text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * linux/net/sunrpc/auth.c
   *
   * Generic RPC client authentication API.
   *
   * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
   */
  
  #include <linux/types.h>
  #include <linux/sched.h>
  #include <linux/cred.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/errno.h>
  #include <linux/hash.h>
  #include <linux/sunrpc/clnt.h>
  #include <linux/sunrpc/gss_api.h>
  #include <linux/spinlock.h>
  
  #include <trace/events/sunrpc.h>
  
  #define RPC_CREDCACHE_DEFAULT_HASHBITS	(4)
  struct rpc_cred_cache {
  	struct hlist_head	*hashtable;
  	unsigned int		hashbits;
  	spinlock_t		lock;
  };
  
  static unsigned int auth_hashbits = RPC_CREDCACHE_DEFAULT_HASHBITS;
  
  static const struct rpc_authops __rcu *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
  	[RPC_AUTH_NULL] = (const struct rpc_authops __force __rcu *)&authnull_ops,
  	[RPC_AUTH_UNIX] = (const struct rpc_authops __force __rcu *)&authunix_ops,
  	NULL,			/* others can be loadable modules */
  };
  
  static LIST_HEAD(cred_unused);
  static unsigned long number_cred_unused;
  
  static struct cred machine_cred = {
  	.usage = ATOMIC_INIT(1),
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	.magic = CRED_MAGIC,
  #endif
  };
  
  /*
   * Return the machine_cred pointer to be used whenever
   * the a generic machine credential is needed.
   */
  const struct cred *rpc_machine_cred(void)
  {
  	return &machine_cred;
  }
  EXPORT_SYMBOL_GPL(rpc_machine_cred);
  
  #define MAX_HASHTABLE_BITS (14)
  static int param_set_hashtbl_sz(const char *val, const struct kernel_param *kp)
  {
  	unsigned long num;
  	unsigned int nbits;
  	int ret;
  
  	if (!val)
  		goto out_inval;
  	ret = kstrtoul(val, 0, &num);
  	if (ret)
  		goto out_inval;
  	nbits = fls(num - 1);
  	if (nbits > MAX_HASHTABLE_BITS || nbits < 2)
  		goto out_inval;
  	*(unsigned int *)kp->arg = nbits;
  	return 0;
  out_inval:
  	return -EINVAL;
  }
  
  static int param_get_hashtbl_sz(char *buffer, const struct kernel_param *kp)
  {
  	unsigned int nbits;
  
  	nbits = *(unsigned int *)kp->arg;
  	return sprintf(buffer, "%u", 1U << nbits);
  }
  
  #define param_check_hashtbl_sz(name, p) __param_check(name, p, unsigned int);
  
  static const struct kernel_param_ops param_ops_hashtbl_sz = {
  	.set = param_set_hashtbl_sz,
  	.get = param_get_hashtbl_sz,
  };
  
  module_param_named(auth_hashtable_size, auth_hashbits, hashtbl_sz, 0644);
  MODULE_PARM_DESC(auth_hashtable_size, "RPC credential cache hashtable size");
  
  static unsigned long auth_max_cred_cachesize = ULONG_MAX;
  module_param(auth_max_cred_cachesize, ulong, 0644);
  MODULE_PARM_DESC(auth_max_cred_cachesize, "RPC credential maximum total cache size");
  
  static u32
  pseudoflavor_to_flavor(u32 flavor) {
  	if (flavor > RPC_AUTH_MAXFLAVOR)
  		return RPC_AUTH_GSS;
  	return flavor;
  }
  
  int
  rpcauth_register(const struct rpc_authops *ops)
  {
  	const struct rpc_authops *old;
  	rpc_authflavor_t flavor;
  
  	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
  		return -EINVAL;
  	old = cmpxchg((const struct rpc_authops ** __force)&auth_flavors[flavor], NULL, ops);
  	if (old == NULL || old == ops)
  		return 0;
  	return -EPERM;
  }
  EXPORT_SYMBOL_GPL(rpcauth_register);
  
  int
  rpcauth_unregister(const struct rpc_authops *ops)
  {
  	const struct rpc_authops *old;
  	rpc_authflavor_t flavor;
  
