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Message-Id: <20191011031746.16220-2-edumazet@google.com>
Date: Thu, 10 Oct 2019 20:17:38 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net 1/9] tcp: add rcu protection around tp->fastopen_rsk
Both tcp_v4_err() and tcp_v6_err() do the following operations
while they do not own the socket lock :
fastopen = tp->fastopen_rsk;
snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
The problem is that without appropriate barrier, the compiler
might reload tp->fastopen_rsk and trigger a NULL deref.
request sockets are protected by RCU, we can simply add
the missing annotations and barriers to solve the issue.
Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/tcp.h | 6 +++---
net/core/request_sock.c | 2 +-
net/ipv4/inet_connection_sock.c | 4 ++--
net/ipv4/tcp.c | 11 ++++++++---
net/ipv4/tcp_fastopen.c | 2 +-
net/ipv4/tcp_input.c | 13 +++++++++----
net/ipv4/tcp_ipv4.c | 4 ++--
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv4/tcp_output.c | 2 +-
net/ipv4/tcp_timer.c | 11 ++++++-----
net/ipv6/tcp_ipv6.c | 2 +-
11 files changed, 35 insertions(+), 24 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 99617e528ea2906b234cadc1fb3d79d0efd46331..668e25a76d69809b5ade30f5774a4c62833b8b9b 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -393,7 +393,7 @@ struct tcp_sock {
/* fastopen_rsk points to request_sock that resulted in this big
* socket. Used to retransmit SYNACKs etc.
*/
- struct request_sock *fastopen_rsk;
+ struct request_sock __rcu *fastopen_rsk;
u32 *saved_syn;
};
@@ -447,8 +447,8 @@ static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
static inline bool tcp_passive_fastopen(const struct sock *sk)
{
- return (sk->sk_state == TCP_SYN_RECV &&
- tcp_sk(sk)->fastopen_rsk != NULL);
+ return sk->sk_state == TCP_SYN_RECV &&
+ rcu_access_pointer(tcp_sk(sk)->fastopen_rsk) != NULL;
}
static inline void fastopen_queue_tune(struct sock *sk, int backlog)
diff --git a/net/core/request_sock.c b/net/core/request_sock.c
index c9bb00008528414486bb58ba4c26b003545c6ae4..f35c2e9984062ba4bed637eaeace4eb9e71dadc0 100644
--- a/net/core/request_sock.c
+++ b/net/core/request_sock.c
@@ -96,7 +96,7 @@ void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
fastopenq = &inet_csk(lsk)->icsk_accept_queue.fastopenq;
- tcp_sk(sk)->fastopen_rsk = NULL;
+ RCU_INIT_POINTER(tcp_sk(sk)->fastopen_rsk, NULL);
spin_lock_bh(&fastopenq->lock);
fastopenq->qlen--;
tcp_rsk(req)->tfo_listener = false;
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index dbcf34ec8dd208d2144a590d40501c4eb82e5111..eb30fc1770def741950215f59a4e3ab0f91c6293 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -906,7 +906,7 @@ static void inet_child_forget(struct sock *sk, struct request_sock *req,
percpu_counter_inc(sk->sk_prot->orphan_count);
if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {
- BUG_ON(tcp_sk(child)->fastopen_rsk != req);
+ BUG_ON(rcu_access_pointer(tcp_sk(child)->fastopen_rsk) != req);
BUG_ON(sk != req->rsk_listener);
/* Paranoid, to prevent race condition if
@@ -915,7 +915,7 @@ static void inet_child_forget(struct sock *sk, struct request_sock *req,
* Also to satisfy an assertion in
* tcp_v4_destroy_sock().
*/
- tcp_sk(child)->fastopen_rsk = NULL;
+ RCU_INIT_POINTER(tcp_sk(child)->fastopen_rsk, NULL);
}
inet_csk_destroy_sock(child);
}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8781a92ea4b6e4ee9ceeb763dae01970e7f4438a..c59d0bd29c5c6fcbe38edb12b37c47ba4ed68899 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -543,7 +543,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
/* Connected or passive Fast Open socket? */
if (state != TCP_SYN_SENT &&
- (state != TCP_SYN_RECV || tp->fastopen_rsk)) {
+ (state != TCP_SYN_RECV || rcu_access_pointer(tp->fastopen_rsk))) {
int target = sock_rcvlowat(sk, 0, INT_MAX);
if (tp->urg_seq == tp->copied_seq &&
@@ -2487,7 +2487,10 @@ void tcp_close(struct sock *sk, long timeout)
}
if (sk->sk_state == TCP_CLOSE) {
- struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+ struct request_sock *req;
+
+ req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
+ lockdep_sock_is_held(sk));
/* We could get here with a non-NULL req if the socket is
* aborted (e.g., closed with unread data) before 3WHS
* finishes.
@@ -3831,8 +3834,10 @@ EXPORT_SYMBOL(tcp_md5_hash_key);
void tcp_done(struct sock *sk)
{
- struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+ struct request_sock *req;
+ req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
+ lockdep_sock_is_held(sk));
if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 3fd451271a7034aab65f02f2bc331254b49f2153..a915ade0c81803a3b190e8c0513220b4e67c35e4 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -253,7 +253,7 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
*/
tp = tcp_sk(child);
- tp->fastopen_rsk = req;
+ rcu_assign_pointer(tp->fastopen_rsk, req);
tcp_rsk(req)->tfo_listener = true;
/* RFC1323: The window in SYN & SYN/ACK segments is never
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3578357abe30e92f818e5b9acf3317be1d997af5..5f9b102c3b55c5a40bceb945d0f5d288f682824c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2666,7 +2666,7 @@ static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
struct tcp_sock *tp = tcp_sk(sk);
bool recovered = !before(tp->snd_una, tp->high_seq);
- if ((flag & FLAG_SND_UNA_ADVANCED || tp->fastopen_rsk) &&
+ if ((flag & FLAG_SND_UNA_ADVANCED || rcu_access_pointer(tp->fastopen_rsk)) &&
tcp_try_undo_loss(sk, false))
return;
@@ -2990,7 +2990,7 @@ void tcp_rearm_rto(struct sock *sk)
/* If the retrans timer is currently being used by Fast Open
* for SYN-ACK retrans purpose, stay put.
