1 files changed, 534 insertions, 0 deletions
diff --git a/pkg/sentry/fs/ramfs/dir.go b/pkg/sentry/fs/ramfs/dir.go
new file mode 100644
index 000000000..cd6e03d66
--- /dev/null
+++ b/pkg/sentry/fs/ramfs/dir.go
@@ -0,0 +1,534 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ramfs
+
+import (
+	"fmt"
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// CreateOps represents operations to create different file types.
+type CreateOps struct {
+	// NewDir creates a new directory.
+	NewDir func(ctx context.Context, dir *fs.Inode, perms fs.FilePermissions) (*fs.Inode, error)
+
+	// NewFile creates a new file.
+	NewFile func(ctx context.Context, dir *fs.Inode, perms fs.FilePermissions) (*fs.Inode, error)
+
+	// NewSymlink creates a new symlink with permissions 0777.
+	NewSymlink func(ctx context.Context, dir *fs.Inode, target string) (*fs.Inode, error)
+
+	// NewBoundEndpoint creates a new socket.
+	NewBoundEndpoint func(ctx context.Context, dir *fs.Inode, ep transport.BoundEndpoint, perms fs.FilePermissions) (*fs.Inode, error)
+
+	// NewFifo creates a new fifo.
+	NewFifo func(ctx context.Context, dir *fs.Inode, perm fs.FilePermissions) (*fs.Inode, error)
+}
+
+// Dir represents a single directory in the filesystem.
+//
+// +stateify savable
+type Dir struct {
+	fsutil.InodeGenericChecker `state:"nosave"`
+	fsutil.InodeIsDirAllocate  `state:"nosave"`
+	fsutil.InodeIsDirTruncate  `state:"nosave"`
+	fsutil.InodeNoopRelease    `state:"nosave"`
+	fsutil.InodeNoopWriteOut   `state:"nosave"`
+	fsutil.InodeNotMappable    `state:"nosave"`
+	fsutil.InodeNotSocket      `state:"nosave"`
+	fsutil.InodeNotSymlink     `state:"nosave"`
+	fsutil.InodeVirtual        `state:"nosave"`
+
+	fsutil.InodeSimpleAttributes
+	fsutil.InodeSimpleExtendedAttributes
+
+	// CreateOps may be provided.
+	//
+	// These may only be modified during initialization (while the application
+	// is not running). No sychronization is performed when accessing these
+	// operations during syscalls.
+	*CreateOps `state:"nosave"`
+
+	// mu protects the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// children are inodes that are in this directory.  A reference is held
+	// on each inode while it is in the map.
+	children map[string]*fs.Inode
+
+	// dentryMap is a sortedDentryMap containing entries for all children.
+	// Its entries are kept up-to-date with d.children.
+	dentryMap *fs.SortedDentryMap
+}
+
+var _ fs.InodeOperations = (*Dir)(nil)
+
+// NewDir returns a new Dir with the given contents and attributes.
+func NewDir(ctx context.Context, contents map[string]*fs.Inode, owner fs.FileOwner, perms fs.FilePermissions) *Dir {
+	d := &Dir{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, perms, linux.RAMFS_MAGIC),
+	}
+
+	if contents == nil {
+		contents = make(map[string]*fs.Inode)
+	}
+	d.children = contents
+
+	// Build the entries map ourselves, rather than calling addChildLocked,
+	// because it will be faster.
+	entries := make(map[string]fs.DentAttr, len(contents))
+	for name, inode := range contents {
+		entries[name] = fs.DentAttr{
+			Type:    inode.StableAttr.Type,
+			InodeID: inode.StableAttr.InodeID,
+		}
+	}
+	d.dentryMap = fs.NewSortedDentryMap(entries)
+
+	// Directories have an extra link, corresponding to '.'.
+	d.AddLink()
+
+	return d
+}
+
+// addChildLocked add the child inode, inheriting its reference.
+func (d *Dir) addChildLocked(ctx context.Context, name string, inode *fs.Inode) {
+	d.children[name] = inode
+	d.dentryMap.Add(name, fs.DentAttr{
+		Type:    inode.StableAttr.Type,
+		InodeID: inode.StableAttr.InodeID,
+	})
+
+	// If the child is a directory, increment this dir's link count,
+	// corresponding to '..' from the subdirectory.
+	if fs.IsDir(inode.StableAttr) {
+		d.AddLink()
+		// ctime updated below.
