memmod: do not use IsBadReadPtr

It should be enough to check for the trailing zero name.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

tun/wintun/memmod/memmod_windows.go

@@ -312,7 +312,7 @@ func (module *Module) buildImportTable() error {
 
 	module.modules = make([]windows.Handle, 0, 16)
 	importDesc := (*IMAGE_IMPORT_DESCRIPTOR)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
-	for !isBadReadPtr(uintptr(unsafe.Pointer(importDesc)), unsafe.Sizeof(*importDesc)) && importDesc.Name != 0 {
+	for importDesc.Name != 0 {
 		handle, err := windows.LoadLibraryEx(windows.BytePtrToString((*byte)(a2p(module.codeBase+uintptr(importDesc.Name)))), 0, windows.LOAD_LIBRARY_SEARCH_SYSTEM32)
 		if err != nil {
 			return fmt.Errorf("Error loading module: %w", err)

tun/wintun/memmod/mksyscall.go

@@ -1,8 +0,0 @@
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
- */
-
-package memmod
-
-//go:generate go run golang.org/x/sys/windows/mkwinsyscall -output zsyscall_windows.go syscall_windows.go

tun/wintun/memmod/syscall_windows.go

@@ -324,8 +324,6 @@ const (
 	DLL_PROCESS_DETACH = 0
 )
 
-//sys	isBadReadPtr(addr uintptr, ucb uintptr) (ret bool) = kernel32.IsBadReadPtr
-
 type SYSTEM_INFO struct {
 	ProcessorArchitecture     uint16
 	Reserved                  uint16

tun/wintun/memmod/zsyscall_windows.go

@@ -1,50 +0,0 @@
-// Code generated by 'go generate'; DO NOT EDIT.
-
-package memmod
-
-import (
-	"syscall"
-	"unsafe"
-
-	"golang.org/x/sys/windows"
-)
-
-var _ unsafe.Pointer
-
-// Do the interface allocations only once for common
-// Errno values.
-const (
-	errnoERROR_IO_PENDING = 997
-)
-
-var (
-	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
-	errERROR_EINVAL     error = syscall.EINVAL
-)
-
-// errnoErr returns common boxed Errno values, to prevent
-// allocations at runtime.
-func errnoErr(e syscall.Errno) error {
-	switch e {
-	case 0:
-		return errERROR_EINVAL
-	case errnoERROR_IO_PENDING:
-		return errERROR_IO_PENDING
-	}
-	// TODO: add more here, after collecting data on the common
-	// error values see on Windows. (perhaps when running
-	// all.bat?)
-	return e
-}
-
-var (
-	modkernel32 = windows.NewLazySystemDLL("kernel32.dll")
-
-	procIsBadReadPtr = modkernel32.NewProc("IsBadReadPtr")
-)
-
-func isBadReadPtr(addr uintptr, ucb uintptr) (ret bool) {
-	r0, _, _ := syscall.Syscall(procIsBadReadPtr.Addr(), 2, uintptr(addr), uintptr(ucb), 0)
-	ret = r0 != 0
-	return
-}