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

Paul Moore
2021-08-11T20:48:23Z

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.

---

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(-)