diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index 94ef92fe806c..1efa3ae2f41e 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -101,6 +101,15 @@ static int rock_continue(struct rock_state *rs)
 		goto out;
 	}
 
+	if ((unsigned)rs->cont_extent >= ISOFS_SB(rs->inode->i_sb)->s_nzones) {
+		printk(KERN_NOTICE "rock: corrupted directory entry. "
+			"extent=%u out of volume (nzones=%lu)\n",
+			(unsigned)rs->cont_extent,
+			ISOFS_SB(rs->inode->i_sb)->s_nzones);
+		ret = -EIO;
+		goto out;
+	}
+
 	if (rs->cont_extent) {
 		struct buffer_head *bh;