Do not allow kqueues to be passed via unix domain sockets.

sys/kern/kern_descrip.c

@@ -2181,7 +2181,8 @@ struct fileops badfileops = {
 	badfo_poll,
 	badfo_kqfilter,
 	badfo_stat,
-	badfo_close
+	badfo_close,
+	0
 };
 
 static int

sys/kern/kern_event.c

@@ -74,7 +74,8 @@ static struct fileops kqueueops = {
 	kqueue_poll,
 	kqueue_kqfilter,
 	kqueue_stat,
-	kqueue_close
+	kqueue_close,
+	0
 };
 
 static void 	knote_attach(struct knote *kn, struct filedesc *fdp);

sys/kern/sys_pipe.c

@@ -104,7 +104,7 @@ static fo_close_t	pipe_close;
 
 static struct fileops pipeops = {
 	pipe_read, pipe_write, pipe_ioctl, pipe_poll, pipe_kqfilter,
-	pipe_stat, pipe_close
+	pipe_stat, pipe_close, DFLAG_PASSABLE
 };
 
 static void	filt_pipedetach(struct knote *kn);

sys/kern/sys_socket.c

@@ -57,7 +57,7 @@
 
 struct	fileops socketops = {
 	soo_read, soo_write, soo_ioctl, soo_poll, soo_kqfilter,
-	soo_stat, soo_close
+	soo_stat, soo_close, DFLAG_PASSABLE
 };
 
 /* ARGSUSED */

sys/kern/uipc_usrreq.c

@@ -1171,6 +1171,13 @@ unp_internalize(controlp, td)
 					error = EBADF;
 					goto out;
 				}
+				fp = fdescp->fd_ofiles[fd];
+				if (!(fp->f_ops->fo_flags & DFLAG_PASSABLE)) {
+					FILEDESC_UNLOCK(fdescp);
+					error = EOPNOTSUPP;
+					goto out;
+				}
+
 			}
 			/*
 			 * Now replace the integer FDs with pointers to

sys/kern/vfs_vnops.c

@@ -73,7 +73,7 @@ static fo_close_t	vn_closefile;
 
 struct 	fileops vnops = {
 	vn_read, vn_write, vn_ioctl, vn_poll, vn_kqfilter,
-	vn_statfile, vn_closefile
+	vn_statfile, vn_closefile, DFLAG_PASSABLE
 };
 
 int

sys/sys/file.h

@@ -80,6 +80,7 @@ typedef	int fo_kqfilter_t(struct file *fp, struct knote *kn);
 typedef	int fo_stat_t(struct file *fp, struct stat *sb,
 		    struct ucred *active_cred, struct thread *td);
 typedef	int fo_close_t(struct file *fp, struct thread *td);
+typedef	int fo_flags_t;
 
 struct fileops {
 	fo_rdwr_t	*fo_read;
@@ -89,8 +90,11 @@ struct fileops {
 	fo_kqfilter_t	*fo_kqfilter;
 	fo_stat_t	*fo_stat;
 	fo_close_t	*fo_close;
+	fo_flags_t	fo_flags;	/* DFLAG_* below */
 };
 
+#define DFLAG_PASSABLE	0x01	/* may be passed via unix sockets. */
+
 /*
  * Kernel descriptor table.
  * One entry for each open kernel vnode and socket.