From: Alexander Bluhm <bluhm@openbsd.org>
Subject: socket locking in soisconnected()
To: tech@openbsd.org
Date: Fri, 17 Jan 2025 23:25:33 +0100

Hi,

Queue 0 is only used for UNIX socket and socket pair.  So the
following code is never reached with TCP.  Replacing "if" with
"assert" makes arguing about TCP input socket locking easier.

ok?

bluhm

Index: kern/uipc_socket2.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_socket2.c,v
diff -u -p -r1.165 uipc_socket2.c
--- kern/uipc_socket2.c	16 Jan 2025 16:35:01 -0000	1.165
+++ kern/uipc_socket2.c	16 Jan 2025 21:01:22 -0000
@@ -100,21 +100,17 @@ soisconnected(struct socket *so)
 	so->so_state |= SS_ISCONNECTED;
 
 	if (head != NULL && so->so_onq == &head->so_q0) {
-		int persocket = solock_persocket(so);
+		KASSERT(solock_persocket(so));
 
-		if (persocket) {
-			soref(head);
-
-			sounlock(so);
-			solock(head);
-			solock(so);
-
-			if (so->so_onq != &head->so_q0) {
-				sounlock(head);
-				sorele(head);
-				return;
-			}
+		soref(head);
+		sounlock(so);
+		solock(head);
+		solock(so);
 
+		if (so->so_onq != &head->so_q0) {
+			sounlock(head);
+			sorele(head);
+			return;
 		}
 
 		soqremque(so, 0);
@@ -122,10 +118,8 @@ soisconnected(struct socket *so)
 		sorwakeup(head);
 		wakeup_one(&head->so_timeo);
 
-		if (persocket) {
-			sounlock(head);
-			sorele(head);
-		}
+		sounlock(head);
+		sorele(head);
 	} else {
 		wakeup(&so->so_timeo);
 		sorwakeup(so);