From 123173f839f2ff327f3f90f39e0b149f9d15f4e9 Mon Sep 17 00:00:00 2001
From: ignoramous <ignoramous@users.noreply.github.com>
Date: Fri, 4 Oct 2024 06:04:38 +0530
Subject: [PATCH 1/3] tcpip/udp: avoid deadlock in forwader.CreateEndpoint

---
 pkg/tcpip/transport/udp/forwarder.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pkg/tcpip/transport/udp/forwarder.go b/pkg/tcpip/transport/udp/forwarder.go
index 7950abe58..d702c54ad 100644
--- a/pkg/tcpip/transport/udp/forwarder.go
+++ b/pkg/tcpip/transport/udp/forwarder.go
@@ -76,15 +76,17 @@ func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint,
 
 	netHdr := r.pkt.Network()
 	if err := ep.net.Bind(tcpip.FullAddress{NIC: r.pkt.NICID, Addr: netHdr.DestinationAddress(), Port: r.id.LocalPort}); err != nil {
+		ep.closeLocked()
 		return nil, err
 	}
 
 	if err := ep.net.Connect(tcpip.FullAddress{NIC: r.pkt.NICID, Addr: netHdr.SourceAddress(), Port: r.id.RemotePort}); err != nil {
+		ep.closeLocked()
 		return nil, err
 	}
 
 	if err := r.stack.RegisterTransportEndpoint([]tcpip.NetworkProtocolNumber{r.pkt.NetworkProtocolNumber}, ProtocolNumber, r.id, ep, ep.portFlags, tcpip.NICID(ep.ops.GetBindToDevice())); err != nil {
-		ep.Close()
+		ep.closeLocked()
 		return nil, err
 	}
 

From 741bf52370b8eaf5ba5a948169e70176133fa23d Mon Sep 17 00:00:00 2001
From: ignoramous <ignoramous@users.noreply.github.com>
Date: Fri, 4 Oct 2024 06:14:17 +0530
Subject: [PATCH 2/3] tcpip/udp: document preconditions for
 endpoint.closeLocked()

---
 pkg/tcpip/transport/udp/endpoint.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 785ea47b2..7e78782f2 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -160,11 +160,16 @@ func (e *endpoint) Abort() {
 // associated with it.
 func (e *endpoint) Close() {
 	e.mu.Lock()
+	e.closeLocked()
+	e.mu.Unlock()
+}
 
+// Preconditions: e.mu is locked.
+// +checklocks:e.mu
+func (e *endpoint) closeLocked() {
 	switch state := e.net.State(); state {
 	case transport.DatagramEndpointStateInitial:
 	case transport.DatagramEndpointStateClosed:
-		e.mu.Unlock()
 		return
 	case transport.DatagramEndpointStateBound, transport.DatagramEndpointStateConnected:
 		id := e.net.Info().ID
@@ -201,7 +206,6 @@ func (e *endpoint) Close() {
 	e.net.Shutdown()
 	e.net.Close()
 	e.readShutdown = true
-	e.mu.Unlock()
 
 	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }

From ab3c4c85a3eed4493fbe448c7c53ce4b9c03c21a Mon Sep 17 00:00:00 2001
From: ignoramous <ignoramous@users.noreply.github.com>
Date: Sat, 5 Oct 2024 00:14:04 +0530
Subject: [PATCH 3/3] tcpip/udp: defer mutex unlock

---
 pkg/tcpip/transport/udp/endpoint.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 7e78782f2..0bd7db350 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -160,8 +160,8 @@ func (e *endpoint) Abort() {
 // associated with it.
 func (e *endpoint) Close() {
 	e.mu.Lock()
+	defer e.mu.Unlock()
 	e.closeLocked()
-	e.mu.Unlock()
 }
 
 // Preconditions: e.mu is locked.