Fix raciness in MountState.kernelSettings access.

fuse/mountstate.go

@@ -35,13 +35,13 @@ type MountState struct {
 	latencies *LatencyMap
 
 	opts           *MountOptions
-	kernelSettings raw.InitIn
 
 	reqMu               sync.Mutex
 	reqPool             []*request
 	readPool            [][]byte
 	reqReaders          int
 	outstandingReadBufs int
+	kernelSettings raw.InitIn
 
 	canSplice bool
 	loops     sync.WaitGroup
@@ -66,7 +66,11 @@ func (ms *MountState) ThreadSanitizerSync() {
 }
 
 func (ms *MountState) KernelSettings() raw.InitIn {
-	return ms.kernelSettings
+	ms.reqMu.Lock()
+	s := ms.kernelSettings
+	ms.reqMu.Unlock()
+
+	return s
 }
 
 func (ms *MountState) MountPoint() string {
@@ -153,7 +157,7 @@ func (ms *MountState) Unmount() (err error) {
 		if err == nil {
 			break
 		}
-		
+
 		fmt.Fprintf(os.Stderr, "umount failed; retrying\n")
 		// Sleep for a bit. This is not pretty, but there is
 		// no way we can be certain that the kernel thinks all

fuse/opcode.go

@@ -85,6 +85,7 @@ func doInit(state *MountState, req *request) {
 		return
 	}
 
+	state.reqMu.Lock()
 	state.kernelSettings = *input
 	state.kernelSettings.Flags = input.Flags & (raw.CAP_ASYNC_READ | raw.CAP_BIG_WRITES | raw.CAP_FILE_OPS)
 	if input.Minor >= 13 {
@@ -94,6 +95,7 @@ func doInit(state *MountState, req *request) {
 			state.opts.MaxWrite = maxW
 		}
 	}
+	state.reqMu.Unlock()
 
 	out := &raw.InitOut{
 		Major:               FUSE_KERNEL_VERSION,