[PATCH v4 3/3] landlock: Optimize scope enforcement

[Günther Noack]

On Sat, Nov 09, 2024 at 12:08:56PM +0100, Mickaël Salaün wrote:
> Do not walk through the domain hierarchy when the required scope is not
> supported by this domain.  This is the same approach as for filesystem
> and network restrictions.
> 
> Cc: Günther Noack <gnoack at google.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
> Cc: Tahera Fahimi <fahimitahera at gmail.com>
> Signed-off-by: Mickaël Salaün <mic at digikod.net>
> Link: https://lore.kernel.org/r/20241109110856.222842-4-mic@digikod.net
> ---
> 
> Changes since v2:
> * Make the unix_scope variable global to the file and remove
>   previous get_current_unix_scope_domain().
> ---
>  security/landlock/task.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/security/landlock/task.c b/security/landlock/task.c
> index 4acbd7c40eee..dc7dab78392e 100644
> --- a/security/landlock/task.c
> +++ b/security/landlock/task.c
> @@ -204,12 +204,17 @@ static bool is_abstract_socket(struct sock *const sock)
>  	return false;
>  }
>  
> +static const struct access_masks unix_scope = {
> +	.scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,
> +};

Optional nit: You could probably inline these two struct access_masks values
into the respective functions where they are used.  (But it's just a minor code
style matter IMHO; both ways are fine.)

> +
>  static int hook_unix_stream_connect(struct sock *const sock,
>  				    struct sock *const other,
>  				    struct sock *const newsk)
>  {
>  	const struct landlock_ruleset *const dom =
> -		landlock_get_current_domain();
> +		landlock_get_applicable_domain(landlock_get_current_domain(),
> +					       unix_scope);
>  
>  	/* Quick return for non-landlocked tasks. */
>  	if (!dom)
> @@ -225,7 +230,8 @@ static int hook_unix_may_send(struct socket *const sock,
>  			      struct socket *const other)
>  {
>  	const struct landlock_ruleset *const dom =
> -		landlock_get_current_domain();
> +		landlock_get_applicable_domain(landlock_get_current_domain(),
> +					       unix_scope);
>  
>  	if (!dom)
>  		return 0;
> @@ -243,6 +249,10 @@ static int hook_unix_may_send(struct socket *const sock,
>  	return 0;
>  }
>  
> +static const struct access_masks signal_scope = {
> +	.scope = LANDLOCK_SCOPE_SIGNAL,
> +};
> +
>  static int hook_task_kill(struct task_struct *const p,
>  			  struct kernel_siginfo *const info, const int sig,
>  			  const struct cred *const cred)
> @@ -256,6 +266,7 @@ static int hook_task_kill(struct task_struct *const p,
>  	} else {
>  		dom = landlock_get_current_domain();
>  	}
> +	dom = landlock_get_applicable_domain(dom, signal_scope);
>  
>  	/* Quick return for non-landlocked tasks. */
>  	if (!dom)
> @@ -279,7 +290,8 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
>  
>  	/* Lock already held by send_sigio() and send_sigurg(). */
>  	lockdep_assert_held(&fown->lock);
> -	dom = landlock_file(fown->file)->fown_domain;
> +	dom = landlock_get_applicable_domain(
> +		landlock_file(fown->file)->fown_domain, signal_scope);
>  
>  	/* Quick return for unowned socket. */
>  	if (!dom)
> -- 
> 2.47.0
> 

Reviewed-by: Günther Noack <gnoack at google.com>

Looks good!

—Günther