[patch] md(4) and preloaded memory disks

[Jaakko Heinonen]

Hi,

I plan to commit the patch below to disallow attaching preloaded memory
disks via ioctl. I didn't find anything that would really use this
undocumented feature.

---

Disallow attaching preloaded memory disks via ioctl.

- The feature is dangerous because the kernel code doesn't check
  validity of the memory address provided from user space.
- It seems that mdconfig(8) never really supported attaching preloaded
  memory disks.
- Preloaded memory disks are automatically attached during md(4)
  initialization. Thus there shouldn't be much use for the feature.

PR:		kern/169683


%%%
Index: sbin/mdconfig/mdconfig.c
===================================================================
--- sbin/mdconfig/mdconfig.c	(revision 242608)
+++ sbin/mdconfig/mdconfig.c	(working copy)
@@ -84,7 +84,7 @@ usage(void)
 "       mdconfig -r -u unit -s size [-o [no]force]\n"
 "       mdconfig -l [-v] [-n] [-u unit]\n"
 "       mdconfig file\n");
-	fprintf(stderr, "\t\ttype = {malloc, preload, vnode, swap}\n");
+	fprintf(stderr, "\t\ttype = {malloc, vnode, swap}\n");
 	fprintf(stderr, "\t\toption = {cluster, compress, reserve}\n");
 	fprintf(stderr, "\t\tsize = %%d (512 byte blocks), %%db (B),\n");
 	fprintf(stderr, "\t\t       %%dk (kB), %%dm (MB), %%dg (GB) or\n");
@@ -148,8 +148,6 @@ main(int argc, char **argv)
 			if (!strcmp(optarg, "malloc")) {
 				mdio.md_type = MD_MALLOC;
 				mdio.md_options |= MD_AUTOUNIT | MD_COMPRESS;
-			} else if (!strcmp(optarg, "preload")) {
-				mdio.md_type = MD_PRELOAD;
 			} else if (!strcmp(optarg, "vnode")) {
 				mdio.md_type = MD_VNODE;
 				mdio.md_options |= MD_CLUSTER | MD_AUTOUNIT | MD_COMPRESS;
Index: sys/dev/md/md.c
===================================================================
--- sys/dev/md/md.c	(revision 242608)
+++ sys/dev/md/md.c	(working copy)
@@ -845,15 +845,20 @@ mdinit(struct md_s *sc)
 	    DEVSTAT_ALL_SUPPORTED, DEVSTAT_TYPE_DIRECT, DEVSTAT_PRIORITY_MAX);
 }
 
-/*
- * XXX: we should check that the range they feed us is mapped.
- * XXX: we should implement read-only.
- */
-
 static int
 mdcreate_preload(struct md_s *sc, struct md_ioctl *mdio)
 {
 
+	/*
+	 * Currently we disallow attaching preloaded memory disks via ioctl.
+	 * Preloaded memory disks are automatically attached in mdinit().
+	 */
+#if 0
+	/*
+	 * XXX: We should check that the range they feed us is mapped and
+	 *      a valid memory disk.
+	 * XXX: We should implement read-only.
+	 */
 	if (mdio->md_options & ~(MD_AUTOUNIT | MD_FORCE))
 		return (EINVAL);
 	if (mdio->md_base == 0)
@@ -863,6 +868,9 @@ mdcreate_preload(struct md_s *sc, struct
 	sc->pl_ptr = (u_char *)(uintptr_t)mdio->md_base;
 	sc->pl_len = (size_t)sc->mediasize;
 	return (0);
+#else
+	return (EOPNOTSUPP);
+#endif
 }
 
 
%%%

-- 
Jaakko