text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Implementation of the kernel access vector cache (AVC).
   *
   * Authors:  Stephen Smalley, <sds@tycho.nsa.gov>
   *	     James Morris <jmorris@redhat.com>
   *
   * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
   *	Replaced the avc_lock spinlock by RCU.
   *
   * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
   */
  #include <linux/types.h>
  #include <linux/stddef.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/dcache.h>
  #include <linux/init.h>
  #include <linux/skbuff.h>
  #include <linux/percpu.h>
  #include <linux/list.h>
  #include <net/sock.h>
  #include <linux/un.h>
  #include <net/af_unix.h>
  #include <linux/ip.h>
  #include <linux/audit.h>
  #include <linux/ipv6.h>
  #include <net/ipv6.h>
  #include "avc.h"
  #include "avc_ss.h"
  #include "classmap.h"
  
  #define AVC_CACHE_SLOTS			512
  #define AVC_DEF_CACHE_THRESHOLD		512
  #define AVC_CACHE_RECLAIM		16
  
  #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  #define avc_cache_stats_incr(field)	this_cpu_inc(avc_cache_stats.field)
  #else
  #define avc_cache_stats_incr(field)	do {} while (0)
  #endif
  
  struct avc_entry {
  	u32			ssid;
  	u32			tsid;
  	u16			tclass;
  	struct av_decision	avd;
  	struct avc_xperms_node	*xp_node;
  };
  
  struct avc_node {
  	struct avc_entry	ae;
  	struct hlist_node	list; /* anchored in avc_cache->slots[i] */
  	struct rcu_head		rhead;
  };
  
  struct avc_xperms_decision_node {
  	struct extended_perms_decision xpd;
  	struct list_head xpd_list; /* list of extended_perms_decision */
  };
  
  struct avc_xperms_node {
  	struct extended_perms xp;
  	struct list_head xpd_head; /* list head of extended_perms_decision */
  };
  
  struct avc_cache {
  	struct hlist_head	slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
  	spinlock_t		slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
  	atomic_t		lru_hint;	/* LRU hint for reclaim scan */
  	atomic_t		active_nodes;
  	u32			latest_notif;	/* latest revocation notification */
  };
  
  struct avc_callback_node {
  	int (*callback) (u32 event);
  	u32 events;
  	struct avc_callback_node *next;
  };
  
  #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  #endif
  
  struct selinux_avc {
  	unsigned int avc_cache_threshold;
  	struct avc_cache avc_cache;
  };
  
  static struct selinux_avc selinux_avc;
  
  void selinux_avc_init(struct selinux_avc **avc)
  {
  	int i;
  
  	selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
  	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
  		INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
  		spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
  	}
  	atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
  	atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
  	*avc = &selinux_avc;
  }
  
  unsigned int avc_get_cache_threshold(struct selinux_avc *avc)
  {
  	return avc->avc_cache_threshold;
  }
  
  void avc_set_cache_threshold(struct selinux_avc *avc,
  			     unsigned int cache_threshold)
  {
  	avc->avc_cache_threshold = cache_threshold;
  }
  
  static struct avc_callback_node *avc_callbacks;
  static struct kmem_cache *avc_node_cachep;
  static struct kmem_cache *avc_xperms_data_cachep;
  static struct kmem_cache *avc_xperms_decision_cachep;
  static struct kmem_cache *avc_xperms_cachep;
  
  static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
  {
  	return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
  }
  
  /**
   * avc_init - Initialize the AVC.
   *
   * Initialize the access vector cache.
   */
  void __init avc_init(void)
  {
  	avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
  					0, SLAB_PANIC, NULL);
  	avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
  					sizeof(struct avc_xperms_node),
  					0, SLAB_PANIC, NULL);
  	avc_xperms_decision_cachep = kmem_cache_create(
  					"avc_xperms_decision_node",
  					sizeof(struct avc_xperms_decision_node),
  					0, SLAB_PANIC, NULL);
  	avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
  					sizeof(struct extended_perms_data),
  					0, SLAB_PANIC, NULL);
  }
  
  int avc_get_hash_stats(struct selinux_avc *avc, char *page)
  {
  	int i, chain_len, max_chain_len, slots_used;
  	struct avc_node *node;
  	struct hlist_head *head;
  
  	rcu_read_lock();
  
  	slots_used = 0;
  	max_chain_len = 0;
  	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
  		head = &avc->avc_cache.slots[i];
  		if (!hlist_empty(head)) {
  			slots_used++;
  			chain_len = 0;
  			hlist_for_each_entry_rcu(node, head, list)
  				chain_len++;
  			if (chain_len > max_chain_len)
  				max_chain_len = chain_len;
  		}
  	}
  
  	rcu_read_unlock();
  
  	return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
  			 "longest chain: %d\n",
  			 atomic_read(&avc->avc_cache.active_nodes),
  			 slots_used, AVC_CACHE_SLOTS, max_chain_len);
  }
  
