Improve Uid & Gid support

The purpose of this PR is to allow file systems to:
1. Create inodes with the UID and GID of the calling process
2. Support chown

Author: Manuel Valls Fernández

conversions.go

@@ -41,7 +41,9 @@ func convertInMessage(
 	inMsg *buffer.InMessage,
 	outMsg *buffer.OutMessage,
 	protocol fusekernel.Protocol) (o interface{}, err error) {
-	switch inMsg.Header().Opcode {
+	header := inMsg.Header()
+
+	switch header.Opcode {
 	case fusekernel.OpLookup:
 		buf := inMsg.ConsumeBytes(inMsg.Len())
 		n := len(buf)
@@ -93,6 +95,14 @@ func convertInMessage(
 			to.Mtime = &t
 		}
 
+		if valid&fusekernel.SetattrUid != 0 {
+			to.Uid = &in.Uid
+		}
+
+		if valid&fusekernel.SetattrGid != 0 {
+			to.Gid = &in.Gid
+		}
+
 	case fusekernel.OpForget:
 		type input fusekernel.ForgetIn
 		in := (*input)(inMsg.Consume(unsafe.Sizeof(input{})))
@@ -132,6 +142,8 @@ func convertInMessage(
 			// opcode is mkdir. But we want the correct mode to go through, so ensure
 			// that os.ModeDir is set.
 			Mode: convertFileMode(in.Mode) | os.ModeDir,
+			Uid:  header.Uid,
+			Gid:  header.Gid,
 		}
 
 	case fusekernel.OpMknod:
@@ -153,6 +165,8 @@ func convertInMessage(
 			Parent: fuseops.InodeID(inMsg.Header().Nodeid),
 			Name:   string(name),
 			Mode:   convertFileMode(in.Mode),
+			Uid:    header.Uid,
+			Gid:    header.Gid,
 		}
 
 	case fusekernel.OpCreate:
@@ -174,6 +188,8 @@ func convertInMessage(
 			Parent: fuseops.InodeID(inMsg.Header().Nodeid),
 			Name:   string(name),
 			Mode:   convertFileMode(in.Mode),
+			Uid:    header.Uid,
+			Gid:    header.Gid,
 		}
 
 	case fusekernel.OpSymlink:
@@ -194,6 +210,8 @@ func convertInMessage(
 			Parent: fuseops.InodeID(inMsg.Header().Nodeid),
 			Name:   string(newName),
 			Target: string(target),
+			Uid:    header.Uid,
+			Gid:    header.Gid,
 		}
 
 	case fusekernel.OpRename:

fuseops/ops.go

@@ -150,6 +150,8 @@ type SetInodeAttributesOp struct {
 	Mode  *os.FileMode
 	Atime *time.Time
 	Mtime *time.Time
+	Uid   *uint32
+	Gid   *uint32
 
 	// Set by the file system: the new attributes for the inode, and the time at
 	// which they should expire. See notes on
@@ -228,6 +230,10 @@ type MkDirOp struct {
 	Name string
 	Mode os.FileMode
 
+	// The uid and gid of the parent process
+	Uid uint32
+	Gid uint32
+
 	// Set by the file system: information about the inode that was created.
 	//
 	// The lookup count for the inode is implicitly incremented. See notes on
@@ -255,6 +261,10 @@ type MkNodeOp struct {
 	Name string
 	Mode os.FileMode
 
+	// The uid and gid of the parent process
+	Uid uint32
+	Gid uint32
+
 	// Set by the file system: information about the inode that was created.
 	//
 	// The lookup count for the inode is implicitly incremented. See notes on
@@ -280,6 +290,10 @@ type CreateFileOp struct {
 	Name string
 	Mode os.FileMode
 
+	// The uid and gid of the parent process
+	Uid uint32
+	Gid uint32
+
 	// Set by the file system: information about the inode that was created.
 	//
 	// The lookup count for the inode is implicitly incremented. See notes on
@@ -306,6 +320,10 @@ type CreateSymlinkOp struct {
 	// The name of the symlink to create.
 	Name string
 
