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488 lines
12 KiB
488 lines
12 KiB
// 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 ([email protected]) |
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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 user_namespace *mnt_userns, struct inode *inode, |
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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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