Re: [PATCH v12 02/25] LSM: Create and manage the lsmblob data structure.

[Stephen Smalley <sds@tycho.nsa.gov>]

On 12/16/19 5:35 PM, Casey Schaufler wrote:
> When more than one security module is exporting data to
> audit and networking sub-systems a single 32 bit integer
> is no longer sufficient to represent the data. Add a
> structure to be used instead.
> 
> The lsmblob structure is currently an array of
> u32 "secids". There is an entry for each of the
> security modules built into the system that would
> use secids if active. The system assigns the module
> a "slot" when it registers hooks. If modules are
> compiled in but not registered there will be unused
> slots.
> 
> A new lsm_id structure, which contains the name
> of the LSM and its slot number, is created. There
> is an instance for each LSM, which assigns the name
> and passes it to the infrastructure to set the slot.
> 
> Reviewed-by: John Johansen <john.johansen@canonical.com>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>   include/linux/lsm_hooks.h  | 12 ++++++--
>   include/linux/security.h   | 58 ++++++++++++++++++++++++++++++++++++++
>   security/apparmor/lsm.c    |  7 ++++-
>   security/commoncap.c       |  7 ++++-
>   security/loadpin/loadpin.c |  8 +++++-
>   security/safesetid/lsm.c   |  8 +++++-
>   security/security.c        | 28 ++++++++++++++----
>   security/selinux/hooks.c   |  8 +++++-
>   security/smack/smack_lsm.c |  7 ++++-
>   security/tomoyo/tomoyo.c   |  8 +++++-
>   security/yama/yama_lsm.c   |  7 ++++-
>   11 files changed, 142 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index c2b1af29a8f0..7eb808cde051 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -2077,6 +2077,14 @@ struct security_hook_heads {
>   #endif
>   } __randomize_layout;
>   
> +/*
> + * Information that identifies a security module.
> + */
> +struct lsm_id {
> +	const char	*lsm;	/* Name of the LSM */
> +	int		slot;	/* Slot in lsmblob if one is allocated */
> +};
> +
>   /*
>    * Security module hook list structure.
>    * For use with generic list macros for common operations.
> @@ -2085,7 +2093,7 @@ struct security_hook_list {
>   	struct hlist_node		list;
>   	struct hlist_head		*head;
>   	union security_list_options	hook;
> -	char				*lsm;
> +	struct lsm_id			*lsmid;
>   } __randomize_layout;
>   
>   /*
> @@ -2114,7 +2122,7 @@ extern struct security_hook_heads security_hook_heads;
>   extern char *lsm_names;
>   
>   extern void security_add_hooks(struct security_hook_list *hooks, int count,
> -				char *lsm);
> +			       struct lsm_id *lsmid);
>   
>   #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
>   #define LSM_FLAG_EXCLUSIVE	BIT(1)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 3e8d4bacd59d..b74dc70088ca 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -128,6 +128,64 @@ enum lockdown_reason {
>   	LOCKDOWN_CONFIDENTIALITY_MAX,
>   };
>   
> +/*
> + * Data exported by the security modules
> + *
> + * Any LSM that provides secid or secctx based hooks must be included.
> + */
> +#define LSMBLOB_ENTRIES ( \
> +	(IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
> +	(IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
> +	(IS_ENABLED(CONFIG_SECURITY_APPARMOR) ? 1 : 0))
> +
> +struct lsmblob {
> +	u32     secid[LSMBLOB_ENTRIES];
> +};
> +
> +#define LSMBLOB_INVALID		-1	/* Not a valid LSM slot number */
> +#define LSMBLOB_NEEDED		-2	/* Slot requested on initialization */
> +#define LSMBLOB_NOT_NEEDED	-3	/* Slot not requested */
> +
> +/**
> + * lsmblob_init - initialize an lsmblob structure.
> + * @blob: Pointer to the data to initialize
> + * @secid: The initial secid value
> + *
> + * Set all secid for all modules to the specified value.
