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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 216E7C433EF for ; Thu, 31 Mar 2022 06:25:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231127AbiCaG1Q (ORCPT ); Thu, 31 Mar 2022 02:27:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230520AbiCaG1N (ORCPT ); Thu, 31 Mar 2022 02:27:13 -0400 Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0828A1ED070; Wed, 30 Mar 2022 23:25:21 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id 45FA080FA; Thu, 31 Mar 2022 06:23:13 +0000 (UTC) Date: Thu, 31 Mar 2022 09:25:20 +0300 From: Tony Lindgren To: Jason Gunthorpe Cc: Lu Baolu , Joerg Roedel , Christoph Hellwig , Ben Skeggs , Kevin Tian , Ashok Raj , Will Deacon , Robin Murphy , Alex Williamson , Eric Auger , Liu Yi L , Jacob jun Pan , David Airlie , Daniel Vetter , Thierry Reding , Jonathan Hunter , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Christoph Hellwig , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, regressions@lists.linux.dev Subject: Re: [PATCH v4 8/9] iommu: Remove unused argument in is_attach_deferred Message-ID: References: <20220216025249.3459465-1-baolu.lu@linux.intel.com> <20220216025249.3459465-9-baolu.lu@linux.intel.com> <20220330142340.GA2111031@nvidia.com> <20220330173323.GA2120790@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220330173323.GA2120790@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, * Jason Gunthorpe [220330 17:31]: > On Wed, Mar 30, 2022 at 08:19:37PM +0300, Tony Lindgren wrote: > > > > > __iommu_probe_device from probe_iommu_group+0x2c/0x38 > > > > probe_iommu_group from bus_for_each_dev+0x74/0xbc > > > > bus_for_each_dev from bus_iommu_probe+0x34/0x2e8 > > > > bus_iommu_probe from bus_set_iommu+0x80/0xc8 > > > > bus_set_iommu from omap_iommu_init+0x88/0xcc > > > > omap_iommu_init from do_one_initcall+0x44/0x24c > > > > > > > > Any ideas for a fix? > > > > > > > > It would be good to fix this quickly so we don't end up with a broken > > > > v5.18-rc1.. > > > > > > > > For reference, this is mainline commit 41bb23e70b50 ("iommu: Remove unused > > > > argument in is_attach_deferred"). > > > > > > Are you confident in the bisection? I don't see how that commit could > > > NULL deref.. > > > > Oops sorry you're right, the breaking commit is a different patch, it's > > 3f6634d997db ("iommu: Use right way to retrieve iommu_ops") instead. I must > > have picked the wrong commit while testing. > > That makes alot more sense > > > > Can you find the code that is the NULL deref? > > > > I can debug a bit more tomorrow. > > Looks like omap's omap_iommu_probe_device() is buggy, it returns 0 on > error paths: > > num_iommus = of_property_count_elems_of_size(dev->of_node, "iommus", > sizeof(phandle)); > if (num_iommus < 0) > return 0; > > This function needs to return an errno -ENODEV > > Otherwise it causes a NULL dev->iommu->iommu_dev and dev_iommu_ops() will > crash. You got it. This fixes the issue for me. Looks like the regression already happened earlier and recent changes just expose it. For reference, fix posted at: https://lore.kernel.org/linux-iommu/20220331062301.24269-1-tony@atomide.com/T/#u Regards, Tony