From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752870AbdFPK1r (ORCPT ); Fri, 16 Jun 2017 06:27:47 -0400 Received: from salamandra.streefland.net ([83.162.229.199]:53314 "EHLO salamandra.streefland.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752830AbdFPK1p (ORCPT ); Fri, 16 Jun 2017 06:27:45 -0400 X-Greylist: delayed 782 seconds by postgrey-1.27 at vger.kernel.org; Fri, 16 Jun 2017 06:27:45 EDT Date: Fri, 16 Jun 2017 12:14:41 +0200 From: Dick Streefland To: linux-kernel@vger.kernel.org Cc: "Eric W. Biederman" Subject: autofs multi-map regression Message-ID: <20170616101440.GA1480@neos> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After a recent upgrade of a Ubuntu xenial machine, a particular autofs multi-map mount setup stopped working. A simplified example is: :::::::::::::: auto.master :::::::::::::: /net /etc/auto.net :::::::::::::: auto.net :::::::::::::: localhost / :/ /loc :/loc Accessing /net/localhost/loc should trigger two nested bind mounts on /net/localhost and /net/localhost/loc, but with the new kernel, it fails with ELOOP: $ ls /net/localhost/loc ls: cannot open directory '/net/localhost/loc': Too many levels of symbolic links The problem is related to the upgrade of the Ubuntu xenial kernel from 4.4.0-38.57 to 4.4.0-78.99. I bisected the regression to commit 731ac92843877f3633325203abc942193c1e9001, which is a Ubuntu backport of this upstream kernel commit: commit 1064f874abc0d05eeed8993815f584d847b72486 Author: Eric W. Biederman Date: Fri Jan 20 18:28:35 2017 +1300 mnt: Tuck mounts under others instead of creating shadow/side mounts. -- Dick