swh:1:snp:32555a3fd8878f019c2ebd6c964bc1edcaeff337
Tip revision: 0e698dfa282211e414076f9dc7e83c1c288314fd authored by Linus Torvalds on 03 May 2020, 21:56:04 UTC
Linux 5.7-rc4
Linux 5.7-rc4
Tip revision: 0e698df
cell.c
// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS cell and server record management
*
* Copyright (C) 2002, 2017 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <linux/inet.h>
#include <linux/namei.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
static unsigned __read_mostly afs_cell_gc_delay = 10;
static unsigned __read_mostly afs_cell_min_ttl = 10 * 60;
static unsigned __read_mostly afs_cell_max_ttl = 24 * 60 * 60;
static void afs_manage_cell(struct work_struct *);
static void afs_dec_cells_outstanding(struct afs_net *net)
{
if (atomic_dec_and_test(&net->cells_outstanding))
wake_up_var(&net->cells_outstanding);
}
/*
* Set the cell timer to fire after a given delay, assuming it's not already
* set for an earlier time.
*/
static void afs_set_cell_timer(struct afs_net *net, time64_t delay)
{
if (net->live) {
atomic_inc(&net->cells_outstanding);
if (timer_reduce(&net->cells_timer, jiffies + delay * HZ))
afs_dec_cells_outstanding(net);
}
}
/*
* Look up and get an activation reference on a cell record under RCU
* conditions. The caller must hold the RCU read lock.
*/
struct afs_cell *afs_lookup_cell_rcu(struct afs_net *net,
const char *name, unsigned int namesz)
{
struct afs_cell *cell = NULL;
struct rb_node *p;
int n, seq = 0, ret = 0;
_enter("%*.*s", namesz, namesz, name);
if (name && namesz == 0)
return ERR_PTR(-EINVAL);
if (namesz > AFS_MAXCELLNAME)
return ERR_PTR(-ENAMETOOLONG);
do {
/* Unfortunately, rbtree walking doesn't give reliable results
* under just the RCU read lock, so we have to check for
* changes.
*/
if (cell)
afs_put_cell(net, cell);
cell = NULL;
ret = -ENOENT;
read_seqbegin_or_lock(&net->cells_lock, &seq);
if (!name) {
cell = rcu_dereference_raw(net->ws_cell);
if (cell) {
afs_get_cell(cell);
ret = 0;
break;
}
ret = -EDESTADDRREQ;
continue;
}
p = rcu_dereference_raw(net->cells.rb_node);
while (p) {
cell = rb_entry(p, struct afs_cell, net_node);
n = strncasecmp(cell->name, name,
min_t(size_t, cell->name_len, namesz));
if (n == 0)
n = cell->name_len - namesz;
if (n < 0) {
p = rcu_dereference_raw(p->rb_left);
} else if (n > 0) {
p = rcu_dereference_raw(p->rb_right);
} else {
if (atomic_inc_not_zero(&cell->usage)) {
ret = 0;
break;
}
/* We want to repeat the search, this time with
* the lock properly locked.
*/
}
cell = NULL;
}
} while (need_seqretry(&net->cells_lock, seq));
done_seqretry(&net->cells_lock, seq);
if (ret != 0 && cell)
afs_put_cell(net, cell);
return ret == 0 ? cell : ERR_PTR(ret);
}
/*
* Set up a cell record and fill in its name, VL server address list and
* allocate an anonymous key
*/
static struct afs_cell *afs_alloc_cell(struct afs_net *net,
const char *name, unsigned int namelen,
const char *addresses)
{
struct afs_vlserver_list *vllist;
struct afs_cell *cell;
int i, ret;
ASSERT(name);
if (namelen == 0)
return ERR_PTR(-EINVAL);
if (namelen > AFS_MAXCELLNAME) {
_leave(" = -ENAMETOOLONG");
return ERR_PTR(-ENAMETOOLONG);
}
/* Prohibit cell names that contain unprintable chars, '/' and '@' or
* that begin with a dot. This also precludes "@cell".
