unix: allow to bind unix sockets only to AF_UNIX addresses

Reported-by: syzbot+2c0bcfd87fb4e8b7b009@syzkaller.appspotmail.com
PiperOrigin-RevId: 285228312

pkg/sentry/socket/netstack/netstack.go

@@ -326,7 +326,7 @@ func AddressAndFamily(sfamily int, addr []byte, strict bool) (tcpip.FullAddress,
 	}
 
 	family := usermem.ByteOrder.Uint16(addr)
-	if family != uint16(sfamily) && (!strict && family != linux.AF_UNSPEC) {
+	if family != uint16(sfamily) && (strict || family != linux.AF_UNSPEC) {
 		return tcpip.FullAddress{}, family, syserr.ErrAddressFamilyNotSupported
 	}
 

pkg/sentry/socket/unix/unix.go

@@ -118,6 +118,9 @@ func (s *SocketOperations) Endpoint() transport.Endpoint {
 func extractPath(sockaddr []byte) (string, *syserr.Error) {
 	addr, _, err := netstack.AddressAndFamily(linux.AF_UNIX, sockaddr, true /* strict */)
 	if err != nil {
+		if err == syserr.ErrAddressFamilyNotSupported {
+			err = syserr.ErrInvalidArgument
+		}
 		return "", err
 	}
 

test/syscalls/linux/socket_unix.cc

@@ -65,6 +65,21 @@ TEST_P(UnixSocketPairTest, BindToBadName) {
       SyscallFailsWithErrno(ENOENT));
 }
 
+TEST_P(UnixSocketPairTest, BindToBadFamily) {
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  constexpr char kBadName[] = "/some/path/that/does/not/exist";
+  sockaddr_un sockaddr;
+  sockaddr.sun_family = AF_INET;
+  memcpy(sockaddr.sun_path, kBadName, sizeof(kBadName));
+
+  EXPECT_THAT(
+      bind(pair->first_fd(), reinterpret_cast<struct sockaddr*>(&sockaddr),
+           sizeof(sockaddr)),
+      SyscallFailsWithErrno(EINVAL));
+}
+
 TEST_P(UnixSocketPairTest, RecvmmsgTimeoutAfterRecv) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
   char sent_data[10];