+	}
+
+	// Given we're now adding this inode to the directory we must also
+	// increase its link count. Similarly we decrement it in removeChildLocked.
+	//
+	// Changing link count updates ctime.
+	inode.AddLink()
+	inode.InodeOperations.NotifyStatusChange(ctx)
+
+	// We've change the directory. This always updates our mtime and ctime.
+	d.NotifyModificationAndStatusChange(ctx)
+}
+
+// AddChild adds a child to this dir.
+func (d *Dir) AddChild(ctx context.Context, name string, inode *fs.Inode) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	d.addChildLocked(ctx, name, inode)
+}
+
+// FindChild returns (child, true) if the directory contains name.
+func (d *Dir) FindChild(name string) (*fs.Inode, bool) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	child, ok := d.children[name]
+	return child, ok
+}
+
+// Children returns the names and DentAttrs of all children. It can be used to
+// implement Readdir for types that embed ramfs.Dir.
+func (d *Dir) Children() ([]string, map[string]fs.DentAttr) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	// Return a copy to prevent callers from modifying our children.
+	names, entries := d.dentryMap.GetAll()
+	namesCopy := make([]string, len(names))
+	copy(namesCopy, names)
+
+	entriesCopy := make(map[string]fs.DentAttr)
+	for k, v := range entries {
+		entriesCopy[k] = v
+	}
+
+	return namesCopy, entriesCopy
+}
+
+// removeChildLocked attempts to remove an entry from this directory.
+func (d *Dir) removeChildLocked(ctx context.Context, name string) (*fs.Inode, error) {
+	inode, ok := d.children[name]
+	if !ok {
+		return nil, syserror.EACCES
+	}
+
+	delete(d.children, name)
+	d.dentryMap.Remove(name)
+	d.NotifyModification(ctx)
+
+	// If the child was a subdirectory, then we must decrement this dir's
+	// link count which was the child's ".." directory entry.
+	if fs.IsDir(inode.StableAttr) {
+		d.DropLink()
+		// ctime changed below.
+	}
+
+	// Given we're now removing this inode to the directory we must also
+	// decrease its link count. Similarly it is increased in addChildLocked.
+	//
+	// Changing link count updates ctime.
+	inode.DropLink()
+	inode.InodeOperations.NotifyStatusChange(ctx)
+
+	// We've change the directory. This always updates our mtime and ctime.
+	d.NotifyModificationAndStatusChange(ctx)
+
+	return inode, nil
+}
+
+// Remove removes the named non-directory.
+func (d *Dir) Remove(ctx context.Context, _ *fs.Inode, name string) error {
+	if len(name) > linux.NAME_MAX {
+		return syserror.ENAMETOOLONG
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	inode, err := d.removeChildLocked(ctx, name)
+	if err != nil {
+		return err
+	}
+
+	// Remove our reference on the inode.
+	inode.DecRef()
+	return nil
+}
+
+// RemoveDirectory removes the named directory.
+func (d *Dir) RemoveDirectory(ctx context.Context, _ *fs.Inode, name string) error {
+	if len(name) > linux.NAME_MAX {
+		return syserror.ENAMETOOLONG
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	// Get the child and make sure it is not empty.
+	childInode, err := d.walkLocked(ctx, name)
+	if err != nil {
+		return err
+	}
+	if ok, err := hasChildren(ctx, childInode); err != nil {
+		return err
+	} else if ok {
+		return syserror.ENOTEMPTY
+	}
+
+	// Child was empty. Proceed with removal.
+	inode, err := d.removeChildLocked(ctx, name)
+	if err != nil {
+		return err
+	}
+
+	// Remove our reference on the inode.
+	inode.DecRef()
+
+	return nil
+}
+
+// Lookup loads an inode at p into a Dirent.
+func (d *Dir) Lookup(ctx context.Context, _ *fs.Inode, p string) (*fs.Dirent, error) {
+	if len(p) > linux.NAME_MAX {
+		return nil, syserror.ENAMETOOLONG
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	inode, err := d.walkLocked(ctx, p)
+	if err != nil {
+		return nil, err
+	}
+
+	// Take a reference on the inode before returning it.  This reference
+	// is owned by the dirent we are about to create.
+	inode.IncRef()
+	return fs.NewDirent(inode, p), nil
+}
+
+// walkLocked must be called with d.mu held.
+func (d *Dir) walkLocked(ctx context.Context, p string) (*fs.Inode, error) {
+	// Lookup a child node.
