Re: [PATCH v9 01/11] LSM: Identify modules by more than name

Kees Cook
2023-04-21T19:15:27Z

On Fri, Apr 21, 2023 at 10:42:49AM -0700, Casey Schaufler wrote:
> Create a struct lsm_id to contain identifying information
> about Linux Security Modules (LSMs). At inception this contains
> the name of the module, an identifier associated with the security
> module and an integer member "attrs" which identifies the API
> related data associated with each security module. The initial set
> of features maps to information that has traditionaly been available
> in /proc/self/attr. They are documented in a new userspace-api file.
> Change the security_add_hooks() interface to use this structure.
> Change the individual modules to maintain their own struct lsm_id
> and pass it to security_add_hooks().
>
> The values are for LSM identifiers are defined in a new UAPI
> header file linux/lsm.h. Each existing LSM has been updated to
> include it's LSMID in the lsm_id.
>
> The LSM ID values are sequential, with the oldest module
> LSM_ID_CAPABILITY being the lowest value and the existing modules
> numbered in the order they were included in the main line kernel.
> This is an arbitrary convention for assigning the values, but
> none better presents itself. The value 0 is defined as being invalid.
> The values 1-99 are reserved for any special case uses which may
> arise in the future. This may include attributes of the LSM
> infrastructure itself, possibly related to namespacing or network
> attribute management. A special range is identified for such attributes
> to help reduce confusion for developers unfamiliar with LSMs.
>
> LSM attribute values are defined for the attributes presented by
> modules that are available today. As with the LSM IDs, The value 0
> is defined as being invalid. The values 1-99 are reserved for any
> special case uses which may arise in the future.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Cc: linux-security-module <linux-security-module@vger.kernel.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

Some nit-picks below...

> [...]
> +/**
> + * struct lsm_id - Identify a Linux Security Module.
> + * @lsm: name of the LSM, must be approved by the LSM maintainers
> + * @id: LSM ID number from uapi/linux/lsm.h
> + *
> + * Contains the information that identifies the LSM.
> + */
> +struct lsm_id {
> + const u8 *lsm;

Since this is a %NUL-terminated string, I'd keep the convention of
leaving this as "char", and perhaps even const. And "name" or "lsm_name"
seems more descriptive:

const char *const name;

> + u64 id;

if this is "id", "name" makes sense above.

--
Kees Cook