Re: [PATCH v12 3/4] selinux: teach SELinux about anonymous inodes

From: Paul Moore <paul@paul-moore.com>
To: Lokesh Gidra <lokeshgidra@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	James Morris <jmorris@namei.org>,
	Stephen Smalley <stephen.smalley.work@gmail.com>,
	Casey Schaufler <casey@schaufler-ca.com>,
	Eric Biggers <ebiggers@kernel.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Eric Paris <eparis@parisplace.org>,
	Daniel Colascione <dancol@dancol.org>,
	Kees Cook <keescook@chromium.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	KP Singh <kpsingh@google.com>,
	David Howells <dhowells@redhat.com>,
	Thomas Cedeno <thomascedeno@google.com>,
	Anders Roxell <anders.roxell@linaro.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Matthew Garrett <matthewgarrett@google.com>,
	Aaron Goidel <acgoide@tycho.nsa.gov>,
	Randy Dunlap <rdunlap@infradead.org>,
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	YueHaibing <yuehaibing@huawei.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Alexey Budankov <alexey.budankov@linux.intel.com>,
	Adrian Reber <areber@redhat.com>,
	Aleksa Sarai <cyphar@cyphar.com>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	LSM List <linux-security-module@vger.kernel.org>,
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	Kalesh Singh <kaleshsingh@google.com>,
	Calin Juravle <calin@google.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Jeffrey Vander Stoep <jeffv@google.com>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	hch@infradead.org, Ondrej Mosnacek <omosnace@redhat.com>
Subject: Re: [PATCH v12 3/4] selinux: teach SELinux about anonymous inodes
Date: Sun, 22 Nov 2020 18:14:37 -0500	[thread overview]
Message-ID: <CAHC9VhQn-E+kTzzwwAiSLLQVtm5u=m5bOz2n-q+oA+8quT2noQ@mail.gmail.com> (raw)
In-Reply-To: <CA+EESO7vqNMXeyk7GZ7syXrTFG54oaf1PUsC7+2ndEBEQeBpdw@mail.gmail.com>

On Wed, Nov 18, 2020 at 5:39 PM Lokesh Gidra <lokeshgidra@google.com> wrote:
> I have created a cuttlefish build and have tested with the attached
> userfaultfd program:

Thanks, that's a good place to start, a few comments:

- While we support Android as a distribution, it isn't a platform that
we common use for development and testing.  At the moment, Fedora is
probably your best choice for that.

- Your test program should be written in vanilla C for the
selinux-testsuite.  Looking at the userfaultfdSimple.cc code that
should be a trivial conversion.

- I think you have a good start on a test for the selinux-testsuite,
please take a look at the test suite and submit a patch against that
repo.  Ondrej (CC'd) currently maintains the test suite and he may
have some additional thoughts.

* https://github.com/SELinuxProject/selinux-testsuite

> 1) Without these kernel patches the program executes without any restrictions
>
> vsoc_x86_64:/ $ ./system/bin/userfaultfdSimple
> api: 170
> features: 511
> ioctls: 9223372036854775811
>
> read: Try again
>
>
> 2) With these patches applied but without any policy the 'permission
> denied' is thrown
>
> vsoc_x86_64:/ $ ./system/bin/userfaultfdSimple
> syscall(userfaultfd): Permission denied
>
> with the following logcat message:
> 11-18 14:21:44.041  3130  3130 W userfaultfdSimp: type=1400
> audit(0.0:107): avc: denied { create } for dev="anon_inodefs"
> ino=45031 scontext=u:r:shell:s0 tcontext=u:object_r:shell:s0
> tclass=anon_inode permissive=0
>
>
> 3) With the attached .te policy file in place the following output is
> observed, confirming that the patch is working as intended.
> vsoc_x86_64:/ $ ./vendor/bin/userfaultfdSimple
> UFFDIO_API: Permission denied
>
> with the following logcat message:
> 11-18 14:33:29.142  2028  2028 W userfaultfdSimp: type=1400
> audit(0.0:104): avc: denied { ioctl } for
> path="anon_inode:[userfaultfd]" dev="anon_inodefs" ino=41169
> ioctlcmd=0xaa3f scontext=u:r:userfaultfdSimple:s0
> tcontext=u:object_r:uffd_t:s0 tclass=anon_inode permissive=0

-- 
paul moore
www.paul-moore.com