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fix(serial) keep serial console mux closed when not needed #1421

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fix(serial) keep serial console mux closed when not needed #1421

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4 changes: 4 additions & 0 deletions jsonrpc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -770,6 +770,8 @@ func rpcSetActiveExtension(extensionId string) error {
_ = unmountATXControl()
case "dc-power":
_ = unmountDCControl()
case "serial-console":
_ = unmountSerialConsole()
}
config.ActiveExtension = extensionId
if err := SaveConfig(); err != nil {
Expand All @@ -780,6 +782,8 @@ func rpcSetActiveExtension(extensionId string) error {
_ = mountATXControl()
case "dc-power":
_ = mountDCControl()
case "serial-console":
_ = mountSerialConsole()
}

// Re-publish MQTT HA Discovery for the new extension
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19 changes: 19 additions & 0 deletions serial.go
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Original file line number Diff line number Diff line change
Expand Up @@ -580,10 +580,20 @@ func initSerialPort() {
_ = mountATXControl()
case "dc-power":
_ = mountDCControl()
case "serial-console":
_ = mountSerialConsole()
}
}

func reopenSerialPort() error {
if serialMux != nil {
serialMux.Close()
serialMux = nil
}
if consoleBroker != nil {
consoleBroker.Close()
consoleBroker = nil
}
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@cursor cursor Bot Apr 18, 2026

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TOCTOU race on nullable globals causes potential panic

Medium Severity

reopenSerialPort now sets serialMux and consoleBroker to nil, making them nullable during normal operation. Previously they were always non-nil after init. The handleSerialChannel OnMessage callback (running on a WebRTC goroutine) reads these unsynchronized globals — the nil check at the top doesn't protect against a concurrent rpcSetActiveExtension call setting them to nil between the check and the subsequent serialMux.Enqueue(...) or consoleBroker.Enqueue(...), causing a nil pointer dereference panic. The same race applies to sendCustomCommand.

Additional Locations (1)
Fix in Cursor Fix in Web

Reviewed by Cursor Bugbot for commit 80c5a5e. Configure here.

if port != nil {
port.Close()
}
Expand All @@ -598,6 +608,10 @@ func reopenSerialPort() error {
return err
}

return nil
}
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cursor[bot] marked this conversation as resolved.

func mountSerialConsole() error {
// new broker (no sink yet—set it in handleSerialChannel.OnOpen)
norm := NormalizationOptions{
Mode: ModeNames, LineEnding: LineEnding_LF, TabRender: "", PreserveANSI: true,
Expand All @@ -619,6 +633,11 @@ func reopenSerialPort() error {
return nil
}

func unmountSerialConsole() error {
_ = reopenSerialPort()
return nil
}

func handleSerialChannel(dataChannel *webrtc.DataChannel) {
scopedLogger := serialLogger.With().
Uint16("data_channel_id", *dataChannel.ID()).Str("service", "serial terminal channel").Logger()
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18 changes: 16 additions & 2 deletions serial_console_helpers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -273,9 +273,16 @@ func NewConsoleBroker(s Sink, norm NormalizationOptions) *ConsoleBroker {
}

func (b *ConsoleBroker) Start() { go b.loop() }
func (b *ConsoleBroker) Close() { close(b.done) }
func (b *ConsoleBroker) SetSink(s Sink) { b.sink = s }
func (b *ConsoleBroker) SetNormOptions(norm NormalizationOptions) { b.norm = norm }
func (b *ConsoleBroker) Close() {
select {
case <-b.done:
return
default:
close(b.done)
}
}
func (b *ConsoleBroker) SetTerminalPaused(v bool) {
if b == nil {
return
Expand Down Expand Up @@ -626,7 +633,14 @@ func (m *SerialMux) Start() {
go m.writer()
}

func (m *SerialMux) Close() { close(m.done) }
func (m *SerialMux) Close() {
select {
case <-m.done:
return
default:
close(m.done)
}
}

func (m *SerialMux) SetEchoEnabled(v bool) { m.echoEnabled.Store(v) }

Expand Down
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