> + */
> +static inline void lsmblob_init(struct lsmblob *blob, u32 secid)
> +{
> +	int i;
> +
> +	for (i = 0; i < LSMBLOB_ENTRIES; i++)
> +		blob->secid[i] = secid;
> +}
> +
> +/**
> + * lsmblob_is_set - report if there is an value in the lsmblob
> + * @blob: Pointer to the exported LSM data
> + *
> + * Returns true if there is a secid set, false otherwise
> + */
> +static inline bool lsmblob_is_set(struct lsmblob *blob)
> +{
> +	struct lsmblob empty = {};
> +
> +	return !!memcmp(blob, &empty, sizeof(*blob));
> +}
> +
> +/**
> + * lsmblob_equal - report if the two lsmblob's are equal
> + * @bloba: Pointer to one LSM data
> + * @blobb: Pointer to the other LSM data
> + *
> + * Returns true if all entries in the two are equal, false otherwise
> + */
> +static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
> +{
> +	return !memcmp(bloba, blobb, sizeof(*bloba));
> +}
> +
>   /* 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/apparmor/lsm.c b/security/apparmor/lsm.c
> index 61b24f4eb355..146d75e5e021 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -1147,6 +1147,11 @@ struct lsm_blob_sizes apparmor_blob_sizes __lsm_ro_after_init = {
>   	.lbs_sock = sizeof(struct aa_sk_ctx),
>   };
>   
> +static struct lsm_id apparmor_lsmid __lsm_ro_after_init = {
> +	.lsm  = "apparmor",
> +	.slot = LSMBLOB_NEEDED
> +};
> +
>   static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
>   	LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
> @@ -1847,7 +1852,7 @@ static int __init apparmor_init(void)
>   		goto buffers_out;
>   	}
>   	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
> -				"apparmor");
> +				&apparmor_lsmid);
>   
>   	/* Report that AppArmor successfully initialized */
>   	apparmor_initialized = 1;
> diff --git a/security/commoncap.c b/security/commoncap.c
> index f4ee0ae106b2..9dcfd2a0e891 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -1339,6 +1339,11 @@ int cap_mmap_file(struct file *file, unsigned long reqprot,
>   
>   #ifdef CONFIG_SECURITY
>   
> +static struct lsm_id capability_lsmid __lsm_ro_after_init = {
> +	.lsm  = "capability",
> +	.slot = LSMBLOB_NOT_NEEDED
> +};
> +
>   static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(capable, cap_capable),
>   	LSM_HOOK_INIT(settime, cap_settime),
> @@ -1363,7 +1368,7 @@ static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
>   static int __init capability_init(void)
>   {
>   	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
> -				"capability");
> +			   &capability_lsmid);
>   	return 0;
>   }
>   
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index ee5cb944f4ad..86317e78899f 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -180,6 +180,11 @@ static int loadpin_load_data(enum kernel_load_data_id id)
>   	return loadpin_read_file(NULL, (enum kernel_read_file_id) id);
>   }
>   
> +static struct lsm_id loadpin_lsmid __lsm_ro_after_init = {
> +	.lsm  = "loadpin",
> +	.slot = LSMBLOB_NOT_NEEDED
> +};
> +
>   static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
>   	LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
> @@ -227,7 +232,8 @@ static int __init loadpin_init(void)
>   	pr_info("ready to pin (currently %senforcing)\n",
>   		enforce ? "" : "not ");
>   	parse_exclude();
> -	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
> +	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks),
> +			   &loadpin_lsmid);
>   	return 0;
>   }
>   
> diff --git a/security/safesetid/lsm.c b/security/safesetid/lsm.c
> index 7760019ad35d..950dfb7f931e 100644
> --- a/security/safesetid/lsm.c
> +++ b/security/safesetid/lsm.c
> @@ -149,6 +149,11 @@ static int safesetid_task_fix_setuid(struct cred *new,
>   	return -EACCES;
>   }
>   
> +static struct lsm_id safesetid_lsmid __lsm_ro_after_init = {
> +	.lsm  = "safesetid",
> +	.slot = LSMBLOB_NOT_NEEDED
> +};
> +
>   static struct security_hook_list safesetid_security_hooks[] = {
>   	LSM_HOOK_INIT(task_fix_setuid, safesetid_task_fix_setuid),
>   	LSM_HOOK_INIT(capable, safesetid_security_capable)
> @@ -157,7 +162,8 @@ static struct security_hook_list safesetid_security_hooks[] = {
>   static int __init safesetid_security_init(void)
>   {
>   	security_add_hooks(safesetid_security_hooks,
> -			   ARRAY_SIZE(safesetid_security_hooks), "safesetid");
> +			   ARRAY_SIZE(safesetid_security_hooks),
> +			   &safesetid_lsmid);
>   
>   	/* Report that SafeSetID successfully initialized */
>   	safesetid_initialized = 1;
> diff --git a/security/security.c b/security/security.c
> index 7fb6e5bcf6ec..a89634af639a 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -308,6 +308,7 @@ static void __init ordered_lsm_init(void)
>   	init_debug("msg_msg blob size  = %d\n", blob_sizes.lbs_msg_msg);
>   	init_debug("sock blob size     = %d\n", blob_sizes.lbs_sock);
>   	init_debug("task blob size     = %d\n", blob_sizes.lbs_task);
> +	init_debug("lsmblob size       = %lu\n", sizeof(struct lsmblob));

nit: Use %zu for sizeof.  Otherwise,
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>

>   
>   	/*
>   	 * Create any kmem_caches needed for blobs
> @@ -435,21 +436,36 @@ static int lsm_append(const char *new, char **result)
>   	return 0;
>   }
>   
> +/*
> + * Current index to use while initializing the lsmblob secid list.
> + */
> +static int lsm_slot __initdata;
> +
>   /**
>    * security_add_hooks - Add a modules hooks to the hook lists.
>    * @hooks: the hooks to add
>    * @count: the number of hooks to add
> - * @lsm: the name of the security module
> + * @lsmid: the the identification information for the security module
>    *
>    * Each LSM has to register its hooks with the infrastructure.
> + * If the LSM is using hooks that export secids allocate a slot
> + * for it in the lsmblob.