  /*
   * using a linked list for extended_perms_decision lookup because the list is
   * always small. i.e. less than 5, typically 1
   */
  static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
  					struct avc_xperms_node *xp_node)
  {
  	struct avc_xperms_decision_node *xpd_node;
  
  	list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
  		if (xpd_node->xpd.driver == driver)
  			return &xpd_node->xpd;
  	}
  	return NULL;
  }
  
  static inline unsigned int
  avc_xperms_has_perm(struct extended_perms_decision *xpd,
  					u8 perm, u8 which)
  {
  	unsigned int rc = 0;
  
  	if ((which == XPERMS_ALLOWED) &&
  			(xpd->used & XPERMS_ALLOWED))
  		rc = security_xperm_test(xpd->allowed->p, perm);
  	else if ((which == XPERMS_AUDITALLOW) &&
  			(xpd->used & XPERMS_AUDITALLOW))
  		rc = security_xperm_test(xpd->auditallow->p, perm);
  	else if ((which == XPERMS_DONTAUDIT) &&
  			(xpd->used & XPERMS_DONTAUDIT))
  		rc = security_xperm_test(xpd->dontaudit->p, perm);
  	return rc;
  }
  
  static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
  				u8 driver, u8 perm)
  {
  	struct extended_perms_decision *xpd;
  	security_xperm_set(xp_node->xp.drivers.p, driver);
  	xpd = avc_xperms_decision_lookup(driver, xp_node);
  	if (xpd && xpd->allowed)
  		security_xperm_set(xpd->allowed->p, perm);
  }
  
  static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
  {
  	struct extended_perms_decision *xpd;
  
  	xpd = &xpd_node->xpd;
  	if (xpd->allowed)
  		kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
  	if (xpd->auditallow)
  		kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
  	if (xpd->dontaudit)
  		kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
  	kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
  }
  
  static void avc_xperms_free(struct avc_xperms_node *xp_node)
  {
  	struct avc_xperms_decision_node *xpd_node, *tmp;
  
  	if (!xp_node)
  		return;
  
  	list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
  		list_del(&xpd_node->xpd_list);
  		avc_xperms_decision_free(xpd_node);
  	}
  	kmem_cache_free(avc_xperms_cachep, xp_node);
  }
  
  static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
  					struct extended_perms_decision *src)
  {
  	dest->driver = src->driver;
  	dest->used = src->used;
  	if (dest->used & XPERMS_ALLOWED)
  		memcpy(dest->allowed->p, src->allowed->p,
  				sizeof(src->allowed->p));
  	if (dest->used & XPERMS_AUDITALLOW)
  		memcpy(dest->auditallow->p, src->auditallow->p,
  				sizeof(src->auditallow->p));
  	if (dest->used & XPERMS_DONTAUDIT)
  		memcpy(dest->dontaudit->p, src->dontaudit->p,
  				sizeof(src->dontaudit->p));
  }
  
  /*
   * similar to avc_copy_xperms_decision, but only copy decision
   * information relevant to this perm
   */
  static inline void avc_quick_copy_xperms_decision(u8 perm,
  			struct extended_perms_decision *dest,
  			struct extended_perms_decision *src)
  {
  	/*
  	 * compute index of the u32 of the 256 bits (8 u32s) that contain this
  	 * command permission
  	 */
  	u8 i = perm >> 5;
  
  	dest->used = src->used;
  	if (dest->used & XPERMS_ALLOWED)
  		dest->allowed->p[i] = src->allowed->p[i];
  	if (dest->used & XPERMS_AUDITALLOW)
  		dest->auditallow->p[i] = src->auditallow->p[i];
  	if (dest->used & XPERMS_DONTAUDIT)
  		dest->dontaudit->p[i] = src->dontaudit->p[i];
  }
  
  static struct avc_xperms_decision_node
  		*avc_xperms_decision_alloc(u8 which)
  {
  	struct avc_xperms_decision_node *xpd_node;
  	struct extended_perms_decision *xpd;
  
  	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
  	if (!xpd_node)
  		return NULL;
  
  	xpd = &xpd_node->xpd;
  	if (which & XPERMS_ALLOWED) {
  		xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
  						GFP_NOWAIT);
  		if (!xpd->allowed)
  			goto error;
  	}
  	if (which & XPERMS_AUDITALLOW) {
  		xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
  						GFP_NOWAIT);
  		if (!xpd->auditallow)
  			goto error;
  	}
  	if (which & XPERMS_DONTAUDIT) {
  		xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
  						GFP_NOWAIT);
  		if (!xpd->dontaudit)
  			goto error;
  	}
  	return xpd_node;
  error:
  	avc_xperms_decision_free(xpd_node);
  	return NULL;
  }
  
