[PATCH net-next 14/20] tcp: annotate races around tp->urg_data
From: Eric Dumazet <hidden>
Date: 2021-11-16 00:28:11
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> tcp_poll() and tcp_ioctl() are reading tp->urg_data without socket lock owned. Also, it is faster to first check tp->urg_data in tcp_poll(), then tp->urg_seq == tp->copied_seq, because tp->urg_seq is located in a different/cold cache line. Signed-off-by: Eric Dumazet <edumazet@google.com> --- net/ipv4/tcp.c | 17 +++++++++-------- net/ipv4/tcp_input.c | 4 ++-- 2 files changed, 11 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 267b2b18f048c4df4cabd819433a99bf8b3f2678..313cf648c349a24ab7a04729180ec9b76b2f6aa2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -545,10 +545,11 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait) if (state != TCP_SYN_SENT && (state != TCP_SYN_RECV || rcu_access_pointer(tp->fastopen_rsk))) { int target = sock_rcvlowat(sk, 0, INT_MAX); + u16 urg_data = READ_ONCE(tp->urg_data); - if (READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq) && - !sock_flag(sk, SOCK_URGINLINE) && - tp->urg_data) + if (urg_data && + READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq) && + !sock_flag(sk, SOCK_URGINLINE)) target++; if (tcp_stream_is_readable(sk, target))
@@ -573,7 +574,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait) } else mask |= EPOLLOUT | EPOLLWRNORM; - if (tp->urg_data & TCP_URG_VALID) + if (urg_data & TCP_URG_VALID) mask |= EPOLLPRI; } else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) { /* Active TCP fastopen socket with defer_connect
@@ -607,7 +608,7 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg) unlock_sock_fast(sk, slow); break; case SIOCATMARK: - answ = tp->urg_data && + answ = READ_ONCE(tp->urg_data) && READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq); break; case SIOCOUTQ:
@@ -1465,7 +1466,7 @@ static int tcp_recv_urg(struct sock *sk, struct msghdr *msg, int len, int flags) char c = tp->urg_data; if (!(flags & MSG_PEEK)) - tp->urg_data = TCP_URG_READ; + WRITE_ONCE(tp->urg_data, TCP_URG_READ); /* Read urgent data. */ msg->msg_flags |= MSG_OOB;
@@ -2465,7 +2466,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len, skip_copy: if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) { - tp->urg_data = 0; + WRITE_ONCE(tp->urg_data, 0); tcp_fast_path_check(sk); }
@@ -2959,7 +2960,7 @@ int tcp_disconnect(struct sock *sk, int flags) tcp_clear_xmit_timers(sk); __skb_queue_purge(&sk->sk_receive_queue); WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); - tp->urg_data = 0; + WRITE_ONCE(tp->urg_data, 0); tcp_write_queue_purge(sk); tcp_fastopen_active_disable_ofo_check(sk); skb_rbtree_purge(&tp->out_of_order_queue);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 246ab7b5e857eb9e802c4805075e89c98cf00636..5ee07a337652696bdebb1117334ff39d88fd0276 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -5591,7 +5591,7 @@ static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) } } - tp->urg_data = TCP_URG_NOTYET; + WRITE_ONCE(tp->urg_data, TCP_URG_NOTYET); WRITE_ONCE(tp->urg_seq, ptr); /* Disable header prediction. */
@@ -5617,7 +5617,7 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *t u8 tmp; if (skb_copy_bits(skb, ptr, &tmp, 1)) BUG(); - tp->urg_data = TCP_URG_VALID | tmp; + WRITE_ONCE(tp->urg_data, TCP_URG_VALID | tmp); if (!sock_flag(sk, SOCK_DEAD)) sk->sk_data_ready(sk); }
--
2.34.0.rc1.387.gb447b232ab-goog