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

[Richard Guy Briggs]

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.

> ---
> 
> Casey Schaufler (1):
>       Smack: Brutalist io_uring support with debug
> 
> Paul Moore (8):
>       audit: prepare audit_context for use in calling contexts beyond
>              syscalls
>       audit,io_uring,io-wq: add some basic audit support to io_uring
>       audit: dev/test patch to force io_uring auditing
>       audit: add filtering for io_uring records
>       fs: add anon_inode_getfile_secure() similar to
>           anon_inode_getfd_secure()
>       io_uring: convert io_uring to the secure anon inode interface
>       lsm,io_uring: add LSM hooks to io_uring
>       selinux: add support for the io_uring access controls
> 
> 
>  fs/anon_inodes.c                    |  29 ++
>  fs/io-wq.c                          |   4 +
>  fs/io_uring.c                       |  69 +++-
>  include/linux/anon_inodes.h         |   4 +
>  include/linux/audit.h               |  26 ++
>  include/linux/lsm_hook_defs.h       |   5 +
>  include/linux/lsm_hooks.h           |  13 +
>  include/linux/security.h            |  16 +
>  include/uapi/linux/audit.h          |   4 +-
>  kernel/audit.h                      |   7 +-
>  kernel/audit_tree.c                 |   3 +-
>  kernel/audit_watch.c                |   3 +-
>  kernel/auditfilter.c                |  15 +-
>  kernel/auditsc.c                    | 483 +++++++++++++++++++-----
>  security/security.c                 |  12 +
>  security/selinux/hooks.c            |  34 ++
>  security/selinux/include/classmap.h |   2 +
>  security/smack/smack_lsm.c          |  64 ++++
>  18 files changed, 678 insertions(+), 115 deletions(-)
> 

- RGB

--
Richard Guy Briggs <rgb at redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635