fusefrontend: Don't chown gocryptfs.diriv files.

The current code has a risk of race-conditions, since we pass a path
containing "/" to Fchownat. We could fix this by opening a file descriptor,
however, this does not seem worth the effort. We also don't chown *.name files.

Author: slackner

internal/fusefrontend/fs.go

@@ -5,7 +5,6 @@ package fusefrontend
 
 import (
 	"os"
-	"path/filepath"
 	"sync"
 	"syscall"
 	"time"
@@ -326,19 +325,8 @@ func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context)
 		return fuse.ToStatus(err)
 	}
 	defer syscall.Close(dirfd)
-	code = fuse.ToStatus(syscallcompat.Fchownat(dirfd, cName, int(uid), int(gid), unix.AT_SYMLINK_NOFOLLOW))
-	if !code.Ok() {
-		return code
-	}
-	if !fs.args.PlaintextNames {
-		// When filename encryption is active, every directory contains
-		// a "gocryptfs.diriv" file. This file should also change the owner.
-		// Instead of checking if "cName" is a directory, we just blindly
-		// execute the chown on "cName/gocryptfs.diriv" and ignore errors.
-		dirIVPath := filepath.Join(cName, nametransform.DirIVFilename)
-		syscallcompat.Fchownat(dirfd, dirIVPath, int(uid), int(gid), unix.AT_SYMLINK_NOFOLLOW)
-	}
-	return fuse.OK
+	err = syscallcompat.Fchownat(dirfd, cName, int(uid), int(gid), unix.AT_SYMLINK_NOFOLLOW)
+	return fuse.ToStatus(err)
 }
 
 // Mknod - FUSE call. Create a device file.

internal/fusefrontend/fs_dir.go

@@ -5,7 +5,6 @@ package fusefrontend
 import (
 	"fmt"
 	"io"
-	"path/filepath"
 	"runtime"
 	"syscall"
 
@@ -124,16 +123,11 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
 		err = syscallcompat.Fchownat(dirfd, cName, int(context.Owner.Uid),
 			int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
 		if err != nil {
-			tlog.Warn.Printf("Mkdir %q: Fchownat(1) %d:%d failed: %v", cName, context.Owner.Uid, context.Owner.Gid, err)
+			tlog.Warn.Printf("Mkdir %q: Fchownat %d:%d failed: %v", cName, context.Owner.Uid, context.Owner.Gid, err)
 			// In case of a failure, we don't want to proceed setting more
 			// permissive modes.
 			return fuse.ToStatus(err)
 		}
-		err = syscallcompat.Fchownat(dirfd, filepath.Join(cName, nametransform.DirIVFilename),
-			int(context.Owner.Uid), int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
-		if err != nil {
-			tlog.Warn.Printf("Mkdir %q: Fchownat(2) %d:%d failed: %v", cName, context.Owner.Uid, context.Owner.Gid, err)
-		}
 	}
 	// Set mode
 	if origMode != mode {