| /* AFS security handling |
| * |
| * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved. |
| * Written by David Howells (dhowells@redhat.com) |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version |
| * 2 of the License, or (at your option) any later version. |
| */ |
| |
| #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(&key_type_rxrpc, cell->anonymous_key->description, |
| 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; |
| } |
| } |
| |
| /* |
| * 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_permits *permits, *xpermits, *replacement, *zap, *new = NULL; |
| afs_access_t caller_access = READ_ONCE(vnode->status.caller_access); |
| size_t size = 0; |
| bool changed = false; |
| int i, j; |
| |
| _enter("{%x:%u},%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 (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest)) { |
| 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 (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest)) |
| 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(sizeof(struct afs_permits) + |
| sizeof(struct afs_permit) * 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); |
| |
| spin_lock(&vnode->lock); |
| zap = rcu_access_pointer(vnode->permit_cache); |
| if (cb_break == afs_cb_break_sum(vnode, vnode->cb_interest) && |
| zap == permits) |
| rcu_assign_pointer(vnode->permit_cache, replacement); |
| else |
| zap = replacement; |
| spin_unlock(&vnode->lock); |
| 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; |
| } |
| |
| /* |
| * 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("{%x:%u},%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); |
| if (ret < 0) { |
| *_access = 0; |
| _leave(" = %d", ret); |
| return ret; |
| } |
| *_access = vnode->status.caller_access; |
| } |
| |
| _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 inode *inode, int mask) |
| { |
| struct afs_vnode *vnode = AFS_FS_I(inode); |
| afs_access_t uninitialized_var(access); |
| struct key *key; |
| int ret; |
| |
| if (mask & MAY_NOT_BLOCK) |
| return -ECHILD; |
| |
| _enter("{{%x:%u},%lx},%x,", |
| vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask); |
| |
| 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"); |
| |
| 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])); |
| |
| } |