[PATCH v7 01/11] lsm: Add LSM hook security_unix_find

[Paul Moore]

On Mon, Mar 23, 2026 at 12:58 PM Günther Noack <gnoack3000 at gmail.com> wrote:
>
> From: Justin Suess <utilityemal77 at gmail.com>
>
> Add an 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.
>
> Consumers of the hook wishing to reference @other are responsible
> for acquiring the unix_state_lock and checking for the SOCK_DEAD flag
> therein, ensuring the socket hasn't died since lookup.
>
> Cc: Günther Noack <gnoack3000 at gmail.com>
> Cc: Tingmao Wang <m at maowtm.org>
> Cc: Mickaël Salaün <mic at digikod.net>
> Cc: Paul Moore <paul at paul-moore.com>
> Signed-off-by: Justin Suess <utilityemal77 at gmail.com>
> Signed-off-by: Günther Noack <gnoack3000 at gmail.com>
> ---
>  include/linux/lsm_hook_defs.h |  5 +++++
>  include/linux/security.h      | 11 +++++++++++
>  net/unix/af_unix.c            | 10 +++++++---
>  security/security.c           | 20 ++++++++++++++++++++
>  4 files changed, 43 insertions(+), 3 deletions(-)

Acked-by: Paul Moore <paul at paul-moore.com>

-- 
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