net/http/fcgi: fix race in child.serve connection read

tz70s · odeke-em · commit 7432bee7b372 · 2020-09-02T10:07:50.000Z
Guards the connection read with a mutex, because typeStdin asynchronously and concurrently writes to the underlying conn. Fixes golang#41167 Change-Id: Ia2610f4fde0bd4b108c54164095ea293980b0301 Reviewed-on: https://go-review.googlesource.com/c/go/+/252417 Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
diff --git a/src/net/http/fcgi/child.go b/src/net/http/fcgi/child.go
@@ -155,9 +155,12 @@ func (c *child) serve() {
 	defer c.cleanUp()
 	var rec record
 	for {
+		c.conn.mutex.Lock()
 		if err := rec.read(c.conn.rwc); err != nil {
+			c.conn.mutex.Unlock()
 			return
 		}
+		c.conn.mutex.Unlock()
 		if err := c.handleRecord(&rec); err != nil {
 			return
 		}

Original file line number	Diff line number	Diff line change
`@@ -155,9 +155,12 @@ func (c *child) serve() {`
`155`	`155`	`defer c.cleanUp()`
`156`	`156`	`var rec record`
`157`	`157`	`for {`
	`158`	`+ c.conn.mutex.Lock()`
`158`	`159`	`if err := rec.read(c.conn.rwc); err != nil {`
	`160`	`+ c.conn.mutex.Unlock()`
`159`	`161`	`return`
`160`	`162`	`}`
	`163`	`+ c.conn.mutex.Unlock()`
`161`	`164`	`if err := c.handleRecord(&rec); err != nil {`
`162`	`165`	`return`
`163`	`166`	`}`