net/http/fcgi: Fix resource leaks

Close the pipe for the body of a request when it is aborted and close
all pipes when child.serve terminates.

Fixes #6934

Change-Id: I1c5e7d2116e1ff106f11a1ef8e99bf70cf04162a
Reviewed-on: https://go-review.googlesource.com/1923Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/fcgi/child.go

@@ -144,6 +144,7 @@ func newChild(rwc io.ReadWriteCloser, handler http.Handler) *child {
 
 func (c *child) serve() {
 	defer c.conn.Close()
+	defer c.cleanUp()
 	var rec record
 	for {
 		if err := rec.read(c.conn.rwc); err != nil {
@@ -159,6 +160,14 @@ var errCloseConn = errors.New("fcgi: connection should be closed")
 
 var emptyBody = ioutil.NopCloser(strings.NewReader(""))
 
+// ErrRequestAborted is returned by Read when a handler attempts to read the
+// body of a request that has been aborted by the web server.
+var ErrRequestAborted = errors.New("fcgi: request aborted by web server")
+
+// ErrConnClosed is returned by Read when a handler attempts to read the body of
+// a request after the connection to the web server has been closed.
+var ErrConnClosed = errors.New("fcgi: connection to web server closed")
+
 func (c *child) handleRecord(rec *record) error {
 	c.mu.Lock()
 	req, ok := c.requests[rec.h.Id]
@@ -227,11 +236,13 @@ func (c *child) handleRecord(rec *record) error {
 		// If the filter role is implemented, read the data stream here.
 		return nil
 	case typeAbortRequest:
-		println("abort")
 		c.mu.Lock()
 		delete(c.requests, rec.h.Id)
 		c.mu.Unlock()
 		c.conn.writeEndRequest(rec.h.Id, 0, statusRequestComplete)
+		if req.pw != nil {
+			req.pw.CloseWithError(ErrRequestAborted)
+		}
 		if !req.keepConn {
 			// connection will close upon return
 			return errCloseConn
@@ -277,6 +288,16 @@ func (c *child) serveRequest(req *request, body io.ReadCloser) {
 	}
 }
 
+func (c *child) cleanUp() {
+	for _, req := range c.requests {
+		if req.pw != nil {
+			// race with call to Close in c.serveRequest doesn't matter because
+			// Pipe(Reader|Writer).Close are idempotent
+			req.pw.CloseWithError(ErrConnClosed)
+		}
+	}
+}
+
 // Serve accepts incoming FastCGI connections on the listener l, creating a new
 // goroutine for each. The goroutine reads requests and then calls handler
 // to reply to them.

src/net/http/fcgi/fcgi_test.go

@@ -8,6 +8,8 @@ import (
 	"bytes"
 	"errors"
 	"io"
+	"io/ioutil"
+	"net/http"
 	"testing"
 )
 
@@ -148,3 +150,105 @@ func TestGetValues(t *testing.T) {
 		t.Errorf(" got: %q\nwant: %q\n", got, want)
 	}
 }
+
+func nameValuePair11(nameData, valueData string) []byte {
+	return bytes.Join(
+		[][]byte{
+			{byte(len(nameData)), byte(len(valueData))},
+			[]byte(nameData),
+			[]byte(valueData),
+		},
+		nil,
+	)
+}
+
+func makeRecord(
+	recordType recType,
+	requestId uint16,
+	contentData []byte,
+) []byte {
+	requestIdB1 := byte(requestId >> 8)
+	requestIdB0 := byte(requestId)
+
+	contentLength := len(contentData)
+	contentLengthB1 := byte(contentLength >> 8)
+	contentLengthB0 := byte(contentLength)
+	return bytes.Join([][]byte{
+		{1, byte(recordType), requestIdB1, requestIdB0, contentLengthB1,
+			contentLengthB0, 0, 0},
+		contentData,
+	},
+		nil)
+}
+
+// a series of FastCGI records that start a request and begin sending the
+// request body
+var streamBeginTypeStdin = bytes.Join([][]byte{
+	// set up request 1
+	makeRecord(typeBeginRequest, 1,
+		[]byte{0, byte(roleResponder), 0, 0, 0, 0, 0, 0}),
+	// add required parameters to request 1
+	makeRecord(typeParams, 1, nameValuePair11("REQUEST_METHOD", "GET")),
+	makeRecord(typeParams, 1, nameValuePair11("SERVER_PROTOCOL", "HTTP/1.1")),
+	makeRecord(typeParams, 1, nil),
+	// begin sending body of request 1
+	makeRecord(typeStdin, 1, []byte("0123456789abcdef")),
+},
+	nil)
+
+var cleanUpTests = []struct {
+	input []byte
+	err   error
+}{
+	// confirm that child.handleRecord closes req.pw after aborting req
+	{
+		bytes.Join([][]byte{
+			streamBeginTypeStdin,
+			makeRecord(typeAbortRequest, 1, nil),
+		},
+			nil),
+		ErrRequestAborted,
+	},
+	// confirm that child.serve closes all pipes after error reading record
+	{
+		bytes.Join([][]byte{
+			streamBeginTypeStdin,
+			nil,
+		},
+			nil),
+		ErrConnClosed,
+	},
+}
+
+type nopWriteCloser struct {
+	io.ReadWriter
+}
+
+func (nopWriteCloser) Close() error {
+	return nil
+}
+
+// Test that child.serve closes the bodies of aborted requests and closes the
+// bodies of all requests before returning. Causes deadlock if either condition
+// isn't met. See issue 6934.
+func TestChildServeCleansUp(t *testing.T) {
+	for _, tt := range cleanUpTests {
+		rc := nopWriteCloser{bytes.NewBuffer(tt.input)}
+		done := make(chan bool)
+		c := newChild(rc, http.HandlerFunc(func(
+			w http.ResponseWriter,
+			r *http.Request,
+		) {
+			// block on reading body of request
+			_, err := io.Copy(ioutil.Discard, r.Body)
+			if err != tt.err {
+				t.Errorf("Expected %#v, got %#v", tt.err, err)
+			}
+			// not reached if body of request isn't closed
+			done <- true
+		}))
+		go c.serve()
+		// wait for body of request to be closed or all goroutines to block
+		<-done
+	}
+}