From 518771e4e247762f60c5594de427a8c86f19bd57 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sun, 3 May 2020 15:22:10 +0200
Subject: fusefrontend_reverse: use inomap for inode number translation

Gets rid of static inode number value limitations.

Fixes https://github.com/rfjakob/gocryptfs/issues/457
---
 internal/fusefrontend_reverse/virtualfile.go | 52 ++++++++++++----------------
 1 file changed, 22 insertions(+), 30 deletions(-)

(limited to 'internal/fusefrontend_reverse/virtualfile.go')

diff --git a/internal/fusefrontend_reverse/virtualfile.go b/internal/fusefrontend_reverse/virtualfile.go
index 963c801..7d1c18c 100644
--- a/internal/fusefrontend_reverse/virtualfile.go
+++ b/internal/fusefrontend_reverse/virtualfile.go
@@ -10,6 +10,7 @@ import (
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
 
+	"github.com/rfjakob/gocryptfs/internal/inomap"
 	"github.com/rfjakob/gocryptfs/internal/nametransform"
 	"github.com/rfjakob/gocryptfs/internal/pathiv"
 	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
@@ -20,19 +21,10 @@ const (
 	// virtualFileMode is the mode to use for virtual files (gocryptfs.diriv and
 	// *.name). They are always readable, as stated in func Access
 	virtualFileMode = syscall.S_IFREG | 0444
-	// inoBaseDirIV is the start of the inode number range that is used
-	// for virtual gocryptfs.diriv files. inoBaseNameFile is the thing for
-	// *.name files.
-	// The value 10^19 is just below 2^60. A power of 10 has been chosen so the
-	// "ls -li" output (which is base-10) is easy to read.
-	// 10^19 is the largest power of 10 that is smaller than
-	// INT64_MAX (=UINT64_MAX/2). This avoids signedness issues.
-	inoBaseDirIV    = uint64(1000000000000000000)
-	inoBaseNameFile = uint64(2000000000000000000)
-	// inoBaseMin marks the start of the inode number space that is
-	// reserved for virtual files. It is the lowest of the inoBaseXXX values
-	// above.
-	inoBaseMin = inoBaseDirIV
+	// We use inomap's `Tag` feature to generate unique inode numbers for
+	// virtual files. These are the tags we use.
+	inoTagDirIV    = 1
+	inoTagNameFile = 2
 )
 
 func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
@@ -42,20 +34,23 @@ func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
 		return nil, fuse.ToStatus(err)
 	}
 	iv := pathiv.Derive(cDir, pathiv.PurposeDirIV)
-	return rfs.newVirtualFile(iv, rfs.args.Cipherdir, dir, inoBaseDirIV)
+	return rfs.newVirtualFile(iv, rfs.args.Cipherdir, dir, inoTagDirIV)
 }
 
 type virtualFile struct {
 	// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
 	nodefs.File
+	// pointer to parent filesystem
+	rfs *ReverseFS
 	// file content
 	content []byte
 	// backing directory
 	cipherdir string
 	// path to a parent file (relative to cipherdir)
 	parentFile string
-	// inode number of a virtual file is inode of parent file plus inoBase
-	inoBase uint64
+	// inomap `Tag`.
+	// Depending on the file type, either `inoTagDirIV` or `inoTagNameFile`.
+	inoTag uint8
 }
 
 // newVirtualFile creates a new in-memory file that does not have a representation
@@ -63,16 +58,17 @@ type virtualFile struct {
 // from "parentFile" (plaintext path relative to "cipherdir").
 // For a "gocryptfs.diriv" file, you would use the parent directory as
 // "parentFile".
-func (rfs *ReverseFS) newVirtualFile(content []byte, cipherdir string, parentFile string, inoBase uint64) (nodefs.File, fuse.Status) {
-	if inoBase < inoBaseMin {
-		log.Panicf("BUG: virtual inode number base %d is below reserved space", inoBase)
+func (rfs *ReverseFS) newVirtualFile(content []byte, cipherdir string, parentFile string, inoTag uint8) (nodefs.File, fuse.Status) {
+	if inoTag == 0 {
+		log.Panicf("BUG: inoTag for virtual file is zero - this will cause ino collisions!")
 	}
 	return &virtualFile{
 		File:       nodefs.NewDefaultFile(),
+		rfs:        rfs,
 		content:    content,
 		cipherdir:  cipherdir,
 		parentFile: parentFile,
-		inoBase:    inoBase,
+		inoTag:     inoTag,
 	}, fuse.OK
 }
 
@@ -97,22 +93,18 @@ func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
 	}
 	defer syscall.Close(dirfd)
 	name := filepath.Base(f.parentFile)
-	var st unix.Stat_t
-	err = syscallcompat.Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
+	var st2 unix.Stat_t
+	err = syscallcompat.Fstatat(dirfd, name, &st2, unix.AT_SYMLINK_NOFOLLOW)
 	if err != nil {
 		tlog.Debug.Printf("GetAttr: Fstatat %q: %v\n", f.parentFile, err)
 		return fuse.ToStatus(err)
 	}
-	if st.Ino > inoBaseMin {
-		tlog.Warn.Printf("virtualFile.GetAttr: parent file inode number %d crosses reserved space, max=%d. Returning EOVERFLOW.",
-			st.Ino, inoBaseMin)
-		return fuse.ToStatus(syscall.EOVERFLOW)
-	}
-	st.Ino = st.Ino + f.inoBase
+	st := syscallcompat.Unix2syscall(st2)
+	q := inomap.NewQIno(uint64(st.Dev), f.inoTag, uint64(st.Ino))
+	st.Ino = f.rfs.inoMap.Translate(q)
 	st.Size = int64(len(f.content))
 	st.Mode = virtualFileMode
 	st.Nlink = 1
-	st2 := syscallcompat.Unix2syscall(st)
-	a.FromStat(&st2)
+	a.FromStat(&st)
 	return fuse.OK
 }
-- 
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