Limit stack usage

Zend/Zend.m4

@@ -146,7 +146,52 @@ _LT_AC_TRY_DLOPEN_SELF([
 ])
 
 dnl Checks for library functions.
-AC_CHECK_FUNCS(getpid kill sigsetjmp)
+AC_CHECK_FUNCS(getpid kill sigsetjmp pthread_getattr_np)
+
+dnl Test whether the target system has __libc_stack_end
+AC_MSG_CHECKING(whether libc has __libc_stack_end)
+
+AC_RUN_IFELSE([AC_LANG_SOURCE([[
+extern void* __libc_stack_end;
+int main()
+{
+  void *test = __libc_stack_end;
+  return 0;
+}
+]])], [
+  AC_DEFINE([HAVE_LIBC_STACK_END], 1, [Define if the target system has __libc_stack_end])
+  AC_MSG_RESULT(yes)
+], [
+  AC_MSG_RESULT(no)
+], [
+  AC_MSG_RESULT(no)
+])
+
+dnl Test whether the stack grows downwards
+dnl Assumes stack is contiguous
+AC_MSG_CHECKING(whether the stack grows downwards)
+
+AC_RUN_IFELSE([AC_LANG_SOURCE([[
+int stack_grows_downwards(void *arg) {
+    void *local;
+    if (arg == (void*)0) {
+        return stack_grows_downwards(&local);
+    }
+    return (void*)&local < arg;
+}
+
+int main() {
+    return stack_grows_downwards((void*)0) ? 0 : 1;
+}
+]])], [
+  AC_DEFINE([ZEND_STACK_GROWS_DOWNWARDS], 1, [Define if the stack grows downwards])
+  AC_DEFINE([ZEND_CHECK_STACK_LIMIT], 1, [Define if checking the stack limit is supported])
+  AC_MSG_RESULT(yes)
+], [
+  AC_MSG_RESULT(no)
+], [
+  AC_MSG_RESULT(no)
+])
 
 ZEND_CHECK_FLOAT_PRECISION
 

Zend/tests/stack_limit_001.phpt

@@ -0,0 +1,46 @@
+--TEST--
+Stack limit 001
+--FILE--
+<?php
+
+class Test1 {
+    public function __destruct() {
+        new Test1;
+    }
+}
+
+class Test2 {
+    public function __clone() {
+        clone $this;
+    }
+}
+
+function replace() {
+    return preg_replace_callback('#.#', function () {
+        return replace();
+    }, 'x');
+}
+
+try {
+    new Test1;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+try {
+    clone new Test2;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+try {
+    replace();
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECTF--
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?

Zend/tests/stack_limit_002.phpt

@@ -0,0 +1,50 @@
+--TEST--
+Stack limit 002
+--FILE--
+<?php
+
+class Test1 {
+    public function __destruct() {
+        new Test1;
+    }
+}
+
+class Test2 {
+    public function __clone() {
+        clone $this;
+    }
+}
+
+function replace() {
+    return preg_replace_callback('#.#', function () {
+        return replace();
+    }, 'x');
+}
+
+$fiber = new Fiber(function (): void {
+    try {
+        new Test1;
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+
+    try {
+        clone new Test2;
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+
+    try {
+        replace();
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?

Zend/tests/stack_limit_003.phpt

@@ -0,0 +1,48 @@
+--TEST--
+Stack limit 003
+--INI--
+zend.max_allowed_stack_size=40K
+--FILE--
+<?php
+
+class Test1 {
+    public function __destruct() {
+        new Test1;
+    }
+}
+
+class Test2 {
+    public function __clone() {
+        clone $this;
+    }
+}
+
+function replace() {
+    return preg_replace_callback('#.#', function () {
+        return replace();
+    }, 'x');
+}
+
+try {
+    new Test1;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+try {
+    clone new Test2;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+try {
+    replace();
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECTF--
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?
+Maximum call stack size reached. Infinite recursion?

