netdev - Re: [RFC PATCH 0/1] lsm: Add hook unix_path

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Message-ID: <aVuaqij9nXhLfAvN@google.com>
Date: Mon, 5 Jan 2026 12:04:10 +0100
From: Günther Noack <gnoack@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: Justin Suess <utilityemal77@...il.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E . Hallyn" <serge@...lyn.com>,
	Simon Horman <horms@...nel.org>,
	Mickaël Salaün <mic@...ikod.net>,
	linux-security-module@...r.kernel.org, Tingmao Wang <m@...wtm.org>,
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH 0/1] lsm: Add hook unix_path_connect

Hello!

On Sun, Jan 04, 2026 at 11:46:46PM -0800, Kuniyuki Iwashima wrote:
> On Wed, Dec 31, 2025 at 1:33 PM Justin Suess <utilityemal77@...il.com> wrote:
> > Motivation
> > ---
> >
> > For AF_UNIX sockets bound to a filesystem path (aka named sockets), one
> > identifying object from a policy perspective is the path passed to
> > connect(2). However, this operation currently restricts LSMs that rely
> > on VFS-based mediation, because the pathname resolved during connect()
> > is not preserved in a form visible to existing hooks before connection
> > establishment.
> 
> Why can't LSM use unix_sk(other)->path in security_unix_stream_connect()
> and security_unix_may_send() ?

Thanks for bringing it up!

That path is set by the process that acts as the listening side for
the socket.  The listening and the connecting process might not live
in the same mount namespace, and in that case, it would not match the
path which is passed by the client in the struct sockaddr_un.

For more details, see
https://lore.kernel.org/all/20260101134102.25938-1-gnoack3000@gmail.com/
and
https://github.com/landlock-lsm/linux/issues/36#issuecomment-2950632277

Justin: Maybe we could add that reasoning to the cover letter in the
next version of the patch?

–Günther