libgeom: Improve type safety of xml2tree code

When resolving references, assert that the type of the object we find
is what we expect.  This will help prevent memory corruption if two
objects of different types somehow end up with the same identifier.

MFC after:	1 week
Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D54454

1 files changed, 44 insertions, 10 deletions

diff --git a/lib/libgeom/geom_xml2tree.c b/lib/libgeom/geom_xml2tree.c
index 81f7de1be263..03210947d431 100644
--- a/lib/libgeom/geom_xml2tree.c
+++ b/lib/libgeom/geom_xml2tree.c
@@ -36,6 +36,7 @@
 #include <sys/stat.h>
 #include <sys/sysctl.h>
 
+#include <assert.h>
 #include <ctype.h>
 #include <err.h>
 #include <errno.h>
@@ -358,14 +359,47 @@ geom_lookupid(const struct gmesh *gmp, const void *id)
 }
 
 static void *
-geom_lookupidptr(struct gmesh *gmp, const void *id)
+geom_lookup_class(const struct gmesh *gmp, const void *id)
 {
 	struct gident *gip;
 
-	gip = geom_lookupid(gmp, id);
-	if (gip)
-		return (gip->lg_ptr);
-	return (NULL);
+	if ((gip = geom_lookupid(gmp, id)) == NULL)
+		return (NULL);
+	assert(gip->lg_what == ISCLASS);
+	return (gip->lg_ptr);
+}
+
+static void *
+geom_lookup_geom(const struct gmesh *gmp, const void *id)
+{
+	struct gident *gip;
+
+	if ((gip = geom_lookupid(gmp, id)) == NULL)
+		return (NULL);
+	assert(gip->lg_what == ISGEOM);
+	return (gip->lg_ptr);
+}
+
+static void *
+geom_lookup_provider(const struct gmesh *gmp, const void *id)
+{
+	struct gident *gip;
+
+	if ((gip = geom_lookupid(gmp, id)) == NULL)
+		return (NULL);
+	assert(gip->lg_what == ISPROVIDER);
+	return (gip->lg_ptr);
+}
+
+static void * __unused
+geom_lookup_consumer(const struct gmesh *gmp, const void *id)
+{
+	struct gident *gip;
+
+	if ((gip = geom_lookupid(gmp, id)) == NULL)
+		return (NULL);
+	assert(gip->lg_what == ISCONSUMER);
+	return (gip->lg_ptr);
 }
 
 int
@@ -441,15 +475,15 @@ geom_xml2tree(struct gmesh *gmp, char *p)
 	/* Substitute all identifiers */
 	LIST_FOREACH(cl, &gmp->lg_class, lg_class) {
 		LIST_FOREACH(ge, &cl->lg_geom, lg_geom) {
-			ge->lg_class = geom_lookupidptr(gmp, ge->lg_class);
+			ge->lg_class = geom_lookup_class(gmp, ge->lg_class);
 			LIST_FOREACH(pr, &ge->lg_provider, lg_provider) {
-				pr->lg_geom = geom_lookupidptr(gmp, pr->lg_geom);
+				pr->lg_geom = geom_lookup_geom(gmp, pr->lg_geom);
 			}
 			LIST_FOREACH(co, &ge->lg_consumer, lg_consumer) {
-				co->lg_geom = geom_lookupidptr(gmp, co->lg_geom);
+				co->lg_geom = geom_lookup_geom(gmp, co->lg_geom);
 				if (co->lg_provider != NULL) {
-					co->lg_provider = geom_lookupidptr(gmp,
-						co->lg_provider);
+					co->lg_provider = geom_lookup_provider(gmp,
+					    co->lg_provider);
 					if (co->lg_provider != NULL) {
 						LIST_INSERT_HEAD(
 						    &co->lg_provider->lg_consumers,