Keep FilePayloads open on server side until after RPC completed.

Prevents URPC FDs from being closed mid-call, especially if they
are used as raw FDs.

PiperOrigin-RevId: 233087955
Change-Id: I815a2ff32cc5f03774605aef0b35a32862f8e633

1 files changed, 3 insertions, 0 deletions

diff --git a/pkg/fd/fd.go b/pkg/fd/fd.go
index f6656ffa1..a2edf2aa6 100644
--- a/pkg/fd/fd.go
+++ b/pkg/fd/fd.go
@@ -158,6 +158,9 @@ func New(fd int) *FD {
 // The returned FD is always blocking (Go 1.9+).
 func NewFromFile(file *os.File) (*FD, error) {
 	fd, err := syscall.Dup(int(file.Fd()))
+	// Technically, the runtime may call the finalizer on file as soon as
+	// Fd() returns.
+	runtime.KeepAlive(file)
 	if err != nil {
 		return &FD{ReadWriter{-1}}, err
 	}