reverse: use incrementing inode number for gocryptfs.longname.*.name …

…files

ed0a12b already fixed the kernel side,
now we also want the .name files to NOT appear hardlinked when just
looking at the inode number.

Relates-to: #802

internal/fusefrontend_reverse/virtualnode.go

@@ -86,8 +86,15 @@ func (n *Node) newVirtualMemNode(content []byte, parentStat *syscall.Stat_t, ino
 	// Adjust inode number and size
 	rn := n.rootNode()
 	st := parentStat
-	q := inomap.NewQIno(uint64(st.Dev), inoTag, uint64(st.Ino))
-	st.Ino = rn.inoMap.Translate(q)
+	if inoTag == inoTagNameFile {
+		// No stable mapping for gocryptfs.longname.*.name files, instead use an
+		// incrementing counter. We don't want two of those files to ever have the
+		// same inode number, even for hard-linked files.
+		st.Ino = rn.inoMap.NextSpillIno()
+	} else {
+		q := inomap.NewQIno(uint64(st.Dev), inoTag, uint64(st.Ino))
+		st.Ino = rn.inoMap.Translate(q)
+	}
 	st.Size = int64(len(content))
 	st.Mode = virtualFileMode
 	st.Nlink = 1

tests/reverse/correctness_test.go

@@ -298,6 +298,10 @@ func TestSeekData(t *testing.T) {
 // gocryptfs.longname.*.name of hardlinked files should not appear hardlinked (as the
 // contents are different).
 //
+// This means that
+// 1) They have a different NodeID, hence the kernel knows it's different files
+// 2) They have a different inode number, hence userspace knows they are not hard-linked.
+//
 // https://github.com/rfjakob/gocryptfs/issues/802
 func TestHardlinkedLongname(t *testing.T) {
 	if plaintextnames {
@@ -335,4 +339,16 @@ func TestHardlinkedLongname(t *testing.T) {
 	if test_helpers.Md5fn(matches[0]) == test_helpers.Md5fn(matches[1]) {
 		t.Errorf("Files %q are identical - that's wrong!", matches)
 	}
+
+	var st0 syscall.Stat_t
+	if err := syscall.Stat(matches[0], &st0); err != nil {
+		t.Fatal(err)
+	}
+	var st1 syscall.Stat_t
+	if err := syscall.Stat(matches[1], &st1); err != nil {
+		t.Fatal(err)
+	}
+	if st0.Ino == st1.Ino {
+		t.Errorf("Files %q have the same inode number - that's wrong!", matches)
+	}
 }

tests/reverse/inomap_test.go

@@ -143,7 +143,7 @@ func TestVirtualFileIno(t *testing.T) {
 	if origInos.child == cipherInos.name {
 		t.Errorf("name ino collision: %d == %d", origInos.child, cipherInos.name)
 	}
-	if origInos.child&mask != cipherInos.name&mask {
-		t.Errorf("name ino mismatch: %#x vs %#x", origInos.child, cipherInos.name)
+	if cipherInos.name < 1<<63 {
+		t.Errorf("name ino should be in spill space, but is actually %#x", cipherInos.name)
 	}
 }