+	if inode, ok := d.children[p]; ok {
+		return inode, nil
+	}
+
+	// fs.InodeOperations.Lookup returns syserror.ENOENT if p
+	// does not exist.
+	return nil, syserror.ENOENT
+}
+
+// createInodeOperationsCommon creates a new child node at this dir by calling
+// makeInodeOperations. It is the common logic for creating a new child.
+func (d *Dir) createInodeOperationsCommon(ctx context.Context, name string, makeInodeOperations func() (*fs.Inode, error)) (*fs.Inode, error) {
+	if len(name) > linux.NAME_MAX {
+		return nil, syserror.ENAMETOOLONG
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	inode, err := makeInodeOperations()
+	if err != nil {
+		return nil, err
+	}
+
+	d.addChildLocked(ctx, name, inode)
+
+	return inode, nil
+}
+
+// Create creates a new Inode with the given name and returns its File.
+func (d *Dir) Create(ctx context.Context, dir *fs.Inode, name string, flags fs.FileFlags, perms fs.FilePermissions) (*fs.File, error) {
+	if d.CreateOps == nil || d.CreateOps.NewFile == nil {
+		return nil, syserror.EACCES
+	}
+
+	inode, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
+		return d.NewFile(ctx, dir, perms)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Take an extra ref on inode, which will be owned by the dirent.
+	inode.IncRef()
+
+	// Create the Dirent and corresponding file.
+	created := fs.NewDirent(inode, name)
+	defer created.DecRef()
+	return created.Inode.GetFile(ctx, created, flags)
+}
+
+// CreateLink returns a new link.
+func (d *Dir) CreateLink(ctx context.Context, dir *fs.Inode, oldname, newname string) error {
+	if d.CreateOps == nil || d.CreateOps.NewSymlink == nil {
+		return syserror.EACCES
+	}
+	_, err := d.createInodeOperationsCommon(ctx, newname, func() (*fs.Inode, error) {
+		return d.NewSymlink(ctx, dir, oldname)
+	})
+	return err
+}
+
+// CreateHardLink creates a new hard link.
+func (d *Dir) CreateHardLink(ctx context.Context, dir *fs.Inode, target *fs.Inode, name string) error {
+	if len(name) > linux.NAME_MAX {
+		return syserror.ENAMETOOLONG
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	// Take an extra reference on the inode and add it to our children.
+	target.IncRef()
+
+	// The link count will be incremented in addChildLocked.
+	d.addChildLocked(ctx, name, target)
+
+	return nil
+}
+
+// CreateDirectory returns a new subdirectory.
+func (d *Dir) CreateDirectory(ctx context.Context, dir *fs.Inode, name string, perms fs.FilePermissions) error {
+	if d.CreateOps == nil || d.CreateOps.NewDir == nil {
+		return syserror.EACCES
+	}
+	_, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
+		return d.NewDir(ctx, dir, perms)
+	})
+	return err
+}
+
+// Bind implements fs.InodeOperations.Bind.
+func (d *Dir) Bind(ctx context.Context, dir *fs.Inode, name string, ep transport.BoundEndpoint, perms fs.FilePermissions) (*fs.Dirent, error) {
+	if d.CreateOps == nil || d.CreateOps.NewBoundEndpoint == nil {
+		return nil, syserror.EACCES
+	}
+	inode, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
+		return d.NewBoundEndpoint(ctx, dir, ep, perms)
+	})
+	if err == syscall.EEXIST {
+		return nil, syscall.EADDRINUSE
+	}
+	if err != nil {
+		return nil, err
+	}
+	// Take another ref on inode which will be donated to the new dirent.
+	inode.IncRef()
+	return fs.NewDirent(inode, name), nil
+}
+
+// CreateFifo implements fs.InodeOperations.CreateFifo.
+func (d *Dir) CreateFifo(ctx context.Context, dir *fs.Inode, name string, perms fs.FilePermissions) error {
+	if d.CreateOps == nil || d.CreateOps.NewFifo == nil {
+		return syserror.EACCES
+	}
+	_, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
+		return d.NewFifo(ctx, dir, perms)
+	})
+	return err
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (d *Dir) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	flags.Pread = true
+	return fs.NewFile(ctx, dirent, flags, &dirFileOperations{dir: d}), nil
+}
+
+// Rename implements fs.InodeOperations.Rename.
+func (*Dir) Rename(ctx context.Context, inode *fs.Inode, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return Rename(ctx, oldParent.InodeOperations, oldName, newParent.InodeOperations, newName, replacement)
+}
+
+// dirFileOperations implements fs.FileOperations for a ramfs directory.
