// SPDX-License-Identifier: GPL-2.0-or-later
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/* AFS security handling
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*
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* Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/ctype.h>
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#include <linux/sched.h>
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#include <linux/hashtable.h>
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#include <keys/rxrpc-type.h>
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#include "internal.h"
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static DEFINE_HASHTABLE(afs_permits_cache, 10);
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static DEFINE_SPINLOCK(afs_permits_lock);
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/*
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* get a key
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*/
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struct key *afs_request_key(struct afs_cell *cell)
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{
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struct key *key;
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_enter("{%x}", key_serial(cell->anonymous_key));
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_debug("key %s", cell->anonymous_key->description);
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key = request_key_net(&key_type_rxrpc, cell->anonymous_key->description,
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cell->net->net, NULL);
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if (IS_ERR(key)) {
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if (PTR_ERR(key) != -ENOKEY) {
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_leave(" = %ld", PTR_ERR(key));
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return key;
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}
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/* act as anonymous user */
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_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
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return key_get(cell->anonymous_key);
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} else {
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/* act as authorised user */
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_leave(" = {%x} [auth]", key_serial(key));
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return key;
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}
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}
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/*
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* Get a key when pathwalk is in rcuwalk mode.
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*/
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struct key *afs_request_key_rcu(struct afs_cell *cell)
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{
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struct key *key;
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_enter("{%x}", key_serial(cell->anonymous_key));
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_debug("key %s", cell->anonymous_key->description);
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key = request_key_net_rcu(&key_type_rxrpc,
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cell->anonymous_key->description,
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cell->net->net);
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if (IS_ERR(key)) {
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if (PTR_ERR(key) != -ENOKEY) {
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_leave(" = %ld", PTR_ERR(key));
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return key;
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}
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/* act as anonymous user */
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_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
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return key_get(cell->anonymous_key);
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} else {
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/* act as authorised user */
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_leave(" = {%x} [auth]", key_serial(key));
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return key;
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}
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}
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/*
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* Dispose of a list of permits.
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*/
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static void afs_permits_rcu(struct rcu_head *rcu)
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{
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struct afs_permits *permits =
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container_of(rcu, struct afs_permits, rcu);
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int i;
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for (i = 0; i < permits->nr_permits; i++)
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key_put(permits->permits[i].key);
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kfree(permits);
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}
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/*
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* Discard a permission cache.
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*/
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void afs_put_permits(struct afs_permits *permits)
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{
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if (permits && refcount_dec_and_test(&permits->usage)) {
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spin_lock(&afs_permits_lock);
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hash_del_rcu(&permits->hash_node);
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spin_unlock(&afs_permits_lock);
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call_rcu(&permits->rcu, afs_permits_rcu);
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}
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}
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/*
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* Clear a permit cache on callback break.
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*/
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void afs_clear_permits(struct afs_vnode *vnode)
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{
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struct afs_permits *permits;
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spin_lock(&vnode->lock);
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permits = rcu_dereference_protected(vnode->permit_cache,
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lockdep_is_held(&vnode->lock));
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RCU_INIT_POINTER(vnode->permit_cache, NULL);
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spin_unlock(&vnode->lock);
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afs_put_permits(permits);
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}
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/*
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* Hash a list of permits. Use simple addition to make it easy to add an extra
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* one at an as-yet indeterminate position in the list.
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*/
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static void afs_hash_permits(struct afs_permits *permits)
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{
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unsigned long h = permits->nr_permits;
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int i;
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for (i = 0; i < permits->nr_permits; i++) {
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h += (unsigned long)permits->permits[i].key / sizeof(void *);
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h += permits->permits[i].access;
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}
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permits->h = h;
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}
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/*
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* Cache the CallerAccess result obtained from doing a fileserver operation
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* that returned a vnode status for a particular key. If a callback break
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* occurs whilst the operation was in progress then we have to ditch the cache
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* as the ACL *may* have changed.
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*/
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void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
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unsigned int cb_break, struct afs_status_cb *scb)
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{
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struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
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afs_access_t caller_access = scb->status.caller_access;
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size_t size = 0;
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bool changed = false;
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int i, j;
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_enter("{%llx:%llu},%x,%x",
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vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);
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rcu_read_lock();
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/* Check for the common case first: We got back the same access as last
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* time we tried and already have it recorded.
