Commit 030305d6 authored Jan 27, 2017 by Bjorn Helgaas

PCI/ASPM: Handle PCI-to-PCIe bridges as roots of PCIe hierarchies

In a struct pcie_link_state, link->root points to the pcie_link_state of
the root of the PCIe hierarchy.  For the topmost link, this points to
itself (link->root = link).  For others, we copy the pointer from the
parent (link->root = link->parent->root).

Previously we recognized that Root Ports originated PCIe hierarchies, but
we treated PCI/PCI-X to PCIe Bridges as being in the middle of the
hierarchy, and when we tried to copy the pointer from link->parent->root,
there was no parent, and we dereferenced a NULL pointer:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
  IP: [<ffffffff9e424350>] pcie_aspm_init_link_state+0x170/0x820

Recognize that PCI/PCI-X to PCIe Bridges originate PCIe hierarchies just
like Root Ports do, so link->root for these devices should also point to
itself.

Fixes: 51ebfc92 ("PCI: Enumerate switches below PCI-to-PCIe bridges")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=193411
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1022181


Tested-by:  <lists@ssl-mail.com>
Tested-by: Jayachandran C. <jnair@caviumnetworks.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.2+

parent 4d191b1b

drivers/pci/pcie/aspm.c

+13 −6

Original line number	Diff line number	Diff line
		@@ -532,25 +532,32 @@ static struct pcie_link_state alloc_pcie_link_state(struct pci_dev pdev)
		link = kzalloc(sizeof(*link), GFP_KERNEL);
		if (!link)
		return NULL;

		INIT_LIST_HEAD(&link->sibling);
		INIT_LIST_HEAD(&link->children);
		INIT_LIST_HEAD(&link->link);
		link->pdev = pdev;
		if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) {

		/*
		* Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe
		* hierarchies.
		*/
		if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT \|\|
		pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE) {
		link->root = link;
		} else {
		struct pcie_link_state *parent;

		parent = pdev->bus->parent->self->link_state;
		if (!parent) {
		kfree(link);
		return NULL;
		}

		link->parent = parent;
		link->root = link->parent->root;
		list_add(&link->link, &parent->children);
		}
		/* Setup a pointer to the root port link */
		if (!link->parent)
		link->root = link;
		else
		link->root = link->parent->root;

		list_add(&link->sibling, &link_list);
		pdev->link_state = link;