linux-kernel - Re: [PATCH v11 0/5] Add new PCI_DEV_FLAGS_NO_RELAXED

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Date:   Tue, 15 Aug 2017 06:58:54 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     dingtianhong@...wei.com, leedom@...lsio.com, ashok.raj@...el.com,
        bhelgaas@...gle.com, helgaas@...nel.org, werner@...lsio.com,
        ganeshgr@...lsio.com, asit.k.mallick@...el.com,
        patrick.j.cramer@...el.com, Suravee.Suthikulpanit@....com,
        Bob.Shaw@....com, l.stach@...gutronix.de, amira@...lanox.com,
        gabriele.paoloni@...wei.com, David.Laight@...lab.com,
        jeffrey.t.kirsher@...el.com, catalin.marinas@....com,
        will.deacon@....com, mark.rutland@....com, robin.murphy@....com,
        alexander.duyck@...il.com, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com
Subject: Re: [PATCH v11 0/5] Add new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag

On Mon, 2017-08-14 at 22:15 -0700, David Miller wrote:
> From: Ding Tianhong <dingtianhong@...wei.com>
> Date: Tue, 15 Aug 2017 11:23:22 +0800
> 
> > Some devices have problems with Transaction Layer Packets with the Relaxed
> > Ordering Attribute set.  This patch set adds a new PCIe Device Flag,
> > PCI_DEV_FLAGS_NO_RELAXED_ORDERING, a set of PCI Quirks to catch some known
> > devices with Relaxed Ordering issues, and a use of this new flag by the
> > cxgb4 driver to avoid using Relaxed Ordering with problematic Root Complex
> > Ports.
>  ...
> 
> Series applied, thanks.

I got a NULL deref in pci_find_pcie_root_port()

Was it expected ?

This local hack seems to fix the issue.

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index af0cc3456dc1b48b1325c06c5edd2ca8cc22a640..cfd8eb5a3d0ba8347d44952ffab28d9c761044d3 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -522,7 +522,7 @@ struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev)
                bridge = pci_upstream_bridge(bridge);
        }
 
-       if (pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT)
+       if (highest_pcie_bridge && pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT)
                return NULL;
 
        return highest_pcie_bridge;