Merge branch 'PHP-8.0'

* PHP-8.0:
  Fixed bug #81070

Author: nikic

Zend/tests/bug81070.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Bug #81070	Setting memory limit to below current usage
+--FILE--
+<?php
+$a = str_repeat("0", 5 * 1024 * 1024);
+ini_set("memory_limit", "3M");
+?>
+--EXPECTF--
+Warning: Failed to set memory limit to 3145728 bytes (Current memory usage is %d bytes) in %s on line %d

Zend/zend_alloc.c

@@ -2658,11 +2658,24 @@ ZEND_API char* ZEND_FASTCALL zend_strndup(const char *s, size_t length)
 	return p;
 }
 
+ZEND_API zend_result zend_set_memory_limit_ex(size_t memory_limit)
+{
+#if ZEND_MM_LIMIT
+	if (memory_limit < ZEND_MM_CHUNK_SIZE) {
+		memory_limit = ZEND_MM_CHUNK_SIZE;
+	}
+	if (UNEXPECTED(memory_limit < AG(mm_heap)->real_size)) {
+		return FAILURE;
+	}
+	AG(mm_heap)->limit = memory_limit;
+#endif
+	return SUCCESS;
+}
 
 ZEND_API void zend_set_memory_limit(size_t memory_limit)
 {
 #if ZEND_MM_LIMIT
-	AG(mm_heap)->limit = (memory_limit >= ZEND_MM_CHUNK_SIZE) ? memory_limit : ZEND_MM_CHUNK_SIZE;
+	AG(mm_heap)->limit = memory_limit >= ZEND_MM_CHUNK_SIZE ? memory_limit : ZEND_MM_CHUNK_SIZE;
 #endif
 }
 

Zend/zend_alloc.h

@@ -220,6 +220,7 @@ ZEND_API void * __zend_realloc(void *p, size_t len) ZEND_ATTRIBUTE_ALLOC_SIZE(2)
 #define pestrdup_rel(s, persistent) ((persistent)?strdup(s):estrdup_rel(s))
 
 ZEND_API void zend_set_memory_limit(size_t memory_limit);
+ZEND_API zend_result zend_set_memory_limit_ex(size_t memory_limit);
 
 ZEND_API void start_memory_manager(void);
 ZEND_API void shutdown_memory_manager(bool silent, bool full_shutdown);

main/main.c

@@ -266,12 +266,17 @@ static PHP_INI_MH(OnSetSerializePrecision)
 /* {{{ PHP_INI_MH */
 static PHP_INI_MH(OnChangeMemoryLimit)
 {
+	size_t value;
 	if (new_value) {
-		PG(memory_limit) = zend_atol(ZSTR_VAL(new_value), ZSTR_LEN(new_value));
+		value = zend_atol(ZSTR_VAL(new_value), ZSTR_LEN(new_value));
 	} else {
-		PG(memory_limit) = Z_L(1)<<30;		/* effectively, no limit */
+		value = Z_L(1)<<30;		/* effectively, no limit */
 	}
-	zend_set_memory_limit(PG(memory_limit));
+	if (zend_set_memory_limit_ex(value) == FAILURE) {
+		zend_error(E_WARNING, "Failed to set memory limit to %zd bytes (Current memory usage is %zd bytes)", value, zend_memory_usage(true));
+		return FAILURE;
+	}
+	PG(memory_limit) = value;
 	return SUCCESS;
 }
 /* }}} */