[PATCH v6 1/9] lsm: Add LSM hook security_unix_find

[Paul Moore]

On Wed, Mar 18, 2026 at 4:48 AM Mickaël Salaün <mic at digikod.net> wrote:
>
> On Tue, Mar 17, 2026 at 05:34:57PM -0400, Paul Moore wrote:
> > On Mar 15, 2026 =?UTF-8?q?G=C3=BCnther=20Noack?= <gnoack3000 at gmail.com> wrote:
> > >
> > > Add a LSM hook security_unix_find.
> > >
> > > This hook is called to check the path of a named unix socket before a
> > > connection is initiated. The peer socket may be inspected as well.
> > >
> > > Why existing hooks are unsuitable:
> > >
> > > Existing socket hooks, security_unix_stream_connect(),
> > > security_unix_may_send(), and security_socket_connect() don't provide
> > > TOCTOU-free / namespace independent access to the paths of sockets.
> > >
> > > (1) We cannot resolve the path from the struct sockaddr in existing hooks.
> > > This requires another path lookup. A change in the path between the
> > > two lookups will cause a TOCTOU bug.
> > >
> > > (2) We cannot use the struct path from the listening socket, because it
> > > may be bound to a path in a different namespace than the caller,
> > > resulting in a path that cannot be referenced at policy creation time.
> > >
> > > Cc: Günther Noack <gnoack3000 at gmail.com>
> > > Cc: Tingmao Wang <m at maowtm.org>
> > > Signed-off-by: Justin Suess <utilityemal77 at gmail.com>
> > > ---
> > >  include/linux/lsm_hook_defs.h |  5 +++++
> > >  include/linux/security.h      | 11 +++++++++++
> > >  net/unix/af_unix.c            | 13 ++++++++++---
> > >  security/security.c           | 20 ++++++++++++++++++++
> > >  4 files changed, 46 insertions(+), 3 deletions(-)
> >
> > Some really minor nitpicky things (below), but nothing critical.
> > However, as we discussed, I would like to see the AppArmor folks comment
> > on the new hook before we merge anything as I know they have an interest
> > here.
>
> John, Georgia, we've been discussing this new hook for a few months now
> but didn't hear from you yet.  We plan to merge this patch series with
> the 7.1 merge window (in a few weeks), so before that I'd like to merge
> it in -next in a few days to get a broader coverage.  I'm pretty sure
> this hook will work well with AppArmor too, but could you please take
> look to confirm?

I probably wasn't as clear as I should have been, my apologies.  The
major reason I held back my ACK on this patch was that I wanted to
hear from the AA folks regarding the hook's suitability for their
needs.  While I don't expect they will have an issue with this hook
as-is, they have expressed interest in the hook, and I would just
assume make sure it is okay for everyone before we send it to Linus.

Since this is a feature addition and not a critical bug fix, I will be
quite upset if this is sent to Linus without review by the AA
developers and my ACK.

-- 
paul-moore.com