  static int avc_add_xperms_decision(struct avc_node *node,
  			struct extended_perms_decision *src)
  {
  	struct avc_xperms_decision_node *dest_xpd;
  
  	node->ae.xp_node->xp.len++;
  	dest_xpd = avc_xperms_decision_alloc(src->used);
  	if (!dest_xpd)
  		return -ENOMEM;
  	avc_copy_xperms_decision(&dest_xpd->xpd, src);
  	list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
  	return 0;
  }
  
  static struct avc_xperms_node *avc_xperms_alloc(void)
  {
  	struct avc_xperms_node *xp_node;
  
  	xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
  	if (!xp_node)
  		return xp_node;
  	INIT_LIST_HEAD(&xp_node->xpd_head);
  	return xp_node;
  }
  
  static int avc_xperms_populate(struct avc_node *node,
  				struct avc_xperms_node *src)
  {
  	struct avc_xperms_node *dest;
  	struct avc_xperms_decision_node *dest_xpd;
  	struct avc_xperms_decision_node *src_xpd;
  
  	if (src->xp.len == 0)
  		return 0;
  	dest = avc_xperms_alloc();
  	if (!dest)
  		return -ENOMEM;
  
  	memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
  	dest->xp.len = src->xp.len;
  
  	/* for each source xpd allocate a destination xpd and copy */
  	list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
  		dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
  		if (!dest_xpd)
  			goto error;
  		avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
  		list_add(&dest_xpd->xpd_list, &dest->xpd_head);
  	}
  	node->ae.xp_node = dest;
  	return 0;
  error:
  	avc_xperms_free(dest);
  	return -ENOMEM;
  
  }
  
  static inline u32 avc_xperms_audit_required(u32 requested,
  					struct av_decision *avd,
  					struct extended_perms_decision *xpd,
  					u8 perm,
  					int result,
  					u32 *deniedp)
  {
  	u32 denied, audited;
  
  	denied = requested & ~avd->allowed;
  	if (unlikely(denied)) {
  		audited = denied & avd->auditdeny;
  		if (audited && xpd) {
  			if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
  				audited &= ~requested;
  		}
  	} else if (result) {
  		audited = denied = requested;
  	} else {
  		audited = requested & avd->auditallow;
  		if (audited && xpd) {
  			if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
  				audited &= ~requested;
  		}
  	}
  
  	*deniedp = denied;
  	return audited;
  }
  
  static inline int avc_xperms_audit(struct selinux_state *state,
  				   u32 ssid, u32 tsid, u16 tclass,
  				   u32 requested, struct av_decision *avd,
  				   struct extended_perms_decision *xpd,
  				   u8 perm, int result,
  				   struct common_audit_data *ad)
  {
  	u32 audited, denied;
  
  	audited = avc_xperms_audit_required(
  			requested, avd, xpd, perm, result, &denied);
  	if (likely(!audited))
  		return 0;
  	return slow_avc_audit(state, ssid, tsid, tclass, requested,
  			audited, denied, result, ad);
  }
  
  static void avc_node_free(struct rcu_head *rhead)
  {
  	struct avc_node *node = container_of(rhead, struct avc_node, rhead);
  	avc_xperms_free(node->ae.xp_node);
  	kmem_cache_free(avc_node_cachep, node);
  	avc_cache_stats_incr(frees);
  }
  
  static void avc_node_delete(struct selinux_avc *avc, struct avc_node *node)
  {
  	hlist_del_rcu(&node->list);
  	call_rcu(&node->rhead, avc_node_free);
  	atomic_dec(&avc->avc_cache.active_nodes);
  }
  
  static void avc_node_kill(struct selinux_avc *avc, struct avc_node *node)
  {
  	avc_xperms_free(node->ae.xp_node);
  	kmem_cache_free(avc_node_cachep, node);
  	avc_cache_stats_incr(frees);
  	atomic_dec(&avc->avc_cache.active_nodes);
  }
  
  static void avc_node_replace(struct selinux_avc *avc,
  			     struct avc_node *new, struct avc_node *old)
  {
  	hlist_replace_rcu(&old->list, &new->list);
  	call_rcu(&old->rhead, avc_node_free);
  	atomic_dec(&avc->avc_cache.active_nodes);
  }
  
  static inline int avc_reclaim_node(struct selinux_avc *avc)
  {
  	struct avc_node *node;
  	int hvalue, try, ecx;
  	unsigned long flags;
  	struct hlist_head *head;
  	spinlock_t *lock;
  
  	for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
  		hvalue = atomic_inc_return(&avc->avc_cache.lru_hint) &
  			(AVC_CACHE_SLOTS - 1);
  		head = &avc->avc_cache.slots[hvalue];
  		lock = &avc->avc_cache.slots_lock[hvalue];
  
  		if (!spin_trylock_irqsave(lock, flags))
  			continue;
  
  		rcu_read_lock();
  		hlist_for_each_entry(node, head, list) {
  			avc_node_delete(avc, node);
  			avc_cache_stats_incr(reclaims);
  			ecx++;
  			if (ecx >= AVC_CACHE_RECLAIM) {
  				rcu_read_unlock();
  				spin_unlock_irqrestore(lock, flags);
  				goto out;
  			}
  		}
  		rcu_read_unlock();
  		spin_unlock_irqrestore(lock, flags);
  	}
  out:
  	return ecx;
  }
  
  static struct avc_node *avc_alloc_node(struct selinux_avc *avc)
  {
  	struct avc_node *node;
  
  	node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
  	if (!node)
  		goto out;
  
