fs/afs/security.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* AFS security handling
  *
  * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/ctype.h>
 #include <linux/sched.h>
 #include <linux/hashtable.h>
 #include <keys/rxrpc-type.h>
 #include "internal.h"

 static DEFINE_HASHTABLE(afs_permits_cache, 10);
 static DEFINE_SPINLOCK(afs_permits_lock);

 /*
  * get a key
  */
 struct key *afs_request_key(struct afs_cell *cell)
 {
 	struct key *key;

 	_enter("{%x}", key_serial(cell->anonymous_key));

 	_debug("key %s", cell->anonymous_key->description);
 	key = request_key_net(&key_type_rxrpc, cell->anonymous_key->description,
 			      cell->net->net, NULL);
 	if (IS_ERR(key)) {
 		if (PTR_ERR(key) != -ENOKEY) {
 			_leave(" = %ld", PTR_ERR(key));
 			return key;
 		}

 		/* act as anonymous user */
 		_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
 		return key_get(cell->anonymous_key);
 	} else {
 		/* act as authorised user */
 		_leave(" = {%x} [auth]", key_serial(key));
 		return key;
 	}
 }

 /*
  * Get a key when pathwalk is in rcuwalk mode.
  */
 struct key *afs_request_key_rcu(struct afs_cell *cell)
 {
 	struct key *key;

 	_enter("{%x}", key_serial(cell->anonymous_key));

 	_debug("key %s", cell->anonymous_key->description);
 	key = request_key_net_rcu(&key_type_rxrpc,
 				  cell->anonymous_key->description,
 				  cell->net->net);
 	if (IS_ERR(key)) {
 		if (PTR_ERR(key) != -ENOKEY) {
 			_leave(" = %ld", PTR_ERR(key));
 			return key;
 		}

 		/* act as anonymous user */
 		_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
 		return key_get(cell->anonymous_key);
 	} else {
 		/* act as authorised user */
 		_leave(" = {%x} [auth]", key_serial(key));
 		return key;
 	}
 }

 /*
  * Dispose of a list of permits.
  */
 static void afs_permits_rcu(struct rcu_head *rcu)
 {
 	struct afs_permits *permits =
 		container_of(rcu, struct afs_permits, rcu);
 	int i;

 	for (i = 0; i < permits->nr_permits; i++)
 		key_put(permits->permits[i].key);
 	kfree(permits);
 }

 /*
  * Discard a permission cache.
  */
 void afs_put_permits(struct afs_permits *permits)
 {
 	if (permits && refcount_dec_and_test(&permits->usage)) {
 		spin_lock(&afs_permits_lock);
 		hash_del_rcu(&permits->hash_node);
 		spin_unlock(&afs_permits_lock);
 		call_rcu(&permits->rcu, afs_permits_rcu);
 	}
 }

 /*
  * Clear a permit cache on callback break.
  */
 void afs_clear_permits(struct afs_vnode *vnode)
 {
 	struct afs_permits *permits;

 	spin_lock(&vnode->lock);
 	permits = rcu_dereference_protected(vnode->permit_cache,
 					    lockdep_is_held(&vnode->lock));
 	RCU_INIT_POINTER(vnode->permit_cache, NULL);
 	spin_unlock(&vnode->lock);

 	afs_put_permits(permits);
 }

 /*
  * Hash a list of permits.  Use simple addition to make it easy to add an extra
  * one at an as-yet indeterminate position in the list.
  */
 static void afs_hash_permits(struct afs_permits *permits)
 {
 	unsigned long h = permits->nr_permits;
 	int i;

 	for (i = 0; i < permits->nr_permits; i++) {
 		h += (unsigned long)permits->permits[i].key / sizeof(void *);
 		h += permits->permits[i].access;
 	}

 	permits->h = h;
 }

 /*
  * Cache the CallerAccess result obtained from doing a fileserver operation
  * that returned a vnode status for a particular key.  If a callback break
  * occurs whilst the operation was in progress then we have to ditch the cache
  * as the ACL *may* have changed.
  */
 void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
 		      unsigned int cb_break, struct afs_status_cb *scb)
 {
 	struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
 	afs_access_t caller_access = scb->status.caller_access;
 	size_t size = 0;
 	bool changed = false;
 	int i, j;

