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

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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: 51ebfc92b7 ("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+
This commit is contained in:
Bjorn Helgaas 2017-01-27 15:00:45 -06:00
parent 4d191b1b63
commit 030305d69f
1 changed files with 13 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/pci/pcie/aspm.c
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@ -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;