From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754531AbdGJQip (ORCPT ); Mon, 10 Jul 2017 12:38:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:49228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754218AbdGJQin (ORCPT ); Mon, 10 Jul 2017 12:38:43 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D530922BCC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Date: Mon, 10 Jul 2017 11:38:30 -0500 From: Bjorn Helgaas To: Lorenzo Pieralisi 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: <20170710163830.GC20365@bhelgaas-glaptop.roam.corp.google.com> References: <20170710123409.9043-1-lorenzo.pieralisi@arm.com> <20170710123409.9043-2-lorenzo.pieralisi@arm.com> <20170710145553.GA20365@bhelgaas-glaptop.roam.corp.google.com> <20170710154924.GA13344@red-moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170710154924.GA13344@red-moon> 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 04:49:24PM +0100, Lorenzo Pieralisi wrote: > 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. Ah, you're right. I created some poor style (checking the return value after intervening code) with 9e808eb6a768, and then 88555b481958 fell into the trap I had laid. I put this on pci/irq-fixups for a continuation of your work and started it off with this patch. I will rebase the branch after -rc1, but that shouldn't be a problem for you because I normally apply patches from email rather than pulling them directly. I'll be on vacation July 14-28, so that probably won't happen until August. Thanks! > > > --- > > > 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 > > >