 	_enter("{%llx:%llu},%x,%x",
 	       vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);

 	rcu_read_lock();

 	/* Check for the common case first: We got back the same access as last
 	 * time we tried and already have it recorded.
 	 */
 	permits = rcu_dereference(vnode->permit_cache);
 	if (permits) {
 		if (!permits->invalidated) {
 			for (i = 0; i < permits->nr_permits; i++) {
 				if (permits->permits[i].key < key)
 					continue;
 				if (permits->permits[i].key > key)
 					break;
 				if (permits->permits[i].access != caller_access) {
 					changed = true;
 					break;
 				}

 				if (afs_cb_is_broken(cb_break, vnode)) {
 					changed = true;
 					break;
 				}

 				/* The cache is still good. */
 				rcu_read_unlock();
 				return;
 			}
 		}

 		changed |= permits->invalidated;
 		size = permits->nr_permits;

 		/* If this set of permits is now wrong, clear the permits
 		 * pointer so that no one tries to use the stale information.
 		 */
 		if (changed) {
 			spin_lock(&vnode->lock);
 			if (permits != rcu_access_pointer(vnode->permit_cache))
 				goto someone_else_changed_it_unlock;
 			RCU_INIT_POINTER(vnode->permit_cache, NULL);
 			spin_unlock(&vnode->lock);

 			afs_put_permits(permits);
 			permits = NULL;
 			size = 0;
 		}
 	}

 	if (afs_cb_is_broken(cb_break, vnode))
 		goto someone_else_changed_it;

 	/* We need a ref on any permits list we want to copy as we'll have to
 	 * drop the lock to do memory allocation.
 	 */
 	if (permits && !refcount_inc_not_zero(&permits->usage))
 		goto someone_else_changed_it;

 	rcu_read_unlock();

 	/* Speculatively create a new list with the revised permission set.  We
 	 * discard this if we find an extant match already in the hash, but
 	 * it's easier to compare with memcmp this way.
 	 *
 	 * We fill in the key pointers at this time, but we don't get the refs
 	 * yet.
 	 */
 	size++;
 	new = kzalloc(struct_size(new, permits, size), GFP_NOFS);
 	if (!new)
 		goto out_put;

 	refcount_set(&new->usage, 1);
 	new->nr_permits = size;
 	i = j = 0;
 	if (permits) {
 		for (i = 0; i < permits->nr_permits; i++) {
 			if (j == i && permits->permits[i].key > key) {
 				new->permits[j].key = key;
 				new->permits[j].access = caller_access;
 				j++;
 			}
 			new->permits[j].key = permits->permits[i].key;
 			new->permits[j].access = permits->permits[i].access;
 			j++;
 		}
 	}

 	if (j == i) {
 		new->permits[j].key = key;
 		new->permits[j].access = caller_access;
 	}

 	afs_hash_permits(new);

 	/* Now see if the permit list we want is actually already available */
 	spin_lock(&afs_permits_lock);

 	hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
 		if (xpermits->h != new->h ||
 		    xpermits->invalidated ||
 		    xpermits->nr_permits != new->nr_permits ||
 		    memcmp(xpermits->permits, new->permits,
 			   new->nr_permits * sizeof(struct afs_permit)) != 0)
 			continue;

 		if (refcount_inc_not_zero(&xpermits->usage)) {
 			replacement = xpermits;
 			goto found;
 		}

 		break;
 	}

 	for (i = 0; i < new->nr_permits; i++)
 		key_get(new->permits[i].key);
 	hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
 	replacement = new;
 	new = NULL;

