linux/net/ipv4/inet_hashtables.c
Eric Dumazet 3cdaedae63 tcp: Fix a connect() race with timewait sockets
When we find a timewait connection in __inet_hash_connect() and reuse
it for a new connection request, we have a race window, releasing bind
list lock and reacquiring it in __inet_twsk_kill() to remove timewait
socket from list.

Another thread might find the timewait socket we already chose, leading to
list corruption and crashes.

Fix is to remove timewait socket from bind list before releasing the bind lock.

Note: This problem happens if sysctl_tcp_tw_reuse is set.

Reported-by: kapil dakhane <kdakhane@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-12-08 20:17:51 -08:00

563 lines
14 KiB
C

/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Generic INET transport hashtables
*
* Authors: Lotsa people, from code originally in tcp
*
* 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/module.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <net/inet_connection_sock.h>
#include <net/inet_hashtables.h>
#include <net/ip.h>
/*
* Allocate and initialize a new local port bind bucket.
* The bindhash mutex for snum's hash chain must be held here.
*/
struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
struct net *net,
struct inet_bind_hashbucket *head,
const unsigned short snum)
{
struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);
if (tb != NULL) {
write_pnet(&tb->ib_net, hold_net(net));
tb->port = snum;
tb->fastreuse = 0;
tb->num_owners = 0;
INIT_HLIST_HEAD(&tb->owners);
hlist_add_head(&tb->node, &head->chain);
}
return tb;
}
/*
* Caller must hold hashbucket lock for this tb with local BH disabled
*/
void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
{
if (hlist_empty(&tb->owners)) {
__hlist_del(&tb->node);
release_net(ib_net(tb));
kmem_cache_free(cachep, tb);
}
}
void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
const unsigned short snum)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
atomic_inc(&hashinfo->bsockets);
inet_sk(sk)->inet_num = snum;
sk_add_bind_node(sk, &tb->owners);
tb->num_owners++;
inet_csk(sk)->icsk_bind_hash = tb;
}
/*
* Get rid of any references to a local port held by the given sock.
*/
static void __inet_put_port(struct sock *sk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
const int bhash = inet_bhashfn(sock_net(sk), inet_sk(sk)->inet_num,
hashinfo->bhash_size);
struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
struct inet_bind_bucket *tb;
atomic_dec(&hashinfo->bsockets);
spin_lock(&head->lock);
tb = inet_csk(sk)->icsk_bind_hash;
__sk_del_bind_node(sk);
tb->num_owners--;
inet_csk(sk)->icsk_bind_hash = NULL;
inet_sk(sk)->inet_num = 0;
inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
spin_unlock(&head->lock);
}
void inet_put_port(struct sock *sk)
{
local_bh_disable();
__inet_put_port(sk);
local_bh_enable();
}
EXPORT_SYMBOL(inet_put_port);
void __inet_inherit_port(struct sock *sk, struct sock *child)
{
struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;
const int bhash = inet_bhashfn(sock_net(sk), inet_sk(child)->inet_num,
table->bhash_size);
struct inet_bind_hashbucket *head = &table->bhash[bhash];
struct inet_bind_bucket *tb;
spin_lock(&head->lock);
tb = inet_csk(sk)->icsk_bind_hash;
sk_add_bind_node(child, &tb->owners);
inet_csk(child)->icsk_bind_hash = tb;
spin_unlock(&head->lock);
}
EXPORT_SYMBOL_GPL(__inet_inherit_port);
static inline int compute_score(struct sock *sk, struct net *net,
const unsigned short hnum, const __be32 daddr,
const int dif)
{
int score = -1;
struct inet_sock *inet = inet_sk(sk);
if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
!ipv6_only_sock(sk)) {
__be32 rcv_saddr = inet->inet_rcv_saddr;
score = sk->sk_family == PF_INET ? 1 : 0;
if (rcv_saddr) {
if (rcv_saddr != daddr)
return -1;
score += 2;
}
if (sk->sk_bound_dev_if) {
if (sk->sk_bound_dev_if != dif)
return -1;
score += 2;
}
}
return score;
}
/*
* Don't inline this cruft. Here are some nice properties to exploit here. The
* BSD API does not allow a listening sock to specify the remote port nor the
* remote address for the connection. So always assume those are both
* wildcarded during the search since they can never be otherwise.
*/
struct sock *__inet_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo,
const __be32 daddr, const unsigned short hnum,
const int dif)
{
struct sock *sk, *result;
struct hlist_nulls_node *node;
unsigned int hash = inet_lhashfn(net, hnum);
struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
int score, hiscore;
