From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932139AbdGJPsT (ORCPT ); Mon, 10 Jul 2017 11:48:19 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:37130 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754467AbdGJPrq (ORCPT ); Mon, 10 Jul 2017 11:47:46 -0400 Date: Mon, 10 Jul 2017 16:49:24 +0100 From: Lorenzo Pieralisi To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Ralf Baechle , Paul Burton , Bjorn Helgaas Subject: Re: [PATCH 2/2] MIPS/PCI: Fix pcibios_scan_bus() NULL check code path Message-ID: <20170710154924.GA13344@red-moon> References: <20170710123409.9043-1-lorenzo.pieralisi@arm.com> <20170710123409.9043-2-lorenzo.pieralisi@arm.com> <20170710145553.GA20365@bhelgaas-glaptop.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170710145553.GA20365@bhelgaas-glaptop.roam.corp.google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 10, 2017 at 09:55:53AM -0500, Bjorn Helgaas wrote: > On Mon, Jul 10, 2017 at 01:34:09PM +0100, Lorenzo Pieralisi wrote: > > If pci_scan_root_bus() fails (ie returns NULL) pcibios_scan_bus() must > > return immediately since the struct pci_bus pointer it returns is not > > valid and cannot be used. > > > > Move code checking the pci_scan_root_bus() return value to reinstate > > proper pcibios_scanbus() error path behaviour. > > > > Signed-off-by: Lorenzo Pieralisi > > Cc: Ralf Baechle > > Cc: Paul Burton > > Cc: Bjorn Helgaas > > I agree this is certainly broken. In fact, I think I broke it with > 9e808eb6a768 ("PCI: Cleanup control flow") in 2015. So probably v4.14 > material? Yes that makes sense, I spotted it since I am preparing patches to remove pci_fixup_irqs() from the kernel (by removing it from all arches that still use it), I think that technically: 88555b481958 ("MIPS: PCI: Support for CONFIG_PCI_DOMAINS_GENERIC") created a possible breakage (ie by using the possible NULL bus pointer), if you merge it in one branch for 4.14 I will base the pci_fixup_irqs() removal on top of it and post the series, just let me know please. Thanks ! Lorenzo > > --- > > arch/mips/pci/pci-legacy.c | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/arch/mips/pci/pci-legacy.c b/arch/mips/pci/pci-legacy.c > > index 174575a..71d62f8 100644 > > --- a/arch/mips/pci/pci-legacy.c > > +++ b/arch/mips/pci/pci-legacy.c > > @@ -89,16 +89,16 @@ static void pcibios_scanbus(struct pci_controller *hose) > > pci_add_resource(&resources, hose->busn_resource); > > bus = pci_scan_root_bus(NULL, next_busno, hose->pci_ops, hose, > > &resources); > > - hose->bus = bus; > > - > > - need_domain_info = need_domain_info || pci_domain_nr(bus); > > - set_pci_need_domain_info(hose, need_domain_info); > > - > > if (!bus) { > > pci_free_resource_list(&resources); > > return; > > } > > > > + hose->bus = bus; > > + > > + need_domain_info = need_domain_info || pci_domain_nr(bus); > > + set_pci_need_domain_info(hose, need_domain_info); > > + > > next_busno = bus->busn_res.end + 1; > > /* Don't allow 8-bit bus number overflow inside the hose - > > reserve some space for bridges. */ > > -- > > 2.10.0 > >