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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 8112BC2BB40 for ; Tue, 8 Dec 2020 17:12:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 403D423B04 for ; Tue, 8 Dec 2020 17:12:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730649AbgLHRM2 (ORCPT ); Tue, 8 Dec 2020 12:12:28 -0500 Received: from bmailout2.hostsharing.net ([83.223.78.240]:47867 "EHLO bmailout2.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730330AbgLHRM2 (ORCPT ); Tue, 8 Dec 2020 12:12:28 -0500 Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (not verified)) by bmailout2.hostsharing.net (Postfix) with ESMTPS id 8F8712800B1AA; Tue, 8 Dec 2020 18:11:28 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id B8441DCE4; Tue, 8 Dec 2020 18:11:45 +0100 (CET) Date: Tue, 8 Dec 2020 18:11:45 +0100 From: Lukas Wunner To: Sasha Levin Cc: Nathan Chancellor , Greg Kroah-Hartman , Mark Brown , Sudip Mukherjee , stable@vger.kernel.org Subject: Re: [PATCH 4.19-stable 4/5] spi: bcm2835aux: Fix use-after-free on unbind Message-ID: <20201208171145.GA3241@wunner.de> References: <70e63c9a7ed172e15b9d1fe82d44603ea9c76288.1607257456.git.lukas@wunner.de> <20201208004901.GB587492@ubuntu-m3-large-x86> <20201208073241.GA29998@wunner.de> <20201208134739.GJ643756@sasha-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201208134739.GJ643756@sasha-vm> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Dec 08, 2020 at 08:47:39AM -0500, Sasha Levin wrote: > On Tue, Dec 08, 2020 at 08:32:41AM +0100, Lukas Wunner wrote: > > On Mon, Dec 07, 2020 at 05:49:01PM -0700, Nathan Chancellor wrote: > > > On Sun, Dec 06, 2020 at 01:31:03PM +0100, Lukas Wunner wrote: > > > > [ Upstream commit e13ee6cc4781edaf8c7321bee19217e3702ed481 ] > > > > > > > > bcm2835aux_spi_remove() accesses the driver's private data after calling > > > > spi_unregister_master() even though that function releases the last > > > > reference on the spi_master and thereby frees the private data. > > > > > > > > Fix by switching over to the new devm_spi_alloc_master() helper which > > > > keeps the private data accessible until the driver has unbound. > > > > > > > > Fixes: b9dd3f6d4172 ("spi: bcm2835aux: Fix controller unregister order") > > > > Signed-off-by: Lukas Wunner > > > > Cc: # v4.4+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation > > > > Cc: # v4.4+: b9dd3f6d4172: spi: bcm2835aux: Fix controller unregister order > > > > Cc: # v4.4+ > > > > Link: https://lore.kernel.org/r/b290b06357d0c0bdee9cecc539b840a90630f101.1605121038.git.lukas@wunner.de > > > > Signed-off-by: Mark Brown > > > > > > Please ensure that commit d853b3406903 ("spi: bcm2835aux: Restore err > > > assignment in bcm2835aux_spi_probe") is picked up with this patch in all > > > of the stable trees that it is applied to. > > > > That shouldn't be necessary as I've made sure that the backports to > > 4.19 and earlier do not exhibit the issue fixed by d853b3406903. > > > > However, nobody is perfect, so if I've missed anything, please let > > me know. > > Could we instead have the backports exhibit the issue (like they did > upstream) and then take d853b3406903 on top? The upstream commit e13ee6cc4781 did not apply cleanly to 4.19 and earlier, several adjustments were required. Could I have made it so that the fixup d853b3406903 would have still been required? Probably, but it seems a little silly to submit a known-bad patch. Thanks, Lukas