netdev - [PATCH v1 net-next 05/12] af_unix: Set drop reason in unix_stream

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Message-ID: <20250110092641.85905-6-kuniyu@amazon.com>
Date: Fri, 10 Jan 2025 18:26:34 +0900
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Simon Horman <horms@...nel.org>
CC: Donald Hunter <donald.hunter@...hat.com>, Kuniyuki Iwashima
	<kuniyu@...zon.com>, Kuniyuki Iwashima <kuni1840@...il.com>,
	<netdev@...r.kernel.org>
Subject: [PATCH v1 net-next 05/12] af_unix: Set drop reason in unix_stream_connect().

connect() to a SOCK_STREAM socket could fail for various reasons.

Let's set drop reasons respectively:

  * NO_SOCKET      : No listening socket found
  * RCV_SHUTDOWN   : The listening socket called shutdown(SHUT_RD)
  * SOCKET_RCVBUFF : The listening socket's accept queue is full
  * INVALID_STATE  : The client is in TCP_ESTABLISHED or TCP_LISTEN
  * SECURITY_HOOK  : LSM refused connect()

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 include/net/dropreason-core.h |  6 ++++++
 net/unix/af_unix.c            | 22 ++++++++++++++++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 8823de6539d1..1b5e962f7f33 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -8,7 +8,9 @@
 	FN(NO_SOCKET)			\
 	FN(SOCKET_CLOSE)		\
 	FN(SOCKET_FILTER)		\
+	FN(SOCKET_INVALID_STATE)	\
 	FN(SOCKET_RCVBUFF)		\
+	FN(SOCKET_RCV_SHUTDOWN)		\
 	FN(PKT_TOO_SMALL)		\
 	FN(TCP_CSUM)			\
 	FN(UDP_CSUM)			\
@@ -142,8 +144,12 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_SOCKET_CLOSE,
 	/** @SKB_DROP_REASON_SOCKET_FILTER: dropped by socket filter */
 	SKB_DROP_REASON_SOCKET_FILTER,
+	/** @SKB_DROP_REASON_SOCKET_INVALID_STATE: sk->sk_state is invalid. */
+	SKB_DROP_REASON_SOCKET_INVALID_STATE,
 	/** @SKB_DROP_REASON_SOCKET_RCVBUFF: socket receive buff is full */
 	SKB_DROP_REASON_SOCKET_RCVBUFF,
+	/** @SKB_DROP_REASON_SOCKET_RCV_SHUTDOWN: socket is shutdown(SHUT_RD) */
+	SKB_DROP_REASON_SOCKET_RCV_SHUTDOWN,
 	/** @SKB_DROP_REASON_PKT_TOO_SMALL: packet size is too small */
 	SKB_DROP_REASON_PKT_TOO_SMALL,
 	/** @SKB_DROP_REASON_TCP_CSUM: TCP checksum error */
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 41b99984008a..b190ea8b8e9d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1534,6 +1534,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	struct sock *sk = sock->sk, *newsk = NULL, *other = NULL;
 	struct unix_sock *u = unix_sk(sk), *newu, *otheru;
 	struct net *net = sock_net(sk);
+	enum skb_drop_reason reason;
 	struct sk_buff *skb = NULL;
 	unsigned char state;
 	long timeo;
@@ -1581,6 +1582,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	other = unix_find_other(net, sunaddr, addr_len, sk->sk_type);
 	if (IS_ERR(other)) {
 		err = PTR_ERR(other);
+		reason = SKB_DROP_REASON_NO_SOCKET;
 		goto out_free_skb;
 	}
 
@@ -1593,15 +1595,22 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 		goto restart;
 	}
 
-	if (other->sk_state != TCP_LISTEN ||
-	    other->sk_shutdown & RCV_SHUTDOWN) {
+	if (other->sk_state != TCP_LISTEN) {
 		err = -ECONNREFUSED;
+		reason = SKB_DROP_REASON_NO_SOCKET;
+		goto out_unlock;
+	}
+
+	if (other->sk_shutdown & RCV_SHUTDOWN) {
+		err = -ECONNREFUSED;
+		reason = SKB_DROP_REASON_SOCKET_RCV_SHUTDOWN;
 		goto out_unlock;
 	}
 
 	if (unix_recvq_full_lockless(other)) {
 		if (!timeo) {
 			err = -EAGAIN;
+			reason = SKB_DROP_REASON_SOCKET_RCVBUFF;
 			goto out_unlock;
 		}
 
@@ -1609,8 +1618,10 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 		sock_put(other);
 
 		err = sock_intr_errno(timeo);
-		if (signal_pending(current))
+		if (signal_pending(current)) {
+			reason = SKB_DROP_REASON_SOCKET_RCVBUFF;
 			goto out_free_skb;
+		}
 
 		goto restart;
 	}
@@ -1621,6 +1632,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	state = READ_ONCE(sk->sk_state);
 	if (unlikely(state != TCP_CLOSE)) {
 		err = state == TCP_ESTABLISHED ? -EISCONN : -EINVAL;
+		reason = SKB_DROP_REASON_SOCKET_INVALID_STATE;
 		goto out_unlock;
 	}
 
@@ -1629,12 +1641,14 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (unlikely(sk->sk_state != TCP_CLOSE)) {
 		err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EINVAL;
 		unix_state_unlock(sk);
+		reason = SKB_DROP_REASON_SOCKET_INVALID_STATE;
 		goto out_unlock;
 	}
 
 	err = security_unix_stream_connect(sk, other, newsk);
 	if (err) {
 		unix_state_unlock(sk);
+		reason = SKB_DROP_REASON_SECURITY_HOOK;
 		goto out_unlock;
 	}
 
@@ -1699,7 +1713,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	unix_state_unlock(other);
 	sock_put(other);
 out_free_skb:
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 out_free_sk:
 	unix_release_sock(newsk, 0);
 out:
-- 
2.39.5 (Apple Git-154)