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

[Paul Moore]

On Mon, Mar 23, 2026 at 10:37 AM Georgia Garcia
<georgia.garcia at canonical.com> wrote:
> On Wed, 2026-03-18 at 09:48 +0100, Mickaël Salaün 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?
>
> Apologies for the long delay replying. I have looked it over and I have
> no objections on the hook, it looks good to me. I would prefer if we
> got a reply from John as well since I'm not 100% confident but he
> should be out this week. In any case,
>
> Reviewed-by: Georgia Garcia <georgia.garcia at canonical.com>

Thanks!  I can understand wanting to wait for John, and if I'm
understanding the other aspects of the discussion (unrelated to this)
I think there still might be some additional discussions or revisions
before this goes anywhere.

-- 
paul-moore.com