diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index bb63254ed848..735d7522a3a9 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -362,6 +362,9 @@ repeat:
 			rs.cont_size = isonum_733(rr->u.CE.size);
 			break;
 		case SIG('E', 'R'):
+			/* Invalid length of ER tag id? */
+			if (rr->u.ER.len_id + offsetof(struct rock_ridge, u.ER.data) > rr->len)
+				goto out;
 			ISOFS_SB(inode->i_sb)->s_rock = 1;
 			printk(KERN_DEBUG "ISO 9660 Extensions: ");
 			{