  	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
  		return -EINVAL;
  
  	old = cmpxchg((const struct rpc_authops ** __force)&auth_flavors[flavor], ops, NULL);
  	if (old == ops || old == NULL)
  		return 0;
  	return -EPERM;
  }
  EXPORT_SYMBOL_GPL(rpcauth_unregister);
  
  static const struct rpc_authops *
  rpcauth_get_authops(rpc_authflavor_t flavor)
  {
  	const struct rpc_authops *ops;
  
  	if (flavor >= RPC_AUTH_MAXFLAVOR)
  		return NULL;
  
  	rcu_read_lock();
  	ops = rcu_dereference(auth_flavors[flavor]);
  	if (ops == NULL) {
  		rcu_read_unlock();
  		request_module("rpc-auth-%u", flavor);
  		rcu_read_lock();
  		ops = rcu_dereference(auth_flavors[flavor]);
  		if (ops == NULL)
  			goto out;
  	}
  	if (!try_module_get(ops->owner))
  		ops = NULL;
  out:
  	rcu_read_unlock();
  	return ops;
  }
  
  static void
  rpcauth_put_authops(const struct rpc_authops *ops)
  {
  	module_put(ops->owner);
  }
  
  /**
   * rpcauth_get_pseudoflavor - check if security flavor is supported
   * @flavor: a security flavor
   * @info: a GSS mech OID, quality of protection, and service value
   *
   * Verifies that an appropriate kernel module is available or already loaded.
   * Returns an equivalent pseudoflavor, or RPC_AUTH_MAXFLAVOR if "flavor" is
   * not supported locally.
   */
  rpc_authflavor_t
  rpcauth_get_pseudoflavor(rpc_authflavor_t flavor, struct rpcsec_gss_info *info)
  {
  	const struct rpc_authops *ops = rpcauth_get_authops(flavor);
  	rpc_authflavor_t pseudoflavor;
  
  	if (!ops)
  		return RPC_AUTH_MAXFLAVOR;
  	pseudoflavor = flavor;
  	if (ops->info2flavor != NULL)
  		pseudoflavor = ops->info2flavor(info);
  
  	rpcauth_put_authops(ops);
  	return pseudoflavor;
  }
  EXPORT_SYMBOL_GPL(rpcauth_get_pseudoflavor);
  
  /**
   * rpcauth_get_gssinfo - find GSS tuple matching a GSS pseudoflavor
   * @pseudoflavor: GSS pseudoflavor to match
   * @info: rpcsec_gss_info structure to fill in
   *
   * Returns zero and fills in "info" if pseudoflavor matches a
   * supported mechanism.
   */
  int
  rpcauth_get_gssinfo(rpc_authflavor_t pseudoflavor, struct rpcsec_gss_info *info)
  {
  	rpc_authflavor_t flavor = pseudoflavor_to_flavor(pseudoflavor);
  	const struct rpc_authops *ops;
  	int result;
  
  	ops = rpcauth_get_authops(flavor);
  	if (ops == NULL)
  		return -ENOENT;
  
  	result = -ENOENT;
  	if (ops->flavor2info != NULL)
  		result = ops->flavor2info(pseudoflavor, info);
  
  	rpcauth_put_authops(ops);
  	return result;
  }
  EXPORT_SYMBOL_GPL(rpcauth_get_gssinfo);
  
  /**
   * rpcauth_list_flavors - discover registered flavors and pseudoflavors
   * @array: array to fill in
   * @size: size of "array"
   *
   * Returns the number of array items filled in, or a negative errno.
   *
   * The returned array is not sorted by any policy.  Callers should not
   * rely on the order of the items in the returned array.
   */
  int
  rpcauth_list_flavors(rpc_authflavor_t *array, int size)
  {
  	const struct rpc_authops *ops;
  	rpc_authflavor_t flavor, pseudos[4];
  	int i, len, result = 0;
  
  	rcu_read_lock();
  	for (flavor = 0; flavor < RPC_AUTH_MAXFLAVOR; flavor++) {
  		ops = rcu_dereference(auth_flavors[flavor]);
  		if (result >= size) {
  			result = -ENOMEM;
  			break;
  		}
  
