tcp/dccp: fix hashdance race for passive sessions
Multiple cpus can process duplicates of incoming ACK messages
matching a SYN_RECV request socket. This is a rare event under
normal operations, but definitely can happen.
Only one must win the race, otherwise corruption would occur.
To fix this without adding new atomic ops, we use logic in
inet_ehash_nolisten() to detect the request was present in the same
ehash bucket where we try to insert the new child.
If request socket was not found, we have to undo the child creation.
This actually removes a spin_lock()/spin_unlock() pair in
reqsk_queue_unlink() for the fast path.
Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 8430bc8..1feb15f 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -523,15 +523,15 @@
struct request_sock *req)
{
struct inet_hashinfo *hashinfo = req_to_sk(req)->sk_prot->h.hashinfo;
- spinlock_t *lock;
- bool found;
+ bool found = false;
- lock = inet_ehash_lockp(hashinfo, req->rsk_hash);
+ if (sk_hashed(req_to_sk(req))) {
+ spinlock_t *lock = inet_ehash_lockp(hashinfo, req->rsk_hash);
- spin_lock(lock);
- found = __sk_nulls_del_node_init_rcu(req_to_sk(req));
- spin_unlock(lock);
-
+ spin_lock(lock);
+ found = __sk_nulls_del_node_init_rcu(req_to_sk(req));
+ spin_unlock(lock);
+ }
if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
reqsk_put(req);
return found;
@@ -811,6 +811,25 @@
}
EXPORT_SYMBOL(inet_csk_reqsk_queue_add);
+struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
+ struct request_sock *req, bool own_req)
+{
+ if (own_req) {
+ inet_csk_reqsk_queue_drop(sk, req);
+ reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
+ inet_csk_reqsk_queue_add(sk, req, child);
+ /* Warning: caller must not call reqsk_put(req);
+ * child stole last reference on it.
+ */
+ return child;
+ }
+ /* Too bad, another child took ownership of the request, undo. */
+ bh_unlock_sock(child);
+ sock_put(child);
+ return NULL;
+}
+EXPORT_SYMBOL(inet_csk_complete_hashdance);
+
/*
* This routine closes sockets which have been at least partially
* opened, but not yet accepted.
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 958728a..ccc5980 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -407,13 +407,13 @@
/* insert a socket into ehash, and eventually remove another one
* (The another one can be a SYN_RECV or TIMEWAIT
*/
-int inet_ehash_insert(struct sock *sk, struct sock *osk)
+bool inet_ehash_insert(struct sock *sk, struct sock *osk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct hlist_nulls_head *list;
struct inet_ehash_bucket *head;
spinlock_t *lock;
- int ret = 0;
+ bool ret = true;
WARN_ON_ONCE(!sk_unhashed(sk));
@@ -423,30 +423,41 @@
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
spin_lock(lock);
- __sk_nulls_add_node_rcu(sk, list);
if (osk) {
- WARN_ON(sk->sk_hash != osk->sk_hash);
- sk_nulls_del_node_init_rcu(osk);
+ WARN_ON_ONCE(sk->sk_hash != osk->sk_hash);
+ ret = sk_nulls_del_node_init_rcu(osk);
}
+ if (ret)
+ __sk_nulls_add_node_rcu(sk, list);
spin_unlock(lock);
return ret;
}
-void __inet_hash_nolisten(struct sock *sk, struct sock *osk)
+bool inet_ehash_nolisten(struct sock *sk, struct sock *osk)
{
- inet_ehash_insert(sk, osk);
- sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+ bool ok = inet_ehash_insert(sk, osk);
+
+ if (ok) {
+ sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+ } else {
+ percpu_counter_inc(sk->sk_prot->orphan_count);
+ sk->sk_state = TCP_CLOSE;
+ sock_set_flag(sk, SOCK_DEAD);
+ inet_csk_destroy_sock(sk);
+ }
+ return ok;
}
-EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
+EXPORT_SYMBOL_GPL(inet_ehash_nolisten);
void __inet_hash(struct sock *sk, struct sock *osk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct inet_listen_hashbucket *ilb;
- if (sk->sk_state != TCP_LISTEN)
- return __inet_hash_nolisten(sk, osk);
-
+ if (sk->sk_state != TCP_LISTEN) {
+ inet_ehash_nolisten(sk, osk);
+ return;
+ }
WARN_ON(!sk_unhashed(sk));
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
@@ -567,7 +578,7 @@
inet_bind_hash(sk, tb, port);
if (sk_unhashed(sk)) {
inet_sk(sk)->inet_sport = htons(port);
- __inet_hash_nolisten(sk, (struct sock *)tw);
+ inet_ehash_nolisten(sk, (struct sock *)tw);
}
if (tw)
inet_twsk_bind_unhash(tw, hinfo);
@@ -584,7 +595,7 @@
tb = inet_csk(sk)->icsk_bind_hash;
spin_lock_bh(&head->lock);
if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
- __inet_hash_nolisten(sk, NULL);
+ inet_ehash_nolisten(sk, NULL);
spin_unlock_bh(&head->lock);
return 0;
} else {
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 4c0892b..4cbe9f0 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -221,8 +221,10 @@
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct sock *child;
+ bool own_req;
- child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst);
+ child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
+ NULL, &own_req);
if (child) {
atomic_set(&req->rsk_refcnt, 1);
sock_rps_save_rxhash(child, skb);
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 93396bf..55be6ac7 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -133,12 +133,14 @@
struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
struct sock *child;
u32 end_seq;
+ bool own_req;
req->num_retrans = 0;
req->num_timeout = 0;
req->sk = NULL;
- child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
+ child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
+ NULL, &own_req);
if (!child)
return NULL;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 30dd45c..1c2648b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1247,7 +1247,9 @@
*/
struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
- struct dst_entry *dst)
+ struct dst_entry *dst,
+ struct request_sock *req_unhash,
+ bool *own_req)
{
struct inet_request_sock *ireq;
struct inet_sock *newinet;
@@ -1323,7 +1325,7 @@
if (__inet_inherit_port(sk, newsk) < 0)
goto put_and_exit;
- __inet_hash_nolisten(newsk, NULL);
+ *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
return newsk;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 1fd5d41..3575dd1 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -580,6 +580,7 @@
const struct tcphdr *th = tcp_hdr(skb);
__be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
bool paws_reject = false;
+ bool own_req;
tmp_opt.saw_tstamp = 0;
if (th->doff > (sizeof(struct tcphdr)>>2)) {
@@ -767,18 +768,14 @@
* ESTABLISHED STATE. If it will be dropped after
* socket is created, wait for troubles.
*/
- child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
+ child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
+ req, &own_req);
if (!child)
goto listen_overflow;
sock_rps_save_rxhash(child, skb);
tcp_synack_rtt_meas(child, req);
- inet_csk_reqsk_queue_drop(sk, req);
- inet_csk_reqsk_queue_add(sk, req, child);
- /* Warning: caller must not call reqsk_put(req);
- * child stole last reference on it.
- */
- return child;
+ return inet_csk_complete_hashdance(sk, child, req, own_req);
listen_overflow:
if (!sysctl_tcp_abort_on_overflow) {
