Fixed GH-12564: The negative fiber.stack_size setting leads to crash

Author: dstogov

Zend/tests/fibers/negative_stack_size.phpt

@@ -0,0 +1,16 @@
+--TEST--
+fiber.stack_size must be a positive number
+--FILE--
+<?php
+ini_set("fiber.stack_size","-1");
+$fiber = new Fiber(function() {});
+try {
+    $fiber->start();
+} catch (Throwable $e) {
+	echo "Exception: " . $e->getMessage()."\n";
+}
+?>
+DONE
+--EXPECTF--
+Warning: fiber.stack_size must be a positive number in %snegative_stack_size.php on line 2
+DONE

Zend/zend.c

@@ -177,7 +177,12 @@ static ZEND_INI_MH(OnSetExceptionStringParamMaxLen) /* {{{ */
 static ZEND_INI_MH(OnUpdateFiberStackSize) /* {{{ */
 {
 	if (new_value) {
-		EG(fiber_stack_size) = zend_atol(ZSTR_VAL(new_value), ZSTR_LEN(new_value));
+		zend_long tmp = zend_atol(ZSTR_VAL(new_value), ZSTR_LEN(new_value));
+		if (tmp < 0) {
+			zend_error(E_WARNING, "fiber.stack_size must be a positive number");
+			return FAILURE;
+		}
+		EG(fiber_stack_size) = tmp;
 	} else {
 		EG(fiber_stack_size) = ZEND_FIBER_DEFAULT_C_STACK_SIZE;
 	}