// 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 ([email protected])
*/
#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 mnt_idmap *idmap, 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]));
}
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