v2api: fix Mkdir crash when using plaintextnames

internal/fusefrontend/node_dir_ops.go

@@ -68,11 +68,21 @@ func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.En
 	if rn.args.PreserveOwner {
 		caller, _ = fuse.FromContext(ctx)
 	}
+
+	var st syscall.Stat_t
+
 	if rn.args.PlaintextNames {
 		err = syscallcompat.MkdiratUser(dirfd, cName, mode, caller)
+		if err != nil {
 			return nil, fs.ToErrno(err)
 		}
-
+		var ust unix.Stat_t
+		err = syscallcompat.Fstatat(dirfd, cName, &ust, unix.AT_SYMLINK_NOFOLLOW)
+		if err != nil {
+			return nil, fs.ToErrno(err)
+		}
+		st = syscallcompat.Unix2syscall(ust)
+	} else {
 		// We need write and execute permissions to create gocryptfs.diriv.
 		// Also, we need read permissions to open the directory (to avoid
 		// race-conditions between getting and setting the mode).
@@ -108,17 +118,13 @@ func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.En
 		}
 		defer syscall.Close(fd)
 
-	// Get unique inode number
-	var st syscall.Stat_t
 		err = syscall.Fstat(fd, &st)
 		if err != nil {
 			tlog.Warn.Printf("Mkdir %q: Fstat failed: %v", cName, err)
 			return nil, fs.ToErrno(err)
 		}
-	// Create child node
-	ch := n.newChild(ctx, &st, out)
 
-	// Set mode
+		// Fix permissions
 		if origMode != mode {
 			// Preserve SGID bit if it was set due to inheritance.
 			origMode = uint32(st.Mode&^0777) | origMode
@@ -127,6 +133,10 @@ func (n *Node) Mkdir(ctx context.Context, name string, mode uint32, out *fuse.En
 				tlog.Warn.Printf("Mkdir %q: Fchmod %#o -> %#o failed: %v", cName, mode, origMode, err)
 			}
 		}
+	}
+
+	// Create child node
+	ch := n.newChild(ctx, &st, out)
 
 	return ch, 0
 }

tests/test_helpers/helpers.go

@@ -280,7 +280,7 @@ func TestRename(t *testing.T, plainDir string) {
 	}
 	err = syscall.Rename(file1, file2)
 	if err != nil {
-		t.Error(err)
+		t.Errorf("Rename: %v", err)
 		return
 	}
 	syscall.Unlink(file2)