 found:
 	spin_unlock(&afs_permits_lock);

 	kfree(new);

 	rcu_read_lock();
 	spin_lock(&vnode->lock);
 	zap = rcu_access_pointer(vnode->permit_cache);
 	if (!afs_cb_is_broken(cb_break, vnode) && zap == permits)
 		rcu_assign_pointer(vnode->permit_cache, replacement);
 	else
 		zap = replacement;
 	spin_unlock(&vnode->lock);
 	rcu_read_unlock();
 	afs_put_permits(zap);
 out_put:
 	afs_put_permits(permits);
 	return;

 someone_else_changed_it_unlock:
 	spin_unlock(&vnode->lock);
 someone_else_changed_it:
 	/* Someone else changed the cache under us - don't recheck at this
 	 * time.
 	 */
 	rcu_read_unlock();
 	return;
 }

 static bool afs_check_permit_rcu(struct afs_vnode *vnode, struct key *key,
 				 afs_access_t *_access)
 {
 	const struct afs_permits *permits;
 	int i;

 	_enter("{%llx:%llu},%x",
 	       vnode->fid.vid, vnode->fid.vnode, key_serial(key));

 	/* check the permits to see if we've got one yet */
 	if (key == vnode->volume->cell->anonymous_key) {
 		*_access = vnode->status.anon_access;
 		_leave(" = t [anon %x]", *_access);
 		return true;
 	}

 	permits = rcu_dereference(vnode->permit_cache);
 	if (permits) {
 		for (i = 0; i < permits->nr_permits; i++) {
 			if (permits->permits[i].key < key)
 				continue;
 			if (permits->permits[i].key > key)
 				break;

 			*_access = permits->permits[i].access;
 			_leave(" = %u [perm %x]", !permits->invalidated, *_access);
 			return !permits->invalidated;
 		}
 	}

 	_leave(" = f");
 	return false;
 }

 /*
  * check with the fileserver to see if the directory or parent directory is
  * permitted to be accessed with this authorisation, and if so, what access it
  * is granted
  */
 int afs_check_permit(struct afs_vnode *vnode, struct key *key,
 		     afs_access_t *_access)
 {
 	struct afs_permits *permits;
 	bool valid = false;
 	int i, ret;

 	_enter("{%llx:%llu},%x",
 	       vnode->fid.vid, vnode->fid.vnode, key_serial(key));

 	/* check the permits to see if we've got one yet */
 	if (key == vnode->volume->cell->anonymous_key) {
 		_debug("anon");
 		*_access = vnode->status.anon_access;
 		valid = true;
 	} else {
 		rcu_read_lock();
 		permits = rcu_dereference(vnode->permit_cache);
 		if (permits) {
 			for (i = 0; i < permits->nr_permits; i++) {
 				if (permits->permits[i].key < key)
 					continue;
 				if (permits->permits[i].key > key)
 					break;

 				*_access = permits->permits[i].access;
 				valid = !permits->invalidated;
 				break;
 			}
 		}
 		rcu_read_unlock();
 	}

 	if (!valid) {
 		/* Check the status on the file we're actually interested in
 		 * (the post-processing will cache the result).
 		 */
 		_debug("no valid permit");

 		ret = afs_fetch_status(vnode, key, false, _access);
 		if (ret < 0) {
 			*_access = 0;
 			_leave(" = %d", ret);
 			return ret;
 		}
 	}

 	_leave(" = 0 [access %x]", *_access);
 	return 0;
 }

 /*
  * check the permissions on an AFS file
  * - AFS ACLs are attached to directories only, and a file is controlled by its
  *   parent directory's ACL
  */
 int afs_permission(struct user_namespace *mnt_userns, struct inode *inode,
 		   int mask)
 {
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	afs_access_t access;
 	struct key *key;
 	int ret = 0;