rcu_read_lock();
begin:
result = NULL;
hiscore = -1;
sk_nulls_for_each_rcu(sk, node, &ilb->head) {
score = compute_score(sk, net, hnum, daddr, dif);
if (score > hiscore) {
result = sk;
hiscore = score;
}
}
/*
* if the nulls value we got at the end of this lookup is
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
goto begin;
if (result) {
if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
result = NULL;
else if (unlikely(compute_score(result, net, hnum, daddr,
dif) < hiscore)) {
sock_put(result);
goto begin;
}
}
rcu_read_unlock();
return result;
}
EXPORT_SYMBOL_GPL(__inet_lookup_listener);
struct sock * __inet_lookup_established(struct net *net,
struct inet_hashinfo *hashinfo,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const u16 hnum,
const int dif)
{
INET_ADDR_COOKIE(acookie, saddr, daddr)
const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
struct sock *sk;
const struct hlist_nulls_node *node;
/* Optimize here for direct hit, only listening connections can
* have wildcards anyways.
*/
unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
unsigned int slot = hash & hashinfo->ehash_mask;
struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
rcu_read_lock();
begin:
sk_nulls_for_each_rcu(sk, node, &head->chain) {
if (INET_MATCH(sk, net, hash, acookie,
saddr, daddr, ports, dif)) {
if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
goto begintw;
if (unlikely(!INET_MATCH(sk, net, hash, acookie,
saddr, daddr, ports, dif))) {
sock_put(sk);
goto begin;
}
goto out;
}
}
/*
* if the nulls value we got at the end of this lookup is
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
if (get_nulls_value(node) != slot)
goto begin;
begintw:
/* Must check for a TIME_WAIT'er before going to listener hash. */
sk_nulls_for_each_rcu(sk, node, &head->twchain) {
if (INET_TW_MATCH(sk, net, hash, acookie,
saddr, daddr, ports, dif)) {
if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) {
sk = NULL;
goto out;
}
if (unlikely(!INET_TW_MATCH(sk, net, hash, acookie,
saddr, daddr, ports, dif))) {
sock_put(sk);
goto begintw;
}
goto out;
}
}
/*
* if the nulls value we got at the end of this lookup is
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
if (get_nulls_value(node) != slot)
goto begintw;
sk = NULL;
out:
rcu_read_unlock();
return sk;
}
EXPORT_SYMBOL_GPL(__inet_lookup_established);
/* called with local bh disabled */
static int __inet_check_established(struct inet_timewait_death_row *death_row,
struct sock *sk, __u16 lport,
struct inet_timewait_sock **twp)
{
struct inet_hashinfo *hinfo = death_row->hashinfo;
struct inet_sock *inet = inet_sk(sk);
__be32 daddr = inet->inet_rcv_saddr;
__be32 saddr = inet->inet_daddr;
int dif = sk->sk_bound_dev_if;
INET_ADDR_COOKIE(acookie, saddr, daddr)
const __portpair ports = INET_COMBINED_PORTS(inet->inet_dport, lport);
struct net *net = sock_net(sk);
unsigned int hash = inet_ehashfn(net, daddr, lport,
saddr, inet->inet_dport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
spinlock_t *lock = inet_ehash_lockp(hinfo, hash);
struct sock *sk2;
const struct hlist_nulls_node *node;
struct inet_timewait_sock *tw;
int twrefcnt = 0;
spin_lock(lock);
/* Check TIME-WAIT sockets first. */
sk_nulls_for_each(sk2, node, &head->twchain) {
tw = inet_twsk(sk2);
if (INET_TW_MATCH(sk2, net, hash, acookie,
saddr, daddr, ports, dif)) {
if (twsk_unique(sk, sk2, twp))
goto unique;
else
goto not_unique;
}
}
tw = NULL;
/* And established part... */
sk_nulls_for_each(sk2, node, &head->chain) {
if (INET_MATCH(sk2, net, hash, acookie,
saddr, daddr, ports, dif))
goto not_unique;
}
unique:
/* Must record num and sport now. Otherwise we will see
* in hash table socket with a funny identity. */
inet->inet_num = lport;
inet->inet_sport = htons(lport);
sk->sk_hash = hash;
WARN_ON(!sk_unhashed(sk));
__sk_nulls_add_node_rcu(sk, &head->chain);
if (tw) {
twrefcnt = inet_twsk_unhash(tw);
NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
}
spin_unlock(lock);
if (twrefcnt)
inet_twsk_put(tw);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
if (twp) {
*twp = tw;
} else if (tw) {
/* Silly. Should hash-dance instead... */
inet_twsk_deschedule(tw, death_row);
inet_twsk_put(tw);
}
return 0;
not_unique:
spin_unlock(lock);
return -EADDRNOTAVAIL;
}
static inline u32 inet_sk_port_offset(const struct sock *sk)
{
const struct inet_sock *inet = inet_sk(sk);
return secure_ipv4_port_ephemeral(inet->inet_rcv_saddr,
inet->inet_daddr,
inet->inet_dport);
}
int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct hlist_nulls_head *list;
