From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: Regression wrt mounting /proc in user namespace in 3.13 Date: Mon, 18 Nov 2013 14:08:30 +0000 Message-ID: <20131118140830.GA22075@mail.hallyn.com> References: <20131115164123.GN28794@redhat.com> <20131116164840.GA4441@mail.hallyn.com> <20131117030653.GA7670@mail.hallyn.com> <20131118031932.GA17621@mail.hallyn.com> <52899D09.5080202@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <52899D09.5080202-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Gao feng Cc: Containers , "Eric W. Biederman" List-Id: containers.vger.kernel.org Quoting Gao feng (gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org): > On 11/18/2013 11:19 AM, Serge E. Hallyn wrote: > > Quoting Serge E. Hallyn (serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org): > >> Low on power and no charger, but a quick test printing out if a mount is > >> !S_ISDIR or has nlink !=2 in fs_fully_visible() gives me: > >> > >> [ 92.939650] nlink is 1 for ino 8733 (0:3) > >> > >> (that's major 0 minor 3) > > > > Ok, so that is for binfmt_misc on /proc/sys/fs/binfmt_misc. The > > underlying directory is empty, and nlink is showing up as 1. > > > > Can we just get the nlink check changed to check for < 3 instead > > of ==2 ? > > > > I already reported this problem to Eric,hi is working on fix this problem. > > nlink is not the right thing to check if a directory is null. since > in all of filesystems, parent dir's nlink is increase only when we > create sub-dir. This whole thing feels very brittle. May I also point out that simply setting perms appears to work just fine instead of overmounting. If I chmod 700 /proc/swaps, unshare my pid and mount namespaces and remount /proc, then /proc/swaps is 700 in the new mount. Since our concern is with a new user namespace, which will be limited to world perms, this should suffice and allow us to skip all this nonsense. Eric? -serge