 	_enter("{{%llx:%llu},%lx},%x,",
 	       vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);

 	if (mask & MAY_NOT_BLOCK) {
 		key = afs_request_key_rcu(vnode->volume->cell);
 		if (IS_ERR(key))
 			return -ECHILD;

 		ret = -ECHILD;
 		if (!afs_check_validity(vnode) ||
 		    !afs_check_permit_rcu(vnode, key, &access))
 			goto error;
 	} else {
 		key = afs_request_key(vnode->volume->cell);
 		if (IS_ERR(key)) {
 			_leave(" = %ld [key]", PTR_ERR(key));
 			return PTR_ERR(key);
 		}

 		ret = afs_validate(vnode, key);
 		if (ret < 0)
 			goto error;

 		/* check the permits to see if we've got one yet */
 		ret = afs_check_permit(vnode, key, &access);
 		if (ret < 0)
 			goto error;
 	}

 	/* interpret the access mask */
 	_debug("REQ %x ACC %x on %s",
 	       mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");

 	ret = 0;
 	if (S_ISDIR(inode->i_mode)) {
 		if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) {
 			if (!(access & AFS_ACE_LOOKUP))
 				goto permission_denied;
 		}
 		if (mask & MAY_WRITE) {
 			if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
 					AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
 				goto permission_denied;
 		}
 	} else {
 		if (!(access & AFS_ACE_LOOKUP))
 			goto permission_denied;
 		if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
 			goto permission_denied;
 		if (mask & (MAY_EXEC | MAY_READ)) {
 			if (!(access & AFS_ACE_READ))
 				goto permission_denied;
 			if (!(inode->i_mode & S_IRUSR))
 				goto permission_denied;
 		} else if (mask & MAY_WRITE) {
 			if (!(access & AFS_ACE_WRITE))
 				goto permission_denied;
 			if (!(inode->i_mode & S_IWUSR))
 				goto permission_denied;
 		}
 	}

 	key_put(key);
 	_leave(" = %d", ret);
 	return ret;

 permission_denied:
 	ret = -EACCES;
 error:
 	key_put(key);
 	_leave(" = %d", ret);
 	return ret;
 }

 void __exit afs_clean_up_permit_cache(void)
 {
 	int i;

 	for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
 		WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));

 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* AFS security handling
	*
	* Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/fs.h>
	#include <linux/ctype.h>
	#include <linux/sched.h>
	#include <linux/hashtable.h>
	#include <keys/rxrpc-type.h>
	#include "internal.h"

	static DEFINE_HASHTABLE(afs_permits_cache, 10);
	static DEFINE_SPINLOCK(afs_permits_lock);

	/*
	* get a key
	*/
	struct key afs_request_key(struct afs_cell cell)
	{
	struct key *key;

	_enter("{%x}", key_serial(cell->anonymous_key));

	_debug("key %s", cell->anonymous_key->description);
	key = request_key_net(&key_type_rxrpc, cell->anonymous_key->description,
	cell->net->net, NULL);
	if (IS_ERR(key)) {
	if (PTR_ERR(key) != -ENOKEY) {
	_leave(" = %ld", PTR_ERR(key));
	return key;
	}

	/* act as anonymous user */
	_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
	return key_get(cell->anonymous_key);
	} else {
	/* act as authorised user */
	_leave(" = {%x} [auth]", key_serial(key));
	return key;
	}
	}

	/*
	* Get a key when pathwalk is in rcuwalk mode.
	*/
	struct key afs_request_key_rcu(struct afs_cell cell)
	{
	struct key *key;

	_enter("{%x}", key_serial(cell->anonymous_key));

	_debug("key %s", cell->anonymous_key->description);
	key = request_key_net_rcu(&key_type_rxrpc,
	cell->anonymous_key->description,
	cell->net->net);
	if (IS_ERR(key)) {
	if (PTR_ERR(key) != -ENOKEY) {
	_leave(" = %ld", PTR_ERR(key));
	return key;
	}

