Enable checkpoint/restore in cases of UDS use.

Previously, processes which used file-system Unix Domain Sockets could not be
checkpoint-ed in runsc because the sockets were saved with their inode
numbers which do not necessarily remain the same upon restore. Now,
the sockets are also saved with their paths so that the new inodes
can be determined for the sockets based on these paths after restoring.
Tests for cases with UDS use are included. Test cleanup to come.

PiperOrigin-RevId: 208268781
Change-Id: Ieaa5d5d9a64914ca105cae199fd8492710b1d7ec

2 files changed, 12 insertions, 7 deletions

diff --git a/pkg/sentry/fs/ramfs/dir.go b/pkg/sentry/fs/ramfs/dir.go
index 04432f28c..d8333194b 100644
--- a/pkg/sentry/fs/ramfs/dir.go
+++ b/pkg/sentry/fs/ramfs/dir.go
@@ -314,17 +314,22 @@ func (d *Dir) CreateDirectory(ctx context.Context, dir *fs.Inode, name string, p
 }
 
 // Bind implements fs.InodeOperations.Bind.
-func (d *Dir) Bind(ctx context.Context, dir *fs.Inode, name string, ep unix.BoundEndpoint, perms fs.FilePermissions) error {
+func (d *Dir) Bind(ctx context.Context, dir *fs.Inode, name string, ep unix.BoundEndpoint, perms fs.FilePermissions) (*fs.Dirent, error) {
 	if d.CreateOps == nil || d.CreateOps.NewBoundEndpoint == nil {
-		return ErrDenied
+		return nil, ErrDenied
 	}
-	_, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
+	inode, err := d.createInodeOperationsCommon(ctx, name, func() (*fs.Inode, error) {
 		return d.NewBoundEndpoint(ctx, dir, ep, perms)
 	})
 	if err == syscall.EEXIST {
-		return syscall.EADDRINUSE
+		return nil, syscall.EADDRINUSE
 	}
-	return err
+	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.
diff --git a/pkg/sentry/fs/ramfs/ramfs.go b/pkg/sentry/fs/ramfs/ramfs.go
index 13e72e775..1028b5f1d 100644
--- a/pkg/sentry/fs/ramfs/ramfs.go
+++ b/pkg/sentry/fs/ramfs/ramfs.go
@@ -279,8 +279,8 @@ func (*Entry) CreateDirectory(context.Context, *fs.Inode, string, fs.FilePermiss
 }
 
 // Bind is not supported by default.
-func (*Entry) Bind(context.Context, *fs.Inode, string, unix.BoundEndpoint, fs.FilePermissions) error {
-	return ErrInvalidOp
+func (*Entry) Bind(context.Context, *fs.Inode, string, unix.BoundEndpoint, fs.FilePermissions) (*fs.Dirent, error) {
+	return nil, ErrInvalidOp
 }
 
 // CreateFifo implements fs.InodeOperations.CreateFifo. CreateFifo is not supported by