Fix JSON Close data race. (#8486)

The JSON stream library has no safe way of aborting while

Since we cannot expect the called to safely handle "Read" and "Close" calls we must handle this.

Also any Read error returned from upstream will crash the server. We preserve the errors and instead always return io.EOF upstream, but send the error on Close.

`readahead v1.3.1` handles Read after Close better.

Updates to `progressReader` is mostly to ensure safety.

Fixes #8481

go.mod

@@ -32,7 +32,7 @@ require (
 	github.com/json-iterator/go v1.1.7
 	github.com/klauspost/compress v1.8.3
 	github.com/klauspost/pgzip v1.2.1
-	github.com/klauspost/readahead v1.3.0
+	github.com/klauspost/readahead v1.3.1
 	github.com/klauspost/reedsolomon v1.9.3
 	github.com/kurin/blazer v0.5.4-0.20190613185654-cf2f27cc0be3
 	github.com/lib/pq v1.0.0

go.sum

@@ -362,6 +362,7 @@ github.com/klauspost/pgzip v1.2.1 h1:oIPZROsWuPHpOdMVWLuJZXwgjhrW8r1yEX8UqMyeNHM
 github.com/klauspost/pgzip v1.2.1/go.mod h1:Ch1tH69qFZu15pkjo5kYi6mth2Zzwzt50oCQKQE9RUs=
 github.com/klauspost/readahead v1.3.0 h1:ur57scQa1RS6oQgdq+6mylmP2u0iR1LFw1zy3Xwqacg=
 github.com/klauspost/readahead v1.3.0/go.mod h1:AH9juHzNH7xqdqFHrMRSHeH2Ps+vFf+kblDqzPFiLJg=
+github.com/klauspost/readahead v1.3.1/go.mod h1:AH9juHzNH7xqdqFHrMRSHeH2Ps+vFf+kblDqzPFiLJg=
 github.com/klauspost/reedsolomon v0.0.0-20190210214925-2b210cf0866d/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=
 github.com/klauspost/reedsolomon v1.9.1 h1:kYrT1MlR4JH6PqOpC+okdb9CDTcwEC/BqpzK4WFyXL8=
 github.com/klauspost/reedsolomon v1.9.1/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=

pkg/s3select/json/reader.go

@@ -17,7 +17,9 @@
 package json
 
 import (
+	"errors"
 	"io"
+	"sync"
 
 	"github.com/minio/minio/pkg/s3select/sql"
 
@@ -67,7 +69,6 @@ func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
 // Close - closes underlying reader.
 func (r *Reader) Close() error {
 	// Close the input.
-	// Potentially racy if the stream decoder is still reading.
 	err := r.readCloser.Close()
 	for range r.valueCh {
 		// Drain values so we don't leak a goroutine.
@@ -78,6 +79,7 @@ func (r *Reader) Close() error {
 
 // NewReader - creates new JSON reader using readCloser.
 func NewReader(readCloser io.ReadCloser, args *ReaderArgs) *Reader {
+	readCloser = &syncReadCloser{rc: readCloser}
 	d := jstream.NewDecoder(readCloser, 0).ObjectAsKVS()
 	return &Reader{
 		args:       args,
@@ -86,3 +88,46 @@ func NewReader(readCloser io.ReadCloser, args *ReaderArgs) *Reader {
 		readCloser: readCloser,
 	}
 }
+
+// syncReadCloser will wrap a readcloser and make it safe to call Close
+// while reads are running.
+// All read errors are also postponed until Close is called and
+// io.EOF is returned instead.
+type syncReadCloser struct {
+	rc    io.ReadCloser
+	errMu sync.Mutex
+	err   error
+}
+
+func (pr *syncReadCloser) Read(p []byte) (n int, err error) {
+	// This ensures that Close will block until Read has completed.
+	// This allows another goroutine to close the reader.
+	pr.errMu.Lock()
+	defer pr.errMu.Unlock()
+	if pr.err != nil {
+		return 0, io.EOF
+	}
+	n, pr.err = pr.rc.Read(p)
+	if pr.err != nil {
+		// Translate any error into io.EOF, so we don't crash:
+		// https://github.com/bcicen/jstream/blob/master/scanner.go#L48
+		return n, io.EOF
+	}
+
+	return n, nil
+}
+
+var errClosed = errors.New("read after close")
+
+func (pr *syncReadCloser) Close() error {
+	pr.errMu.Lock()
+	defer pr.errMu.Unlock()
+	if pr.err == errClosed {
+		return nil
+	}
+	if pr.err != nil {
+		return pr.err
+	}
+	pr.err = errClosed
+	return pr.rc.Close()
+}

pkg/s3select/json/reader_test.go

@@ -33,6 +33,7 @@ func TestNewReader(t *testing.T) {
 		t.Fatal(err)
 	}
 	for _, file := range files {
+		t.Run(file.Name(), func(t *testing.T) {
 			f, err := os.Open(filepath.Join("testdata", file.Name()))
 			if err != nil {
 				t.Fatal(err)
@@ -49,6 +50,26 @@ func TestNewReader(t *testing.T) {
 			if err != io.EOF {
 				t.Fatalf("Reading failed with %s, %s", err, file.Name())
 			}
+		})
+
+		t.Run(file.Name()+"-close", func(t *testing.T) {
+			f, err := os.Open(filepath.Join("testdata", file.Name()))
+			if err != nil {
+				t.Fatal(err)
+			}
+			r := NewReader(f, &ReaderArgs{})
+			r.Close()
+			var record sql.Record
+			for {
+				record, err = r.Read(record)
+				if err != nil {
+					break
+				}
+			}
+			if err != io.EOF {
+				t.Fatalf("Reading failed with %s, %s", err, file.Name())
+			}
+		})
 	}
 }
 

pkg/s3select/progress.go

@@ -18,8 +18,10 @@ package s3select
 
 import (
 	"compress/bzip2"
+	"errors"
 	"fmt"
 	"io"
+	"sync"
 	"sync/atomic"
 
 	gzip "github.com/klauspost/pgzip"
@@ -50,13 +52,29 @@ type progressReader struct {
 	rc              io.ReadCloser
 	scannedReader   *countUpReader
 	processedReader *countUpReader
+
+	closedMu sync.Mutex
+	closed   bool
 }
 
 func (pr *progressReader) Read(p []byte) (n int, err error) {
+	// This ensures that Close will block until Read has completed.
+	// This allows another goroutine to close the reader.
+	pr.closedMu.Lock()
+	defer pr.closedMu.Unlock()
+	if pr.closed {
+		return 0, errors.New("progressReader: read after Close")
+	}
 	return pr.processedReader.Read(p)
 }
 
 func (pr *progressReader) Close() error {
+	pr.closedMu.Lock()
+	defer pr.closedMu.Unlock()
+	if pr.closed {
+		return nil
+	}
+	pr.closed = true
 	return pr.rc.Close()
 }