*/
if (name[0] == '.')
return ERR_PTR(-EINVAL);
for (i = 0; i < namelen; i++) {
char ch = name[i];
if (!isprint(ch) || ch == '/' || ch == '@')
return ERR_PTR(-EINVAL);
}
_enter("%*.*s,%s", namelen, namelen, name, addresses);
cell = kzalloc(sizeof(struct afs_cell), GFP_KERNEL);
if (!cell) {
_leave(" = -ENOMEM");
return ERR_PTR(-ENOMEM);
}
cell->net = net;
cell->name_len = namelen;
for (i = 0; i < namelen; i++)
cell->name[i] = tolower(name[i]);
atomic_set(&cell->usage, 2);
INIT_WORK(&cell->manager, afs_manage_cell);
INIT_LIST_HEAD(&cell->proc_volumes);
rwlock_init(&cell->proc_lock);
rwlock_init(&cell->vl_servers_lock);
/* Provide a VL server list, filling it in if we were given a list of
* addresses to use.
*/
if (addresses) {
vllist = afs_parse_text_addrs(net,
addresses, strlen(addresses), ':',
VL_SERVICE, AFS_VL_PORT);
if (IS_ERR(vllist)) {
ret = PTR_ERR(vllist);
goto parse_failed;
}
vllist->source = DNS_RECORD_FROM_CONFIG;
vllist->status = DNS_LOOKUP_NOT_DONE;
cell->dns_expiry = TIME64_MAX;
} else {
ret = -ENOMEM;
vllist = afs_alloc_vlserver_list(0);
if (!vllist)
goto error;
vllist->source = DNS_RECORD_UNAVAILABLE;
vllist->status = DNS_LOOKUP_NOT_DONE;
cell->dns_expiry = ktime_get_real_seconds();
}
rcu_assign_pointer(cell->vl_servers, vllist);
cell->dns_source = vllist->source;
cell->dns_status = vllist->status;
smp_store_release(&cell->dns_lookup_count, 1); /* vs source/status */
_leave(" = %p", cell);
return cell;
parse_failed:
if (ret == -EINVAL)
printk(KERN_ERR "kAFS: bad VL server IP address\n");
error:
kfree(cell);
_leave(" = %d", ret);
return ERR_PTR(ret);
}
/*
* afs_lookup_cell - Look up or create a cell record.
* @net: The network namespace
* @name: The name of the cell.
* @namesz: The strlen of the cell name.
* @vllist: A colon/comma separated list of numeric IP addresses or NULL.
* @excl: T if an error should be given if the cell name already exists.
*
* Look up a cell record by name and query the DNS for VL server addresses if
* needed. Note that that actual DNS query is punted off to the manager thread
* so that this function can return immediately if interrupted whilst allowing
* cell records to be shared even if not yet fully constructed.
*/
struct afs_cell *afs_lookup_cell(struct afs_net *net,
const char *name, unsigned int namesz,
const char *vllist, bool excl)
{
struct afs_cell *cell, *candidate, *cursor;
struct rb_node *parent, **pp;
enum afs_cell_state state;
int ret, n;
_enter("%s,%s", name, vllist);
if (!excl) {
rcu_read_lock();
cell = afs_lookup_cell_rcu(net, name, namesz);
rcu_read_unlock();
if (!IS_ERR(cell))
goto wait_for_cell;
}
/* Assume we're probably going to create a cell and preallocate and
* mostly set up a candidate record. We can then use this to stash the
* name, the net namespace and VL server addresses.
*
* We also want to do this before we hold any locks as it may involve
* upcalling to userspace to make DNS queries.
*/
candidate = afs_alloc_cell(net, name, namesz, vllist);
if (IS_ERR(candidate)) {
_leave(" = %ld", PTR_ERR(candidate));
return candidate;
}
/* Find the insertion point and check to see if someone else added a
* cell whilst we were allocating.
