syscall: avoid memory corruption in mksyscall_windows.go with *bool parameters

Windows type PBOOL is a pointer to a 4 byte value, where 0 means false
and not-0 means true. That means we should use uint32 here, not bool,
since Go bools can be 1 byte. Since a *bool is never a "real" valid
Windows type, converting on both in and out is probably sufficient,
since *bool shouldn't ever be used as something with significance for
its particular address.

Updates: #34364
Change-Id: I4c1b91cd9a39d91e23dae6f894b9a49f7fba2c0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/196122
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/syscall/mksyscall_windows.go

@@ -117,6 +117,18 @@ func (p *Param) BoolTmpVarCode() string {
 	return fmt.Sprintf(code, tmp, p.Name, tmp, tmp)
 }
 
+// BoolPointerTmpVarCode returns source code for bool temp variable.
+func (p *Param) BoolPointerTmpVarCode() string {
+	const code = `var %s uint32
+	if *%s {
+		%s = 1
+	} else {
+		%s = 0
+	}`
+	tmp := p.tmpVar()
+	return fmt.Sprintf(code, tmp, p.Name, tmp, tmp)
+}
+
 // SliceTmpVarCode returns source code for slice temp variable.
 func (p *Param) SliceTmpVarCode() string {
 	const code = `var %s *%s
@@ -152,6 +164,8 @@ func (p *Param) TmpVarCode() string {
 	switch {
 	case p.Type == "bool":
 		return p.BoolTmpVarCode()
+	case p.Type == "*bool":
+		return p.BoolPointerTmpVarCode()
 	case strings.HasPrefix(p.Type, "[]"):
 		return p.SliceTmpVarCode()
 	default:
@@ -159,6 +173,16 @@ func (p *Param) TmpVarCode() string {
 	}
 }
 
+// TmpVarReadbackCode returns source code for reading back the temp variable into the original variable.
+func (p *Param) TmpVarReadbackCode() string {
+	switch {
+	case p.Type == "*bool":
+		return fmt.Sprintf("*%s = %s != 0", p.Name, p.tmpVar())
+	default:
+		return ""
+	}
+}
+
 // TmpVarHelperCode returns source code for helper's temp variable.
 func (p *Param) TmpVarHelperCode() string {
 	if p.Type != "string" {
@@ -174,6 +198,8 @@ func (p *Param) SyscallArgList() []string {
 	t := p.HelperType()
 	var s string
 	switch {
+	case t == "*bool":
+		s = fmt.Sprintf("unsafe.Pointer(&%s)", p.tmpVar())
 	case t[0] == '*':
 		s = fmt.Sprintf("unsafe.Pointer(%s)", p.Name)
 	case t == "bool":
@@ -876,7 +902,7 @@ func {{.Name}}({{.ParamList}}) {{template "results" .}}{
 
 {{define "funcbody"}}
 func {{.HelperName}}({{.HelperParamList}}) {{template "results" .}}{
-{{template "tmpvars" .}}	{{template "syscall" .}}
+{{template "tmpvars" .}}	{{template "syscall" .}}	{{template "tmpvarsreadback" .}}
 {{template "seterror" .}}{{template "printtrace" .}}	return
 }
 {{end}}
@@ -891,6 +917,9 @@ func {{.HelperName}}({{.HelperParamList}}) {{template "results" .}}{
 
 {{define "syscall"}}{{.Rets.SetReturnValuesCode}}{{.Syscall}}(proc{{.DLLFuncName}}.Addr(), {{.ParamCount}}, {{.SyscallParamList}}){{end}}
 
+{{define "tmpvarsreadback"}}{{range .Params}}{{if .TmpVarReadbackCode}}
+{{.TmpVarReadbackCode}}{{end}}{{end}}{{end}}
+
 {{define "seterror"}}{{if .Rets.SetErrorCode}}	{{.Rets.SetErrorCode}}
 {{end}}{{end}}