net/http: fix data race in client

Fixes golang#73522

Co-authored-by: Damien Neil <[email protected]>
Change-Id: I6fb408a0b03bc387f443e17e6f9d0bac32eff31e
Reviewed-on: https://go-review.googlesource.com/c/go/+/694815
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Damien Neil <[email protected]>
Reviewed-by: Damien Neil <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: 2 people

src/net/http/transport.go

@@ -722,7 +722,7 @@ func (t *Transport) roundTrip(req *Request) (_ *Response, err error) {
 			if e, ok := err.(transportReadFromServerError); ok {
 				err = e.err
 			}
-			if b, ok := req.Body.(*readTrackingBody); ok && !b.didClose {
+			if b, ok := req.Body.(*readTrackingBody); ok && !b.didClose.Load() {
 				// Issue 49621: Close the request body if pconn.roundTrip
 				// didn't do so already. This can happen if the pconn
 				// write loop exits without reading the write request.
@@ -752,8 +752,8 @@ var errCannotRewind = errors.New("net/http: cannot rewind body after connection
 
 type readTrackingBody struct {
 	io.ReadCloser
-	didRead  bool
-	didClose bool
+	didRead  bool // not atomic.Bool because only one goroutine (the user's) should be accessing
+	didClose atomic.Bool
 }
 
 func (r *readTrackingBody) Read(data []byte) (int, error) {
@@ -762,7 +762,9 @@ func (r *readTrackingBody) Read(data []byte) (int, error) {
 }
 
 func (r *readTrackingBody) Close() error {
-	r.didClose = true
+	if !r.didClose.CompareAndSwap(false, true) {
+		return nil
+	}
 	return r.ReadCloser.Close()
 }
 
@@ -784,10 +786,10 @@ func setupRewindBody(req *Request) *Request {
 // rewindBody takes care of closing req.Body when appropriate
 // (in all cases except when rewindBody returns req unmodified).
 func rewindBody(req *Request) (rewound *Request, err error) {
-	if req.Body == nil || req.Body == NoBody || (!req.Body.(*readTrackingBody).didRead && !req.Body.(*readTrackingBody).didClose) {
+	if req.Body == nil || req.Body == NoBody || (!req.Body.(*readTrackingBody).didRead && !req.Body.(*readTrackingBody).didClose.Load()) {
 		return req, nil // nothing to rewind
 	}
-	if !req.Body.(*readTrackingBody).didClose {
+	if !req.Body.(*readTrackingBody).didClose.Load() {
 		req.closeBody()
 	}
 	if req.GetBody == nil {