+	// The uid and gid of the parent process
+	Uid uint32
+	Gid uint32
+
 	// The target of the symlink.
 	Target string
 

samples/memfs/inode.go

@@ -352,7 +352,9 @@ func (in *inode) WriteAt(p []byte, off int64) (n int, err error) {
 func (in *inode) SetAttributes(
 	size *uint64,
 	mode *os.FileMode,
-	mtime *time.Time) {
+	mtime *time.Time,
+	uid *uint32,
+	gid *uint32) {
 	// Update the modification time.
 	in.attrs.Mtime = time.Now()
 
@@ -381,4 +383,14 @@ func (in *inode) SetAttributes(
 	if mtime != nil {
 		in.attrs.Mtime = *mtime
 	}
+
+	// Change uid?
+	if uid != nil {
+		in.attrs.Uid = *uid
+	}
+
+	// Change gid?
+	if gid != nil {
+		in.attrs.Gid = *gid
+	}
 }

samples/memfs/memfs.go

@@ -31,10 +31,6 @@ import (
 type memFS struct {
 	fuseutil.NotImplementedFileSystem
 
-	// The UID and GID that every inode receives.
-	uid uint32
-	gid uint32
-
 	/////////////////////////
 	// Mutable state
 	/////////////////////////
@@ -73,8 +69,6 @@ func NewMemFS(
 	// Set up the basic struct.
 	fs := &memFS{
 		inodes: make([]*inode, fuseops.RootInodeID+1),
-		uid:    uid,
-		gid:    gid,
 	}
 
 	// Set up the root inode.
@@ -250,7 +244,7 @@ func (fs *memFS) SetInodeAttributes(
 	inode := fs.getInodeOrDie(op.Inode)
 
 	// Handle the request.
-	inode.SetAttributes(op.Size, op.Mode, op.Mtime)
+	inode.SetAttributes(op.Size, op.Mode, op.Mtime, op.Uid, op.Gid)
 
 	// Fill in the response.
 	op.Attributes = inode.attrs
@@ -283,8 +277,8 @@ func (fs *memFS) MkDir(
 	childAttrs := fuseops.InodeAttributes{
 		Nlink: 1,
 		Mode:  op.Mode,
-		Uid:   fs.uid,
-		Gid:   fs.gid,
+		Uid:   op.Uid,
+		Gid:   op.Gid,
 	}
 
 	// Allocate a child.
@@ -311,15 +305,17 @@ func (fs *memFS) MkNode(
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
 
-	op.Entry, err = fs.createFile(op.Parent, op.Name, op.Mode)
+	op.Entry, err = fs.createFile(op.Parent, op.Name, op.Mode, op.Uid, op.Gid)
 	return
 }
 
 // LOCKS_REQUIRED(fs.mu)
 func (fs *memFS) createFile(
 	parentID fuseops.InodeID,
 	name string,
-	mode os.FileMode) (entry fuseops.ChildInodeEntry, err error) {
+	mode os.FileMode,
+	uid uint32,
+	gid uint32) (entry fuseops.ChildInodeEntry, err error) {
 	// Grab the parent, which we will update shortly.
 	parent := fs.getInodeOrDie(parentID)
 
@@ -340,8 +336,8 @@ func (fs *memFS) createFile(
 		Mtime:  now,
 		Ctime:  now,
 		Crtime: now,
-		Uid:    fs.uid,
-		Gid:    fs.gid,
+		Uid:    uid,
+		Gid:    gid,
 	}
 
 	// Allocate a child.
@@ -368,7 +364,7 @@ func (fs *memFS) CreateFile(
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
 
-	op.Entry, err = fs.createFile(op.Parent, op.Name, op.Mode)
+	op.Entry, err = fs.createFile(op.Parent, op.Name, op.Mode, op.Uid, op.Gid)
 	return
 }
 
@@ -398,8 +394,8 @@ func (fs *memFS) CreateSymlink(
 		Mtime:  now,
 		Ctime:  now,
 		Crtime: now,
-		Uid:    fs.uid,
-		Gid:    fs.gid,
+		Uid:    op.Uid,
+		Gid:    op.Gid,
 	}
 
 	// Allocate a child.