never send procError after the socket closed

Signed-off-by: lifubang <lifubang@acmcoder.com>

libcontainer/init_linux.go

@@ -107,7 +107,11 @@ func startInitialization() (retErr error) {
 
 	defer func() {
 		// If this defer is ever called, this means initialization has failed.
-		// Send the error back to the parent process in the form of an initError.
+		// Send the error back to the parent process in the form of an initError
+		// if the sync socket has not been closed.
+		if syncPipe.isClosed() {
+			return
+		}
 		ierr := initError{Message: retErr.Error()}
 		if err := writeSyncArg(syncPipe, procError, ierr); err != nil {
 			fmt.Fprintln(os.Stderr, err)

libcontainer/sync_unix.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sync/atomic"
 
 	"golang.org/x/sys/unix"
 )
@@ -14,7 +15,8 @@ import (
 // which ends up making things like json.Decoder hang forever if the packet is
 // bigger than the internal read buffer.
 type syncSocket struct {
-	f *os.File
+	f      *os.File
+	closed atomic.Bool
 }
 
 func newSyncSocket(f *os.File) *syncSocket {
@@ -26,9 +28,15 @@ func (s *syncSocket) File() *os.File {
 }
 
 func (s *syncSocket) Close() error {
+	// Even with errors from Close(), we have to assume the pipe was closed.
+	s.closed.Store(true)
 	return s.f.Close()
 }
 
+func (s *syncSocket) isClosed() bool {
+	return s.closed.Load()
+}
+
 func (s *syncSocket) WritePacket(b []byte) (int, error) {
 	return s.f.Write(b)
 }