Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964805AbWJZAcO (ORCPT ); Wed, 25 Oct 2006 20:32:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964838AbWJZAcO (ORCPT ); Wed, 25 Oct 2006 20:32:14 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:37289 "EHLO ZenIV.linux.org.uk") by vger.kernel.org with ESMTP id S964805AbWJZAcN (ORCPT ); Wed, 25 Oct 2006 20:32:13 -0400 Date: Thu, 26 Oct 2006 01:32:02 +0100 From: Al Viro To: Alan Cox Cc: David Howells , sds@tycho.nsa.gov, jmorris@namei.org, chrisw@sous-sol.org, selinux@tycho.nsa.gov, linux-kernel@vger.kernel.org, aviro@redhat.com Subject: Re: Security issues with local filesystem caching Message-ID: <20061026003202.GH29920@ftp.linux.org.uk> References: <16969.1161771256@redhat.com> <1161819459.7615.42.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1161819459.7615.42.camel@localhost.localdomain> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1298 Lines: 22 On Thu, Oct 26, 2006 at 12:37:39AM +0100, Alan Cox wrote: > Ar Mer, 2006-10-25 am 11:14 +0100, ysgrifennodd David Howells: > > Currently, CacheFiles temporarily changes fsuid and fsgid to 0 whilst doing its > > own pathwalk through the cache and whilst creating files and directories in the > > cache. This allows it to deal with DAC security directly. All the directories > > it creates are given permissions mask 0700 and all files 0000. > > That seems sensible and fine. It is precisely why we added a separate > fsuid in the first place so that the user space nfsd could take on an fs > identity without breaking signal and other security based forms. I see a problem with that; not sure if that's what Christoph is objecting to. What about access to cache tree by root process that has nothing to do with that daemon? Should it get free access to that stuff, regardless of what policy might say about access to cached files? Or should we at least try to make sure that we have the instances in cache no more permissive than originals on NFS? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/