From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766Ab2HORII (ORCPT ); Wed, 15 Aug 2012 13:08:08 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35887 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751457Ab2HORIG (ORCPT ); Wed, 15 Aug 2012 13:08:06 -0400 Date: Wed, 15 Aug 2012 18:07:58 +0100 From: Andy Whitcroft To: Casey Schaufler Cc: Miklos Szeredi , viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, nbd@openwrt.org, neilb@suse.de, hramrach@centrum.cz, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, ricwheeler@gmail.com, dhowells@redhat.com, hpj@urpla.net, sedat.dilek@googlemail.com, penberg@kernel.org, goran.cetusic@gmail.com, romain@orebokech.com, mszeredi@suse.cz Subject: Re: [PATCH 12/13] ovl: switch to __inode_permission() Message-ID: <20120815170758.GP29100@dm> References: <1345045700-9062-1-git-send-email-miklos@szeredi.hu> <1345045700-9062-13-git-send-email-miklos@szeredi.hu> <502BD587.6090807@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <502BD587.6090807@schaufler-ca.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 15, 2012 at 09:59:51AM -0700, Casey Schaufler wrote: > On 8/15/2012 8:48 AM, Miklos Szeredi wrote: > > From: Andy Whitcroft > > > > When checking permissions on an overlayfs inode we do not take into > > account either device cgroup restrictions nor security permissions. > > This allows a user to mount an overlayfs layer over a restricted device > > directory and by pass those permissions to open otherwise restricted > > files. > > Why is this a good idea? Either you're not including enough context > about the conditions under which this can occur, or you're suggesting > the introduction of a trivial mechanism for bypassing all file access > controls. This does not seem right. It is stating that the unprotected case is how things was before this patch switches us over to __inode_permisssions. The patch is closing the hole indicated. -apw > > > > Switch over to __inode_permissions. > > > > Signed-off-by: Andy Whitcroft > > Signed-off-by: Miklos Szeredi > > --- > > fs/overlayfs/inode.c | 12 +----------- > > 1 files changed, 1 insertions(+), 11 deletions(-) > > > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > > index e854720..f3a534f 100644 > > --- a/fs/overlayfs/inode.c > > +++ b/fs/overlayfs/inode.c > > @@ -100,19 +100,9 @@ int ovl_permission(struct inode *inode, int mask) > > if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && > > (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) > > goto out_dput; > > - > > - /* > > - * Nobody gets write access to an immutable file. > > - */ > > - err = -EACCES; > > - if (IS_IMMUTABLE(realinode)) > > - goto out_dput; > > } > > > > - if (realinode->i_op->permission) > > - err = realinode->i_op->permission(realinode, mask); > > - else > > - err = generic_permission(realinode, mask); > > + err = __inode_permission(realinode, mask); > > out_dput: > > dput(alias); > > return err; >