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*/
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permits = rcu_dereference(vnode->permit_cache);
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if (permits) {
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if (!permits->invalidated) {
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for (i = 0; i < permits->nr_permits; i++) {
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if (permits->permits[i].key < key)
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continue;
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if (permits->permits[i].key > key)
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break;
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if (permits->permits[i].access != caller_access) {
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changed = true;
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break;
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}
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if (afs_cb_is_broken(cb_break, vnode)) {
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changed = true;
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break;
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}
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/* The cache is still good. */
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rcu_read_unlock();
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return;
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}
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}
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changed |= permits->invalidated;
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size = permits->nr_permits;
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/* If this set of permits is now wrong, clear the permits
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* pointer so that no one tries to use the stale information.
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*/
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if (changed) {
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spin_lock(&vnode->lock);
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if (permits != rcu_access_pointer(vnode->permit_cache))
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goto someone_else_changed_it_unlock;
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RCU_INIT_POINTER(vnode->permit_cache, NULL);
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spin_unlock(&vnode->lock);
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afs_put_permits(permits);
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permits = NULL;
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size = 0;
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}
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}
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if (afs_cb_is_broken(cb_break, vnode))
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goto someone_else_changed_it;
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/* We need a ref on any permits list we want to copy as we'll have to
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* drop the lock to do memory allocation.
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*/
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if (permits && !refcount_inc_not_zero(&permits->usage))
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goto someone_else_changed_it;
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rcu_read_unlock();
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/* Speculatively create a new list with the revised permission set. We
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* discard this if we find an extant match already in the hash, but
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* it's easier to compare with memcmp this way.
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*
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* We fill in the key pointers at this time, but we don't get the refs
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* yet.
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*/
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size++;
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new = kzalloc(sizeof(struct afs_permits) +
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sizeof(struct afs_permit) * size, GFP_NOFS);
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if (!new)
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goto out_put;
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refcount_set(&new->usage, 1);
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new->nr_permits = size;
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i = j = 0;
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if (permits) {
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for (i = 0; i < permits->nr_permits; i++) {
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if (j == i && permits->permits[i].key > key) {
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new->permits[j].key = key;
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new->permits[j].access = caller_access;
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j++;
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}
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new->permits[j].key = permits->permits[i].key;
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new->permits[j].access = permits->permits[i].access;
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j++;
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}
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}
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if (j == i) {
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new->permits[j].key = key;
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new->permits[j].access = caller_access;
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}
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afs_hash_permits(new);
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/* Now see if the permit list we want is actually already available */
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spin_lock(&afs_permits_lock);
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hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
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if (xpermits->h != new->h ||
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xpermits->invalidated ||
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xpermits->nr_permits != new->nr_permits ||
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memcmp(xpermits->permits, new->permits,
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new->nr_permits * sizeof(struct afs_permit)) != 0)
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continue;
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if (refcount_inc_not_zero(&xpermits->usage)) {
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replacement = xpermits;
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goto found;
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}
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break;
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}
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for (i = 0; i < new->nr_permits; i++)
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key_get(new->permits[i].key);
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hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
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replacement = new;
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new = NULL;
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found:
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spin_unlock(&afs_permits_lock);
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kfree(new);
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rcu_read_lock();
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spin_lock(&vnode->lock);
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zap = rcu_access_pointer(vnode->permit_cache);
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if (!afs_cb_is_broken(cb_break, vnode) && zap == permits)
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rcu_assign_pointer(vnode->permit_cache, replacement);
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else
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zap = replacement;
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spin_unlock(&vnode->lock);
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rcu_read_unlock();
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afs_put_permits(zap);
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out_put:
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afs_put_permits(permits);
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return;
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someone_else_changed_it_unlock:
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spin_unlock(&vnode->lock);
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someone_else_changed_it:
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/* Someone else changed the cache under us - don't recheck at this
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* time.
