Fix bind() on overlays.

InodeOperations.Bind now returns a Dirent which will be cached in the Dirent
tree.

When an overlay is in-use, Bind cannot return the Dirent created by the upper
filesystem because the Dirent does not know about the overlay. Instead,
overlayBind must create a new overlay-aware Inode and Dirent and return that.
This is analagous to how Lookup and overlayLookup work.

PiperOrigin-RevId: 208670710
Change-Id: I6390affbcf94c38656b4b458e248739b4853da29

1 files changed, 17 insertions, 1 deletions

diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index 34e62a4a2..e18e095a0 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -364,7 +364,23 @@ func overlayBind(ctx context.Context, o *overlayEntry, name string, data unix.Bo
 	if o.upper == nil {
 		return nil, syserror.EOPNOTSUPP
 	}
-	return o.upper.InodeOperations.Bind(ctx, o.upper, name, data, perm)
+	d, err := o.upper.InodeOperations.Bind(ctx, o.upper, name, data, perm)
+	if err != nil {
+		return nil, err
+	}
+
+	// Grab the inode and drop the dirent, we don't need it.
+	inode := d.Inode
+	inode.IncRef()
+	d.DecRef()
+
+	// Create a new overlay entry and dirent for the socket.
+	entry, err := newOverlayEntry(ctx, inode, nil, false)
+	if err != nil {
+		inode.DecRef()
+		return nil, err
+	}
+	return NewDirent(newOverlayInode(ctx, entry, inode.MountSource), name), nil
 }
 
 func overlayBoundEndpoint(o *overlayEntry, path string) unix.BoundEndpoint {