  	INIT_HLIST_NODE(&node->list);
  	avc_cache_stats_incr(allocations);
  
  	if (atomic_inc_return(&avc->avc_cache.active_nodes) >
  	    avc->avc_cache_threshold)
  		avc_reclaim_node(avc);
  
  out:
  	return node;
  }
  
  static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
  {
  	node->ae.ssid = ssid;
  	node->ae.tsid = tsid;
  	node->ae.tclass = tclass;
  	memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
  }
  
  static inline struct avc_node *avc_search_node(struct selinux_avc *avc,
  					       u32 ssid, u32 tsid, u16 tclass)
  {
  	struct avc_node *node, *ret = NULL;
  	int hvalue;
  	struct hlist_head *head;
  
  	hvalue = avc_hash(ssid, tsid, tclass);
  	head = &avc->avc_cache.slots[hvalue];
  	hlist_for_each_entry_rcu(node, head, list) {
  		if (ssid == node->ae.ssid &&
  		    tclass == node->ae.tclass &&
  		    tsid == node->ae.tsid) {
  			ret = node;
  			break;
  		}
  	}
  
  	return ret;
  }
  
  /**
   * avc_lookup - Look up an AVC entry.
   * @ssid: source security identifier
   * @tsid: target security identifier
   * @tclass: target security class
   *
   * Look up an AVC entry that is valid for the
   * (@ssid, @tsid), interpreting the permissions
   * based on @tclass.  If a valid AVC entry exists,
   * then this function returns the avc_node.
   * Otherwise, this function returns NULL.
   */
  static struct avc_node *avc_lookup(struct selinux_avc *avc,
  				   u32 ssid, u32 tsid, u16 tclass)
  {
  	struct avc_node *node;
  
  	avc_cache_stats_incr(lookups);
  	node = avc_search_node(avc, ssid, tsid, tclass);
  
  	if (node)
  		return node;
  
  	avc_cache_stats_incr(misses);
  	return NULL;
  }
  
  static int avc_latest_notif_update(struct selinux_avc *avc,
  				   int seqno, int is_insert)
  {
  	int ret = 0;
  	static DEFINE_SPINLOCK(notif_lock);
  	unsigned long flag;
  
  	spin_lock_irqsave(&notif_lock, flag);
  	if (is_insert) {
  		if (seqno < avc->avc_cache.latest_notif) {
  			pr_warn("SELinux: avc:  seqno %d < latest_notif %d\n",
  			       seqno, avc->avc_cache.latest_notif);
  			ret = -EAGAIN;
  		}
  	} else {
  		if (seqno > avc->avc_cache.latest_notif)
  			avc->avc_cache.latest_notif = seqno;
  	}
  	spin_unlock_irqrestore(&notif_lock, flag);
  
  	return ret;
  }
  
  /**
   * avc_insert - Insert an AVC entry.
   * @ssid: source security identifier
   * @tsid: target security identifier
   * @tclass: target security class
   * @avd: resulting av decision
   * @xp_node: resulting extended permissions
   *
   * Insert an AVC entry for the SID pair
   * (@ssid, @tsid) and class @tclass.
   * The access vectors and the sequence number are
   * normally provided by the security server in
   * response to a security_compute_av() call.  If the
   * sequence number @avd->seqno is not less than the latest
   * revocation notification, then the function copies
   * the access vectors into a cache entry, returns
   * avc_node inserted. Otherwise, this function returns NULL.
   */
  static struct avc_node *avc_insert(struct selinux_avc *avc,
  				   u32 ssid, u32 tsid, u16 tclass,
  				   struct av_decision *avd,
  				   struct avc_xperms_node *xp_node)
  {
  	struct avc_node *pos, *node = NULL;
  	int hvalue;
  	unsigned long flag;
  	spinlock_t *lock;
  	struct hlist_head *head;
  
  	if (avc_latest_notif_update(avc, avd->seqno, 1))
  		return NULL;
  
  	node = avc_alloc_node(avc);
  	if (!node)
  		return NULL;
  
  	avc_node_populate(node, ssid, tsid, tclass, avd);
  	if (avc_xperms_populate(node, xp_node)) {
  		avc_node_kill(avc, node);
  		return NULL;
  	}
  
  	hvalue = avc_hash(ssid, tsid, tclass);
  	head = &avc->avc_cache.slots[hvalue];
  	lock = &avc->avc_cache.slots_lock[hvalue];
  	spin_lock_irqsave(lock, flag);
  	hlist_for_each_entry(pos, head, list) {
  		if (pos->ae.ssid == ssid &&
  			pos->ae.tsid == tsid &&
  			pos->ae.tclass == tclass) {
  			avc_node_replace(avc, node, pos);
  			goto found;
  		}
  	}
  	hlist_add_head_rcu(&node->list, head);
  found:
  	spin_unlock_irqrestore(lock, flag);
  	return node;
  }
  
