longnames: fix fsstress failure, use dirfd

Using dirfd-relative operations allows safe lockless handling
of the ".name" files.

1 files changed, 155 insertions, 40 deletions

diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index fb82c6b..9e67a6a 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -5,6 +5,7 @@ package fusefrontend
 import (
 	"encoding/base64"
 	"os"
+	"path/filepath"
 	"sync"
 	"syscall"
 	"time"
@@ -111,18 +112,38 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
-	// Create .name file to store the long file name if needed
-	if !fs.args.PlaintextNames {
-		err = fs.nameTransform.WriteLongName(cPath, path)
+
+	// Handle long file name
+	cName := filepath.Base(cPath)
+	if nametransform.IsLongContent(cName) {
+		dirfd, err := os.Open(filepath.Dir(cPath))
+		if err != nil {
+			return nil, fuse.ToStatus(err)
+		}
+		defer dirfd.Close()
+
+		// Create ".name"
+		err = fs.nameTransform.WriteLongName(dirfd, cName, path)
+		if err != nil {
+			return nil, fuse.ToStatus(err)
+		}
+
+		// Create content
+		fdRaw, err := syscall.Openat(int(dirfd.Fd()), cName, iflags|os.O_CREATE, mode)
 		if err != nil {
+			nametransform.DeleteLongName(dirfd, cName)
 			return nil, fuse.ToStatus(err)
 		}
+		fd := os.NewFile(uintptr(fdRaw), cName)
+
+		return NewFile(fd, writeOnly, fs.contentEnc), fuse.OK
 	}
-	f, err := os.OpenFile(cPath, iflags|os.O_CREATE, os.FileMode(mode))
+
+	fd, err := os.OpenFile(cPath, iflags|os.O_CREATE, os.FileMode(mode))
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
-	return NewFile(f, writeOnly, fs.contentEnc), fuse.OK
+	return NewFile(fd, writeOnly, fs.contentEnc), fuse.OK
 }
 
 func (fs *FS) Chmod(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
@@ -155,13 +176,31 @@ func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context)
 	if err != nil {
 		return fuse.ToStatus(err)
 	}
-	if !fs.args.PlaintextNames {
-		// Create .name file to store the long file name if needed
-		err = fs.nameTransform.WriteLongName(cPath, path)
+
+	// Handle long file name
+	cName := filepath.Base(cPath)
+	if nametransform.IsLongContent(cName) {
+		dirfd, err := os.Open(filepath.Dir(cPath))
 		if err != nil {
 			return fuse.ToStatus(err)
 		}
+		defer dirfd.Close()
+
+		// Create ".name"
+		err = fs.nameTransform.WriteLongName(dirfd, cName, path)
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+
+		// Create device node
+		err = syscall.Mknodat(int(dirfd.Fd()), cName, uint32(mode), int(dev))
+		if err != nil {
+			nametransform.DeleteLongName(dirfd, cName)
+		}
+
+		return fuse.ToStatus(err)
 	}
+
 	return fs.FileSystem.Mknod(cPath, mode, dev, context)
 }
 
@@ -227,11 +266,28 @@ func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
 	if err != nil {
 		return fuse.ToStatus(err)
 	}
-	err = syscall.Unlink(cPath)
-	// Delete .name file
-	if err == nil && !fs.args.PlaintextNames {
-		nametransform.DeleteLongName(cPath)
+
+	cName := filepath.Base(cPath)
+	if nametransform.IsLongContent(cName) {
+		dirfd, err := os.Open(filepath.Dir(cPath))
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+		defer dirfd.Close()
+		// Delete content
+		err = syscall.Unlinkat(int(dirfd.Fd()), cName)
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+		// Delete ".name"
+		err = nametransform.DeleteLongName(dirfd, cName)
+		if err != nil {
+			toggledlog.Warn.Printf("Unlink: could not delete .name file: %v", err)
+		}
+		return fuse.ToStatus(err)
 	}
+
+	err = syscall.Unlink(cPath)
 	return fuse.ToStatus(err)
 }
 
@@ -244,8 +300,8 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
 	if err != nil {
 		return fuse.ToStatus(err)
 	}
-	// Old filesystem: symlinks are encrypted like paths (CBC)
-	// TODO drop compatibility and simplify code
+	// Before v0.5, symlinks were encrypted like paths (CBC)
+	// TODO drop compatibility and simplify code?
 	if !fs.args.DirIV {
 		cTarget, err := fs.encryptPath(target)
 		if err != nil {
@@ -255,18 +311,36 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
 		err = os.Symlink(cTarget, cPath)
 		return fuse.ToStatus(err)
 	}
-	// Since gocryptfs v0.5 symlinks are encrypted like file contents (GCM)
+
 	cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil)
 	cTarget := base64.URLEncoding.EncodeToString(cBinTarget)
-	if !fs.args.PlaintextNames {
-		// Create .name file to store the long file name if needed
-		err = fs.nameTransform.WriteLongName(cPath, linkName)
+
+	// Handle long file name
+	cName := filepath.Base(cPath)
+	if nametransform.IsLongContent(cName) {
+		dirfd, err := os.Open(filepath.Dir(cPath))
 		if err != nil {
 			return fuse.ToStatus(err)
 		}
+		defer dirfd.Close()
+
+		// Create ".name"
+		err = fs.nameTransform.WriteLongName(dirfd, cName, linkName)
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+
+		// Create symlink
+		// TODO use syscall.Symlinkat once it is available in Go
+		err = syscall.Symlink(cTarget, cPath)
+		if err != nil {
+			nametransform.DeleteLongName(dirfd, cName)
+		}
+
+		return fuse.ToStatus(err)
 	}
+
 	err = os.Symlink(cTarget, cPath)
-	toggledlog.Debug.Printf("Symlink: os.Symlink(%s, %s) = %v", cTarget, cPath, err)
 	return fuse.ToStatus(err)
 }
 