*/
write_seqlock(&net->cells_lock);
pp = &net->cells.rb_node;
parent = NULL;
while (*pp) {
parent = *pp;
cursor = rb_entry(parent, struct afs_cell, net_node);
n = strncasecmp(cursor->name, name,
min_t(size_t, cursor->name_len, namesz));
if (n == 0)
n = cursor->name_len - namesz;
if (n < 0)
pp = &(*pp)->rb_left;
else if (n > 0)
pp = &(*pp)->rb_right;
else
goto cell_already_exists;
}
cell = candidate;
candidate = NULL;
rb_link_node_rcu(&cell->net_node, parent, pp);
rb_insert_color(&cell->net_node, &net->cells);
atomic_inc(&net->cells_outstanding);
write_sequnlock(&net->cells_lock);
queue_work(afs_wq, &cell->manager);
wait_for_cell:
_debug("wait_for_cell");
wait_var_event(&cell->state,
({
state = smp_load_acquire(&cell->state); /* vs error */
state == AFS_CELL_ACTIVE || state == AFS_CELL_FAILED;
}));
/* Check the state obtained from the wait check. */
if (state == AFS_CELL_FAILED) {
ret = cell->error;
goto error;
}
_leave(" = %p [cell]", cell);
return cell;
cell_already_exists:
_debug("cell exists");
cell = cursor;
if (excl) {
ret = -EEXIST;
} else {
afs_get_cell(cursor);
ret = 0;
}
write_sequnlock(&net->cells_lock);
kfree(candidate);
if (ret == 0)
goto wait_for_cell;
goto error_noput;
error:
afs_put_cell(net, cell);
error_noput:
_leave(" = %d [error]", ret);
return ERR_PTR(ret);
}
/*
* set the root cell information
* - can be called with a module parameter string
* - can be called from a write to /proc/fs/afs/rootcell
*/
int afs_cell_init(struct afs_net *net, const char *rootcell)
{
struct afs_cell *old_root, *new_root;
const char *cp, *vllist;
size_t len;
_enter("");
if (!rootcell) {
/* module is loaded with no parameters, or built statically.
* - in the future we might initialize cell DB here.
*/
_leave(" = 0 [no root]");
return 0;
}
cp = strchr(rootcell, ':');
if (!cp) {
_debug("kAFS: no VL server IP addresses specified");
vllist = NULL;
len = strlen(rootcell);
} else {
vllist = cp + 1;
len = cp - rootcell;
}
/* allocate a cell record for the root cell */
new_root = afs_lookup_cell(net, rootcell, len, vllist, false);
if (IS_ERR(new_root)) {
_leave(" = %ld", PTR_ERR(new_root));
return PTR_ERR(new_root);
}
if (!test_and_set_bit(AFS_CELL_FL_NO_GC, &new_root->flags))
afs_get_cell(new_root);
/* install the new cell */
write_seqlock(&net->cells_lock);
old_root = rcu_access_pointer(net->ws_cell);
rcu_assign_pointer(net->ws_cell, new_root);
write_sequnlock(&net->cells_lock);
afs_put_cell(net, old_root);
_leave(" = 0");
return 0;
}
/*
* Update a cell's VL server address list from the DNS.
*/
static int afs_update_cell(struct afs_cell *cell)
{
struct afs_vlserver_list *vllist, *old = NULL, *p;
unsigned int min_ttl = READ_ONCE(afs_cell_min_ttl);
unsigned int max_ttl = READ_ONCE(afs_cell_max_ttl);
time64_t now, expiry = 0;
int ret = 0;
_enter("%s", cell->name);
vllist = afs_dns_query(cell, &expiry);
if (IS_ERR(vllist)) {
ret = PTR_ERR(vllist);
_debug("%s: fail %d", cell->name, ret);
if (ret == -ENOMEM)
goto out_wake;
ret = -ENOMEM;
vllist = afs_alloc_vlserver_list(0);
if (!vllist)
goto out_wake;
switch (ret) {
case -ENODATA:
case -EDESTADDRREQ:
vllist->status = DNS_LOOKUP_GOT_NOT_FOUND;
break;
case -EAGAIN:
case -ECONNREFUSED:
vllist->status = DNS_LOOKUP_GOT_TEMP_FAILURE;
break;
default:
vllist->status = DNS_LOOKUP_GOT_LOCAL_FAILURE;
break;
}
}
_debug("%s: got list %d %d", cell->name, vllist->source, vllist->status);
cell->dns_status = vllist->status;
now = ktime_get_real_seconds();
if (min_ttl > max_ttl)
max_ttl = min_ttl;
if (expiry < now + min_ttl)
expiry = now + min_ttl;
else if (expiry > now + max_ttl)
expiry = now + max_ttl;
_debug("%s: status %d", cell->name, vllist->status);
if (vllist->source == DNS_RECORD_UNAVAILABLE) {
switch (vllist->status) {
case DNS_LOOKUP_GOT_NOT_FOUND:
/* The DNS said that the cell does not exist or there
* weren't any addresses to be had.