  /**
   * avc_audit_pre_callback - SELinux specific information
   * will be called by generic audit code
   * @ab: the audit buffer
   * @a: audit_data
   */
  static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
  {
  	struct common_audit_data *ad = a;
  	struct selinux_audit_data *sad = ad->selinux_audit_data;
  	u32 av = sad->audited;
  	const char **perms;
  	int i, perm;
  
  	audit_log_format(ab, "avc:  %s ", sad->denied ? "denied" : "granted");
  
  	if (av == 0) {
  		audit_log_format(ab, " null");
  		return;
  	}
  
  	perms = secclass_map[sad->tclass-1].perms;
  
  	audit_log_format(ab, " {");
  	i = 0;
  	perm = 1;
  	while (i < (sizeof(av) * 8)) {
  		if ((perm & av) && perms[i]) {
  			audit_log_format(ab, " %s", perms[i]);
  			av &= ~perm;
  		}
  		i++;
  		perm <<= 1;
  	}
  
  	if (av)
  		audit_log_format(ab, " 0x%x", av);
  
  	audit_log_format(ab, " } for ");
  }
  
  /**
   * avc_audit_post_callback - SELinux specific information
   * will be called by generic audit code
   * @ab: the audit buffer
   * @a: audit_data
   */
  static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
  {
  	struct common_audit_data *ad = a;
  	struct selinux_audit_data *sad = ad->selinux_audit_data;
  	char *scontext;
  	u32 scontext_len;
  	int rc;
  
  	rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
  				     &scontext_len);
  	if (rc)
  		audit_log_format(ab, " ssid=%d", sad->ssid);
  	else {
  		audit_log_format(ab, " scontext=%s", scontext);
  		kfree(scontext);
  	}
  
  	rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
  				     &scontext_len);
  	if (rc)
  		audit_log_format(ab, " tsid=%d", sad->tsid);
  	else {
  		audit_log_format(ab, " tcontext=%s", scontext);
  		kfree(scontext);
  	}
  
  	audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);
  
  	if (sad->denied)
  		audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
  
  	/* in case of invalid context report also the actual context string */
  	rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
  					   &scontext_len);
  	if (!rc && scontext) {
  		if (scontext_len && scontext[scontext_len - 1] == '\0')
  			scontext_len--;
  		audit_log_format(ab, " srawcon=");
  		audit_log_n_untrustedstring(ab, scontext, scontext_len);
  		kfree(scontext);
  	}
  
  	rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
  					   &scontext_len);
  	if (!rc && scontext) {
  		if (scontext_len && scontext[scontext_len - 1] == '\0')
  			scontext_len--;
  		audit_log_format(ab, " trawcon=");
  		audit_log_n_untrustedstring(ab, scontext, scontext_len);
  		kfree(scontext);
  	}
  }
  
  /* This is the slow part of avc audit with big stack footprint */
  noinline int slow_avc_audit(struct selinux_state *state,
  			    u32 ssid, u32 tsid, u16 tclass,
  			    u32 requested, u32 audited, u32 denied, int result,
  			    struct common_audit_data *a)
  {
  	struct common_audit_data stack_data;
  	struct selinux_audit_data sad;
  
  	if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
  		return -EINVAL;
  
  	if (!a) {
  		a = &stack_data;
  		a->type = LSM_AUDIT_DATA_NONE;
  	}
  
  	sad.tclass = tclass;
  	sad.requested = requested;
  	sad.ssid = ssid;
  	sad.tsid = tsid;
  	sad.audited = audited;
  	sad.denied = denied;
  	sad.result = result;
  	sad.state = state;
  
  	a->selinux_audit_data = &sad;
  
  	common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
  	return 0;
  }
  
  /**
   * avc_add_callback - Register a callback for security events.
   * @callback: callback function
   * @events: security events
   *
   * Register a callback function for events in the set @events.
   * Returns %0 on success or -%ENOMEM if insufficient memory
   * exists to add the callback.
   */
  int __init avc_add_callback(int (*callback)(u32 event), u32 events)
  {
  	struct avc_callback_node *c;
  	int rc = 0;
  
  	c = kmalloc(sizeof(*c), GFP_KERNEL);
  	if (!c) {
  		rc = -ENOMEM;
  		goto out;
  	}
  
  	c->callback = callback;
  	c->events = events;
  	c->next = avc_callbacks;
  	avc_callbacks = c;
  out:
  	return rc;
  }
  