*/
- if (tp->fastopen_rsk)
+ if (rcu_access_pointer(tp->fastopen_rsk))
return;
if (!tp->packets_out) {
@@ -6087,6 +6087,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
{
+ struct request_sock *req;
+
tcp_try_undo_loss(sk, false);
/* Reset rtx states to prevent spurious retransmits_timed_out() */
@@ -6096,7 +6098,9 @@ static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
* we no longer need req so release it.
*/
- reqsk_fastopen_remove(sk, tcp_sk(sk)->fastopen_rsk, false);
+ req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
+ lockdep_sock_is_held(sk));
+ reqsk_fastopen_remove(sk, req, false);
/* Re-arm the timer because data may have been sent out.
* This is similar to the regular data transmission case
@@ -6171,7 +6175,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
tcp_mstamp_refresh(tp);
tp->rx_opt.saw_tstamp = 0;
- req = tp->fastopen_rsk;
+ req = rcu_dereference_protected(tp->fastopen_rsk,
+ lockdep_sock_is_held(sk));
if (req) {
bool req_stolen;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 492bf6a6b0237a677aae5d7ef365a5fc7356e238..ffa366099eb29145c37341ca00976844cd1185dc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -478,7 +478,7 @@ int tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
icsk = inet_csk(sk);
tp = tcp_sk(sk);
/* XXX (TFO) - tp->snd_una should be ISN (tcp_create_openreq_child() */
- fastopen = tp->fastopen_rsk;
+ fastopen = rcu_dereference(tp->fastopen_rsk);
snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
if (sk->sk_state != TCP_LISTEN &&
!between(seq, snd_una, tp->snd_nxt)) {
@@ -2121,7 +2121,7 @@ void tcp_v4_destroy_sock(struct sock *sk)
if (inet_csk(sk)->icsk_bind_hash)
inet_put_port(sk);
- BUG_ON(tp->fastopen_rsk);
+ BUG_ON(rcu_access_pointer(tp->fastopen_rsk));
/* If socket is aborted during connect operation */
tcp_free_fastopen_req(tp);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index bb140a5db8c066e57f1018fd47bccd4628def642..5401dbd39c8fd34d147e0202a410dfc7cefafc26 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -541,7 +541,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
newtp->rx_opt.mss_clamp = req->mss;
tcp_ecn_openreq_child(newtp, req);
newtp->fastopen_req = NULL;
- newtp->fastopen_rsk = NULL;
+ RCU_INIT_POINTER(newtp->fastopen_rsk, NULL);
__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index fec6d67bfd146dc78f0f25173fd71b8b8cc752fe..84ae4d1449ea7eb9da2c536363b88807f35a4283 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2482,7 +2482,7 @@ bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
/* Don't do any loss probe on a Fast Open connection before 3WHS
* finishes.
*/
- if (tp->fastopen_rsk)
+ if (rcu_access_pointer(tp->fastopen_rsk))
return false;
early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 05be564414e9b4aad64321e381fc0afa10980190..dd5a6317a8018a45ad609f832ced6df2937ad453 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -386,15 +386,13 @@ abort: tcp_write_err(sk);
* Timer for Fast Open socket to retransmit SYNACK. Note that the
* sk here is the child socket, not the parent (listener) socket.
*/
-static void tcp_fastopen_synack_timer(struct sock *sk)
+static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
{
struct inet_connection_sock *icsk = inet_csk(sk);
int max_retries = icsk->icsk_syn_retries ? :
sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
struct tcp_sock *tp = tcp_sk(sk);
- struct request_sock *req;
- req = tcp_sk(sk)->fastopen_rsk;
req->rsk_ops->syn_ack_timeout(req);
if (req->num_timeout >= max_retries) {
@@ -435,11 +433,14 @@ void tcp_retransmit_timer(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
+ struct request_sock *req;
- if (tp->fastopen_rsk) {
+ req = rcu_dereference_protected(tp->fastopen_rsk,
+ lockdep_sock_is_held(sk));
+ if (req) {
WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
sk->sk_state != TCP_FIN_WAIT1);
- tcp_fastopen_synack_timer(sk);
+ tcp_fastopen_synack_timer(sk, req);
/* Before we receive ACK to our SYN-ACK don't retransmit
* anything else (e.g., data or FIN segments).
*/
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index e3d9f4559c99f252eba448845cce434bc53f3fd8..45a95e032bdfe8ffb05309bed8a967ee08690293 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -406,7 +406,7 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
tp = tcp_sk(sk);
/* XXX (TFO) - tp->snd_una should be ISN (tcp_create_openreq_child() */
- fastopen = tp->fastopen_rsk;
+ fastopen = rcu_dereference(tp->fastopen_rsk);
snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
if (sk->sk_state != TCP_LISTEN &&
!between(seq, snd_una, tp->snd_nxt)) {
--
2.23.0.700.g56cf767bdb-goog
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