@@ -286,35 +360,61 @@ func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (cod
 	// That directory may still be in the DirIV cache, clear it.
 	fs.nameTransform.DirIVCache.Clear()
 
-	if !fs.args.PlaintextNames {
-		// Create .name file to store the new long file name if needed
-		err = fs.nameTransform.WriteLongName(cNewPath, newPath)
+	// Handle long source file name
+	var oldDirFd *os.File
+	var finalOldDirFd int
+	var finalOldPath = cOldPath
+	cOldName := filepath.Base(cOldPath)
+	if nametransform.IsLongContent(cOldName) {
+		oldDirFd, err = os.Open(filepath.Dir(cOldPath))
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+		defer oldDirFd.Close()
+		finalOldDirFd = int(oldDirFd.Fd())
+		finalOldPath = cOldName
+	}
+	// Handle long destination file name
+	var newDirFd *os.File
+	var finalNewDirFd int
+	var finalNewPath = cNewPath
+	cNewName := filepath.Base(cNewPath)
+	if nametransform.IsLongContent(cNewName) {
+		newDirFd, err = os.Open(filepath.Dir(cNewPath))
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+		defer newDirFd.Close()
+		finalNewDirFd = int(newDirFd.Fd())
+		finalNewPath = cNewName
+		// Create destination .name file
+		err = fs.nameTransform.WriteLongName(newDirFd, cNewName, newPath)
 		if err != nil {
 			return fuse.ToStatus(err)
 		}
 	}
-
 	// Actual rename
-	err = os.Rename(cOldPath, cNewPath)
-
-	if lerr, ok := err.(*os.LinkError); ok && lerr.Err == syscall.ENOTEMPTY {
-		// If an empty directory is overwritten we will always get
-		// ENOTEMPTY as the "empty" directory will still contain gocryptfs.diriv.
+	err = syscall.Renameat(finalOldDirFd, finalOldPath, finalNewDirFd, finalNewPath)
+	if err == syscall.ENOTEMPTY {
+		// If an empty directory is overwritten we will always get ENOTEMPTY as
+		// the "empty" directory will still contain gocryptfs.diriv.
 		// Handle that case by removing the target directory and trying again.
 		toggledlog.Debug.Printf("Rename: Handling ENOTEMPTY")
 		if fs.Rmdir(newPath, context) == fuse.OK {
-			err = os.Rename(cOldPath, cNewPath)
+			err = syscall.Renameat(finalOldDirFd, finalOldPath, finalNewDirFd, finalNewPath)
 		}
 	}
-	if err == nil {
-		// Rename succeeded - delete old long name file
-		nametransform.DeleteLongName(cOldPath)
-	} else {
-		// Rename has failed - undo long name file creation
-		nametransform.DeleteLongName(cNewPath)
+	if err != nil {
+		if newDirFd != nil {
+			// Roll back .name creation
+			nametransform.DeleteLongName(newDirFd, cNewName)
+		}
+		return fuse.ToStatus(err)
 	}
-
-	return fuse.ToStatus(err)
+	if oldDirFd != nil {
+		nametransform.DeleteLongName(oldDirFd, cOldName)
+	}
+	return fuse.OK
 }
 
 func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
@@ -329,13 +429,28 @@ func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code
 	if err != nil {
 		return fuse.ToStatus(err)
 	}
-	if !fs.args.PlaintextNames {
-		// Create .name file to store the long file name if needed
-		err = fs.nameTransform.WriteLongName(cNewPath, newPath)
+
+	// Handle long file name
+	cNewName := filepath.Base(cNewPath)
+	if nametransform.IsLongContent(cNewName) {
+		dirfd, err := os.Open(filepath.Dir(cNewPath))
+		if err != nil {
+			return fuse.ToStatus(err)
+		}
+		defer dirfd.Close()
+		err = fs.nameTransform.WriteLongName(dirfd, cNewName, newPath)
 		if err != nil {
 			return fuse.ToStatus(err)
 		}
+		// TODO Use syscall.Linkat once it is available in Go (it is not in Go
+		// 1.6).
+		err = syscall.Link(cOldPath, cNewPath)
+		if err != nil {
+			nametransform.DeleteLongName(dirfd, cNewName)
+			return fuse.ToStatus(err)
+		}
 	}
+
 	return fuse.ToStatus(os.Link(cOldPath, cNewPath))
 }