[PATCH v2 2/3] landlock: access_mask_subset() helper

[Mickaël Salaün]

On Sun, Jan 25, 2026 at 08:58:52PM +0100, Günther Noack wrote:
> This helper function checks whether an access_mask_t has a subset of the
> bits enabled than another one.  This expresses the intent a bit smoother
> in the code and does not cost us anything when it gets inlined.
> 
> Signed-off-by: Günther Noack <gnoack3000 at gmail.com>
> ---
>  security/landlock/access.h | 6 ++++++
>  security/landlock/fs.c     | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/security/landlock/access.h b/security/landlock/access.h
> index 7961c6630a2d..5c0caef9eaf6 100644
> --- a/security/landlock/access.h
> +++ b/security/landlock/access.h
> @@ -97,4 +97,10 @@ landlock_upgrade_handled_access_masks(struct access_masks access_masks)
>  	return access_masks;
>  }
>  
> +/** access_mask_subset - true iff a has a subset of the bits of b. */
> +static inline bool access_mask_subset(access_mask_t a, access_mask_t b)

What about renaming "a" to "subset" and "b" to "superset"?

> +{
> +	return (a | b) == b;
> +}
> +
>  #endif /* _SECURITY_LANDLOCK_ACCESS_H */
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 8205673c8b1c..bf8e37fcc7c0 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -1704,7 +1704,7 @@ static int hook_file_open(struct file *const file)
>  		ARRAY_SIZE(layer_masks));
>  #endif /* CONFIG_AUDIT */
>  
> -	if ((open_access_request & allowed_access) == open_access_request)
> +	if (access_mask_subset(open_access_request, allowed_access))
>  		return 0;
>  
>  	/* Sets access to reflect the actual request. */
> -- 
> 2.52.0
> 
>