Re: [RFC PATCH v2 0/9] Add LSM access controls and auditing to io_uring

[Richard Guy Briggs <rgb@redhat.com>]

On 2021-08-25 21:34, Paul Moore wrote:
> On Wed, Aug 25, 2021 at 9:16 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> >
> > On 2021-08-24 16:57, Richard Guy Briggs wrote:
> > > On 2021-08-11 16:48, Paul Moore wrote:
> > > > Draft #2 of the patchset which brings auditing and proper LSM access
> > > > controls to the io_uring subsystem.  The original patchset was posted
> > > > in late May and can be found via lore using the link below:
> > > >
> > > > https://lore.kernel.org/linux-security-module/162163367115.8379.8459012634106035341.stgit@sifl/
> > > >
> > > > This draft should incorporate all of the feedback from the original
> > > > posting as well as a few smaller things I noticed while playing
> > > > further with the code.  The big change is of course the selective
> > > > auditing in the io_uring op servicing, but that has already been
> > > > discussed quite a bit in the original thread so I won't go into
> > > > detail here; the important part is that we found a way to move
> > > > forward and this draft captures that.  For those of you looking to
> > > > play with these patches, they are based on Linus' v5.14-rc5 tag and
> > > > on my test system they boot and appear to function without problem;
> > > > they pass the selinux-testsuite and audit-testsuite and I have not
> > > > noticed any regressions in the normal use of the system.  If you want
> > > > to get a copy of these patches straight from git you can use the
> > > > "working-io_uring" branch in the repo below:
> > > >
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git
> > > >
> > > > Beyond the existing test suite tests mentioned above, I've cobbled
> > > > together some very basic, very crude tests to exercise some of the
> > > > things I care about from a LSM/audit perspective.  These tests are
> > > > pretty awful (I'm not kidding), but they might be helpful for the
> > > > other LSM/audit developers who want to test things:
> > > >
> > > > https://drop.paul-moore.com/90.kUgq
> > > >
> > > > There are currently two tests: 'iouring.2' and 'iouring.3';
> > > > 'iouring.1' was lost in a misguided and overzealous 'rm' command.
> > > > The first test is standalone and basically tests the SQPOLL
> > > > functionality while the second tests sharing io_urings across process
> > > > boundaries and the credential/personality sharing mechanism.  The
> > > > console output of both tests isn't particularly useful, the more
> > > > interesting bits are in the audit and LSM specific logs.  The
> > > > 'iouring.2' command requires no special arguments to run but the
> > > > 'iouring.3' test is split into a "server" and "client"; the server
> > > > should be run without argument:
> > > >
> > > >   % ./iouring.3s
> > > >   >>> server started, pid = 11678
> > > >   >>> memfd created, fd = 3
> > > >   >>> io_uring created; fd = 5, creds = 1
> > > >
> > > > ... while the client should be run with two arguments: the first is
> > > > the PID of the server process, the second is the "memfd" fd number:
> > > >
> > > >   % ./iouring.3c 11678 3
> > > >   >>> client started, server_pid = 11678 server_memfd = 3
> > > >   >>> io_urings = 5 (server) / 5 (client)
> > > >   >>> io_uring ops using creds = 1
> > > >   >>> async op result: 36
> > > >   >>> async op result: 36
> > > >   >>> async op result: 36
> > > >   >>> async op result: 36
> > > >   >>> START file contents
> > > >   What is this life if, full of care,
> > > >   we have no time to stand and stare.
> > > >   >>> END file contents
> > > >
> > > > The tests were hacked together from various sources online,
> > > > attribution and links to additional info can be found in the test
> > > > sources, but I expect these tests to die a fiery death in the not
> > > > to distant future as I work to add some proper tests to the SELinux
> > > > and audit test suites.
> > > >
> > > > As I believe these patches should spend a full -rcX cycle in
> > > > linux-next, my current plan is to continue to solicit feedback on
> > > > these patches while they undergo additional testing (next up is
> > > > verification of the audit filter code for io_uring).  Assuming no
> > > > critical issues are found on the mailing lists or during testing, I
> > > > will post a proper patchset later with the idea of merging it into
> > > > selinux/next after the upcoming merge window closes.
> > > >
> > > > Any comments, feedback, etc. are welcome.
> > >
> > > Thanks for the tests.  I have a bunch of userspace patches to add to the
> > > last set I posted and these tests will help exercise them.  I also have
> > > one more kernel patch to post...  I'll dive back into that now.  I had
> > > wanted to post them before now but got distracted with AUDIT_TRIM
> > > breakage.
> >
> > Please tell me about liburing.h that is needed for these.  There is one
> > in tools/io_uring/liburing.h but I don't think that one is right.
> >
> > The next obvious one would be include/uapi/linux/io_uring.h
> >
> > I must be missing something obvious here...
> 
> You are looking for the liburing header files, the upstream is here:
> -> https://github.com/axboe/liburing
> 
> If you are on a RH/IBM based distro it is likely called liburing[-devel]:

Found it but struct io_uring missing "features" in everything except
rawhide.  Forced upgrade of my test VMs.  :-)

audit-testsuite still passes.

I'm getting:
	# ./iouring.2                                                
	Kernel thread io_uring-sq is not running.                                      
	Unable to setup io_uring: Permission denied

	# ./iouring.3s
	>>> server started, pid = 2082                                                 
	>>> memfd created, fd = 3                                                      
	io_uring_queue_init: Permission denied

I have CONFIG_IO_URING=y set, what else is needed?

> % dnf whatprovides */liburing.h
> Last metadata expiration check: 0:38:37 ago on Wed 25 Aug 2021 08:54:22 PM EDT.
> liburing-devel-2.0-2.fc35.i686 : Development files for Linux-native io_uring I/O
>                               : access library
> Repo        : rawhide
> Matched from:
> Filename    : /usr/include/liburing.h
> 
> liburing-devel-2.0-2.fc35.x86_64 : Development files for Linux-native io_uring
>                                 : I/O access library
> Repo        : @System
> Matched from:
> Filename    : /usr/include/liburing.h
> 
> liburing-devel-2.0-2.fc35.x86_64 : Development files for Linux-native io_uring
>                                 : I/O access library
> Repo        : rawhide
> Matched from:
> Filename    : /usr/include/liburing.h
> 
> -- 
> paul moore

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
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