  		if (ops == NULL)
  			continue;
  		if (ops->list_pseudoflavors == NULL) {
  			array[result++] = ops->au_flavor;
  			continue;
  		}
  		len = ops->list_pseudoflavors(pseudos, ARRAY_SIZE(pseudos));
  		if (len < 0) {
  			result = len;
  			break;
  		}
  		for (i = 0; i < len; i++) {
  			if (result >= size) {
  				result = -ENOMEM;
  				break;
  			}
  			array[result++] = pseudos[i];
  		}
  	}
  	rcu_read_unlock();
  	return result;
  }
  EXPORT_SYMBOL_GPL(rpcauth_list_flavors);
  
  struct rpc_auth *
  rpcauth_create(const struct rpc_auth_create_args *args, struct rpc_clnt *clnt)
  {
  	struct rpc_auth	*auth = ERR_PTR(-EINVAL);
  	const struct rpc_authops *ops;
  	u32 flavor = pseudoflavor_to_flavor(args->pseudoflavor);
  
  	ops = rpcauth_get_authops(flavor);
  	if (ops == NULL)
  		goto out;
  
  	auth = ops->create(args, clnt);
  
  	rpcauth_put_authops(ops);
  	if (IS_ERR(auth))
  		return auth;
  	if (clnt->cl_auth)
  		rpcauth_release(clnt->cl_auth);
  	clnt->cl_auth = auth;
  
  out:
  	return auth;
  }
  EXPORT_SYMBOL_GPL(rpcauth_create);
  
  void
  rpcauth_release(struct rpc_auth *auth)
  {
  	if (!refcount_dec_and_test(&auth->au_count))
  		return;
  	auth->au_ops->destroy(auth);
  }
  
  static DEFINE_SPINLOCK(rpc_credcache_lock);
  
  /*
   * On success, the caller is responsible for freeing the reference
   * held by the hashtable
   */
  static bool
  rpcauth_unhash_cred_locked(struct rpc_cred *cred)
  {
  	if (!test_and_clear_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags))
  		return false;
  	hlist_del_rcu(&cred->cr_hash);
  	return true;
  }
  
  static bool
  rpcauth_unhash_cred(struct rpc_cred *cred)
  {
  	spinlock_t *cache_lock;
  	bool ret;
  
  	if (!test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags))
  		return false;
  	cache_lock = &cred->cr_auth->au_credcache->lock;
  	spin_lock(cache_lock);
  	ret = rpcauth_unhash_cred_locked(cred);
  	spin_unlock(cache_lock);
  	return ret;
  }
  
  /*
   * Initialize RPC credential cache
   */
  int
  rpcauth_init_credcache(struct rpc_auth *auth)
  {
  	struct rpc_cred_cache *new;
  	unsigned int hashsize;
  
  	new = kmalloc(sizeof(*new), GFP_KERNEL);
  	if (!new)
  		goto out_nocache;
  	new->hashbits = auth_hashbits;
  	hashsize = 1U << new->hashbits;
  	new->hashtable = kcalloc(hashsize, sizeof(new->hashtable[0]), GFP_KERNEL);
  	if (!new->hashtable)
  		goto out_nohashtbl;
  	spin_lock_init(&new->lock);
  	auth->au_credcache = new;
  	return 0;
  out_nohashtbl:
  	kfree(new);
  out_nocache:
  	return -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(rpcauth_init_credcache);
  
  char *
  rpcauth_stringify_acceptor(struct rpc_cred *cred)
  {
  	if (!cred->cr_ops->crstringify_acceptor)
  		return NULL;
  	return cred->cr_ops->crstringify_acceptor(cred);
  }
  EXPORT_SYMBOL_GPL(rpcauth_stringify_acceptor);
  
  /*
   * Destroy a list of credentials
   */
  static inline
  void rpcauth_destroy_credlist(struct list_head *head)
  {
  	struct rpc_cred *cred;
  
  	while (!list_empty(head)) {
  		cred = list_entry(head->next, struct rpc_cred, cr_lru);
  		list_del_init(&cred->cr_lru);
  		put_rpccred(cred);
  	}
  }
  
  static void
  rpcauth_lru_add_locked(struct rpc_cred *cred)
  {
  	if (!list_empty(&cred->cr_lru))
  		return;
  	number_cred_unused++;
  	list_add_tail(&cred->cr_lru, &cred_unused);
  }
  