*/
cell->dns_expiry = expiry;
break;
case DNS_LOOKUP_BAD:
case DNS_LOOKUP_GOT_LOCAL_FAILURE:
case DNS_LOOKUP_GOT_TEMP_FAILURE:
case DNS_LOOKUP_GOT_NS_FAILURE:
default:
cell->dns_expiry = now + 10;
break;
}
} else {
cell->dns_expiry = expiry;
}
/* Replace the VL server list if the new record has servers or the old
* record doesn't.
*/
write_lock(&cell->vl_servers_lock);
p = rcu_dereference_protected(cell->vl_servers, true);
if (vllist->nr_servers > 0 || p->nr_servers == 0) {
rcu_assign_pointer(cell->vl_servers, vllist);
cell->dns_source = vllist->source;
old = p;
}
write_unlock(&cell->vl_servers_lock);
afs_put_vlserverlist(cell->net, old);
out_wake:
smp_store_release(&cell->dns_lookup_count,
cell->dns_lookup_count + 1); /* vs source/status */
wake_up_var(&cell->dns_lookup_count);
_leave(" = %d", ret);
return ret;
}
/*
* Destroy a cell record
*/
static void afs_cell_destroy(struct rcu_head *rcu)
{
struct afs_cell *cell = container_of(rcu, struct afs_cell, rcu);
_enter("%p{%s}", cell, cell->name);
ASSERTCMP(atomic_read(&cell->usage), ==, 0);
afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers));
key_put(cell->anonymous_key);
kfree(cell);
_leave(" [destroyed]");
}
/*
* Queue the cell manager.
*/
static void afs_queue_cell_manager(struct afs_net *net)
{
int outstanding = atomic_inc_return(&net->cells_outstanding);
_enter("%d", outstanding);
if (!queue_work(afs_wq, &net->cells_manager))
afs_dec_cells_outstanding(net);
}
/*
* Cell management timer. We have an increment on cells_outstanding that we
* need to pass along to the work item.
*/
void afs_cells_timer(struct timer_list *timer)
{
struct afs_net *net = container_of(timer, struct afs_net, cells_timer);
_enter("");
if (!queue_work(afs_wq, &net->cells_manager))
afs_dec_cells_outstanding(net);
}
/*
* Get a reference on a cell record.
*/
struct afs_cell *afs_get_cell(struct afs_cell *cell)
{
atomic_inc(&cell->usage);
return cell;
}
/*
* Drop a reference on a cell record.
*/
void afs_put_cell(struct afs_net *net, struct afs_cell *cell)
{
time64_t now, expire_delay;
if (!cell)
return;
_enter("%s", cell->name);
now = ktime_get_real_seconds();
cell->last_inactive = now;
expire_delay = 0;
if (cell->vl_servers->nr_servers)
expire_delay = afs_cell_gc_delay;
if (atomic_dec_return(&cell->usage) > 1)
return;
/* 'cell' may now be garbage collected. */
afs_set_cell_timer(net, expire_delay);
}
/*
* Allocate a key to use as a placeholder for anonymous user security.
*/
static int afs_alloc_anon_key(struct afs_cell *cell)
{
struct key *key;
char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp;
/* Create a key to represent an anonymous user. */
memcpy(keyname, "afs@", 4);
dp = keyname + 4;
cp = cell->name;
do {
*dp++ = tolower(*cp);
} while (*cp++);
key = rxrpc_get_null_key(keyname);
if (IS_ERR(key))
return PTR_ERR(key);
cell->anonymous_key = key;
_debug("anon key %p{%x}",
cell->anonymous_key, key_serial(cell->anonymous_key));
return 0;
}
/*
* Activate a cell.
