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

[Paul Moore]

On Wed, Nov 18, 2020 at 5:39 PM Lokesh Gidra <lokeshgidra at 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