netdev - [PATCH net-next 14/20] tcp: annotate races around tp->urg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 15 Nov 2021 11:02:43 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Arjun Roy <arjunroy@...gle.com>
Subject: [PATCH net-next 14/20] tcp: annotate races around tp->urg_data

From: Eric Dumazet <edumazet@...gle.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@...gle.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