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From:   Lokesh Gidra <lokeshgidra@google.com>
Date:   Mon, 23 Nov 2020 11:20:58 -0800
Message-ID: <CA+EESO6qfCCZ5K1sWWrcBm6VM0w3LWkiOfAh3dhM-eVigVYYWA@mail.gmail.com>
Subject: Re: [PATCH v12 3/4] selinux: teach SELinux about anonymous inodes
To:     Paul Moore <paul@paul-moore.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>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        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>,
        SElinux list <selinux@vger.kernel.org>,
        Kalesh Singh <kaleshsingh@google.com>,
        Calin Juravle <calin@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Jeffrey Vander Stoep <jeffv@google.com>,
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        "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
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        Ondrej Mosnacek <omosnace@redhat.com>
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On Sun, Nov 22, 2020 at 3:14 PM Paul Moore <paul@paul-moore.com> wrote:
>
> 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.
>
I tried setting up a debian/ubuntu system for testing using the
instructions on the selinux-testsuite page, but the system kept
freezing after 'setenforce 1'. I'll try with fedora now.

> - 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

Thanks a lot for the inputs. I'll start working on this.
>
> > 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