[RFC PATCH 07/29] lsm: rework lsm_active_cnt and lsm_idlist[]

[Casey Schaufler]

On 4/9/2025 11:49 AM, Paul Moore wrote:
> Move the LSM count and lsm_id list declarations out of a header that is
> visible across the kernel and into a header that is limited to the LSM
> framework.  This not only helps keep the include/linux headers smaller
> and cleaner, it helps prevent misuse of these variables.
>
> During the move, lsm_active_cnt was renamed to lsm_count for the sake
> of brevity.

lsm_count could be mistaken to be the number of LSMs compiled in
as opposed to the number that are active. Hence lsm_active_cnt.

>
> Signed-off-by: Paul Moore <paul at paul-moore.com>
> ---
>  include/linux/security.h | 2 --
>  security/lsm.h           | 5 +++++
>  security/lsm_init.c      | 8 +-------
>  security/lsm_syscalls.c  | 8 +++++---
>  security/security.c      | 3 +++
>  5 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index cc9b54d95d22..8aac21787a9f 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -167,8 +167,6 @@ struct lsm_prop {
>  };
>  
>  extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
> -extern u32 lsm_active_cnt;
> -extern const struct lsm_id *lsm_idlist[];
>  
>  /* These functions are in security/commoncap.c */
>  extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
> diff --git a/security/lsm.h b/security/lsm.h
> index 0e1731bad4a7..af343072199d 100644
> --- a/security/lsm.h
> +++ b/security/lsm.h
> @@ -7,6 +7,11 @@
>  #define _LSM_H_
>  
>  #include <linux/lsm_hooks.h>
> +#include <linux/lsm_count.h>
> +
> +/* List of configured LSMs */
> +extern unsigned int lsm_count;
> +extern const struct lsm_id *lsm_idlist[];
>  
>  /* LSM blob configuration */
>  extern struct lsm_blob_sizes blob_sizes;
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index edf2f4140eaa..981ddb20f48e 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -22,8 +22,8 @@ static __initdata const char *lsm_order_cmdline;
>  static __initdata const char *lsm_order_legacy;
>  
>  /* Ordered list of LSMs to initialize. */
> -static __initdata struct lsm_info *lsm_order[MAX_LSM_COUNT + 1];
>  static __initdata struct lsm_info *lsm_exclusive;
> +static __initdata struct lsm_info *lsm_order[MAX_LSM_COUNT + 1];
>  
>  static __initdata bool debug;
>  #define init_debug(...)							\
> @@ -211,12 +211,6 @@ static void __init initialize_lsm(struct lsm_info *lsm)
>  	}
>  }
>  
> -/*
> - * Current index to use while initializing the lsm id list.
> - */
> -u32 lsm_active_cnt __ro_after_init;
> -const struct lsm_id *lsm_idlist[MAX_LSM_COUNT];
> -
>  /* Populate ordered LSMs list from comma-separated LSM name list. */
>  static void __init ordered_lsm_parse(const char *order, const char *origin)
>  {
> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index 8440948a690c..3fb0d77ae65c 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -17,6 +17,8 @@
>  #include <linux/lsm_hooks.h>
>  #include <uapi/linux/lsm.h>
>  
> +#include "lsm.h"
> +
>  /**
>   * lsm_name_to_attr - map an LSM attribute name to its ID
>   * @name: name of the attribute
> @@ -96,7 +98,7 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
>  SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, u32 __user *, size,
>  		u32, flags)
>  {
> -	u32 total_size = lsm_active_cnt * sizeof(*ids);
> +	u32 total_size = lsm_count * sizeof(*ids);
>  	u32 usize;
>  	int i;
>  
> @@ -112,9 +114,9 @@ SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, u32 __user *, size,
>  	if (usize < total_size)
>  		return -E2BIG;
>  
> -	for (i = 0; i < lsm_active_cnt; i++)
> +	for (i = 0; i < lsm_count; i++)
>  		if (put_user(lsm_idlist[i]->id, ids++))
>  			return -EFAULT;
>  
> -	return lsm_active_cnt;
> +	return lsm_count;
>  }
> diff --git a/security/security.c b/security/security.c
> index 8d370a4c5e74..a3e8dd640b39 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -73,6 +73,9 @@ const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX + 1] = {
>  	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
>  };
>  
> +unsigned int lsm_count __ro_after_init;
> +const struct lsm_id *lsm_idlist[MAX_LSM_COUNT];
> +
>  struct lsm_blob_sizes blob_sizes;
>  
>  struct kmem_cache *lsm_file_cache;