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

["Mickaël Salaün" <mic@digikod.net>]

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@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@gmail.com>
> > Cc: Tingmao Wang <m@maowtm.org>
> > Signed-off-by: Justin Suess <utilityemal77@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?