>    */
>   void __init security_add_hooks(struct security_hook_list *hooks, int count,
> -				char *lsm)
> +			       struct lsm_id *lsmid)
>   {
>   	int i;
>   
> +	if (lsmid->slot == LSMBLOB_NEEDED) {
> +		if (lsm_slot >= LSMBLOB_ENTRIES)
> +			panic("%s Too many LSMs registered.\n", __func__);
> +		lsmid->slot = lsm_slot++;
> +		init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
> +			   lsmid->slot);
> +	}
> +
>   	for (i = 0; i < count; i++) {
> -		hooks[i].lsm = lsm;
> +		hooks[i].lsmid = lsmid;
>   		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
>   	}
>   
> @@ -458,7 +474,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
>   	 * and fix this up afterwards.
>   	 */
>   	if (slab_is_available()) {
> -		if (lsm_append(lsm, &lsm_names) < 0)
> +		if (lsm_append(lsmid->lsm, &lsm_names) < 0)
>   			panic("%s - Cannot get early memory.\n", __func__);
>   	}
>   }
> @@ -1906,7 +1922,7 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>   	struct security_hook_list *hp;
>   
>   	hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
> -		if (lsm != NULL && strcmp(lsm, hp->lsm))
> +		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
>   			continue;
>   		return hp->hook.getprocattr(p, name, value);
>   	}
> @@ -1919,7 +1935,7 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
>   	struct security_hook_list *hp;
>   
>   	hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
> -		if (lsm != NULL && strcmp(lsm, hp->lsm))
> +		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
>   			continue;
>   		return hp->hook.setprocattr(name, value, size);
>   	}
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 0839b2fbbf9b..97f2ee6e4080 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6860,6 +6860,11 @@ static int selinux_perf_event_write(struct perf_event *event)
>   }
>   #endif
>   
> +static struct lsm_id selinux_lsmid __lsm_ro_after_init = {
> +	.lsm  = "selinux",
> +	.slot = LSMBLOB_NEEDED
> +};
> +
>   static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(binder_set_context_mgr, selinux_binder_set_context_mgr),
>   	LSM_HOOK_INIT(binder_transaction, selinux_binder_transaction),
> @@ -7128,7 +7133,8 @@ static __init int selinux_init(void)
>   
>   	hashtab_cache_init();
>   
> -	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
> +	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks),
> +			   &selinux_lsmid);
>   
>   	if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
>   		panic("SELinux: Unable to register AVC netcache callback\n");
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 4cecdfdcd913..82cbb3eeec76 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4585,6 +4585,11 @@ struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = {
>   	.lbs_sock = sizeof(struct socket_smack),
>   };
>   
> +static struct lsm_id smack_lsmid __lsm_ro_after_init = {
> +	.lsm  = "smack",
> +	.slot = LSMBLOB_NEEDED
> +};
> +
>   static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(ptrace_access_check, smack_ptrace_access_check),
>   	LSM_HOOK_INIT(ptrace_traceme, smack_ptrace_traceme),
> @@ -4783,7 +4788,7 @@ static __init int smack_init(void)
>   	/*
>   	 * Register with LSM
>   	 */
> -	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
> +	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), &smack_lsmid);
>   	smack_enabled = 1;
>   
>   	pr_info("Smack:  Initializing.\n");
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index 716c92ec941a..f1968e80f06d 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -529,6 +529,11 @@ static void tomoyo_task_free(struct task_struct *task)
>   	}
>   }
>   
> +static struct lsm_id tomoyo_lsmid __lsm_ro_after_init = {
> +	.lsm  = "tomoyo",
> +	.slot = LSMBLOB_NOT_NEEDED
> +};
> +
>   /*
>    * tomoyo_security_ops is a "struct security_operations" which is used for
>    * registering TOMOYO.
> @@ -581,7 +586,8 @@ static int __init tomoyo_init(void)
>   	struct tomoyo_task *s = tomoyo_task(current);
>   
>   	/* register ourselves with the security framework */
> -	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
> +	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks),
> +			   &tomoyo_lsmid);
>   	pr_info("TOMOYO Linux initialized\n");
>   	s->domain_info = &tomoyo_kernel_domain;
>   	atomic_inc(&tomoyo_kernel_domain.users);
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index 94dc346370b1..0f0cf7136929 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -421,6 +421,11 @@ static int yama_ptrace_traceme(struct task_struct *parent)
>   	return rc;
>   }
>   
> +static struct lsm_id yama_lsmid __lsm_ro_after_init = {
> +	.lsm  = "yama",
> +	.slot = LSMBLOB_NOT_NEEDED
> +};
> +
>   static struct security_hook_list yama_hooks[] __lsm_ro_after_init = {
>   	LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
>   	LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
> @@ -477,7 +482,7 @@ static inline void yama_init_sysctl(void) { }
>   static int __init yama_init(void)
>   {
>   	pr_info("Yama: becoming mindful.\n");
> -	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
> +	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), &yama_lsmid);
>   	yama_init_sysctl();
>   	return 0;
>   }
>