Re: [PATCH 2/6] landlock: Implement LANDLOCK_SCOPE_PATHNAME_UNIX_SOCKET

["Mickaël Salaün" <mic@digikod.net>]

On Sun, Dec 28, 2025 at 12:45:41PM +0000, Tingmao Wang wrote:
> Extend the existing abstract UNIX socket scoping to pathname sockets as
> well.  Basically all of the logic is reused between the two types, just
> that pathname sockets scoping are controlled by another bit, and has its
> own audit request type (since the current one is named
> "abstract_unix_socket").
> 
> Closes: https://github.com/landlock-lsm/linux/issues/51
> Signed-off-by: Tingmao Wang <m@maowtm.org>

Great, thanks!

> ---
> 
> There is an argument that there should only really be one audit request
> type for both sockets, since the only difference is whether path= is
> followed by a normal path, or by a hex string starting with 00.  But I'm
> not sure if we can change this at this point, so I have created a new
> request type.

It is the correct approach to add a dedicated request type, which
enables to filter on it, and doesn't have performance impact.

> 
>  security/landlock/audit.c |  4 +++
>  security/landlock/audit.h |  1 +
>  security/landlock/task.c  | 74 ++++++++++++++++++++++++++++++---------
>  3 files changed, 62 insertions(+), 17 deletions(-)

> diff --git a/security/landlock/task.c b/security/landlock/task.c
> index 6dfcc1860d6e..9fbb0ada440b 100644
> --- a/security/landlock/task.c
> +++ b/security/landlock/task.c

> +/*
> + * UNIX sockets can have three types of addresses: pathname (a filesystem path),
> + * unnamed (not bound to an address), and abstract (sun_path[0] is '\0').
> + * Unnamed sockets include those created with socketpair() and unbound sockets.
> + * We do not restrict unnamed sockets since they have no address to identify.
> + */
>  static int hook_unix_stream_connect(struct sock *const sock,
>  				    struct sock *const other,
>  				    struct sock *const newsk)
>  {
>  	size_t handle_layer;
> +	access_mask_t scope;
> +	enum landlock_request_type request_type;
>  	const struct landlock_cred_security *const subject =
>  		landlock_get_applicable_subject(current_cred(), unix_scope,
>  						&handle_layer);
> +	const struct unix_address *addr;
>  
>  	/* Quick return for non-landlocked tasks. */
>  	if (!subject)
>  		return 0;
>  


> -	if (!is_abstract_socket(other))
> +	addr = unix_sk(other)->addr;
> +	/* Unnamed sockets are not restricted. */
> +	if (!addr)
>  		return 0;
>  
> -	if (!sock_is_scoped(other, subject->domain))
> +	if (sock_addr_is_abstract(addr)) {
> +		scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;
> +		request_type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET;
> +	} else {
> +		/* Pathname socket. */
> +		scope = LANDLOCK_SCOPE_PATHNAME_UNIX_SOCKET;
> +		request_type = LANDLOCK_REQUEST_SCOPE_PATHNAME_UNIX_SOCKET;
> +	}
> +
> +	if (!sock_is_scoped(other, subject->domain, scope))
>  		return 0;

We should be able to factor out this hunk for both hooks, and then also
fold is_abstract_socket() in this new helper.

>  
>  	landlock_log_denial(subject, &(struct landlock_request) {
> -		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
> +		.type = request_type,
>  		.audit = {
>  			.type = LSM_AUDIT_DATA_NET,
>  			.u.net = &(struct lsm_network_audit) {
> @@ -299,9 +326,12 @@ static int hook_unix_may_send(struct socket *const sock,
>  			      struct socket *const other)
>  {
>  	size_t handle_layer;
> +	access_mask_t scope;
> +	enum landlock_request_type request_type;
>  	const struct landlock_cred_security *const subject =
>  		landlock_get_applicable_subject(current_cred(), unix_scope,
>  						&handle_layer);
> +	const struct unix_address *addr;
>  
>  	if (!subject)
>  		return 0;
> @@ -313,14 +343,24 @@ static int hook_unix_may_send(struct socket *const sock,
>  	if (unix_peer(sock->sk) == other->sk)
>  		return 0;
>  
> -	if (!is_abstract_socket(other->sk))
> +	addr = unix_sk(other->sk)->addr;
> +	/* Unnamed sockets are not restricted. */
> +	if (!addr)
>  		return 0;
>  
> -	if (!sock_is_scoped(other->sk, subject->domain))
> +	if (sock_addr_is_abstract(addr)) {
> +		scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;
> +		request_type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET;
> +	} else {
> +		scope = LANDLOCK_SCOPE_PATHNAME_UNIX_SOCKET;
> +		request_type = LANDLOCK_REQUEST_SCOPE_PATHNAME_UNIX_SOCKET;
> +	}
> +
> +	if (!sock_is_scoped(other->sk, subject->domain, scope))
>  		return 0;
>  
>  	landlock_log_denial(subject, &(struct landlock_request) {
> -		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
> +		.type = request_type,
>  		.audit = {
>  			.type = LSM_AUDIT_DATA_NET,
>  			.u.net = &(struct lsm_network_audit) {
> -- 
> 2.52.0
>