diff --git a/libsepol/src/mls.c b/libsepol/src/mls.c
index 2dc5f2b2..8047d914 100644
--- a/libsepol/src/mls.c
+++ b/libsepol/src/mls.c
@@ -312,7 +312,7 @@ int mls_context_isvalid(const policydb_t * p, const context_struct_t * c)
 	if (!c->user || c->user > p->p_users.nprim)
 		return 0;
 	usrdatum = p->user_val_to_struct[c->user - 1];
-	if (!mls_range_contains(usrdatum->exp_range, c->range))
+	if (!usrdatum || !mls_range_contains(usrdatum->exp_range, c->range))
 		return 0;	/* user may not be associated with range */
 
 	return 1;
diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
index c225ac6c..5f888d3a 100644
--- a/libsepol/src/policydb.c
+++ b/libsepol/src/policydb.c
@@ -1074,7 +1074,7 @@ int policydb_index_others(sepol_handle_t * handle,
 
 	free(p->user_val_to_struct);
 	p->user_val_to_struct = (user_datum_t **)
-	    malloc(p->p_users.nprim * sizeof(user_datum_t *));
+	    calloc(p->p_users.nprim, sizeof(user_datum_t *));
 	if (!p->user_val_to_struct)
 		return -1;
 
@@ -4006,12 +4006,12 @@ int policydb_reindex_users(policydb_t * p)
 		free(p->sym_val_to_name[i]);
 
 	p->user_val_to_struct = (user_datum_t **)
-	    malloc(p->p_users.nprim * sizeof(user_datum_t *));
+	    calloc(p->p_users.nprim, sizeof(user_datum_t *));
 	if (!p->user_val_to_struct)
 		return -1;
 
 	p->sym_val_to_name[i] = (char **)
-	    malloc(p->symtab[i].nprim * sizeof(char *));
+	    calloc(p->symtab[i].nprim, sizeof(char *));
 	if (!p->sym_val_to_name[i])
 		return -1;
 
diff --git a/libsepol/src/users.c b/libsepol/src/users.c
index ce54c2ba..3ffb166b 100644
--- a/libsepol/src/users.c
+++ b/libsepol/src/users.c
@@ -19,12 +19,17 @@ static int user_to_record(sepol_handle_t * handle,
 
 	const char *name = policydb->p_user_val_to_name[user_idx];
 	user_datum_t *usrdatum = policydb->user_val_to_struct[user_idx];
-	ebitmap_t *roles = &(usrdatum->roles.roles);
+	ebitmap_t *roles;
 	ebitmap_node_t *rnode;
 	unsigned bit;
 
 	sepol_user_t *tmp_record = NULL;
 
+	if (!usrdatum)
+		goto err;
+
+	roles = &(usrdatum->roles.roles);
+
 	if (sepol_user_create(handle, &tmp_record) < 0)
 		goto err;
 
@@ -234,6 +239,7 @@ int sepol_user_modify(sepol_handle_t * handle,
 		if (!tmp_ptr)
 			goto omem;
 		policydb->user_val_to_struct = tmp_ptr;
+		policydb->user_val_to_struct[policydb->p_users.nprim] = NULL;
 
 		tmp_ptr = realloc(policydb->sym_val_to_name[SYM_USERS],
 				  (policydb->p_users.nprim +
@@ -241,6 +247,7 @@ int sepol_user_modify(sepol_handle_t * handle,
 		if (!tmp_ptr)
 			goto omem;
 		policydb->sym_val_to_name[SYM_USERS] = tmp_ptr;
+		policydb->p_user_val_to_name[policydb->p_users.nprim] = NULL;
 
 		/* Need to copy the user name */
 		name = strdup(cname);