Don't allow rename across different gofer or tmpfs mounts.

Fixes #2651.

PiperOrigin-RevId: 311193661

1 files changed, 5 insertions, 6 deletions

diff --git a/pkg/sentry/fs/tmpfs/tmpfs.go b/pkg/sentry/fs/tmpfs/tmpfs.go
index 3c2b583ae..b095312fe 100644
--- a/pkg/sentry/fs/tmpfs/tmpfs.go
+++ b/pkg/sentry/fs/tmpfs/tmpfs.go
@@ -39,14 +39,13 @@ var fsInfo = fs.Info{
 
 // rename implements fs.InodeOperations.Rename for tmpfs nodes.
 func rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
-	op, ok := oldParent.InodeOperations.(*Dir)
-	if !ok {
-		return syserror.EXDEV
-	}
-	np, ok := newParent.InodeOperations.(*Dir)
-	if !ok {
+	// Don't allow renames across different mounts.
+	if newParent.MountSource != oldParent.MountSource {
 		return syserror.EXDEV
 	}
+
+	op := oldParent.InodeOperations.(*Dir)
+	np := newParent.InodeOperations.(*Dir)
 	return ramfs.Rename(ctx, op.ramfsDir, oldName, np.ramfsDir, newName, replacement)
 }