Fix OSS-Fuzz #427814456

The first warning may trigger an error handler, destroying the operand
and its string. So we need to protect the string in that case.
Care was taken to avoid unnecessary refcounts and to avoid touching the
hot code path.

Closes phpGH-18951.

Author: ndossche

NEWS

@@ -8,6 +8,7 @@ PHP                                                                        NEWS
 - Core:
   . Fixed bug GH-18833 (Use after free with weakmaps dependent on destruction
     order). (Daniil Gentili)
+  . Fix OSS-Fuzz #427814456. (nielsdos)
 
 - Curl:
   . Fix memory leaks when returning refcounted value from curl callback.

Zend/tests/numeric_strings/oss_fuzz_427814456.phpt

@@ -0,0 +1,11 @@
+--TEST--
+OSS-Fuzz #427814456
+--FILE--
+<?php
+set_error_handler(function(){unset($GLOBALS['x']);});
+$x = str_repeat("3e33", random_int(2, 2));
+$x & true;
+echo "Done\n";
+?>
+--EXPECT--
+Done

Zend/zend_operators.c

@@ -401,6 +401,7 @@ static zend_never_inline zend_long ZEND_FASTCALL zendi_try_get_long(const zval *
 				zend_long lval;
 				double dval;
 				bool trailing_data = false;
+				zend_string *op_str = NULL; /* protect against error handlers */
 
 				/* For BC reasons we allow errors so that we can warn on leading numeric string */
 				type = is_numeric_string_ex(Z_STRVAL_P(op), Z_STRLEN_P(op), &lval, &dval,
@@ -410,6 +411,9 @@ static zend_never_inline zend_long ZEND_FASTCALL zendi_try_get_long(const zval *
 					return 0;
 				}
 				if (UNEXPECTED(trailing_data)) {
+					if (type != IS_LONG) {
+						op_str = zend_string_copy(Z_STR_P(op));
+					}
 					zend_error(E_WARNING, "A non-numeric value encountered");
 					if (UNEXPECTED(EG(exception))) {
 						*failed = 1;
@@ -425,11 +429,12 @@ static zend_never_inline zend_long ZEND_FASTCALL zendi_try_get_long(const zval *
 					 */
 					lval = zend_dval_to_lval_cap(dval);
 					if (!zend_is_long_compatible(dval, lval)) {
-						zend_incompatible_string_to_long_error(Z_STR_P(op));
+						zend_incompatible_string_to_long_error(op_str ? op_str : Z_STR_P(op));
 						if (UNEXPECTED(EG(exception))) {
 							*failed = 1;
 						}
 					}
+					zend_tmp_string_release(op_str);
 					return lval;
 				}
 			}