spinlock_t *lock;
struct inet_ehash_bucket *head;
int twrefcnt = 0;
WARN_ON(!sk_unhashed(sk));
sk->sk_hash = inet_sk_ehashfn(sk);
head = inet_ehash_bucket(hashinfo, sk->sk_hash);
list = &head->chain;
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
spin_lock(lock);
__sk_nulls_add_node_rcu(sk, list);
if (tw) {
WARN_ON(sk->sk_hash != tw->tw_hash);
twrefcnt = inet_twsk_unhash(tw);
}
spin_unlock(lock);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
return twrefcnt;
}
EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
static void __inet_hash(struct sock *sk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct inet_listen_hashbucket *ilb;
if (sk->sk_state != TCP_LISTEN) {
__inet_hash_nolisten(sk, NULL);
return;
}
WARN_ON(!sk_unhashed(sk));
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
spin_lock(&ilb->lock);
__sk_nulls_add_node_rcu(sk, &ilb->head);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
spin_unlock(&ilb->lock);
}
void inet_hash(struct sock *sk)
{
if (sk->sk_state != TCP_CLOSE) {
local_bh_disable();
__inet_hash(sk);
local_bh_enable();
}
}
EXPORT_SYMBOL_GPL(inet_hash);
void inet_unhash(struct sock *sk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
spinlock_t *lock;
int done;
if (sk_unhashed(sk))
return;
if (sk->sk_state == TCP_LISTEN)
lock = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)].lock;
else
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
spin_lock_bh(lock);
done =__sk_nulls_del_node_init_rcu(sk);
if (done)
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
spin_unlock_bh(lock);
}
EXPORT_SYMBOL_GPL(inet_unhash);
int __inet_hash_connect(struct inet_timewait_death_row *death_row,
struct sock *sk, u32 port_offset,
int (*check_established)(struct inet_timewait_death_row *,
struct sock *, __u16, struct inet_timewait_sock **),
int (*hash)(struct sock *sk, struct inet_timewait_sock *twp))
{
struct inet_hashinfo *hinfo = death_row->hashinfo;
const unsigned short snum = inet_sk(sk)->inet_num;
struct inet_bind_hashbucket *head;
struct inet_bind_bucket *tb;
int ret;
struct net *net = sock_net(sk);
int twrefcnt = 1;
if (!snum) {
int i, remaining, low, high, port;
static u32 hint;
u32 offset = hint + port_offset;
struct hlist_node *node;
struct inet_timewait_sock *tw = NULL;
inet_get_local_port_range(&low, &high);
remaining = (high - low) + 1;
local_bh_disable();
for (i = 1; i <= remaining; i++) {
port = low + (i + offset) % remaining;
head = &hinfo->bhash[inet_bhashfn(net, port,
hinfo->bhash_size)];
spin_lock(&head->lock);
/* Does not bother with rcv_saddr checks,
* because the established check is already
* unique enough.
*/
inet_bind_bucket_for_each(tb, node, &head->chain) {
if (net_eq(ib_net(tb), net) &&
tb->port == port) {
if (tb->fastreuse >= 0)
goto next_port;
WARN_ON(hlist_empty(&tb->owners));
if (!check_established(death_row, sk,
port, &tw))
goto ok;
goto next_port;
}
}
tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
net, head, port);
if (!tb) {
spin_unlock(&head->lock);
break;
}
tb->fastreuse = -1;
goto ok;
next_port:
spin_unlock(&head->lock);
}
local_bh_enable();
return -EADDRNOTAVAIL;
ok:
hint += i;
/* Head lock still held and bh's disabled */
inet_bind_hash(sk, tb, port);
if (sk_unhashed(sk)) {
inet_sk(sk)->inet_sport = htons(port);
twrefcnt += hash(sk, tw);
}
if (tw)
twrefcnt += inet_twsk_bind_unhash(tw, hinfo);
spin_unlock(&head->lock);
if (tw) {
inet_twsk_deschedule(tw, death_row);
while (twrefcnt) {
twrefcnt--;
inet_twsk_put(tw);
}
}
ret = 0;
goto out;
}
head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)];
tb = inet_csk(sk)->icsk_bind_hash;
spin_lock_bh(&head->lock);
if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
hash(sk, NULL);
spin_unlock_bh(&head->lock);
return 0;
} else {
spin_unlock(&head->lock);
/* No definite answer... Walk to established hash table */
ret = check_established(death_row, sk, snum, NULL);
out:
local_bh_enable();
return ret;
}
}
/*
* Bind a port for a connect operation and hash it.
*/
int inet_hash_connect(struct inet_timewait_death_row *death_row,
struct sock *sk)
{
return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
__inet_check_established, __inet_hash_nolisten);
}
EXPORT_SYMBOL_GPL(inet_hash_connect);
void inet_hashinfo_init(struct inet_hashinfo *h)
{
int i;
atomic_set(&h->bsockets, 0);
for (i = 0; i < INET_LHTABLE_SIZE; i++) {
spin_lock_init(&h->listening_hash[i].lock);
INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].head,
i + LISTENING_NULLS_BASE);
}
}
EXPORT_SYMBOL_GPL(inet_hashinfo_init);