net/http: A race condition in the http.response.write
#53912
Comments
nan01ab
changed the title
http.response.write
nan01ab
changed the title
http.response.writehttp.response.write
|
please show code that can reproduce the issue |
nan01ab
changed the title
http.response.writehttp.response.write
A demo version: package main
import (
"io"
"net/http"
"sync"
)
type Handler struct {
buf []byte
}
// just for demo
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
var wg sync.WaitGroup
wg.Add(1) // avoid early exits
go func() {
defer wg.Done()
if hijack, ok := w.(http.Hijacker); ok {
conn, _, err := hijack.Hijack()
if err != nil {
return
}
conn.Close()
}
}()
w.Write(h.buf) // should return OK or ErrHijack, not panic
wg.Wait()
}
func main() {
go http.ListenAndServe("127.0.0.1:8080", &Handler{
buf: make([]byte, 4096),
})
var wg sync.WaitGroup
wg.Add(8)
for i := 0; i < 8; i++ {
go func() {
defer wg.Done()
for {
res, err := http.Get("http://127.0.0.1:8080/")
if err != nil {
continue
}
io.Copy(io.Discard, res.Body)
res.Body.Close()
}
}()
}
wg.Wait()
}go run hijack.go panic: or: go run hijack.go goroutine 23757 [running]: |
A race condition in the
func (w *response) write(lenData int, dataB []byte, dataS string) (n int, err error)What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes.
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
calling the
Hijack()from a goroutine while the http request is being processed.What did you expect to see?
Any
Writeoperation on the http.ResponseWriter should return OK orErrHijacked.Return OK: before the
Hijack()is called.Return ErrHijacked: after the
Hijack()is called.What did you see instead?
A panic happened.
In the statement
if w.conn.hijacked(),writewill return ErrHijacked ifconn.hijacked()is true and theconn.hijacked()is protected byconn's Mutex. But the following operations are not protected byconn's Mutex.If the request was hijacked after
if w.conn.hijacked(), Thebufio.Writerinresponsemay be modified concurrently.The text was updated successfully, but these errors were encountered: