16:55           ` James Morris
2020-04-22 17:12             ` Casey Schaufler
2020-04-23 22:24               ` Casey Schaufler
2020-04-27 16:18                 ` Casey Schaufler
2020-04-27 16:48                   ` Stephen Smalley
2020-04-27 17:12                     ` Casey Schaufler
2020-04-29 17:02                     ` Stephen Smalley
2020-04-27 17:15             ` Casey Schaufler
2020-04-27 19:40               ` Stephen Smalley

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