From 9f56b33e0c8701085189aa77463f1b471b70a705 Mon Sep 17 00:00:00 2001
From: Sebastian Lackner
Date: Sat, 25 Nov 2017 01:56:56 +0100
Subject: fusefrontend: Fix longname handling for renames with existing target

Fixes https://github.com/rfjakob/gocryptfs/issues/170

Steps to reproduce the problem:

* Create a regular forward mount point
* Create a file with a shortname and one with a long filename
* Try to run 'mv <shortname> <longname>'

This should actually work and replace the existing file, but instead it
fails with:

    mv: cannot move '<shortname>' to '<longname>': File exists

The problem is the creation of the .name file. If the target already exists
we can safely ignore the EEXIST error and just keep the existing .name file.
---
 internal/fusefrontend/fs.go         | 8 +++++++-
 internal/nametransform/longnames.go | 6 +++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

(limited to 'internal')

diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index 3c442a5..b4819fd 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -517,7 +517,13 @@ func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (cod
 		finalNewPath = cNewName
 		// Create destination .name file
 		err = fs.nameTransform.WriteLongName(newDirFd, cNewName, newPath)
-		if err != nil {
+		// Failure to write the .name file is expected when the target path already
+		// exists. Since hashes are pretty unique, there is no need to modify the
+		// file anyway. We still set newDirFd to nil to ensure that we do not delete
+		// the file on error.
+		if err == syscall.EEXIST {
+			newDirFd = nil
+		} else if err != nil {
 			return fuse.ToStatus(err)
 		}
 	}
diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
index 8af191d..7cd904e 100644
--- a/internal/nametransform/longnames.go
+++ b/internal/nametransform/longnames.go
@@ -114,7 +114,11 @@ func (n *NameTransform) WriteLongName(dirfd *os.File, hashName string, plainName
 	fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), hashName+LongNameSuffix,
 		syscall.O_WRONLY|syscall.O_CREAT|syscall.O_EXCL, 0600)
 	if err != nil {
-		tlog.Warn.Printf("WriteLongName: Openat: %v", err)
+		// Don't warn if the file already exists - this is allowed for renames
+		// and should be handled by the caller.
+		if err != syscall.EEXIST {
+			tlog.Warn.Printf("WriteLongName: Openat: %v", err)
+		}
 		return err
 	}
 	fd := os.NewFile(uintptr(fdRaw), hashName+LongNameSuffix)
-- 
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