Fixed permissions for the root.

samples/memfs/fs.go

@@ -57,9 +57,10 @@ func NewMemFS(
 		inodes: make([]*inode, fuse.RootInodeID+1),
 	}
 
-	// Set up the root inode.
+	// Set up the root inode. Its ownership information will later be modified in
+	// Init.
 	rootAttrs := fuse.InodeAttributes{
-		Mode: 0777 | os.ModeDir,
+		Mode: 0700 | os.ModeDir,
 	}
 
 	fs.inodes[fuse.RootInodeID] = newInode(rootAttrs)
@@ -70,6 +71,10 @@ func NewMemFS(
 	return fs
 }
 
+////////////////////////////////////////////////////////////////////////
+// Helpers
+////////////////////////////////////////////////////////////////////////
+
 func (fs *memFS) checkInvariants() {
 	// Check reserved inodes.
 	for i := 0; i < fuse.RootInodeID; i++ {
@@ -109,13 +114,6 @@ func (fs *memFS) checkInvariants() {
 	}
 }
 
-func (fs *memFS) Init(
-	ctx context.Context,
-	req *fuse.InitRequest) (resp *fuse.InitResponse, err error) {
-	resp = &fuse.InitResponse{}
-	return
-}
-
 // Find the given inode and return it with its lock held. Panic if it doesn't
 // exist.
 //
@@ -171,6 +169,29 @@ func (fs *memFS) allocateInode(
 	return
 }
 
+////////////////////////////////////////////////////////////////////////
+// FileSystem methods
+////////////////////////////////////////////////////////////////////////
+
+func (fs *memFS) Init(
+	ctx context.Context,
+	req *fuse.InitRequest) (resp *fuse.InitResponse, err error) {
+	resp = &fuse.InitResponse{}
+
+	fs.mu.RLock()
+	defer fs.mu.RUnlock()
+
+	// Update the root inode's ownership information to match the credentials of
+	// the mounting process.
+	root := fs.getInodeForModifyingOrDie(fuse.RootInodeID)
+	defer root.mu.Unlock()
+
+	root.attributes.Uid = req.Header.Uid
+	root.attributes.Gid = req.Header.Gid
+
+	return
+}
+
 func (fs *memFS) LookUpInode(
 	ctx context.Context,
 	req *fuse.LookUpInodeRequest) (resp *fuse.LookUpInodeResponse, err error) {

samples/memfs/inode.go

@@ -59,6 +59,10 @@ type inode struct {
 	contents []byte // GUARDED_BY(mu)
 }
 
+////////////////////////////////////////////////////////////////////////
+// Helpers
+////////////////////////////////////////////////////////////////////////
+
 func newInode(attrs fuse.InodeAttributes) (in *inode) {
 	in = &inode{
 		dir:        (attrs.Mode&os.ModeDir != 0),
@@ -112,6 +116,10 @@ func (inode *inode) checkInvariants() {
 	}
 }
 
+////////////////////////////////////////////////////////////////////////
+// Public methods
+////////////////////////////////////////////////////////////////////////
+
 // Find an entry for the given child name and return its inode ID.
 //
 // REQUIRES: inode.dir