*/
static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
{
struct hlist_node **p;
struct afs_cell *pcell;
int ret;
if (!cell->anonymous_key) {
ret = afs_alloc_anon_key(cell);
if (ret < 0)
return ret;
}
#ifdef CONFIG_AFS_FSCACHE
cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
&afs_cell_cache_index_def,
cell->name, strlen(cell->name),
NULL, 0,
cell, 0, true);
#endif
ret = afs_proc_cell_setup(cell);
if (ret < 0)
return ret;
mutex_lock(&net->proc_cells_lock);
for (p = &net->proc_cells.first; *p; p = &(*p)->next) {
pcell = hlist_entry(*p, struct afs_cell, proc_link);
if (strcmp(cell->name, pcell->name) < 0)
break;
}
cell->proc_link.pprev = p;
cell->proc_link.next = *p;
rcu_assign_pointer(*p, &cell->proc_link.next);
if (cell->proc_link.next)
cell->proc_link.next->pprev = &cell->proc_link.next;
afs_dynroot_mkdir(net, cell);
mutex_unlock(&net->proc_cells_lock);
return 0;
}
/*
* Deactivate a cell.
*/
static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
{
_enter("%s", cell->name);
afs_proc_cell_remove(cell);
mutex_lock(&net->proc_cells_lock);
hlist_del_rcu(&cell->proc_link);
afs_dynroot_rmdir(net, cell);
mutex_unlock(&net->proc_cells_lock);
#ifdef CONFIG_AFS_FSCACHE
fscache_relinquish_cookie(cell->cache, NULL, false);
cell->cache = NULL;
#endif
_leave("");
}
/*
* Manage a cell record, initialising and destroying it, maintaining its DNS
* records.
*/
static void afs_manage_cell(struct work_struct *work)
{
struct afs_cell *cell = container_of(work, struct afs_cell, manager);
struct afs_net *net = cell->net;
bool deleted;
int ret, usage;
_enter("%s", cell->name);
again:
_debug("state %u", cell->state);
switch (cell->state) {
case AFS_CELL_INACTIVE:
case AFS_CELL_FAILED:
write_seqlock(&net->cells_lock);
usage = 1;
deleted = atomic_try_cmpxchg_relaxed(&cell->usage, &usage, 0);
if (deleted)
rb_erase(&cell->net_node, &net->cells);
write_sequnlock(&net->cells_lock);
if (deleted)
goto final_destruction;
if (cell->state == AFS_CELL_FAILED)
goto done;
smp_store_release(&cell->state, AFS_CELL_UNSET);
wake_up_var(&cell->state);
goto again;
case AFS_CELL_UNSET:
smp_store_release(&cell->state, AFS_CELL_ACTIVATING);
wake_up_var(&cell->state);
goto again;
case AFS_CELL_ACTIVATING:
ret = afs_activate_cell(net, cell);
if (ret < 0)
goto activation_failed;
smp_store_release(&cell->state, AFS_CELL_ACTIVE);
wake_up_var(&cell->state);
goto again;
case AFS_CELL_ACTIVE:
if (atomic_read(&cell->usage) > 1) {
if (test_and_clear_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags)) {
ret = afs_update_cell(cell);
if (ret < 0)
cell->error = ret;
}
goto done;
}
smp_store_release(&cell->state, AFS_CELL_DEACTIVATING);
wake_up_var(&cell->state);
goto again;
case AFS_CELL_DEACTIVATING:
if (atomic_read(&cell->usage) > 1)
goto reverse_deactivation;
afs_deactivate_cell(net, cell);
smp_store_release(&cell->state, AFS_CELL_INACTIVE);
wake_up_var(&cell->state);
goto again;
default:
break;
}
_debug("bad state %u", cell->state);
BUG(); /* Unhandled state */
activation_failed:
cell->error = ret;
afs_deactivate_cell(net, cell);
smp_store_release(&cell->state, AFS_CELL_FAILED); /* vs error */
wake_up_var(&cell->state);
goto again;
reverse_deactivation:
smp_store_release(&cell->state, AFS_CELL_ACTIVE);
wake_up_var(&cell->state);
_leave(" [deact->act]");
return;
done:
_leave(" [done %u]", cell->state);
return;
final_destruction:
call_rcu(&cell->rcu, afs_cell_destroy);
afs_dec_cells_outstanding(net);
_leave(" [destruct %d]", atomic_read(&net->cells_outstanding));
}
/*
* Manage the records of cells known to a network namespace. This includes
* updating the DNS records and garbage collecting unused cells that were
* automatically added.
