Re: [PATCH v1 2/8] LSM: Add an LSM identifier for external use

Paul Moore
2022-11-09T23:34:07Z

On Tue, Oct 25, 2022 at 2:45 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Add an integer member "id" to the struct lsm_id. This value is
> a unique identifier associated with each security module. The
> values are defined in a new UAPI header file. 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. The first 32 values (0 - 31) are reserved
> for some as yet unknown but important use.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
> include/linux/lsm_hooks.h | 1 +
> include/uapi/linux/lsm.h | 32 ++++++++++++++++++++++++++++++++
> security/apparmor/lsm.c | 2 ++
> security/bpf/hooks.c | 2 ++
> security/commoncap.c | 2 ++
> security/landlock/setup.c | 2 ++
> security/loadpin/loadpin.c | 2 ++
> security/lockdown/lockdown.c | 2 ++
> security/safesetid/lsm.c | 2 ++
> security/selinux/hooks.c | 2 ++
> security/smack/smack_lsm.c | 2 ++
> security/tomoyo/tomoyo.c | 2 ++
> security/yama/yama_lsm.c | 2 ++
> 13 files changed, 55 insertions(+)
> create mode 100644 include/uapi/linux/lsm.h

Unless you're getting paid by the patch, I'd rather you combine
patches 1/8 and 2/8 into a single patch. They are both pretty small,
very related, and I don't want to see 1/8 merged anywhere without 2/8.

> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index e383e468f742..dd4b4d95a172 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1607,6 +1607,7 @@ struct security_hook_heads {
> */
> struct lsm_id {
> const char *lsm; /* Name of the LSM */
> + int id; /* LSM ID */
> };

At the very least let's define lsm_id::id as an 'unsigned int' type,
but since we are going to see the lsm_id::id token used as part of the
kernel ABI (likely not in this struct) I agree with Greg's comments
about making the size more explicit. I would suggest __u32/u32 as
32-bits should be plenty for this token.

Given the other upstream discussions we may want to do something
similar with lsm_id::lsm and __u8/u8. I'm pretty sure I saw a similar
comment (by Greg?) elsewhere in this patchset when I was quickly
skimming these on my phone while away ...

--
paul-moore.com