x/net/http2: data race in Transport on req.Header

[tombergan]

Repro here:
https://go-review.googlesource.com/c/29243/10/http2/transport_test.go

The relevant code from transport.go:

func (rl *clientConnReadLoop) endStreamError(cs *clientStream, err error) {
	var code func()
	if err == nil {
		err = io.EOF
		code = cs.copyTrailers
	}
	cs.bufPipe.closeWithErrorAndCode(err, code)

	// The above line closes resp.Body. At that point it should be safe for
	// callers to reuse the req. However, req.Header is read below, which
	// can race with reuses of req.

	delete(rl.activeRes, cs.ID)
	if isConnectionCloseRequest(cs.req) { // req.Header read here
		rl.closeWhenIdle = true
	}

	select {
	case cs.resc <- resAndError{err: err}:
	default:
	}
}

func isConnectionCloseRequest(req *http.Request) bool {
	return req.Close || httplex.HeaderValuesContainsToken(req.Header["Connection"], "close")
}

The simple fix is to move cs.bufPipe.closeWithErrorAndCode after the isConnectionCloseRequest call, however, we should audit that cs.req is never used after cs.bufPipe is closed as there may be other instances of this race.

[gopherbot]

Change https://golang.org/cl/75530 mentions this issue: http2: fix transport data race on reused *http.Request objects

[gopherbot]

Change https://golang.org/cl/80078 mentions this issue: net/http: update bundled http2