	/* act as anonymous user */
	_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
	return key_get(cell->anonymous_key);
	} else {
	/* act as authorised user */
	_leave(" = {%x} [auth]", key_serial(key));
	return key;
	}
	}

	/*
	* Dispose of a list of permits.
	*/
	static void afs_permits_rcu(struct rcu_head *rcu)
	{
	struct afs_permits *permits =
	container_of(rcu, struct afs_permits, rcu);
	int i;

	for (i = 0; i < permits->nr_permits; i++)
	key_put(permits->permits[i].key);
	kfree(permits);
	}

	/*
	* Discard a permission cache.
	*/
	void afs_put_permits(struct afs_permits *permits)
	{
	if (permits && refcount_dec_and_test(&permits->usage)) {
	spin_lock(&afs_permits_lock);
	hash_del_rcu(&permits->hash_node);
	spin_unlock(&afs_permits_lock);
	call_rcu(&permits->rcu, afs_permits_rcu);
	}
	}

	/*
	* Clear a permit cache on callback break.
	*/
	void afs_clear_permits(struct afs_vnode *vnode)
	{
	struct afs_permits *permits;

	spin_lock(&vnode->lock);
	permits = rcu_dereference_protected(vnode->permit_cache,
	lockdep_is_held(&vnode->lock));
	RCU_INIT_POINTER(vnode->permit_cache, NULL);
	spin_unlock(&vnode->lock);

	afs_put_permits(permits);
	}

	/*
	* Hash a list of permits. Use simple addition to make it easy to add an extra
	* one at an as-yet indeterminate position in the list.
	*/
	static void afs_hash_permits(struct afs_permits *permits)
	{
	unsigned long h = permits->nr_permits;
	int i;

	for (i = 0; i < permits->nr_permits; i++) {
	h += (unsigned long)permits->permits[i].key / sizeof(void *);
	h += permits->permits[i].access;
	}

	permits->h = h;
	}

	/*
	* Cache the CallerAccess result obtained from doing a fileserver operation
	* that returned a vnode status for a particular key. If a callback break
	* occurs whilst the operation was in progress then we have to ditch the cache
	* as the ACL may have changed.
	*/
	void afs_cache_permit(struct afs_vnode vnode, struct key key,
	unsigned int cb_break, struct afs_status_cb *scb)
	{
	struct afs_permits permits, xpermits, replacement, zap, *new = NULL;
	afs_access_t caller_access = scb->status.caller_access;
	size_t size = 0;
	bool changed = false;
	int i, j;

	_enter("{%llx:%llu},%x,%x",
	vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);

	rcu_read_lock();

	/* Check for the common case first: We got back the same access as last
	* time we tried and already have it recorded.
	*/
	permits = rcu_dereference(vnode->permit_cache);
	if (permits) {
	if (!permits->invalidated) {
	for (i = 0; i < permits->nr_permits; i++) {
	if (permits->permits[i].key < key)
	continue;
	if (permits->permits[i].key > key)
	break;
	if (permits->permits[i].access != caller_access) {
	changed = true;
	break;
	}

	if (afs_cb_is_broken(cb_break, vnode)) {
	changed = true;
	break;
	}

	/* The cache is still good. */
	rcu_read_unlock();
	return;
	}
	}

	changed \|= permits->invalidated;
	size = permits->nr_permits;

	/* If this set of permits is now wrong, clear the permits
	* pointer so that no one tries to use the stale information.
	*/
	if (changed) {
	spin_lock(&vnode->lock);
	if (permits != rcu_access_pointer(vnode->permit_cache))
	goto someone_else_changed_it_unlock;
	RCU_INIT_POINTER(vnode->permit_cache, NULL);
	spin_unlock(&vnode->lock);

	afs_put_permits(permits);
	permits = NULL;
	size = 0;
	}
	}

	if (afs_cb_is_broken(cb_break, vnode))
	goto someone_else_changed_it;

