Re: [PATCH 23/28] security: Introduce LSM_ORDER_LAST

[Stefan Berger]

On 3/3/23 13:25, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs willing to be
> the last, e.g. the 'integrity' LSM, without changing the kernel command
> line or configuration.
>
> As for LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled and put
> at the end of the LSM list in no particular order.

I think you should describe the reason for the change for LSM_ORDER_MUTABLE as well.


> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
>   include/linux/lsm_hooks.h |  1 +
>   security/security.c       | 12 +++++++++---
>   2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 21a8ce23108..05c4b831d99 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -93,6 +93,7 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
>   enum lsm_order {
>   	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
>   	LSM_ORDER_MUTABLE = 0,
> +	LSM_ORDER_LAST = 1,
>   };
>   
>   struct lsm_info {
> diff --git a/security/security.c b/security/security.c
> index 322090a50cd..24f52ba3218 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -284,9 +284,9 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
>   		bool found = false;
>   
>   		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
> -			if (lsm->order == LSM_ORDER_MUTABLE &&
> -			    strcmp(lsm->name, name) == 0) {
> -				append_ordered_lsm(lsm, origin);
> +			if (strcmp(lsm->name, name) == 0) {
> +				if (lsm->order == LSM_ORDER_MUTABLE)
> +					append_ordered_lsm(lsm, origin);
>   				found = true;
>   			}
>   		}
> @@ -306,6 +306,12 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
>   		}
>   	}
>   
> +	/* LSM_ORDER_LAST is always last. */
> +	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
> +		if (lsm->order == LSM_ORDER_LAST)
> +			append_ordered_lsm(lsm, "   last");
> +	}
> +
>   	/* Disable all LSMs not in the ordered list. */
>   	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
>   		if (exists_ordered_lsm(lsm))