From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1165542AbdEYUJt (ORCPT ); Thu, 25 May 2017 16:09:49 -0400 Received: from quartz.orcorp.ca ([184.70.90.242]:32817 "EHLO quartz.orcorp.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1165527AbdEYUJq (ORCPT ); Thu, 25 May 2017 16:09:46 -0400 Date: Thu, 25 May 2017 14:09:31 -0600 From: Jason Gunthorpe To: Stefan Berger Cc: jarkko.sakkinen@linux.intel.com, tpmdd-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tpm: vtpm_proxy: Do not run tpm2_shutdown Message-ID: <20170525200931.GA12733@obsidianresearch.com> References: <1495717956-14252-1-git-send-email-stefanb@linux.vnet.ibm.com> <20170525155059.GA5151@obsidianresearch.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Broken-Reverse-DNS: no host name found for IP address 10.0.0.156 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 25, 2017 at 04:04:24PM -0400, Stefan Berger wrote: > On 05/25/2017 11:50 AM, Jason Gunthorpe wrote: > >On Thu, May 25, 2017 at 09:12:36AM -0400, Stefan Berger wrote: > >>The tpm2_shutdown does not work with the VTPM proxy driver since the > >>function only gets called when the backend file descriptor is already > >>closed and at this point no data can be sent anymore. A proper shutdown > >>would have to be initated by a user space application, such as a container > >>management stack, that sends the command via the character device before > >>terminating the TPM emulator. > >> > >>To avoid the tpm2_shutdown we introduce a TPM_CHIP_FLAG_NO_SHUTDOWN flag > >>that only the VTPM proxy driver sets. This also avoids misleading kernel > >>log messages. > >This seems strange to me.. > > > >Why isn't ops null if the fd has gone away? > > > >What is the call flow that hits this? > > In this function here. > > static void tpm_del_char_device(struct tpm_chip *chip) > { > cdev_device_del(&chip->cdev, &chip->dev); > > /* Make the chip unavailable. */ > mutex_lock(&idr_lock); > idr_replace(&dev_nums_idr, NULL, chip->dev_num); > mutex_unlock(&idr_lock); > > /* Make the driver uncallable. */ > down_write(&chip->ops_sem); > if (chip->flags & TPM_CHIP_FLAG_TPM2) > tpm2_shutdown(chip, TPM2_SU_CLEAR); > chip->ops = NULL; > up_write(&chip->ops_sem); > } > > The request cannot be deliver because the anonymous fd has been closed > already. The driver must always be able to process requests until tpm_del_char_device completes, so this is triggering an existing bug in vtpm. This change in core behvior is not going to fix the bug. eg a request from sysfs/etc could come in between vtpm fd closure and tpm_del_char_device, and it still must be handled properly. I guess you need to have transmit command fail fast once the fd is closed. Jason