	/* We need a ref on any permits list we want to copy as we'll have to
	* drop the lock to do memory allocation.
	*/
	if (permits && !refcount_inc_not_zero(&permits->usage))
	goto someone_else_changed_it;

	rcu_read_unlock();

	/* Speculatively create a new list with the revised permission set. We
	* discard this if we find an extant match already in the hash, but
	* it's easier to compare with memcmp this way.
	*
	* We fill in the key pointers at this time, but we don't get the refs
	* yet.
	*/
	size++;
	new = kzalloc(struct_size(new, permits, size), GFP_NOFS);
	if (!new)
	goto out_put;

	refcount_set(&new->usage, 1);
	new->nr_permits = size;
	i = j = 0;
	if (permits) {
	for (i = 0; i < permits->nr_permits; i++) {
	if (j == i && permits->permits[i].key > key) {
	new->permits[j].key = key;
	new->permits[j].access = caller_access;
	j++;
	}
	new->permits[j].key = permits->permits[i].key;
	new->permits[j].access = permits->permits[i].access;
	j++;
	}
	}

	if (j == i) {
	new->permits[j].key = key;
	new->permits[j].access = caller_access;
	}

	afs_hash_permits(new);

	/* Now see if the permit list we want is actually already available */
	spin_lock(&afs_permits_lock);

	hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
	if (xpermits->h != new->h \|\|
	xpermits->invalidated \|\|
	xpermits->nr_permits != new->nr_permits \|\|
	memcmp(xpermits->permits, new->permits,
	new->nr_permits * sizeof(struct afs_permit)) != 0)
	continue;

	if (refcount_inc_not_zero(&xpermits->usage)) {
	replacement = xpermits;
	goto found;
	}

	break;
	}

	for (i = 0; i < new->nr_permits; i++)
	key_get(new->permits[i].key);
	hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
	replacement = new;
	new = NULL;

	found:
	spin_unlock(&afs_permits_lock);

	kfree(new);

	rcu_read_lock();
	spin_lock(&vnode->lock);
	zap = rcu_access_pointer(vnode->permit_cache);
	if (!afs_cb_is_broken(cb_break, vnode) && zap == permits)
	rcu_assign_pointer(vnode->permit_cache, replacement);
	else
	zap = replacement;
	spin_unlock(&vnode->lock);
	rcu_read_unlock();
	afs_put_permits(zap);
	out_put:
	afs_put_permits(permits);
	return;

	someone_else_changed_it_unlock:
	spin_unlock(&vnode->lock);
	someone_else_changed_it:
	/* Someone else changed the cache under us - don't recheck at this
	* time.
	*/
	rcu_read_unlock();
	return;
	}

	static bool afs_check_permit_rcu(struct afs_vnode vnode, struct key key,
	afs_access_t *_access)
	{
	const struct afs_permits *permits;
	int i;

	_enter("{%llx:%llu},%x",
	vnode->fid.vid, vnode->fid.vnode, key_serial(key));

	/* check the permits to see if we've got one yet */
	if (key == vnode->volume->cell->anonymous_key) {
	*_access = vnode->status.anon_access;
	_leave(" = t [anon %x]", *_access);
	return true;
	}

	permits = rcu_dereference(vnode->permit_cache);
	if (permits) {
	for (i = 0; i < permits->nr_permits; i++) {
	if (permits->permits[i].key < key)
	continue;
	if (permits->permits[i].key > key)
	break;

	*_access = permits->permits[i].access;
	_leave(" = %u [perm %x]", !permits->invalidated, *_access);
	return !permits->invalidated;
	}
	}

	_leave(" = f");
	return false;
	}

	/*
	* check with the fileserver to see if the directory or parent directory is
	* permitted to be accessed with this authorisation, and if so, what access it
	* is granted
	*/
	int afs_check_permit(struct afs_vnode vnode, struct key key,
	afs_access_t *_access)
	{
	struct afs_permits *permits;
	bool valid = false;
	int i, ret;

