Fix infinite recursion on deprecated attribute evaluation

Fixes phpGH-17711
Fixes phpGH-18022
Closes phpGH-17712

Author: iluuu1994

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.4.7
 
+- Core:
+  . Fixed bug GH-17711 and GH-18022 (Infinite recursion on deprecated attribute
+    evaluation). (ilutov)
 
 27 Mar 2025, PHP 8.4.6RC1
 

Zend/tests/attributes/deprecated/class_constants/gh17711.phpt

@@ -0,0 +1,28 @@
+--TEST--
+GH-17711: Infinite recursion through deprecated class constants self-referencing through deprecation message
+--FILE--
+<?php
+
+class C {
+    #[\Deprecated(self::C)]
+    const C = TEST;
+}
+
+const TEST = 'Message';
+var_dump(C::C);
+
+class D {
+    #[\Deprecated(Alias::C)]
+    const C = 'test';
+}
+
+class_alias('D', 'Alias');
+var_dump(D::C);
+
+?>
+--EXPECTF--
+Deprecated: Constant C::C is deprecated, Message in %s on line %d
+string(7) "Message"
+
+Deprecated: Constant D::C is deprecated, test in %s on line %d
+string(4) "test"

Zend/zend_API.c

@@ -1439,7 +1439,7 @@ ZEND_API HashTable *zend_separate_class_constants_table(zend_class_entry *class_
 
 	ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&class_type->constants_table, key, c) {
 		if (c->ce == class_type) {
-			if (Z_TYPE(c->value) == IS_CONSTANT_AST) {
+			if (Z_TYPE(c->value) == IS_CONSTANT_AST || (ZEND_CLASS_CONST_FLAGS(c) & ZEND_ACC_DEPRECATED)) {
 				new_c = zend_arena_alloc(&CG(arena), sizeof(zend_class_constant));
 				memcpy(new_c, c, sizeof(zend_class_constant));
 				c = new_c;

Zend/zend_compile.c

@@ -8822,6 +8822,10 @@ static void zend_compile_class_const_decl(zend_ast *ast, uint32_t flags, zend_as
 
 			if (deprecated) {
 				ZEND_CLASS_CONST_FLAGS(c) |= ZEND_ACC_DEPRECATED;
+				/* For deprecated constants, we need to flag the zval for recursion
+				 * detection. Make sure the zval is separated out of shm. */
+				ce->ce_flags |= ZEND_ACC_HAS_AST_CONSTANTS;
+				ce->ce_flags &= ~ZEND_ACC_CONSTANTS_UPDATED;
 			}
 		}
 	}

Zend/zend_constants.c

@@ -353,8 +353,10 @@ ZEND_API zval *zend_get_class_constant_ex(zend_string *class_name, zend_string *
 			}
 
 			if (UNEXPECTED(ZEND_CLASS_CONST_FLAGS(c) & ZEND_ACC_DEPRECATED)) {
-				if ((flags & ZEND_FETCH_CLASS_SILENT) == 0) {
+				if ((flags & ZEND_FETCH_CLASS_SILENT) == 0 && !CONST_IS_RECURSIVE(c)) {
+					CONST_PROTECT_RECURSION(c);
 					zend_deprecated_class_constant(c, constant_name);
+					CONST_UNPROTECT_RECURSION(c);
 					if (EG(exception)) {
 						goto failure;
 					}

Zend/zend_constants.h

@@ -27,6 +27,17 @@
 #define CONST_NO_FILE_CACHE		(1<<1)				/* Can't be saved in file cache */
 #define CONST_DEPRECATED		(1<<2)				/* Deprecated */
 #define CONST_OWNED				(1<<3)				/* constant should be destroyed together with class */
+#define CONST_RECURSIVE			(1<<4)				/* Recursion protection for constant evaluation */
+
+#define CONST_IS_RECURSIVE(c) (Z_CONSTANT_FLAGS((c)->value) & CONST_RECURSIVE)
+#define CONST_PROTECT_RECURSION(c) \
+	do { \
+		Z_CONSTANT_FLAGS((c)->value) |= CONST_RECURSIVE; \
+	} while (0)
+#define CONST_UNPROTECT_RECURSION(c) \
+	do { \
+		Z_CONSTANT_FLAGS((c)->value) &= ~CONST_RECURSIVE; \
+	} while (0)
 
 #define	PHP_USER_CONSTANT   0x7fffff /* a constant defined in user space */
 

Zend/zend_vm_def.h

@@ -6094,8 +6094,10 @@ ZEND_VM_HANDLER(181, ZEND_FETCH_CLASS_CONSTANT, VAR|CONST|UNUSED|CLASS_FETCH, CO
 			}
 
 			bool is_constant_deprecated = ZEND_CLASS_CONST_FLAGS(c) & ZEND_ACC_DEPRECATED;
-			if (UNEXPECTED(is_constant_deprecated)) {
+			if (UNEXPECTED(is_constant_deprecated) && !CONST_IS_RECURSIVE(c)) {
+				CONST_PROTECT_RECURSION(c);
 				zend_deprecated_class_constant(c, constant_name);
+				CONST_UNPROTECT_RECURSION(c);
 
 				if (EG(exception)) {
 					ZVAL_UNDEF(EX_VAR(opline->result.var));

Zend/zend_vm_execute.h

@@ -3800,6 +3800,11 @@ static bool preload_try_resolve_constants(zend_class_entry *ce)
 		ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&ce->constants_table, key, c) {
 			val = &c->value;
 			if (Z_TYPE_P(val) == IS_CONSTANT_AST) {
+				/* For deprecated constants, we need to flag the zval for recursion
+				 * detection. Make sure the zval is separated out of shm. */
+				if (ZEND_CLASS_CONST_FLAGS(c) & ZEND_ACC_DEPRECATED) {
+					ok = false;
+				}
 				if (EXPECTED(zend_update_class_constant(c, key, c->ce) == SUCCESS)) {
 					was_changed = changed = true;
 				} else {