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

[Mickaël Salaün]

On Sun, Mar 15, 2026 at 11:21:42PM +0100, Günther Noack wrote:
> From: Justin Suess <utilityemal77 at gmail.com>
> 
> Add a LSM hook security_unix_find.

Add an LSM hook...

> 
> This hook is called to check the path of a named unix socket before a

UNIX socket

> 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(-)