Set CLOEXEC option to sockets

hostinet/socket.go: the Sentry doesn't spawn new processes, but it doesn't hurt to protect the socket from leaking.
unet/unet.go: should be setting closing on exec. The FD is explicitly donated to children when needed.

PiperOrigin-RevId: 200135682
Change-Id: Ia8a45ced1e00a19420c8611b12e7a8ee770f89cb

2 files changed, 4 insertions, 4 deletions

diff --git a/pkg/sentry/socket/hostinet/socket.go b/pkg/sentry/socket/hostinet/socket.go
index 8f901df6c..d0f3054dc 100644
--- a/pkg/sentry/socket/hostinet/socket.go
+++ b/pkg/sentry/socket/hostinet/socket.go
@@ -193,7 +193,7 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 
 	// Conservatively ignore all flags specified by the application and add
 	// SOCK_NONBLOCK since socketOperations requires it.
-	fd, syscallErr := accept4(s.fd, peerAddrPtr, peerAddrlenPtr, syscall.SOCK_NONBLOCK)
+	fd, syscallErr := accept4(s.fd, peerAddrPtr, peerAddrlenPtr, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
 	if blocking {
 		var ch chan struct{}
 		for syscallErr == syserror.ErrWouldBlock {
@@ -207,7 +207,7 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 				s.EventRegister(&e, waiter.EventIn)
 				defer s.EventUnregister(&e)
 			}
-			fd, syscallErr = accept4(s.fd, peerAddrPtr, peerAddrlenPtr, syscall.SOCK_NONBLOCK)
+			fd, syscallErr = accept4(s.fd, peerAddrPtr, peerAddrlenPtr, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
 		}
 	}
 
@@ -545,7 +545,7 @@ func (p *socketProvider) Socket(t *kernel.Task, stypeflags unix.SockType, protoc
 	// Conservatively ignore all flags specified by the application and add
 	// SOCK_NONBLOCK since socketOperations requires it. Pass a protocol of 0
 	// to simplify the syscall filters, since 0 and IPPROTO_* are equivalent.
-	fd, err := syscall.Socket(p.family, stype|syscall.SOCK_NONBLOCK, 0)
+	fd, err := syscall.Socket(p.family, stype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
 		return nil, syserr.FromError(err)
 	}
diff --git a/pkg/unet/unet.go b/pkg/unet/unet.go
index 59b6c5568..f4800e0d9 100644
--- a/pkg/unet/unet.go
+++ b/pkg/unet/unet.go
@@ -201,7 +201,7 @@ func (s *Socket) enterFD() (int, bool) {
 // SocketPair creates a pair of connected sockets.
 func SocketPair(packet bool) (*Socket, *Socket, error) {
 	// Make a new pair.
-	fds, err := syscall.Socketpair(syscall.AF_UNIX, socketType(packet), 0)
+	fds, err := syscall.Socketpair(syscall.AF_UNIX, socketType(packet)|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
 		return nil, nil, err
 	}