From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932865AbcBDAer (ORCPT ); Wed, 3 Feb 2016 19:34:47 -0500 Received: from quartz.orcorp.ca ([184.70.90.242]:45774 "EHLO quartz.orcorp.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbcBDAeq (ORCPT ); Wed, 3 Feb 2016 19:34:46 -0500 Date: Wed, 3 Feb 2016 17:34:37 -0700 From: Jason Gunthorpe To: Jarkko Sakkinen Cc: Peter Huewe , stable@vger.kernel.org, tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [tpmdd-devel] [PATCH] tpm: fix rollback/cleanup before tpm_chip_register() Message-ID: <20160204003437.GB26123@obsidianresearch.com> References: <1454205942-13033-1-git-send-email-jarkko.sakkinen@linux.intel.com> <20160202231353.GA32711@obsidianresearch.com> <20160203160235.GA15567@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160203160235.GA15567@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Broken-Reverse-DNS: no host name found for IP address 10.0.0.160 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 03, 2016 at 08:02:35AM -0800, Jarkko Sakkinen wrote: > Would s/the platform device/the parent device/ be better? Yes > > > + /* Associate character device with the platform device only after > > > + * it is properly initialized. > > > + */ > > > + dev_set_drvdata(pdev, chip); > > > + devm_add_action(pdev, (void (*)(void *)) tpm_dev_release, > > > &chip->dev); > > > > No, a release function can never be called naked. The action needs > > to do put_device, which is the error unwind for device_initialize(). > > Got it (already from your first comment)! > > What does "called naked" even mean? I just don't understand the > english here and want to be sure that I understand what you are saying > and not make false assumptions. 'called naked' would refer to just open coding a call to tpm_dev_release, using it as a devm_add_action is the same as open coding. The function must only ever be called by put_device. > > > @@ -162,7 +165,10 @@ static int tpm_add_char_device(struct tpm_chip *chip) > > > MINOR(chip->dev.devt), rc); > > > > > > cdev_del(&chip->cdev); > > > - return rc; > > > + } else { > > > + devm_remove_action(chip->dev.parent, > > > + (void (*)(void *)) tpm_dev_release, > > > + &chip->dev); > > > > This is in the wrong place, the devm should be canceled only if > > tpm_chip_register returns success, at that point the caller's contract > > is to guarentee a call to tpm_chip_unregister, and > > tpm_chip_unregister does the put_device that calls the release > > function. > > rc == 0 at that point i.e. success. I don't see the problem here. It should not be in tpm_add_char_device I'm also not completely sure about the error handling around tpm_register - if it fails the tpm_chip should not be destroyed, and I think it does.. It would probably be ideal to just rely on devm to always do the final put_device and avoid the devm_remove_action entirely. I think this means a get_device will be needed in tpm_register after device_add ? Didn't look closely at how all the refs balance. Jason