  static void
  rpcauth_lru_add(struct rpc_cred *cred)
  {
  	if (!list_empty(&cred->cr_lru))
  		return;
  	spin_lock(&rpc_credcache_lock);
  	rpcauth_lru_add_locked(cred);
  	spin_unlock(&rpc_credcache_lock);
  }
  
  static void
  rpcauth_lru_remove_locked(struct rpc_cred *cred)
  {
  	if (list_empty(&cred->cr_lru))
  		return;
  	number_cred_unused--;
  	list_del_init(&cred->cr_lru);
  }
  
  static void
  rpcauth_lru_remove(struct rpc_cred *cred)
  {
  	if (list_empty(&cred->cr_lru))
  		return;
  	spin_lock(&rpc_credcache_lock);
  	rpcauth_lru_remove_locked(cred);
  	spin_unlock(&rpc_credcache_lock);
  }
  
  /*
   * Clear the RPC credential cache, and delete those credentials
   * that are not referenced.
   */
  void
  rpcauth_clear_credcache(struct rpc_cred_cache *cache)
  {
  	LIST_HEAD(free);
  	struct hlist_head *head;
  	struct rpc_cred	*cred;
  	unsigned int hashsize = 1U << cache->hashbits;
  	int		i;
  
  	spin_lock(&rpc_credcache_lock);
  	spin_lock(&cache->lock);
  	for (i = 0; i < hashsize; i++) {
  		head = &cache->hashtable[i];
  		while (!hlist_empty(head)) {
  			cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
  			rpcauth_unhash_cred_locked(cred);
  			/* Note: We now hold a reference to cred */
  			rpcauth_lru_remove_locked(cred);
  			list_add_tail(&cred->cr_lru, &free);
  		}
  	}
  	spin_unlock(&cache->lock);
  	spin_unlock(&rpc_credcache_lock);
  	rpcauth_destroy_credlist(&free);
  }
  
  /*
   * Destroy the RPC credential cache
   */
  void
  rpcauth_destroy_credcache(struct rpc_auth *auth)
  {
  	struct rpc_cred_cache *cache = auth->au_credcache;
  
  	if (cache) {
  		auth->au_credcache = NULL;
  		rpcauth_clear_credcache(cache);
  		kfree(cache->hashtable);
  		kfree(cache);
  	}
  }
  EXPORT_SYMBOL_GPL(rpcauth_destroy_credcache);
  
  
  #define RPC_AUTH_EXPIRY_MORATORIUM (60 * HZ)
  
  /*
   * Remove stale credentials. Avoid sleeping inside the loop.
   */
  static long
  rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
  {
  	struct rpc_cred *cred, *next;
  	unsigned long expired = jiffies - RPC_AUTH_EXPIRY_MORATORIUM;
  	long freed = 0;
  
  	list_for_each_entry_safe(cred, next, &cred_unused, cr_lru) {
  
  		if (nr_to_scan-- == 0)
  			break;
  		if (refcount_read(&cred->cr_count) > 1) {
  			rpcauth_lru_remove_locked(cred);
  			continue;
  		}
  		/*
  		 * Enforce a 60 second garbage collection moratorium
  		 * Note that the cred_unused list must be time-ordered.
  		 */
  		if (!time_in_range(cred->cr_expire, expired, jiffies))
  			continue;
  		if (!rpcauth_unhash_cred(cred))
  			continue;
  
  		rpcauth_lru_remove_locked(cred);
  		freed++;
  		list_add_tail(&cred->cr_lru, free);
  	}
  	return freed ? freed : SHRINK_STOP;
  }
  
  static unsigned long
  rpcauth_cache_do_shrink(int nr_to_scan)
  {
  	LIST_HEAD(free);
  	unsigned long freed;
  
  	spin_lock(&rpc_credcache_lock);
  	freed = rpcauth_prune_expired(&free, nr_to_scan);
  	spin_unlock(&rpc_credcache_lock);
  	rpcauth_destroy_credlist(&free);
  
  	return freed;
  }
  
  /*
   * Run memory cache shrinker.
   */
  static unsigned long
  rpcauth_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
  
  {
  	if ((sc->gfp_mask & GFP_KERNEL) != GFP_KERNEL)
  		return SHRINK_STOP;
  
