From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9782DC28CC0 for ; Wed, 29 May 2019 11:01:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7078621019 for ; Wed, 29 May 2019 11:01:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726015AbfE2LBC (ORCPT ); Wed, 29 May 2019 07:01:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54048 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbfE2LBB (ORCPT ); Wed, 29 May 2019 07:01:01 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9B7E181109; Wed, 29 May 2019 11:01:01 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-173.rdu2.redhat.com [10.10.120.173]) by smtp.corp.redhat.com (Postfix) with ESMTP id 894035D704; Wed, 29 May 2019 11:00:58 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <155905930702.7587.7100265859075976147.stgit@warthog.procyon.org.uk> <155905933492.7587.6968545866041839538.stgit@warthog.procyon.org.uk> To: Jann Horn , casey@schaufler-ca.com Cc: dhowells@redhat.com, Al Viro , raven@themaw.net, linux-fsdevel , Linux API , linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module , kernel list Subject: Re: [PATCH 3/7] vfs: Add a mount-notification facility MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <14346.1559127657.1@warthog.procyon.org.uk> Date: Wed, 29 May 2019 12:00:57 +0100 Message-ID: <14347.1559127657@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 29 May 2019 11:01:01 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Jann Horn wrote: > > +void post_mount_notification(struct mount *changed, > > + struct mount_notification *notify) > > +{ > > + const struct cred *cred = current_cred(); > > This current_cred() looks bogus to me. Can't mount topology changes > come from all sorts of places? For example, umount_mnt() from > umount_tree() from dissolve_on_fput() from __fput(), which could > happen pretty much anywhere depending on where the last reference gets > dropped? IIRC, that's what Casey argued is the right thing to do from a security PoV. Casey? Maybe I should pass in NULL creds in the case that an event is being generated because an object is being destroyed due to the last usage[*] being removed. [*] Usage, not ref - Superblocks are a bit weird in their accounting. David