  /**
   * avc_update_node Update an AVC entry
   * @event : Updating event
   * @perms : Permission mask bits
   * @ssid,@tsid,@tclass : identifier of an AVC entry
   * @seqno : sequence number when decision was made
   * @xpd: extended_perms_decision to be added to the node
   * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
   *
   * if a valid AVC entry doesn't exist,this function returns -ENOENT.
   * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
   * otherwise, this function updates the AVC entry. The original AVC-entry object
   * will release later by RCU.
   */
  static int avc_update_node(struct selinux_avc *avc,
  			   u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
  			   u32 tsid, u16 tclass, u32 seqno,
  			   struct extended_perms_decision *xpd,
  			   u32 flags)
  {
  	int hvalue, rc = 0;
  	unsigned long flag;
  	struct avc_node *pos, *node, *orig = NULL;
  	struct hlist_head *head;
  	spinlock_t *lock;
  
  	/*
  	 * If we are in a non-blocking code path, e.g. VFS RCU walk,
  	 * then we must not add permissions to a cache entry
  	 * because we will not audit the denial.  Otherwise,
  	 * during the subsequent blocking retry (e.g. VFS ref walk), we
  	 * will find the permissions already granted in the cache entry
  	 * and won't audit anything at all, leading to silent denials in
  	 * permissive mode that only appear when in enforcing mode.
  	 *
  	 * See the corresponding handling of MAY_NOT_BLOCK in avc_audit()
  	 * and selinux_inode_permission().
  	 */
  	if (flags & AVC_NONBLOCKING)
  		return 0;
  
  	node = avc_alloc_node(avc);
  	if (!node) {
  		rc = -ENOMEM;
  		goto out;
  	}
  
  	/* Lock the target slot */
  	hvalue = avc_hash(ssid, tsid, tclass);
  
  	head = &avc->avc_cache.slots[hvalue];
  	lock = &avc->avc_cache.slots_lock[hvalue];
  
  	spin_lock_irqsave(lock, flag);
  
  	hlist_for_each_entry(pos, head, list) {
  		if (ssid == pos->ae.ssid &&
  		    tsid == pos->ae.tsid &&
  		    tclass == pos->ae.tclass &&
  		    seqno == pos->ae.avd.seqno){
  			orig = pos;
  			break;
  		}
  	}
  
  	if (!orig) {
  		rc = -ENOENT;
  		avc_node_kill(avc, node);
  		goto out_unlock;
  	}
  
  	/*
  	 * Copy and replace original node.
  	 */
  
  	avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
  
  	if (orig->ae.xp_node) {
  		rc = avc_xperms_populate(node, orig->ae.xp_node);
  		if (rc) {
  			avc_node_kill(avc, node);
  			goto out_unlock;
  		}
  	}
  
  	switch (event) {
  	case AVC_CALLBACK_GRANT:
  		node->ae.avd.allowed |= perms;
  		if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
  			avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
  		break;
  	case AVC_CALLBACK_TRY_REVOKE:
  	case AVC_CALLBACK_REVOKE:
  		node->ae.avd.allowed &= ~perms;
  		break;
  	case AVC_CALLBACK_AUDITALLOW_ENABLE:
  		node->ae.avd.auditallow |= perms;
  		break;
  	case AVC_CALLBACK_AUDITALLOW_DISABLE:
  		node->ae.avd.auditallow &= ~perms;
  		break;
  	case AVC_CALLBACK_AUDITDENY_ENABLE:
  		node->ae.avd.auditdeny |= perms;
  		break;
  	case AVC_CALLBACK_AUDITDENY_DISABLE:
  		node->ae.avd.auditdeny &= ~perms;
  		break;
  	case AVC_CALLBACK_ADD_XPERMS:
  		avc_add_xperms_decision(node, xpd);
  		break;
  	}
  	avc_node_replace(avc, node, orig);
  out_unlock:
  	spin_unlock_irqrestore(lock, flag);
  out:
  	return rc;
  }
  
  /**
   * avc_flush - Flush the cache
   */
  static void avc_flush(struct selinux_avc *avc)
  {
  	struct hlist_head *head;
  	struct avc_node *node;
  	spinlock_t *lock;
  	unsigned long flag;
  	int i;
  
  	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
  		head = &avc->avc_cache.slots[i];
  		lock = &avc->avc_cache.slots_lock[i];
  
  		spin_lock_irqsave(lock, flag);
  		/*
  		 * With preemptable RCU, the outer spinlock does not
  		 * prevent RCU grace periods from ending.
  		 */
  		rcu_read_lock();
  		hlist_for_each_entry(node, head, list)
  			avc_node_delete(avc, node);
  		rcu_read_unlock();
  		spin_unlock_irqrestore(lock, flag);
  	}
  }
  