Zend/tests/stack_limit_004.phpt

@@ -0,0 +1,36 @@
+--TEST--
+Stack limit 004
+--FILE--
+<?php
+
+class Test1 {
+    public function __destruct() {
+        new Test1;
+    }
+}
+
+$callback = function (): int {
+    try {
+        new Test1;
+    } catch (Error $e) {
+        return count($e->getTrace());
+    }
+
+    throw new \Exception();
+};
+
+ini_set('fiber.stack_size', '100K');
+$fiber = new Fiber($callback);
+$fiber->start();
+$depth1 = $fiber->getReturn();
+
+ini_set('fiber.stack_size', '50K');
+$fiber = new Fiber($callback);
+$fiber->start();
+$depth2 = $fiber->getReturn();
+
+var_dump($depth1 > $depth2);
+
+?>
+--EXPECT--
+bool(true)

Zend/tests/stack_limit_005.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Stack limit 005
+--INI--
+zend.max_allowed_stack_size=50K
+--FILE--
+<?php
+
+$test
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+    ->f()->f()->f()->f()->f()->f()->f()->f()->f()->f()
+;
+
+--EXPECTF--
+Fatal error: Maximum call stack size reached. Try splitting expression in %s on line 3

Zend/zend.c

@@ -35,6 +35,7 @@
 #include "zend_attributes.h"
 #include "zend_observer.h"
 #include "zend_fibers.h"
+#include "zend_call_stack.h"
 #include "Optimizer/zend_optimizer.h"
 
 static size_t global_map_ptr_last = 0;
@@ -173,13 +174,50 @@ static ZEND_INI_MH(OnSetExceptionStringParamMaxLen) /* {{{ */
 }
 /* }}} */
 
+#ifdef ZEND_CHECK_STACK_LIMIT
+static ZEND_INI_MH(OnUpdateMaxAllowedStackSize) /* {{{ */
+{
+	EG(max_allowed_stack_size) = (size_t) zend_ini_parse_uquantity_warn(new_value, entry->name);
+	if (EG(max_allowed_stack_size)) {
+		return SUCCESS;
+	}
+
+	/* Don't detect the stack size if we can't detect the stack base */
+	if (zend_call_stack_base() != NULL) {
+		size_t limit = zend_call_stack_limit();
+		if (limit != 0) {
+			EG(max_allowed_stack_size) = limit;
+			return SUCCESS;
+		}
+	}
+
+	EG(max_allowed_stack_size) = 2 * 1024 * 1024;
+
+	return SUCCESS;
+}
+/* }}} */
+
+static ZEND_INI_MH(OnUpdateReservedStackSize) /* {{{ */
+{
+	EG(reserved_stack_size) = (size_t) zend_ini_parse_uquantity_warn(new_value, entry->name);
+
+	return SUCCESS;
+}
+/* }}} */
+#endif /* ZEND_CHECK_STACK_LIMIT */
+
 static ZEND_INI_MH(OnUpdateFiberStackSize) /* {{{ */
 {
+	zend_long size;
+
 	if (new_value) {
-		EG(fiber_stack_size) = zend_ini_parse_quantity_warn(new_value, entry->name);
+		size = zend_ini_parse_quantity_warn(new_value, entry->name);
 	} else {
-		EG(fiber_stack_size) = ZEND_FIBER_DEFAULT_C_STACK_SIZE;
+		size = ZEND_FIBER_DEFAULT_C_STACK_SIZE;
 	}
+
+	EG(fiber_stack_size) = size;
+
 	return SUCCESS;
 }
 /* }}} */
@@ -203,6 +241,12 @@ ZEND_INI_BEGIN()
 	STD_ZEND_INI_BOOLEAN("zend.exception_ignore_args",	"0",	ZEND_INI_ALL,		OnUpdateBool, exception_ignore_args, zend_executor_globals, executor_globals)
 	STD_ZEND_INI_ENTRY("zend.exception_string_param_max_len",	"15",	ZEND_INI_ALL,	OnSetExceptionStringParamMaxLen,	exception_string_param_max_len,		zend_executor_globals,	executor_globals)
 	STD_ZEND_INI_ENTRY("fiber.stack_size",		NULL,			ZEND_INI_ALL,		OnUpdateFiberStackSize,		fiber_stack_size,	zend_executor_globals, 		executor_globals)
+#ifdef ZEND_CHECK_STACK_LIMIT
+	/* The maximum allowed call stack size. 0: auto detect. For fibers, this is fiber.stack_size. */
+	STD_ZEND_INI_ENTRY("zend.max_allowed_stack_size",	"0",	ZEND_INI_PERDIR,	OnUpdateMaxAllowedStackSize,	max_allowed_stack_size,		zend_executor_globals,	executor_globals)
+	/* Substracted from the max allowed stack size, as a buffer, when checking for overflow. */
+	STD_ZEND_INI_ENTRY("zend.reserved_stack_size",	"12288",	ZEND_INI_PERDIR,	OnUpdateReservedStackSize,	reserved_stack_size,		zend_executor_globals,	executor_globals)
+#endif
 
 ZEND_INI_END()