[release-branch.go1.14] net/http: fix cancelation of requests with a readTrackingBody wrapper

Use the original *Request in the reqCanceler map, not the transient
wrapper created to handle body rewinding.

Change the key of reqCanceler to a struct{*Request}, to make it more
difficult to accidentally use the wrong request as the key.

Updates #40453.
Fixes #41016.

Change-Id: I4e61ee9ff2c794fb4c920a3a66c9a0458693d757
Reviewed-on: https://go-review.googlesource.com/c/go/+/245357
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/250299
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

2 files changed, 85 insertions, 30 deletions

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index 5a77e91368..a01a375228 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -100,7 +100,7 @@ type Transport struct {
 	idleLRU      connLRU
 
 	reqMu       sync.Mutex
-	reqCanceler map[*Request]func(error)
+	reqCanceler map[cancelKey]func(error)
 
 	altMu    sync.Mutex   // guards changing altProto only
 	altProto atomic.Value // of nil or map[string]RoundTripper, key is URI scheme
@@ -273,6 +273,13 @@ type Transport struct {
 	ForceAttemptHTTP2 bool
 }
 
+// A cancelKey is the key of the reqCanceler map.
+// We wrap the *Request in this type since we want to use the original request,
+// not any transient one created by roundTrip.
+type cancelKey struct {
+	req *Request
+}
+
 func (t *Transport) writeBufferSize() int {
 	if t.WriteBufferSize > 0 {
 		return t.WriteBufferSize
@@ -433,9 +440,10 @@ func ProxyURL(fixedURL *url.URL) func(*Request) (*url.URL, error) {
 // optional extra headers to write and stores any error to return
 // from roundTrip.
 type transportRequest struct {
-	*Request                        // original request, not to be mutated
-	extra    Header                 // extra headers to write, or nil
-	trace    *httptrace.ClientTrace // optional
+	*Request                         // original request, not to be mutated
+	extra     Header                 // extra headers to write, or nil
+	trace     *httptrace.ClientTrace // optional
+	cancelKey cancelKey
 
 	mu  sync.Mutex // guards err
 	err error      // first setError value for mapRoundTripError to consider
@@ -512,6 +520,7 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 	}
 
 	origReq := req
+	cancelKey := cancelKey{origReq}
 	req = setupRewindBody(req)
 
 	if altRT := t.alternateRoundTripper(req); altRT != nil {
@@ -546,7 +555,7 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 		}
 
 		// treq gets modified by roundTrip, so we need to recreate for each retry.
-		treq := &transportRequest{Request: req, trace: trace}
+		treq := &transportRequest{Request: req, trace: trace, cancelKey: cancelKey}
 		cm, err := t.connectMethodForRequest(treq)
 		if err != nil {
 			req.closeBody()
@@ -559,7 +568,7 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 		// to send it requests.
 		pconn, err := t.getConn(treq, cm)
 		if err != nil {
-			t.setReqCanceler(req, nil)
+			t.setReqCanceler(cancelKey, nil)
 			req.closeBody()
 			return nil, err
 		}
@@ -567,7 +576,7 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 		var resp *Response
 		if pconn.alt != nil {
 			// HTTP/2 path.
-			t.setReqCanceler(req, nil) // not cancelable with CancelRequest
+			t.setReqCanceler(cancelKey, nil) // not cancelable with CancelRequest
 			resp, err = pconn.alt.RoundTrip(req)
 		} else {
 			resp, err = pconn.roundTrip(treq)
@@ -756,14 +765,14 @@ func (t *Transport) CloseIdleConnections() {
 // cancelable context instead. CancelRequest cannot cancel HTTP/2
 // requests.
 func (t *Transport) CancelRequest(req *Request) {
-	t.cancelRequest(req, errRequestCanceled)
+	t.cancelRequest(cancelKey{req}, errRequestCanceled)
 }
 
 // Cancel an in-flight request, recording the error value.
-func (t *Transport) cancelRequest(req *Request, err error) {
+func (t *Transport) cancelRequest(key cancelKey, err error) {
 	t.reqMu.Lock()
-	cancel := t.reqCanceler[req]
-	delete(t.reqCanceler, req)
+	cancel := t.reqCanceler[key]
+	delete(t.reqCanceler, key)
 	t.reqMu.Unlock()
 	if cancel != nil {
 		cancel(err)
@@ -1096,16 +1105,16 @@ func (t *Transport) removeIdleConnLocked(pconn *persistConn) bool {
 	return removed
 }
 
-func (t *Transport) setReqCanceler(r *Request, fn func(error)) {
+func (t *Transport) setReqCanceler(key cancelKey, fn func(error)) {
 	t.reqMu.Lock()
 	defer t.reqMu.Unlock()
 	if t.reqCanceler == nil {
-		t.reqCanceler = make(map[*Request]func(error))
+		t.reqCanceler = make(map[cancelKey]func(error))
 	}
 	if fn != nil {
-		t.reqCanceler[r] = fn
+		t.reqCanceler[key] = fn
 	} else {
-		delete(t.reqCanceler, r)
+		delete(t.reqCanceler, key)
 	}
 }
 
