[PATCH v35 04/29] LSM: provide lsm name and id slot mappings

[John Johansen]

On 4/18/22 07:59, Casey Schaufler wrote:
> Provide interfaces to map LSM slot numbers and LSM names.
> Update the LSM registration code to save this information.
> 
> Acked-by: Paul Moore <paul at paul-moore.com>
> Reviewed-by: Kees Cook <keescook at chromium.org>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>


Reviewed-by: John Johansen <john.johansen at canonical.com>

> ---
>  include/linux/security.h |  4 ++++
>  security/security.c      | 45 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index ed51baa94a30..d00870d2b416 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -195,6 +195,10 @@ static inline bool lsmblob_equal(const struct lsmblob *bloba,
>  	return !memcmp(bloba, blobb, sizeof(*bloba));
>  }
>  
> +/* Map lsm names to blob slot numbers */
> +extern int lsm_name_to_slot(char *name);
> +extern const char *lsm_slot_to_name(int slot);
> +
>  /* These functions are in security/commoncap.c */
>  extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
>  		       int cap, unsigned int opts);
> diff --git a/security/security.c b/security/security.c
> index 49fa61028da2..d1ddbb857af1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -477,6 +477,50 @@ static int lsm_append(const char *new, char **result)
>   * Current index to use while initializing the lsmblob secid list.
>   */
>  static int lsm_slot __lsm_ro_after_init;
> +static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES] __lsm_ro_after_init;
> +
> +/**
> + * lsm_name_to_slot - Report the slot number for a security module
> + * @name: name of the security module
> + *
> + * Look up the slot number for the named security module.
> + * Returns the slot number or LSMBLOB_INVALID if @name is not
> + * a registered security module name.
> + */
> +int lsm_name_to_slot(char *name)
> +{
> +	int i;
> +
> +	for (i = 0; i < lsm_slot; i++)
> +		if (strcmp(lsm_slotlist[i]->lsm, name) == 0)
> +			return i;
> +
> +	return LSMBLOB_INVALID;
> +}
> +
> +/**
> + * lsm_slot_to_name - Get the name of the security module in a slot
> + * @slot: index into the interface LSM slot list.
> + *
> + * Provide the name of the security module associated with
> + * a interface LSM slot.
> + *
> + * If @slot is LSMBLOB_INVALID return the value
> + * for slot 0 if it has been set, otherwise NULL.
> + *
> + * Returns a pointer to the name string or NULL.
> + */
> +const char *lsm_slot_to_name(int slot)
> +{
> +	if (slot == LSMBLOB_INVALID)
> +		slot = 0;
> +	else if (slot >= LSMBLOB_ENTRIES || slot < 0)
> +		return NULL;
> +
> +	if (lsm_slotlist[slot] == NULL)
> +		return NULL;
> +	return lsm_slotlist[slot]->lsm;
> +}
>  
>  /**
>   * security_add_hooks - Add a modules hooks to the hook lists.
> @@ -498,6 +542,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
>  	if (lsmid->slot == LSMBLOB_NEEDED) {
>  		if (lsm_slot >= LSMBLOB_ENTRIES)
>  			panic("%s Too many LSMs registered.\n", __func__);
> +		lsm_slotlist[lsm_slot] = lsmid;
>  		lsmid->slot = lsm_slot++;
>  		init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
>  			   lsmid->slot);