Merge pull request #20609 from DaanDeMeyer/recursive-template

core: Try to prevent infinite recursive template instantiation

src/basic/unit-file.c

@@ -598,9 +598,11 @@ int unit_file_find_fragment(
         if (name_type < 0)
                 return name_type;
 
-        r = add_names(unit_ids_map, unit_name_map, unit_name, NULL, name_type, instance, &names, unit_name);
-        if (r < 0)
-                return r;
+        if (ret_names) {
+                r = add_names(unit_ids_map, unit_name_map, unit_name, NULL, name_type, instance, &names, unit_name);
+                if (r < 0)
+                        return r;
+        }
 
         /* First try to load fragment under the original name */
         r = unit_ids_map_get(unit_ids_map, unit_name, &fragment);
@@ -619,7 +621,7 @@ int unit_file_find_fragment(
                         return log_debug_errno(r, "Cannot load template %s: %m", template);
         }
 
-        if (fragment) {
+        if (fragment && ret_names) {
                 const char *fragment_basename = basename(fragment);
 
                 if (!streq(fragment_basename, unit_name)) {
@@ -631,7 +633,8 @@ int unit_file_find_fragment(
         }
 
         *ret_fragment_path = fragment;
-        *ret_names = TAKE_PTR(names);
+        if (ret_names)
+                *ret_names = TAKE_PTR(names);
 
         return 0;
 }

src/basic/unit-name.c

@@ -8,6 +8,7 @@
 #include "alloc-util.h"
 #include "glob-util.h"
 #include "hexdecoct.h"
+#include "memory-util.h"
 #include "path-util.h"
 #include "special.h"
 #include "string-util.h"
@@ -797,3 +798,26 @@ bool slice_name_is_valid(const char *name) {
 
         return true;
 }
+
+bool unit_name_prefix_equal(const char *a, const char *b) {
+        const char *p, *q;
+
+        assert(a);
+        assert(b);
+
+        if (!unit_name_is_valid(a, UNIT_NAME_ANY) || !unit_name_is_valid(b, UNIT_NAME_ANY))
+                return false;
+
+        p = strchr(a, '@');
+        if (!p)
+                p = strrchr(a, '.');
+
+        q = strchr(b, '@');
+        if (!q)
+                q = strrchr(b, '.');
+
+        assert(p);
+        assert(q);
+
+        return memcmp_nn(a, p - a, b, q - b) == 0;
+}

src/basic/unit-name.h

@@ -62,3 +62,5 @@ static inline int unit_name_mangle(const char *name, UnitNameMangle flags, char
 int slice_build_parent_slice(const char *slice, char **ret);
 int slice_build_subslice(const char *slice, const char *name, char **subslice);
 bool slice_name_is_valid(const char *name);
+
+bool unit_name_prefix_equal(const char *a, const char *b);