From 79e2364933bbd34dceb0b9025e4e7d145fdf4492 Mon Sep 17 00:00:00 2001 From: Bhasker Hariharan Date: Mon, 30 Nov 2020 20:11:33 -0800 Subject: Fix deadlock in UDP handleControlPacket path. Fixing the sendto deadlock exposed yet another deadlock where a lock inversion occurs on the handleControlPacket path where e.mu and demuxer.epsByNIC.mu are acquired in reverse order from say when RegisterTransportEndpoint is called in endpoint.Connect(). This fix sidesteps the issue by just making endpoint.state an atomic and gets rid of the need to acquire e.mu in e.HandleControlPacket. PiperOrigin-RevId: 344939895 --- pkg/tcpip/transport/udp/endpoint.go | 66 ++++++++++++++++++++++--------------- 1 file changed, 39 insertions(+), 27 deletions(-) (limited to 'pkg/tcpip/transport/udp/endpoint.go') diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go index 776c1af43..912d33da8 100644 --- a/pkg/tcpip/transport/udp/endpoint.go +++ b/pkg/tcpip/transport/udp/endpoint.go @@ -16,6 +16,7 @@ package udp import ( "fmt" + "sync/atomic" "gvisor.dev/gvisor/pkg/sleep" "gvisor.dev/gvisor/pkg/sync" @@ -95,9 +96,11 @@ type endpoint struct { rcvClosed bool // The following fields are protected by the mu mutex. - mu sync.RWMutex `state:"nosave"` - sndBufSize int - sndBufSizeMax int + mu sync.RWMutex `state:"nosave"` + sndBufSize int + sndBufSizeMax int + // state must be read/set using the EndpointState()/setEndpointState() + // methods. state EndpointState route *stack.Route `state:"manual"` dstPort uint16 @@ -198,6 +201,20 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue return e } +// setEndpointState updates the state of the endpoint to state atomically. This +// method is unexported as the only place we should update the state is in this +// package but we allow the state to be read freely without holding e.mu. +// +// Precondition: e.mu must be held to call this method. +func (e *endpoint) setEndpointState(state EndpointState) { + atomic.StoreUint32((*uint32)(&e.state), uint32(state)) +} + +// EndpointState() returns the current state of the endpoint. +func (e *endpoint) EndpointState() EndpointState { + return EndpointState(atomic.LoadUint32((*uint32)(&e.state))) +} + // UniqueID implements stack.TransportEndpoint.UniqueID. func (e *endpoint) UniqueID() uint64 { return e.uniqueID @@ -223,7 +240,7 @@ func (e *endpoint) Close() { e.mu.Lock() e.shutdownFlags = tcpip.ShutdownRead | tcpip.ShutdownWrite - switch e.state { + switch e.EndpointState() { case StateBound, StateConnected: e.stack.UnregisterTransportEndpoint(e.RegisterNICID, e.effectiveNetProtos, ProtocolNumber, e.ID, e, e.boundPortFlags, e.boundBindToDevice) e.stack.ReleasePort(e.effectiveNetProtos, ProtocolNumber, e.ID.LocalAddress, e.ID.LocalPort, e.boundPortFlags, e.boundBindToDevice, tcpip.FullAddress{}) @@ -252,7 +269,7 @@ func (e *endpoint) Close() { } // Update the state. - e.state = StateClosed + e.setEndpointState(StateClosed) e.mu.Unlock() @@ -316,7 +333,7 @@ func (e *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMess // // Returns true for retry if preparation should be retried. func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpip.Error) { - switch e.state { + switch e.EndpointState() { case StateInitial: case StateConnected: return false, nil @@ -338,7 +355,7 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpi // The state changed when we released the shared locked and re-acquired // it in exclusive mode. Try again. - if e.state != StateInitial { + if e.EndpointState() != StateInitial { return true, nil } @@ -453,7 +470,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c e.mu.Lock() // Recheck state after lock was re-acquired. - if e.state != StateConnected { + if e.EndpointState() != StateConnected { err = tcpip.ErrInvalidEndpointState } if err == nil && route.IsResolutionRequired() { @@ -464,7 +481,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c e.mu.RLock() // Recheck