From b57a38ae433d2bc7bc8c1de70c7d5c47eaa76ccb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Witold=20Kr=C4=99cicki?= <wpk@culm.net>
Date: Fri, 15 Feb 2019 11:28:58 +0100
Subject: [PATCH] Fix a race in socket code when internal_{accept, send,
 receive} is called from event loop on an socket and, in the meantime, someone
 has closed this socket.

---
 lib/isc/unix/socket.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 4a3365cb47..00ea6a27cf 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -2816,6 +2816,11 @@ internal_accept(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	socket_log(sock, NULL, TRACE,
 		   "internal_accept called, locked socket");
 
@@ -3051,6 +3056,11 @@ internal_recv(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	dev = ISC_LIST_HEAD(sock->recv_list);
 	if (dev == NULL) {
 		goto finish;
@@ -3105,6 +3115,11 @@ internal_send(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	dev = ISC_LIST_HEAD(sock->send_list);
 	if (dev == NULL) {
 		goto finish;