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*/
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rcu_read_unlock();
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return;
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}
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static bool afs_check_permit_rcu(struct afs_vnode *vnode, struct key *key,
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afs_access_t *_access)
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{
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const struct afs_permits *permits;
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int i;
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_enter("{%llx:%llu},%x",
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vnode->fid.vid, vnode->fid.vnode, key_serial(key));
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/* check the permits to see if we've got one yet */
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if (key == vnode->volume->cell->anonymous_key) {
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*_access = vnode->status.anon_access;
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_leave(" = t [anon %x]", *_access);
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return true;
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}
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permits = rcu_dereference(vnode->permit_cache);
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if (permits) {
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for (i = 0; i < permits->nr_permits; i++) {
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if (permits->permits[i].key < key)
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continue;
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if (permits->permits[i].key > key)
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break;
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*_access = permits->permits[i].access;
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_leave(" = %u [perm %x]", !permits->invalidated, *_access);
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return !permits->invalidated;
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}
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}
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_leave(" = f");
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return false;
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}
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/*
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* check with the fileserver to see if the directory or parent directory is
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* permitted to be accessed with this authorisation, and if so, what access it
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* is granted
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*/
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int afs_check_permit(struct afs_vnode *vnode, struct key *key,
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afs_access_t *_access)
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{
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struct afs_permits *permits;
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bool valid = false;
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int i, ret;
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_enter("{%llx:%llu},%x",
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vnode->fid.vid, vnode->fid.vnode, key_serial(key));
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/* check the permits to see if we've got one yet */
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if (key == vnode->volume->cell->anonymous_key) {
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_debug("anon");
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*_access = vnode->status.anon_access;
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valid = true;
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} else {
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rcu_read_lock();
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permits = rcu_dereference(vnode->permit_cache);
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if (permits) {
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for (i = 0; i < permits->nr_permits; i++) {
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if (permits->permits[i].key < key)
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continue;
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if (permits->permits[i].key > key)
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break;
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*_access = permits->permits[i].access;
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valid = !permits->invalidated;
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break;
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}
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}
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rcu_read_unlock();
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}
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if (!valid) {
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/* Check the status on the file we're actually interested in
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* (the post-processing will cache the result).
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*/
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_debug("no valid permit");
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ret = afs_fetch_status(vnode, key, false, _access);
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if (ret < 0) {
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*_access = 0;
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_leave(" = %d", ret);
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return ret;
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}
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}
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_leave(" = 0 [access %x]", *_access);
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return 0;
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}
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/*
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* check the permissions on an AFS file
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* - AFS ACLs are attached to directories only, and a file is controlled by its
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* parent directory's ACL
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*/
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int afs_permission(struct inode *inode, int mask)
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{
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struct afs_vnode *vnode = AFS_FS_I(inode);
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afs_access_t access;
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struct key *key;
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int ret = 0;
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_enter("{{%llx:%llu},%lx},%x,",
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vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
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if (mask & MAY_NOT_BLOCK) {
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key = afs_request_key_rcu(vnode->volume->cell);
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if (IS_ERR(key))
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return -ECHILD;
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ret = -ECHILD;
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if (!afs_check_validity(vnode) ||
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!afs_check_permit_rcu(vnode, key, &access))
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goto error;
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} else {
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key = afs_request_key(vnode->volume->cell);
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if (IS_ERR(key)) {
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_leave(" = %ld [key]", PTR_ERR(key));
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return PTR_ERR(key);
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}
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ret = afs_validate(vnode, key);
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if (ret < 0)
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goto error;
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/* check the permits to see if we've got one yet */
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ret = afs_check_permit(vnode, key, &access);
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if (ret < 0)
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goto error;
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}
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/* interpret the access mask */
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_debug("REQ %x ACC %x on %s",
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mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
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ret = 0;
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if (S_ISDIR(inode->i_mode)) {
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if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) {
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if (!(access & AFS_ACE_LOOKUP))
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goto permission_denied;
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}
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if (mask & MAY_WRITE) {
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if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
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AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
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goto permission_denied;
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}
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} else {
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if (!(access & AFS_ACE_LOOKUP))
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goto permission_denied;
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if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
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goto permission_denied;
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if (mask & (MAY_EXEC | MAY_READ)) {
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if (!(access & AFS_ACE_READ))
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goto permission_denied;
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if (!(inode->i_mode & S_IRUSR))
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goto permission_denied;
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} else if (mask & MAY_WRITE) {
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if (!(access & AFS_ACE_WRITE))
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goto permission_denied;
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if (!(inode->i_mode & S_IWUSR))
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goto permission_denied;
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}
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}
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key_put(key);
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_leave(" = %d", ret);
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return ret;
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permission_denied:
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ret = -EACCES;
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error:
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key_put(key);
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_leave(" = %d", ret);
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return ret;
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}
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void __exit afs_clean_up_permit_cache(void)
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{
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int i;
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for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
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WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));
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}
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