Try to fix the mess I made of devname, with the minimal subset of the

larger minor/major patch which was posted for testing.

sys/fs/devfs/devfs_devs.c

@@ -114,6 +114,8 @@ struct devfs_dirent **
 devfs_itode (struct devfs_mount *dm, int inode)
 {
 
+	if (inode < 0)
+		return (NULL);
 	if (inode < NDEVFSINO)
 		return (&dm->dm_dirent[inode]);
 	if (devfs_overflow == NULL)
@@ -127,6 +129,8 @@ struct cdev **
 devfs_itod (int inode)
 {
 
+	if (inode < 0)
+		return (NULL);
 	if (inode < NDEVFSINO)
 		return (&devfs_inot[inode]);
 	if (devfs_overflow == NULL)
@@ -270,10 +274,7 @@ devfs_populate(struct devfs_mount *dm)
 			if (dev == NULL && de != NULL) {
 				dd = de->de_dir;
 				*dep = NULL;
-				TAILQ_REMOVE(&dd->de_dlist, de, de_list);
-				if (de->de_vnode)
-					de->de_vnode->v_data = NULL;
-				FREE(de, M_DEVFS);
+				devfs_delete(dd, de);
 				devfs_dropref(i);
 				continue;
 			}

sys/fs/devfs/devfs_vnops.c

@@ -61,6 +61,7 @@
 #include <sys/proc.h>
 #include <sys/stat.h>
 #include <sys/sx.h>
+#include <sys/sysctl.h>
 #include <sys/time.h>
 #include <sys/ttycom.h>
 #include <sys/unistd.h>
@@ -113,6 +114,25 @@ static vop_symlink_t	devfs_symlink;
 extern struct vop_vector devfs_vnodeops;
 extern struct vop_vector devfs_specops;
 
+static u_int
+devfs_random(void)
+{
+	static u_int devfs_seed;
+
+	while (devfs_seed == 0) {
+		/*
+		 * Make sure people don't make stupid assumptions
+		 * about device major/minor numbers in userspace.
+		 * We do this late to get entropy and for the same
+		 * reason we force a reseed, but it may not be
+		 * late enough for entropy to be available.
+		 */
+		arc4rand(&devfs_seed, sizeof devfs_seed, 1);
+		devfs_seed &= 0xf0f;
+	}
+	return (devfs_seed);
+}
+
 static int
 devfs_fp_check(struct file *fp, struct cdev **devp, struct cdevsw **dswp)
 {
@@ -441,7 +461,8 @@ devfs_getattr(ap)
 		vap->va_mtime = dev->si_mtime;
 		fix(dev->si_ctime);
 		vap->va_ctime = dev->si_ctime;
-		vap->va_rdev = dev->si_udev;
+
+		vap->va_rdev = de->de_inode ^ devfs_random();
 	}
 	vap->va_gen = 0;
 	vap->va_flags = 0;
@@ -1432,6 +1453,43 @@ static struct vop_vector devfs_specops = {
 	.vop_write =		VOP_PANIC,
 };
 
+dev_t
+dev2udev(struct cdev *x)
+{
+	if (x == NULL)
+		return (NODEV);
+	return (x->si_inode ^ devfs_random());
+}
+
+/*
+ * Helper sysctl for devname(3).  We're given a struct cdev * and return
+ * the name, if any, registered by the device driver.
+ */
+static int
+sysctl_devname(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	dev_t ud;
+	struct cdev *dev, **dp;
+
+	error = SYSCTL_IN(req, &ud, sizeof (ud));
+	if (error)
+		return (error);
+	if (ud == NODEV)
+		return(EINVAL);
+	dp = devfs_itod(ud ^ devfs_random());
+	if (dp == NULL)
+		return(ENOENT);
+	dev = *dp;
+	if (dev == NULL)
+		return(ENOENT);
+	return(SYSCTL_OUT(req, dev->si_name, strlen(dev->si_name) + 1));
+	return (error);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_ANYBODY,
+	NULL, 0, sysctl_devname, "", "devname(3) handler");
+
 /*
  * Our calling convention to the device drivers used to be that we passed
  * vnode.h IO_* flags to read()/write(), but we're moving to fcntl.h O_ 

sys/kern/kern_conf.c

@@ -317,14 +317,6 @@ freedev(struct cdev *dev)
 	free(dev, M_DEVT);
 }
 
-dev_t
-dev2udev(struct cdev *x)
-{
-	if (x == NULL)
-		return (NODEV);
-	return (x->si_udev);
-}
-
 struct cdev *
 findcdev(dev_t udev)
 {
@@ -792,30 +784,3 @@ clone_cleanup(struct clonedevs **cdp)
 	free(cd, M_DEVBUF);
 	*cdp = NULL;
 }
-
-/*
- * Helper sysctl for devname(3).  We're given a struct cdev * and return
- * the name, if any, registered by the device driver.
- */
-static int
-sysctl_devname(SYSCTL_HANDLER_ARGS)
-{
-	int error;
-	dev_t ud;
-	struct cdev *dev;
-
-	error = SYSCTL_IN(req, &ud, sizeof (ud));
-	if (error)
-		return (error);
-	if (ud == NODEV)
-		return(EINVAL);
-	dev = findcdev(ud);
-	if (dev == NULL)
-		error = ENOENT;
-	else
-		error = SYSCTL_OUT(req, dev->si_name, strlen(dev->si_name) + 1);
-	return (error);
-}
-
-SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_ANYBODY,
-	NULL, 0, sysctl_devname, "", "devname(3) handler");