  	/* nothing left, don't come back */
  	if (list_empty(&cred_unused))
  		return SHRINK_STOP;
  
  	return rpcauth_cache_do_shrink(sc->nr_to_scan);
  }
  
  static unsigned long
  rpcauth_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
  
  {
  	return number_cred_unused * sysctl_vfs_cache_pressure / 100;
  }
  
  static void
  rpcauth_cache_enforce_limit(void)
  {
  	unsigned long diff;
  	unsigned int nr_to_scan;
  
  	if (number_cred_unused <= auth_max_cred_cachesize)
  		return;
  	diff = number_cred_unused - auth_max_cred_cachesize;
  	nr_to_scan = 100;
  	if (diff < nr_to_scan)
  		nr_to_scan = diff;
  	rpcauth_cache_do_shrink(nr_to_scan);
  }
  
  /*
   * Look up a process' credentials in the authentication cache
   */
  struct rpc_cred *
  rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
  		int flags, gfp_t gfp)
  {
  	LIST_HEAD(free);
  	struct rpc_cred_cache *cache = auth->au_credcache;
  	struct rpc_cred	*cred = NULL,
  			*entry, *new;
  	unsigned int nr;
  
  	nr = auth->au_ops->hash_cred(acred, cache->hashbits);
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(entry, &cache->hashtable[nr], cr_hash) {
  		if (!entry->cr_ops->crmatch(acred, entry, flags))
  			continue;
  		cred = get_rpccred(entry);
  		if (cred)
  			break;
  	}
  	rcu_read_unlock();
  
  	if (cred != NULL)
  		goto found;
  
  	new = auth->au_ops->crcreate(auth, acred, flags, gfp);
  	if (IS_ERR(new)) {
  		cred = new;
  		goto out;
  	}
  
  	spin_lock(&cache->lock);
  	hlist_for_each_entry(entry, &cache->hashtable[nr], cr_hash) {
  		if (!entry->cr_ops->crmatch(acred, entry, flags))
  			continue;
  		cred = get_rpccred(entry);
  		if (cred)
  			break;
  	}
  	if (cred == NULL) {
  		cred = new;
  		set_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
  		refcount_inc(&cred->cr_count);
  		hlist_add_head_rcu(&cred->cr_hash, &cache->hashtable[nr]);
  	} else
  		list_add_tail(&new->cr_lru, &free);
  	spin_unlock(&cache->lock);
  	rpcauth_cache_enforce_limit();
  found:
  	if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags) &&
  	    cred->cr_ops->cr_init != NULL &&
  	    !(flags & RPCAUTH_LOOKUP_NEW)) {
  		int res = cred->cr_ops->cr_init(auth, cred);
  		if (res < 0) {
  			put_rpccred(cred);
  			cred = ERR_PTR(res);
  		}
  	}
  	rpcauth_destroy_credlist(&free);
  out:
  	return cred;
  }
  EXPORT_SYMBOL_GPL(rpcauth_lookup_credcache);
  
  struct rpc_cred *
  rpcauth_lookupcred(struct rpc_auth *auth, int flags)
  {
  	struct auth_cred acred;
  	struct rpc_cred *ret;
  	const struct cred *cred = current_cred();
  
  	memset(&acred, 0, sizeof(acred));
  	acred.cred = cred;
  	ret = auth->au_ops->lookup_cred(auth, &acred, flags);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(rpcauth_lookupcred);
  
  void
  rpcauth_init_cred(struct rpc_cred *cred, const struct auth_cred *acred,
  		  struct rpc_auth *auth, const struct rpc_credops *ops)
  {
  	INIT_HLIST_NODE(&cred->cr_hash);
  	INIT_LIST_HEAD(&cred->cr_lru);
  	refcount_set(&cred->cr_count, 1);
  	cred->cr_auth = auth;
  	cred->cr_flags = 0;
  	cred->cr_ops = ops;
  	cred->cr_expire = jiffies;
  	cred->cr_cred = get_cred(acred->cred);
  }
  EXPORT_SYMBOL_GPL(rpcauth_init_cred);
  
  static struct rpc_cred *
  rpcauth_bind_root_cred(struct rpc_task *task, int lookupflags)
  {
  	struct rpc_auth *auth = task->tk_client->cl_auth;
  	struct auth_cred acred = {
  		.cred = get_task_cred(&init_task),
  	};
  	struct rpc_cred *ret;
  