  /**
   * avc_ss_reset - Flush the cache and revalidate migrated permissions.
   * @seqno: policy sequence number
   */
  int avc_ss_reset(struct selinux_avc *avc, u32 seqno)
  {
  	struct avc_callback_node *c;
  	int rc = 0, tmprc;
  
  	avc_flush(avc);
  
  	for (c = avc_callbacks; c; c = c->next) {
  		if (c->events & AVC_CALLBACK_RESET) {
  			tmprc = c->callback(AVC_CALLBACK_RESET);
  			/* save the first error encountered for the return
  			   value and continue processing the callbacks */
  			if (!rc)
  				rc = tmprc;
  		}
  	}
  
  	avc_latest_notif_update(avc, seqno, 0);
  	return rc;
  }
  
  /*
   * Slow-path helper function for avc_has_perm_noaudit,
   * when the avc_node lookup fails. We get called with
   * the RCU read lock held, and need to return with it
   * still held, but drop if for the security compute.
   *
   * Don't inline this, since it's the slow-path and just
   * results in a bigger stack frame.
   */
  static noinline
  struct avc_node *avc_compute_av(struct selinux_state *state,
  				u32 ssid, u32 tsid,
  				u16 tclass, struct av_decision *avd,
  				struct avc_xperms_node *xp_node)
  {
  	rcu_read_unlock();
  	INIT_LIST_HEAD(&xp_node->xpd_head);
  	security_compute_av(state, ssid, tsid, tclass, avd, &xp_node->xp);
  	rcu_read_lock();
  	return avc_insert(state->avc, ssid, tsid, tclass, avd, xp_node);
  }
  
  static noinline int avc_denied(struct selinux_state *state,
  			       u32 ssid, u32 tsid,
  			       u16 tclass, u32 requested,
  			       u8 driver, u8 xperm, unsigned int flags,
  			       struct av_decision *avd)
  {
  	if (flags & AVC_STRICT)
  		return -EACCES;
  
  	if (enforcing_enabled(state) &&
  	    !(avd->flags & AVD_FLAGS_PERMISSIVE))
  		return -EACCES;
  
  	avc_update_node(state->avc, AVC_CALLBACK_GRANT, requested, driver,
  			xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
  	return 0;
  }
  
  /*
   * The avc extended permissions logic adds an additional 256 bits of
   * permissions to an avc node when extended permissions for that node are
   * specified in the avtab. If the additional 256 permissions is not adequate,
   * as-is the case with ioctls, then multiple may be chained together and the
   * driver field is used to specify which set contains the permission.
   */
  int avc_has_extended_perms(struct selinux_state *state,
  			   u32 ssid, u32 tsid, u16 tclass, u32 requested,
  			   u8 driver, u8 xperm, struct common_audit_data *ad)
  {
  	struct avc_node *node;
  	struct av_decision avd;
  	u32 denied;
  	struct extended_perms_decision local_xpd;
  	struct extended_perms_decision *xpd = NULL;
  	struct extended_perms_data allowed;
  	struct extended_perms_data auditallow;
  	struct extended_perms_data dontaudit;
  	struct avc_xperms_node local_xp_node;
  	struct avc_xperms_node *xp_node;
  	int rc = 0, rc2;
  
  	xp_node = &local_xp_node;
  	if (WARN_ON(!requested))
  		return -EACCES;
  
  	rcu_read_lock();
  
  	node = avc_lookup(state->avc, ssid, tsid, tclass);
  	if (unlikely(!node)) {
  		node = avc_compute_av(state, ssid, tsid, tclass, &avd, xp_node);
  	} else {
  		memcpy(&avd, &node->ae.avd, sizeof(avd));
  		xp_node = node->ae.xp_node;
  	}
  	/* if extended permissions are not defined, only consider av_decision */
  	if (!xp_node || !xp_node->xp.len)
  		goto decision;
  
  	local_xpd.allowed = &allowed;
  	local_xpd.auditallow = &auditallow;
  	local_xpd.dontaudit = &dontaudit;
  
  	xpd = avc_xperms_decision_lookup(driver, xp_node);
  	if (unlikely(!xpd)) {
  		/*
  		 * Compute the extended_perms_decision only if the driver
  		 * is flagged
  		 */
  		if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
  			avd.allowed &= ~requested;
  			goto decision;
  		}
  		rcu_read_unlock();
  		security_compute_xperms_decision(state, ssid, tsid, tclass,
  						 driver, &local_xpd);
  		rcu_read_lock();
  		avc_update_node(state->avc, AVC_CALLBACK_ADD_XPERMS, requested,
  				driver, xperm, ssid, tsid, tclass, avd.seqno,
  				&local_xpd, 0);
  	} else {
  		avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
  	}
  	xpd = &local_xpd;
  
  	if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
  		avd.allowed &= ~requested;
  
  decision:
  	denied = requested & ~(avd.allowed);
  	if (unlikely(denied))
  		rc = avc_denied(state, ssid, tsid, tclass, requested,
  				driver, xperm, AVC_EXTENDED_PERMS, &avd);
  
  	rcu_read_unlock();
  
  	rc2 = avc_xperms_audit(state, ssid, tsid, tclass, requested,
  			&avd, xpd, xperm, rc, ad);
  	if (rc2)
  		return rc2;
  	return rc;
  }
  
