From mboxrd@z Thu Jan 1 00:00:00 1970 From: jgunthorpe@obsidianresearch.com (Jason Gunthorpe) Date: Thu, 25 May 2017 14:09:31 -0600 Subject: [PATCH] tpm: vtpm_proxy: Do not run tpm2_shutdown In-Reply-To: References: <1495717956-14252-1-git-send-email-stefanb@linux.vnet.ibm.com> <20170525155059.GA5151@obsidianresearch.com> Message-ID: <20170525200931.GA12733@obsidianresearch.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.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 -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html