  	ret = auth->au_ops->lookup_cred(auth, &acred, lookupflags);
  	put_cred(acred.cred);
  	return ret;
  }
  
  static struct rpc_cred *
  rpcauth_bind_machine_cred(struct rpc_task *task, int lookupflags)
  {
  	struct rpc_auth *auth = task->tk_client->cl_auth;
  	struct auth_cred acred = {
  		.principal = task->tk_client->cl_principal,
  		.cred = init_task.cred,
  	};
  
  	if (!acred.principal)
  		return NULL;
  	return auth->au_ops->lookup_cred(auth, &acred, lookupflags);
  }
  
  static struct rpc_cred *
  rpcauth_bind_new_cred(struct rpc_task *task, int lookupflags)
  {
  	struct rpc_auth *auth = task->tk_client->cl_auth;
  
  	return rpcauth_lookupcred(auth, lookupflags);
  }
  
  static int
  rpcauth_bindcred(struct rpc_task *task, const struct cred *cred, int flags)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_cred *new = NULL;
  	int lookupflags = 0;
  	struct rpc_auth *auth = task->tk_client->cl_auth;
  	struct auth_cred acred = {
  		.cred = cred,
  	};
  
  	if (flags & RPC_TASK_ASYNC)
  		lookupflags |= RPCAUTH_LOOKUP_NEW;
  	if (task->tk_op_cred)
  		/* Task must use exactly this rpc_cred */
  		new = get_rpccred(task->tk_op_cred);
  	else if (cred != NULL && cred != &machine_cred)
  		new = auth->au_ops->lookup_cred(auth, &acred, lookupflags);
  	else if (cred == &machine_cred)
  		new = rpcauth_bind_machine_cred(task, lookupflags);
  
  	/* If machine cred couldn't be bound, try a root cred */
  	if (new)
  		;
  	else if (cred == &machine_cred || (flags & RPC_TASK_ROOTCREDS))
  		new = rpcauth_bind_root_cred(task, lookupflags);
  	else if (flags & RPC_TASK_NULLCREDS)
  		new = authnull_ops.lookup_cred(NULL, NULL, 0);
  	else
  		new = rpcauth_bind_new_cred(task, lookupflags);
  	if (IS_ERR(new))
  		return PTR_ERR(new);
  	put_rpccred(req->rq_cred);
  	req->rq_cred = new;
  	return 0;
  }
  
  void
  put_rpccred(struct rpc_cred *cred)
  {
  	if (cred == NULL)
  		return;
  	rcu_read_lock();
  	if (refcount_dec_and_test(&cred->cr_count))
  		goto destroy;
  	if (refcount_read(&cred->cr_count) != 1 ||
  	    !test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags))
  		goto out;
  	if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0) {
  		cred->cr_expire = jiffies;
  		rpcauth_lru_add(cred);
  		/* Race breaker */
  		if (unlikely(!test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags)))
  			rpcauth_lru_remove(cred);
  	} else if (rpcauth_unhash_cred(cred)) {
  		rpcauth_lru_remove(cred);
  		if (refcount_dec_and_test(&cred->cr_count))
  			goto destroy;
  	}
  out:
  	rcu_read_unlock();
  	return;
  destroy:
  	rcu_read_unlock();
  	cred->cr_ops->crdestroy(cred);
  }
  EXPORT_SYMBOL_GPL(put_rpccred);
  
  /**
   * rpcauth_marshcred - Append RPC credential to end of @xdr
   * @task: controlling RPC task
   * @xdr: xdr_stream containing initial portion of RPC Call header
   *
   * On success, an appropriate verifier is added to @xdr, @xdr is
   * updated to point past the verifier, and zero is returned.
   * Otherwise, @xdr is in an undefined state and a negative errno
   * is returned.
   */
  int rpcauth_marshcred(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
  
  	return ops->crmarshal(task, xdr);
  }
  
  /**
   * rpcauth_wrap_req_encode - XDR encode the RPC procedure
   * @task: controlling RPC task
   * @xdr: stream where on-the-wire bytes are to be marshalled
   *
   * On success, @xdr contains the encoded and wrapped message.
   * Otherwise, @xdr is in an undefined state.
   */
  int rpcauth_wrap_req_encode(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	kxdreproc_t encode = task->tk_msg.rpc_proc->p_encode;
  
  	encode(task->tk_rqstp, xdr, task->tk_msg.rpc_argp);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(rpcauth_wrap_req_encode);
  