  /**
   * avc_has_perm_noaudit - Check permissions but perform no auditing.
   * @ssid: source security identifier
   * @tsid: target security identifier
   * @tclass: target security class
   * @requested: requested permissions, interpreted based on @tclass
   * @flags:  AVC_STRICT, AVC_NONBLOCKING, or 0
   * @avd: access vector decisions
   *
   * Check the AVC to determine whether the @requested permissions are granted
   * for the SID pair (@ssid, @tsid), interpreting the permissions
   * based on @tclass, and call the security server on a cache miss to obtain
   * a new decision and add it to the cache.  Return a copy of the decisions
   * in @avd.  Return %0 if all @requested permissions are granted,
   * -%EACCES if any permissions are denied, or another -errno upon
   * other errors.  This function is typically called by avc_has_perm(),
   * but may also be called directly to separate permission checking from
   * auditing, e.g. in cases where a lock must be held for the check but
   * should be released for the auditing.
   */
  inline int avc_has_perm_noaudit(struct selinux_state *state,
  				u32 ssid, u32 tsid,
  				u16 tclass, u32 requested,
  				unsigned int flags,
  				struct av_decision *avd)
  {
  	struct avc_node *node;
  	struct avc_xperms_node xp_node;
  	int rc = 0;
  	u32 denied;
  
  	if (WARN_ON(!requested))
  		return -EACCES;
  
  	rcu_read_lock();
  
  	node = avc_lookup(state->avc, ssid, tsid, tclass);
  	if (unlikely(!node))
  		node = avc_compute_av(state, ssid, tsid, tclass, avd, &xp_node);
  	else
  		memcpy(avd, &node->ae.avd, sizeof(*avd));
  
  	denied = requested & ~(avd->allowed);
  	if (unlikely(denied))
  		rc = avc_denied(state, ssid, tsid, tclass, requested, 0, 0,
  				flags, avd);
  
  	rcu_read_unlock();
  	return rc;
  }
  
  /**
   * avc_has_perm - Check permissions and perform any appropriate auditing.
   * @ssid: source security identifier
   * @tsid: target security identifier
   * @tclass: target security class
   * @requested: requested permissions, interpreted based on @tclass
   * @auditdata: auxiliary audit data
   *
   * Check the AVC to determine whether the @requested permissions are granted
   * for the SID pair (@ssid, @tsid), interpreting the permissions
   * based on @tclass, and call the security server on a cache miss to obtain
   * a new decision and add it to the cache.  Audit the granting or denial of
   * permissions in accordance with the policy.  Return %0 if all @requested
   * permissions are granted, -%EACCES if any permissions are denied, or
   * another -errno upon other errors.
   */
  int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
  		 u32 requested, struct common_audit_data *auditdata)
  {
  	struct av_decision avd;
  	int rc, rc2;
  
  	rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
  				  &avd);
  
  	rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
  			auditdata, 0);
  	if (rc2)
  		return rc2;
  	return rc;
  }
  
  int avc_has_perm_flags(struct selinux_state *state,
  		       u32 ssid, u32 tsid, u16 tclass, u32 requested,
  		       struct common_audit_data *auditdata,
  		       int flags)
  {
  	struct av_decision avd;
  	int rc, rc2;
  
  	rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested,
  				  (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
  				  &avd);
  
  	rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
  			auditdata, flags);
  	if (rc2)
  		return rc2;
  	return rc;
  }
  
  u32 avc_policy_seqno(struct selinux_state *state)
  {
  	return state->avc->avc_cache.latest_notif;
  }
  
  void avc_disable(void)
  {
  	/*
  	 * If you are looking at this because you have realized that we are
  	 * not destroying the avc_node_cachep it might be easy to fix, but
  	 * I don't know the memory barrier semantics well enough to know.  It's
  	 * possible that some other task dereferenced security_ops when
  	 * it still pointed to selinux operations.  If that is the case it's
  	 * possible that it is about to use the avc and is about to need the
  	 * avc_node_cachep.  I know I could wrap the security.c security_ops call
  	 * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
  	 * the cache and get that memory back.
  	 */
  	if (avc_node_cachep) {
  		avc_flush(selinux_state.avc);
  		/* kmem_cache_destroy(avc_node_cachep); */
  	}
  }
  