Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756207AbdCGVba (ORCPT ); Tue, 7 Mar 2017 16:31:30 -0500 Received: from mail.kernel.org ([198.145.29.136]:48606 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755925AbdCGVb0 (ORCPT ); Tue, 7 Mar 2017 16:31:26 -0500 Date: Tue, 7 Mar 2017 15:20:59 -0600 From: Bjorn Helgaas To: Yinghai Lu Cc: Bjorn Helgaas , Rajat Jain , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI/aspm: Fix link->downstream setting Message-ID: <20170307212059.GH21358@bhelgaas-glaptop.roam.corp.google.com> References: <20170301082540.23995-1-yinghai@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170301082540.23995-1-yinghai@kernel.org> 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 Content-Length: 2407 Lines: 68 On Wed, Mar 01, 2017 at 12:25:40AM -0800, Yinghai Lu wrote: > ~ # echo 1 > /sys/bus/pci/devices/0000\:0b\:00.0/remove > ... > BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 > IP: pcie_config_aspm_link+0x5d/0x2b0 > Call Trace: > pcie_aspm_exit_link_state+0x75/0x130 > pci_stop_bus_device+0xa4/0xb0 > pci_stop_and_remove_bus_device_locked+0x1a/0x30 > remove_store+0x50/0x70 > dev_attr_store+0x18/0x30 > sysfs_kf_write+0x44/0x60 > kernfs_fop_write+0x10e/0x190 > __vfs_write+0x28/0x110 > ? rcu_read_lock_sched_held+0x5d/0x80 > ? rcu_sync_lockdep_assert+0x2c/0x60 > ? __sb_start_write+0x173/0x1a0 > ? vfs_write+0xb3/0x180 > vfs_write+0xc4/0x180 > SyS_write+0x49/0xa0 > do_syscall_64+0xa6/0x1c0 > entry_SYSCALL64_slow_path+0x25/0x25 > ---[ end trace bd187ee0267df5d9 ]--- > > set downstream even with blacklist path. > > Signed-off-by: Yinghai Lu Applied with Rajat's ack to for-linus for v4.11, thanks! I added a stable tag, since I think this bug has been there a long time and it causes a NULL pointer dereference. > --- > drivers/pci/pcie/aspm.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > Index: linux-2.6/drivers/pci/pcie/aspm.c > =================================================================== > --- linux-2.6.orig/drivers/pci/pcie/aspm.c > +++ linux-2.6/drivers/pci/pcie/aspm.c > @@ -478,7 +478,7 @@ static void aspm_calc_l1ss_info(struct p > > static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist) > { > - struct pci_dev *child, *parent = link->pdev; > + struct pci_dev *child = link->downstream, *parent = link->pdev; > struct pci_bus *linkbus = parent->subordinate; > struct aspm_register_info upreg, dwreg; > > @@ -491,9 +491,7 @@ static void pcie_aspm_cap_init(struct pc > > /* Get upstream/downstream components' register state */ > pcie_get_aspm_reg(parent, &upreg); > - child = pci_function_0(linkbus); > pcie_get_aspm_reg(child, &dwreg); > - link->downstream = child; > > /* > * If ASPM not supported, don't mess with the clocks and link, > @@ -800,6 +798,7 @@ static struct pcie_link_state *alloc_pci > INIT_LIST_HEAD(&link->children); > INIT_LIST_HEAD(&link->link); > link->pdev = pdev; > + link->downstream = pci_function_0(pdev->subordinate); > > /* > * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe