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tcp/dccp: fix hashdance race for passive sessions

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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: e994b2f0fb ("tcp: do not lock listener to process SYN packets")
Fixes: 079096f103 ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2015-10-22 08:20:46 -07:00
committed by David S. Miller
parent 7b1311807f
commit 5e0724d027
14 changed files with 102 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
net/ipv4/inet_hashtables.c
View File

@@ -407,13 +407,13 @@ static u32 inet_sk_port_offset(const struct sock *sk)
/* 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 @@ int inet_ehash_insert(struct sock *sk, struct sock *osk)
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 @@ ok:
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 @@ ok:
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 {