  /**
   * rpcauth_wrap_req - XDR encode and wrap the RPC procedure
   * @task: controlling RPC task
   * @xdr: stream where on-the-wire bytes are to be marshalled
   *
   * On success, @xdr contains the encoded and wrapped message,
   * and zero is returned. Otherwise, @xdr is in an undefined
   * state and a negative errno is returned.
   */
  int rpcauth_wrap_req(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
  
  	return ops->crwrap_req(task, xdr);
  }
  
  /**
   * rpcauth_checkverf - Validate verifier in RPC Reply header
   * @task: controlling RPC task
   * @xdr: xdr_stream containing RPC Reply header
   *
   * On success, @xdr is updated to point past the verifier and
   * zero is returned. Otherwise, @xdr is in an undefined state
   * and a negative errno is returned.
   */
  int
  rpcauth_checkverf(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
  
  	return ops->crvalidate(task, xdr);
  }
  
  /**
   * rpcauth_unwrap_resp_decode - Invoke XDR decode function
   * @task: controlling RPC task
   * @xdr: stream where the Reply message resides
   *
   * Returns zero on success; otherwise a negative errno is returned.
   */
  int
  rpcauth_unwrap_resp_decode(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	kxdrdproc_t decode = task->tk_msg.rpc_proc->p_decode;
  
  	return decode(task->tk_rqstp, xdr, task->tk_msg.rpc_resp);
  }
  EXPORT_SYMBOL_GPL(rpcauth_unwrap_resp_decode);
  
  /**
   * rpcauth_unwrap_resp - Invoke unwrap and decode function for the cred
   * @task: controlling RPC task
   * @xdr: stream where the Reply message resides
   *
   * Returns zero on success; otherwise a negative errno is returned.
   */
  int
  rpcauth_unwrap_resp(struct rpc_task *task, struct xdr_stream *xdr)
  {
  	const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
  
  	return ops->crunwrap_resp(task, xdr);
  }
  
  bool
  rpcauth_xmit_need_reencode(struct rpc_task *task)
  {
  	struct rpc_cred *cred = task->tk_rqstp->rq_cred;
  
  	if (!cred || !cred->cr_ops->crneed_reencode)
  		return false;
  	return cred->cr_ops->crneed_reencode(task);
  }
  
  int
  rpcauth_refreshcred(struct rpc_task *task)
  {
  	struct rpc_cred	*cred;
  	int err;
  
  	cred = task->tk_rqstp->rq_cred;
  	if (cred == NULL) {
  		err = rpcauth_bindcred(task, task->tk_msg.rpc_cred, task->tk_flags);
  		if (err < 0)
  			goto out;
  		cred = task->tk_rqstp->rq_cred;
  	}
  
  	err = cred->cr_ops->crrefresh(task);
  out:
  	if (err < 0)
  		task->tk_status = err;
  	return err;
  }
  
  void
  rpcauth_invalcred(struct rpc_task *task)
  {
  	struct rpc_cred *cred = task->tk_rqstp->rq_cred;
  
  	if (cred)
  		clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
  }
  
  int
  rpcauth_uptodatecred(struct rpc_task *task)
  {
  	struct rpc_cred *cred = task->tk_rqstp->rq_cred;
  
  	return cred == NULL ||
  		test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0;
  }
  
  static struct shrinker rpc_cred_shrinker = {
  	.count_objects = rpcauth_cache_shrink_count,
  	.scan_objects = rpcauth_cache_shrink_scan,
  	.seeks = DEFAULT_SEEKS,
  };
  
  int __init rpcauth_init_module(void)
  {
  	int err;
  
  	err = rpc_init_authunix();
  	if (err < 0)
  		goto out1;
  	err = register_shrinker(&rpc_cred_shrinker);
  	if (err < 0)
  		goto out2;
  	return 0;
  out2:
  	rpc_destroy_authunix();
  out1:
  	return err;
  }
  
  void rpcauth_remove_module(void)
  {
  	rpc_destroy_authunix();
  	unregister_shrinker(&rpc_cred_shrinker);
  }
  