	_enter("{%llx:%llu},%x",
	vnode->fid.vid, vnode->fid.vnode, key_serial(key));

	/* check the permits to see if we've got one yet */
	if (key == vnode->volume->cell->anonymous_key) {
	_debug("anon");
	*_access = vnode->status.anon_access;
	valid = true;
	} else {
	rcu_read_lock();
	permits = rcu_dereference(vnode->permit_cache);
	if (permits) {
	for (i = 0; i < permits->nr_permits; i++) {
	if (permits->permits[i].key < key)
	continue;
	if (permits->permits[i].key > key)
	break;

	*_access = permits->permits[i].access;
	valid = !permits->invalidated;
	break;
	}
	}
	rcu_read_unlock();
	}

	if (!valid) {
	/* Check the status on the file we're actually interested in
	* (the post-processing will cache the result).
	*/
	_debug("no valid permit");

	ret = afs_fetch_status(vnode, key, false, _access);
	if (ret < 0) {
	*_access = 0;
	_leave(" = %d", ret);
	return ret;
	}
	}

	_leave(" = 0 [access %x]", *_access);
	return 0;
	}

	/*
	* check the permissions on an AFS file
	* - AFS ACLs are attached to directories only, and a file is controlled by its
	* parent directory's ACL
	*/
	int afs_permission(struct user_namespace mnt_userns, struct inode inode,
	int mask)
	{
	struct afs_vnode *vnode = AFS_FS_I(inode);
	afs_access_t access;
	struct key *key;
	int ret = 0;

	_enter("{{%llx:%llu},%lx},%x,",
	vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);

	if (mask & MAY_NOT_BLOCK) {
	key = afs_request_key_rcu(vnode->volume->cell);
	if (IS_ERR(key))
	return -ECHILD;

	ret = -ECHILD;
	if (!afs_check_validity(vnode) \|\|
	!afs_check_permit_rcu(vnode, key, &access))
	goto error;
	} else {
	key = afs_request_key(vnode->volume->cell);
	if (IS_ERR(key)) {
	_leave(" = %ld [key]", PTR_ERR(key));
	return PTR_ERR(key);
	}

	ret = afs_validate(vnode, key);
	if (ret < 0)
	goto error;

	/* check the permits to see if we've got one yet */
	ret = afs_check_permit(vnode, key, &access);
	if (ret < 0)
	goto error;
	}

	/* interpret the access mask */
	_debug("REQ %x ACC %x on %s",
	mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");

	ret = 0;
	if (S_ISDIR(inode->i_mode)) {
	if (mask & (MAY_EXEC \| MAY_READ \| MAY_CHDIR)) {
	if (!(access & AFS_ACE_LOOKUP))
	goto permission_denied;
	}
	if (mask & MAY_WRITE) {
	if (!(access & (AFS_ACE_DELETE \| /* rmdir, unlink, rename from */
	AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
	goto permission_denied;
	}
	} else {
	if (!(access & AFS_ACE_LOOKUP))
	goto permission_denied;
	if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
	goto permission_denied;
	if (mask & (MAY_EXEC \| MAY_READ)) {
	if (!(access & AFS_ACE_READ))
	goto permission_denied;
	if (!(inode->i_mode & S_IRUSR))
	goto permission_denied;
	} else if (mask & MAY_WRITE) {
	if (!(access & AFS_ACE_WRITE))
	goto permission_denied;
	if (!(inode->i_mode & S_IWUSR))
	goto permission_denied;
	}
	}

	key_put(key);
	_leave(" = %d", ret);
	return ret;

	permission_denied:
	ret = -EACCES;
	error:
	key_put(key);
	_leave(" = %d", ret);
	return ret;
	}

	void __exit afs_clean_up_permit_cache(void)
	{
	int i;

	for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
	WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));

	}