state after lock was re-acquired. - if e.state != StateConnected { + if e.EndpointState() != StateConnected { err = tcpip.ErrInvalidEndpointState } return ch, err @@ -934,7 +951,7 @@ func (e *endpoint) Disconnect() *tcpip.Error { e.mu.Lock() defer e.mu.Unlock() - if e.state != StateConnected { + if e.EndpointState() != StateConnected { return nil } var ( @@ -957,7 +974,7 @@ func (e *endpoint) Disconnect() *tcpip.Error { if err != nil { return err } - e.state = StateBound + e.setEndpointState(StateBound) boundPortFlags = e.boundPortFlags } else { if e.ID.LocalPort != 0 { @@ -965,7 +982,7 @@ func (e *endpoint) Disconnect() *tcpip.Error { e.stack.ReleasePort(e.effectiveNetProtos, ProtocolNumber, e.ID.LocalAddress, e.ID.LocalPort, boundPortFlags, e.boundBindToDevice, tcpip.FullAddress{}) e.boundPortFlags = ports.Flags{} } - e.state = StateInitial + e.setEndpointState(StateInitial) } e.stack.UnregisterTransportEndpoint(e.RegisterNICID, e.effectiveNetProtos, ProtocolNumber, e.ID, e, boundPortFlags, e.boundBindToDevice) @@ -990,7 +1007,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error { nicID := addr.NIC var localPort uint16 - switch e.state { + switch e.EndpointState() { case StateInitial: case StateBound, StateConnected: localPort = e.ID.LocalPort @@ -1025,7 +1042,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error { RemoteAddress: r.RemoteAddress, } - if e.state == StateInitial { + if e.EndpointState() == StateInitial { id.LocalAddress = r.LocalAddress } @@ -1059,7 +1076,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error { e.RegisterNICID = nicID e.effectiveNetProtos = netProtos - e.state = StateConnected + e.setEndpointState(StateConnected) e.rcvMu.Lock() e.rcvReady = true @@ -1081,7 +1098,7 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error { // A socket in the bound state can still receive multicast messages, // so we need to notify waiters on shutdown. - if e.state != StateBound && e.state != StateConnected { + if state := e.EndpointState(); state != StateBound && state != StateConnected { return tcpip.ErrNotConnected } @@ -1132,7 +1149,7 @@ func (e *endpoint) registerWithStack(nicID tcpip.NICID, netProtos []tcpip.Networ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error { // Don't allow binding once endpoint is not in the initial state // anymore. - if e.state != StateInitial { + if e.EndpointState() != StateInitial { return tcpip.ErrInvalidEndpointState } @@ -1176,7 +1193,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error { e.effectiveNetProtos = netProtos // Mark endpoint as bound. - e.state = StateBound + e.setEndpointState(StateBound) e.rcvMu.Lock() e.rcvReady = true @@ -1208,7 +1225,7 @@ func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) { defer e.mu.RUnlock() addr := e.ID.LocalAddress - if e.state == StateConnected { + if e.EndpointState() == StateConnected { addr = e.route.LocalAddress } @@ -1224,7 +1241,7 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) { e.mu.RLock() defer e.mu.RUnlock() - if e.state != StateConnected { + if e.EndpointState() != StateConnected { return tcpip.FullAddress{}, tcpip.ErrNotConnected } @@ -1356,25 +1373,20 @@ func (e *endpoint) HandlePacket(id stack.TransportEndpointID, pkt *stack.PacketB // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket. func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, pkt *stack.PacketBuffer) { if typ == stack.ControlPortUnreachable { - e.mu.RLock() - if e.state == StateConnected { + if e.EndpointState() == StateConnected { e.lastErrorMu.Lock() e.lastError = tcpip.ErrConnectionRefused e.lastErrorMu.Unlock() - e.mu.RUnlock() e.waiterQueue.Notify(waiter.EventErr) return } - e.mu.RUnlock() } } // State implements tcpip.Endpoint.State. func (e *endpoint) State() uint32 { - e.mu.Lock() - defer e.mu.Unlock() - return uint32(e.state) + return uint32(e.EndpointState()) } // Info returns a copy of the endpoint info. -- cgit v1.2.3