+//
+// +stateify savable
+type dirFileOperations struct {
+	fsutil.DirFileOperations        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+
+	// dirCursor contains the name of the last directory entry that was
+	// serialized.
+	dirCursor string
+
+	// dir is the ramfs dir that this file corresponds to.
+	dir *Dir
+}
+
+var _ fs.FileOperations = (*dirFileOperations)(nil)
+
+// Seek implements fs.FileOperations.Seek.
+func (dfo *dirFileOperations) Seek(ctx context.Context, file *fs.File, whence fs.SeekWhence, offset int64) (int64, error) {
+	return fsutil.SeekWithDirCursor(ctx, file, whence, offset, &dfo.dirCursor)
+}
+
+// IterateDir implements DirIterator.IterateDir.
+func (dfo *dirFileOperations) IterateDir(ctx context.Context, dirCtx *fs.DirCtx, offset int) (int, error) {
+	dfo.dir.mu.Lock()
+	defer dfo.dir.mu.Unlock()
+
+	n, err := fs.GenericReaddir(dirCtx, dfo.dir.dentryMap)
+	return offset + n, err
+}
+
+// Readdir implements FileOperations.Readdir.
+func (dfo *dirFileOperations) Readdir(ctx context.Context, file *fs.File, serializer fs.DentrySerializer) (int64, error) {
+	root := fs.RootFromContext(ctx)
+	if root != nil {
+		defer root.DecRef()
+	}
+	dirCtx := &fs.DirCtx{
+		Serializer: serializer,
+		DirCursor:  &dfo.dirCursor,
+	}
+	dfo.dir.InodeSimpleAttributes.NotifyAccess(ctx)
+	return fs.DirentReaddir(ctx, file.Dirent, dfo, root, dirCtx, file.Offset())
+}
+
+// hasChildren is a helper method that determines whether an arbitrary inode
+// (not necessarily ramfs) has any children.
+func hasChildren(ctx context.Context, inode *fs.Inode) (bool, error) {
+	// Take an extra ref on inode which will be given to the dirent and
+	// dropped when that dirent is destroyed.
+	inode.IncRef()
+	d := fs.NewTransientDirent(inode)
+	defer d.DecRef()
+
+	file, err := inode.GetFile(ctx, d, fs.FileFlags{Read: true})
+	if err != nil {
+		return false, err
+	}
+	defer file.DecRef()
+
+	ser := &fs.CollectEntriesSerializer{}
+	if err := file.Readdir(ctx, ser); err != nil {
+		return false, err
+	}
+	// We will always write "." and "..", so ignore those two.
+	if ser.Written() > 2 {
+		return true, nil
+	}
+	return false, nil
+}
+
+// Rename renames from a *ramfs.Dir to another *ramfs.Dir.
+func Rename(ctx context.Context, oldParent fs.InodeOperations, oldName string, newParent fs.InodeOperations, newName string, replacement bool) error {
+	op, ok := oldParent.(*Dir)
+	if !ok {
+		return syserror.EXDEV
+	}
+	np, ok := newParent.(*Dir)
+	if !ok {
+		return syserror.EXDEV
+	}
+	if len(newName) > linux.NAME_MAX {
+		return syserror.ENAMETOOLONG
+	}
+
+	np.mu.Lock()
+	defer np.mu.Unlock()
+
+	// Is this is an overwriting rename?
+	if replacement {
+		replaced, ok := np.children[newName]
+		if !ok {
+			panic(fmt.Sprintf("Dirent claims rename is replacement, but %q is missing from %+v", newName, np))
+		}
+
+		// Non-empty directories cannot be replaced.
+		if fs.IsDir(replaced.StableAttr) {
+			if ok, err := hasChildren(ctx, replaced); err != nil {
+				return err
+			} else if ok {
+				return syserror.ENOTEMPTY
+			}
+		}
+
+		// Remove the replaced child and drop our reference on it.
+		inode, err := np.removeChildLocked(ctx, newName)
+		if err != nil {
+			return err
+		}
+		inode.DecRef()
+	}
+
+	// Be careful, we may have already grabbed this mutex above.
+	if op != np {
+		op.mu.Lock()
+		defer op.mu.Unlock()
+	}
+
+	// Do the swap.
+	n := op.children[oldName]
+	op.removeChildLocked(ctx, oldName)
+	np.addChildLocked(ctx, newName, n)
+
+	return nil
+}