Update github.com/containerd/containerd to v1.5.7

... to include a fix for
https://github.com/advisories/GHSA-c2h3-6mxw-7mvq .

(Note that Skopeo doesn't depend on the vulnerable code,
so this is primarily to avoid dependency checker warnings.)

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/google.golang.org/grpc/internal/binarylog/sink.go

@@ -69,7 +69,8 @@ type writerSink struct {
 func (ws *writerSink) Write(e *pb.GrpcLogEntry) error {
 	b, err := proto.Marshal(e)
 	if err != nil {
-		grpclogLogger.Infof("binary logging: failed to marshal proto message: %v", err)
+		grpclogLogger.Errorf("binary logging: failed to marshal proto message: %v", err)
+		return err
 	}
 	hdr := make([]byte, 4)
 	binary.BigEndian.PutUint32(hdr, uint32(len(b)))
@@ -85,24 +86,27 @@ func (ws *writerSink) Write(e *pb.GrpcLogEntry) error {
 func (ws *writerSink) Close() error { return nil }
 
 type bufferedSink struct {
-	mu     sync.Mutex
-	closer io.Closer
-	out    Sink          // out is built on buf.
-	buf    *bufio.Writer // buf is kept for flush.
+	mu             sync.Mutex
+	closer         io.Closer
+	out            Sink          // out is built on buf.
+	buf            *bufio.Writer // buf is kept for flush.
+	flusherStarted bool
 
-	writeStartOnce sync.Once
-	writeTicker    *time.Ticker
+	writeTicker *time.Ticker
+	done        chan struct{}
 }
 
 func (fs *bufferedSink) Write(e *pb.GrpcLogEntry) error {
-	// Start the write loop when Write is called.
-	fs.writeStartOnce.Do(fs.startFlushGoroutine)
 	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if !fs.flusherStarted {
+		// Start the write loop when Write is called.
+		fs.startFlushGoroutine()
+		fs.flusherStarted = true
+	}
 	if err := fs.out.Write(e); err != nil {
-		fs.mu.Unlock()
 		return err
 	}
-	fs.mu.Unlock()
 	return nil
 }
 
@@ -113,7 +117,12 @@ const (
 func (fs *bufferedSink) startFlushGoroutine() {
 	fs.writeTicker = time.NewTicker(bufFlushDuration)
 	go func() {
-		for range fs.writeTicker.C {
+		for {
+			select {
+			case <-fs.done:
+				return
+			case <-fs.writeTicker.C:
+			}
 			fs.mu.Lock()
 			if err := fs.buf.Flush(); err != nil {
 				grpclogLogger.Warningf("failed to flush to Sink: %v", err)
@@ -124,10 +133,12 @@ func (fs *bufferedSink) startFlushGoroutine() {
 }
 
 func (fs *bufferedSink) Close() error {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
 	if fs.writeTicker != nil {
 		fs.writeTicker.Stop()
 	}
-	fs.mu.Lock()
+	close(fs.done)
 	if err := fs.buf.Flush(); err != nil {
 		grpclogLogger.Warningf("failed to flush to Sink: %v", err)
 	}
@@ -137,7 +148,6 @@ func (fs *bufferedSink) Close() error {
 	if err := fs.out.Close(); err != nil {
 		grpclogLogger.Warningf("failed to close the Sink: %v", err)
 	}
-	fs.mu.Unlock()
 	return nil
 }
 
@@ -155,5 +165,6 @@ func NewBufferedSink(o io.WriteCloser) Sink {
 		closer: o,
 		out:    newWriterSink(bufW),
 		buf:    bufW,
+		done:   make(chan struct{}),
 	}
 }