Re: [PATCH v11 0/5] Add new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag

[Eric Dumazet]

On Mon, 2017-08-14 at 22:15 -0700, David Miller wrote:
> From: Ding Tianhong <dingtianhong@xxxxxxxxxx>
> 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;