@@ -1113,17 +1122,17 @@ func (t *Transport) setReqCanceler(r *Request, fn func(error)) {
 // for the request, we don't set the function and return false.
 // Since CancelRequest will clear the canceler, we can use the return value to detect if
 // the request was canceled since the last setReqCancel call.
-func (t *Transport) replaceReqCanceler(r *Request, fn func(error)) bool {
+func (t *Transport) replaceReqCanceler(key cancelKey, fn func(error)) bool {
 	t.reqMu.Lock()
 	defer t.reqMu.Unlock()
-	_, ok := t.reqCanceler[r]
+	_, ok := t.reqCanceler[key]
 	if !ok {
 		return false
 	}
 	if fn != nil {
-		t.reqCanceler[r] = fn
+		t.reqCanceler[key] = fn
 	} else {
-		delete(t.reqCanceler, r)
+		delete(t.reqCanceler, key)
 	}
 	return true
 }
@@ -1327,12 +1336,12 @@ func (t *Transport) getConn(treq *transportRequest, cm connectMethod) (pc *persi
 		// set request canceler to some non-nil function so we
 		// can detect whether it was cleared between now and when
 		// we enter roundTrip
-		t.setReqCanceler(req, func(error) {})
+		t.setReqCanceler(treq.cancelKey, func(error) {})
 		return pc, nil
 	}
 
 	cancelc := make(chan error, 1)
-	t.setReqCanceler(req, func(err error) { cancelc <- err })
+	t.setReqCanceler(treq.cancelKey, func(err error) { cancelc <- err })
 
 	// Queue for permission to dial.
 	t.queueForDial(w)
@@ -2075,7 +2084,7 @@ func (pc *persistConn) readLoop() {
 		}
 
 		if !hasBody || bodyWritable {
-			pc.t.setReqCanceler(rc.req, nil)
+			pc.t.setReqCanceler(rc.cancelKey, nil)
 
 			// Put the idle conn back into the pool before we send the response
 			// so if they process it quickly and make another request, they'll
@@ -2148,7 +2157,7 @@ func (pc *persistConn) readLoop() {
 		// reading the response body. (or for cancellation or death)
 		select {
 		case bodyEOF := <-waitForBodyRead:
-			pc.t.setReqCanceler(rc.req, nil) // before pc might return to idle pool
+			pc.t.setReqCanceler(rc.cancelKey, nil) // before pc might return to idle pool
 			alive = alive &&
 				bodyEOF &&
 				!pc.sawEOF &&
@@ -2162,7 +2171,7 @@ func (pc *persistConn) readLoop() {
 			pc.t.CancelRequest(rc.req)
 		case <-rc.req.Context().Done():
 			alive = false
-			pc.t.cancelRequest(rc.req, rc.req.Context().Err())
+			pc.t.cancelRequest(rc.cancelKey, rc.req.Context().Err())
 		case <-pc.closech:
 			alive = false
 		}
@@ -2403,8 +2412,9 @@ type responseAndError struct {
 }
 
 type requestAndChan struct {
-	req *Request
-	ch  chan responseAndError // unbuffered; always send in select on callerGone
+	req       *Request
+	cancelKey cancelKey
+	ch        chan responseAndError // unbuffered; always send in select on callerGone
 
 	// whether the Transport (as opposed to the user client code)
 	// added the Accept-Encoding gzip header. If the Transport
@@ -2466,7 +2476,7 @@ var (
 
 func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err error) {
 	testHookEnterRoundTrip()
-	if !pc.t.replaceReqCanceler(req.Request, pc.cancelRequest) {
+	if !pc.t.replaceReqCanceler(req.cancelKey, pc.cancelRequest) {
 		pc.t.putOrCloseIdleConn(pc)
 		return nil, errRequestCanceled
 	}
@@ -2518,7 +2528,7 @@ func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err err
 
 	defer func() {
 		if err != nil {
-			pc.t.setReqCanceler(req.Request, nil)
+			pc.t.setReqCanceler(req.cancelKey, nil)
 		}
 	}()
 
@@ -2534,6 +2544,7 @@ func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err err
 	resc := make(chan responseAndError)
 	pc.reqch <- requestAndChan{
 		req:        req.Request,
+		cancelKey:  req.cancelKey,
 		ch:         resc,
 		addedGzip:  requestedGzip,
 		continueCh: continueCh,
@@ -2585,10 +2596,10 @@ func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err err
 			}
 			return re.res, nil
 		case <-cancelChan:
-			pc.t.CancelRequest(req.Request)
+			pc.t.cancelRequest(req.cancelKey, errRequestCanceled)
 			cancelChan = nil
 		case <-ctxDoneChan:
-			pc.t.cancelRequest(req.Request, req.Context().Err())
+			pc.t.cancelRequest(req.cancelKey, req.Context().Err())
 			cancelChan = nil
 			ctxDoneChan = nil
 		}
diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index ba12e834c5..fa0c370c1f 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -2346,6 +2346,50 @@ func TestTransportCancelRequest(t *testing.T) {
 	}
 }
 
+func testTransportCancelRequestInDo(t *testing.T, body io.Reader) {
+	setParallel(t)
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping test in -short mode")
+	}
+	unblockc := make(chan bool)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		<-unblockc
+	}))
+	defer ts.Close()
+	defer close(unblockc)
+
+	c := ts.Client()
+	tr := c.Transport.(*Transport)
+
+	donec := make(chan bool)
+	req, _ := NewRequest("GET", ts.URL, body)
+	go func() {
+		defer close(donec)
+		c.Do(req)
+	}()
+	start := time.Now()
+	timeout := 10 * time.Second
+	for time.Since(start) < timeout {
+		time.Sleep(100 * time.Millisecond)
+		tr.CancelRequest(req)
+		select {
+		case <-donec:
+			return
+		default:
+		}
+	}
+	t.Errorf("Do of canceled request has not returned after %v", timeout)
+}
+
+func TestTransportCancelRequestInDo(t *testing.T) {
+	testTransportCancelRequestInDo(t, nil)
+}
+
+func TestTransportCancelRequestWithBodyInDo(t *testing.T) {
+	testTransportCancelRequestInDo(t, bytes.NewBuffer([]byte{0}))
+}
+
 func TestTransportCancelRequestInDial(t *testing.T) {
 	defer afterTest(t)
 	if testing.Short() {