os: support Stat and LStat for CON device on Windows

\\.\con and CON need to be opened with GENERIC_READ access, else
CreateFile will fail with ERROR_INVALID_PARAMETER.

Special-case ERROR_INVALID_PARAMETER in os.[L]Stat so it retries with
GENERIC_READ access.

Fixes #34900.

Change-Id: I5010e736d0189c8ada4fc0eca98d71a438c41426
Reviewed-on: https://go-review.googlesource.com/c/go/+/560755
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: David Chase <drchase@google.com>

src/os/stat_test.go

@@ -9,18 +9,25 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
 )
 
+type testStatAndLstatParams struct {
+	isLink     bool
+	statCheck  func(*testing.T, string, fs.FileInfo)
+	lstatCheck func(*testing.T, string, fs.FileInfo)
+}
+
 // testStatAndLstat verifies that all os.Stat, os.Lstat os.File.Stat and os.Readdir work.
-func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCheck func(*testing.T, string, fs.FileInfo)) {
+func testStatAndLstat(t *testing.T, path string, params testStatAndLstatParams) {
 	// test os.Stat
 	sfi, err := os.Stat(path)
 	if err != nil {
 		t.Error(err)
 		return
 	}
-	statCheck(t, path, sfi)
+	params.statCheck(t, path, sfi)
 
 	// test os.Lstat
 	lsfi, err := os.Lstat(path)
@@ -28,9 +35,9 @@ func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCh
 		t.Error(err)
 		return
 	}
-	lstatCheck(t, path, lsfi)
+	params.lstatCheck(t, path, lsfi)
 
-	if isLink {
+	if params.isLink {
 		if os.SameFile(sfi, lsfi) {
 			t.Errorf("stat and lstat of %q should not be the same", path)
 		}
@@ -53,13 +60,13 @@ func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCh
 		t.Error(err)
 		return
 	}
-	statCheck(t, path, sfi2)
+	params.statCheck(t, path, sfi2)
 
 	if !os.SameFile(sfi, sfi2) {
 		t.Errorf("stat of open %q file and stat of %q should be the same", path, path)
 	}
 
-	if isLink {
+	if params.isLink {
 		if os.SameFile(sfi2, lsfi) {
 			t.Errorf("stat of opened %q file and lstat of %q should not be the same", path, path)
 		}
@@ -69,12 +76,13 @@ func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCh
 		}
 	}
 
-	// test fs.FileInfo returned by os.Readdir
-	if len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
-		// skip os.Readdir test of directories with slash at the end
+	parentdir, base := filepath.Split(path)
+	if parentdir == "" || base == "" {
+		// skip os.Readdir test of files without directory or file name component,
+		// such as directories with slash at the end or Windows device names.
 		return
 	}
-	parentdir := filepath.Dir(path)
+
 	parent, err := os.Open(parentdir)
 	if err != nil {
 		t.Error(err)
@@ -88,7 +96,6 @@ func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCh
 		return
 	}
 	var lsfi2 fs.FileInfo
-	base := filepath.Base(path)
 	for _, fi2 := range fis {
 		if fi2.Name() == base {
 			lsfi2 = fi2
@@ -99,7 +106,7 @@ func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCh
 		t.Errorf("failed to find %q in its parent", path)
 		return
 	}
-	lstatCheck(t, path, lsfi2)
+	params.lstatCheck(t, path, lsfi2)
 
 	if !os.SameFile(lsfi, lsfi2) {
 		t.Errorf("lstat of %q file in %q directory and %q should be the same", lsfi2.Name(), parentdir, path)
@@ -140,19 +147,34 @@ func testIsFile(t *testing.T, path string, fi fs.FileInfo) {
 }
 
 func testDirStats(t *testing.T, path string) {
-	testStatAndLstat(t, path, false, testIsDir, testIsDir)
+	params := testStatAndLstatParams{
+		isLink:     false,
+		statCheck:  testIsDir,
+		lstatCheck: testIsDir,
+	}
+	testStatAndLstat(t, path, params)
 }
 
 func testFileStats(t *testing.T, path string) {
-	testStatAndLstat(t, path, false, testIsFile, testIsFile)
+	params := testStatAndLstatParams{
+		isLink:     false,
+		statCheck:  testIsFile,
+		lstatCheck: testIsFile,
+	}
+	testStatAndLstat(t, path, params)
 }
 
 func testSymlinkStats(t *testing.T, path string, isdir bool) {
-	if isdir {
-		testStatAndLstat(t, path, true, testIsDir, testIsSymlink)
-	} else {
-		testStatAndLstat(t, path, true, testIsFile, testIsSymlink)
+	params := testStatAndLstatParams{
+		isLink:     true,
+		lstatCheck: testIsSymlink,
 	}
+	if isdir {
+		params.statCheck = testIsDir
+	} else {
+		params.statCheck = testIsFile
+	}
+	testStatAndLstat(t, path, params)
 }
 
 func testSymlinkSameFile(t *testing.T, path, link string) {
@@ -294,3 +316,24 @@ func TestSymlinkWithTrailingSlash(t *testing.T) {
 		t.Errorf("os.Stat(%q) and os.Stat(%q) are not the same file", dir, dirlinkWithSlash)
 	}
 }
+
+func TestStatConsole(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("skipping on non-Windows")
+	}
+	t.Parallel()
+	consoleNames := []string{
+		"CONIN$",
+		"CONOUT$",
+		"CON",
+	}
+	for _, name := range consoleNames {
+		params := testStatAndLstatParams{
+			isLink:     false,
+			statCheck:  testIsFile,
+			lstatCheck: testIsFile,
+		}
+		testStatAndLstat(t, name, params)
+		testStatAndLstat(t, `\\.\`+name, params)
+	}
+}

src/os/stat_windows.go

@@ -74,7 +74,16 @@ func stat(funcname, name string, followSurrogates bool) (FileInfo, error) {
 	// save information about the link target.
 	// Set FILE_FLAG_BACKUP_SEMANTICS so that CreateFile will create the handle
 	// even if name refers to a directory.
-	h, err := syscall.CreateFile(namep, 0, 0, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS|syscall.FILE_FLAG_OPEN_REPARSE_POINT, 0)
+	var flags uint32 = syscall.FILE_FLAG_BACKUP_SEMANTICS | syscall.FILE_FLAG_OPEN_REPARSE_POINT
+	h, err := syscall.CreateFile(namep, 0, 0, nil, syscall.OPEN_EXISTING, flags, 0)
+
+	if err == windows.ERROR_INVALID_PARAMETER {
+		// Console handles, like "\\.\con", require generic read access. See
+		// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew#consoles.
+		// We haven't set it previously because it is normally not required
+		// to read attributes and some files may not allow it.
+		h, err = syscall.CreateFile(namep, syscall.GENERIC_READ, 0, nil, syscall.OPEN_EXISTING, flags, 0)
+	}
 	if err != nil {
 		// Since CreateFile failed, we can't determine whether name refers to a
 		// name surrogate, or some other kind of reparse point. Since we can't return a