*
* Note that constructed cell records may only be removed from net->cells by
* this work item, so it is safe for this work item to stash a cursor pointing
* into the tree and then return to caller (provided it skips cells that are
* still under construction).
*
* Note also that we were given an increment on net->cells_outstanding by
* whoever queued us that we need to deal with before returning.
*/
void afs_manage_cells(struct work_struct *work)
{
struct afs_net *net = container_of(work, struct afs_net, cells_manager);
struct rb_node *cursor;
time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
bool purging = !net->live;
_enter("");
/* Trawl the cell database looking for cells that have expired from
* lack of use and cells whose DNS results have expired and dispatch
* their managers.
*/
read_seqlock_excl(&net->cells_lock);
for (cursor = rb_first(&net->cells); cursor; cursor = rb_next(cursor)) {
struct afs_cell *cell =
rb_entry(cursor, struct afs_cell, net_node);
unsigned usage;
bool sched_cell = false;
usage = atomic_read(&cell->usage);
_debug("manage %s %u", cell->name, usage);
ASSERTCMP(usage, >=, 1);
if (purging) {
if (test_and_clear_bit(AFS_CELL_FL_NO_GC, &cell->flags))
usage = atomic_dec_return(&cell->usage);
ASSERTCMP(usage, ==, 1);
}
if (usage == 1) {
struct afs_vlserver_list *vllist;
time64_t expire_at = cell->last_inactive;
read_lock(&cell->vl_servers_lock);
vllist = rcu_dereference_protected(
cell->vl_servers,
lockdep_is_held(&cell->vl_servers_lock));
if (vllist->nr_servers > 0)
expire_at += afs_cell_gc_delay;
read_unlock(&cell->vl_servers_lock);
if (purging || expire_at <= now)
sched_cell = true;
else if (expire_at < next_manage)
next_manage = expire_at;
}
if (!purging) {
if (test_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags))
sched_cell = true;
}
if (sched_cell)
queue_work(afs_wq, &cell->manager);
}
read_sequnlock_excl(&net->cells_lock);
/* Update the timer on the way out. We have to pass an increment on
* cells_outstanding in the namespace that we are in to the timer or
* the work scheduler.
*/
if (!purging && next_manage < TIME64_MAX) {
now = ktime_get_real_seconds();
if (next_manage - now <= 0) {
if (queue_work(afs_wq, &net->cells_manager))
atomic_inc(&net->cells_outstanding);
} else {
afs_set_cell_timer(net, next_manage - now);
}
}
afs_dec_cells_outstanding(net);
_leave(" [%d]", atomic_read(&net->cells_outstanding));
}
/*
* Purge in-memory cell database.
*/
void afs_cell_purge(struct afs_net *net)
{
struct afs_cell *ws;
_enter("");
write_seqlock(&net->cells_lock);
ws = rcu_access_pointer(net->ws_cell);
RCU_INIT_POINTER(net->ws_cell, NULL);
write_sequnlock(&net->cells_lock);
afs_put_cell(net, ws);
_debug("del timer");
if (del_timer_sync(&net->cells_timer))
atomic_dec(&net->cells_outstanding);
_debug("kick mgr");
afs_queue_cell_manager(net);
_debug("wait");
wait_var_event(&net->cells_outstanding,
!atomic_read(&net->cells_outstanding));
_leave("");
}