Create a correctly-sized slice to proxy *uint16

Fixes the below issue seen in the containerd test suite.
```
fatal error: checkptr: converted pointer straddles multiple allocations
```

Also adds `-gcflags=all=-d=checkptr` to all the test runs on CI, to
avoid this regressing in future. This requires testing with Go 1.14 or
newer, so CI now runs on Go 1.15, as Go 1.14 did not recommend using
checkptr on Windows.

And _that_ requires the Visual Studio 2019 build image on AppVeyor.

Signed-off-by: Paul "TBBle" Hampson <[email protected]>

appveyor.yml

@@ -1,14 +1,14 @@
 version: 0.1.{build}
 
-image: Visual Studio 2017
+image: Visual Studio 2019
 
 clone_folder: c:\gopath\src\github.com\Microsoft\hcsshim
 
 environment:
   GOPATH: c:\gopath
   PATH: "%GOPATH%\\bin;C:\\gometalinter-2.0.12-windows-amd64;%PATH%"
 
-stack: go 1.13.4
+stack: go 1.15
 
 build_script:
   - appveyor DownloadFile https://github.com/alecthomas/gometalinter/releases/download/v2.0.12/gometalinter-2.0.12-windows-amd64.zip
@@ -19,16 +19,16 @@ build_script:
   - go build ./cmd/tar2ext4
   - go build ./cmd/wclayer
   - go build ./cmd/device-util
-  - go build ./internal/tools/grantvmgroupaccess 
+  - go build ./internal/tools/grantvmgroupaccess
   - go build ./internal/tools/uvmboot
   - go build ./internal/tools/zapdir
-  - go test -v ./... -tags admin
+  - go test -gcflags=all=-d=checkptr -v ./... -tags admin
   - cd test
-  - go test -v ./internal -tags admin
-  - go test -c ./containerd-shim-runhcs-v1/ -tags functional
-  - go test -c ./cri-containerd/ -tags functional
-  - go test -c ./functional/ -tags functional
-  - go test -c ./runhcs/ -tags functional
+  - go test -gcflags=all=-d=checkptr -v ./internal -tags admin
+  - go test -gcflags=all=-d=checkptr -c ./containerd-shim-runhcs-v1/ -tags functional
+  - go test -gcflags=all=-d=checkptr -c ./cri-containerd/ -tags functional
+  - go test -gcflags=all=-d=checkptr -c ./functional/ -tags functional
+  - go test -gcflags=all=-d=checkptr -c ./runhcs/ -tags functional
   - go build -o sample-logging-driver.exe ./cri-containerd/helpers/log.go
 
 artifacts:

internal/safefile/safeopen.go

@@ -177,7 +177,7 @@ func LinkRelative(oldname string, oldroot *os.File, newname string, newroot *os.
 	linkinfo := (*winapi.FileLinkInformation)(unsafe.Pointer(linkinfoBuffer))
 	linkinfo.RootDirectory = parent.Fd()
 	linkinfo.FileNameLength = uint32(len(newbase16) * 2)
-	copy((*[32768]uint16)(unsafe.Pointer(&linkinfo.FileName[0]))[:], newbase16)
+	copy(winapi.Uint16BufferToSlice(&linkinfo.FileName[0], len(newbase16)), newbase16)
 
 	var iosb winapi.IOStatusBlock
 	status := winapi.NtSetInformationFile(

internal/winapi/utils.go

@@ -2,11 +2,23 @@ package winapi
 
 import (
 	"errors"
+	"reflect"
 	"syscall"
 	"unicode/utf16"
 	"unsafe"
 )
 
+// Uint16BufferToSlice wraps a uint16 pointer-and-length into a slice
+// for easier interop with Go APIs
+func Uint16BufferToSlice(buffer *uint16, bufferLength int) (result []uint16) {
+	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&result))
+	hdr.Data = uintptr(unsafe.Pointer(buffer))
+	hdr.Cap = bufferLength
+	hdr.Len = bufferLength
+
+	return
+}
+
 type UnicodeString struct {
 	Length        uint16
 	MaximumLength uint16
@@ -15,12 +27,9 @@ type UnicodeString struct {
 
 //String converts a UnicodeString to a golang string
 func (uni UnicodeString) String() string {
-	p := (*[0xffff]uint16)(unsafe.Pointer(uni.Buffer))
-
 	// UnicodeString is not guaranteed to be null terminated, therefore
 	// use the UnicodeString's Length field
-	lengthInChars := uni.Length / 2
-	return syscall.UTF16ToString(p[:lengthInChars])
+	return syscall.UTF16ToString(Uint16BufferToSlice(uni.Buffer, int(uni.Length/2)))
 }
 
 // NewUnicodeString allocates a new UnicodeString and copies `s` into
@@ -36,7 +45,7 @@ func NewUnicodeString(s string) (*UnicodeString, error) {
 		MaximumLength: uint16(len(ws) * 2),
 		Buffer:        &make([]uint16, len(ws))[0],
 	}
-	copy((*[32768]uint16)(unsafe.Pointer(uni.Buffer))[:], ws)
+	copy(Uint16BufferToSlice(uni.Buffer, len(ws)), ws)
 	return uni, nil
 }
 

internal/winapi/winapi_test.go

@@ -3,12 +3,10 @@ package winapi
 import (
 	"testing"
 	"unicode/utf16"
-	"unsafe"
 )
 
-func wideStringsEqual(target, actual []uint16, actualLengthInBytes int) bool {
-	actualLength := actualLengthInBytes / 2
-	if len(target) != actualLength {
+func wideStringsEqual(target, actual []uint16) bool {
+	if len(target) != len(actual) {
 		return false
 	}
 
@@ -38,13 +36,10 @@ func TestNewUnicodeString(t *testing.T) {
 			t.Fatalf("Expected new Unicode String maximum length to be %d for target string %s, got %d instead", targetLength, target, uni.MaximumLength)
 		}
 
-		uniBufferStringAsSlice := (*[32768]uint16)(unsafe.Pointer(uni.Buffer))[:]
+		uniBufferStringAsSlice := Uint16BufferToSlice(uni.Buffer, len(target))
 
-		// since we have to do casting to convert the unicode string's buffer into a uint16 slice
-		// the length of the actual slice will not be the true length of the contents in the unicode buffer
-		// therefore we need to use the unicode string's length field when comparing
-		if !wideStringsEqual(targetWideString, uniBufferStringAsSlice, int(uni.Length)) {
-			t.Fatalf("Expected wide string %v, got %v instead", targetWideString, uniBufferStringAsSlice[:uni.Length])
+		if !wideStringsEqual(targetWideString, uniBufferStringAsSlice) {
+			t.Fatalf("Expected wide string %v, got %v instead", targetWideString, uniBufferStringAsSlice)
 		}
 	}
 }