Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752478AbdHHLVo (ORCPT ); Tue, 8 Aug 2017 07:21:44 -0400 Received: from foss.arm.com ([217.140.101.70]:60374 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227AbdHHLVn (ORCPT ); Tue, 8 Aug 2017 07:21:43 -0400 Date: Tue, 8 Aug 2017 12:21:44 +0100 From: Will Deacon To: Robin Murphy Cc: Artem Savkov , iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, joro@8bytes.org Subject: Re: [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device Message-ID: <20170808112144.GE13355@arm.com> References: <20170808092614.GB12887@arm.com> <1502187962-16861-1-git-send-email-asavkov@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1651 Lines: 48 [+ Joerg] On Tue, Aug 08, 2017 at 11:37:40AM +0100, Robin Murphy wrote: > On 08/08/17 11:26, Artem Savkov wrote: > > Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device" > > removed fwspec assignment in legacy_binding path as redundant which is > > wrong. It needs to be updated after fwspec initialisation in > > arm_smmu_register_legacy_master() as it is dereferenced later. Without > > this there is a NULL-pointer dereference panic during boot on some hosts. > > Reviewed-by: Robin Murphy > > Thanks for fixing it up, and sorry for failing to document the > unfortunately subtle logic in the first place! Well, I was the one that messed it up: Acked-by: Will Deacon Joerg, can you pick this up as a fix for 4.13, please? Will > > Signed-off-by: Artem Savkov > > --- > > drivers/iommu/arm-smmu.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > > index b97188a..2d80fa8 100644 > > --- a/drivers/iommu/arm-smmu.c > > +++ b/drivers/iommu/arm-smmu.c > > @@ -1519,6 +1519,13 @@ static int arm_smmu_add_device(struct device *dev) > > > > if (using_legacy_binding) { > > ret = arm_smmu_register_legacy_master(dev, &smmu); > > + > > + /* > > + * If dev->iommu_fwspec is initally NULL, arm_smmu_register_legacy_master() > > + * will allocate/initialise a new one. Thus we need to update fwspec for > > + * later use. > > + */ > > + fwspec = dev->iommu_fwspec; > > if (ret) > > goto out_free; > > } else if (fwspec && fwspec->ops == &arm_smmu_ops) { > > >