This is a note to let you know that I've just added the patch titled
PCI/ASPM: Deal with missing root ports in link state handling
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: pci-aspm-deal-with-missing-root-ports-in-link-state-handling.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From ee8bdfb6568d86bb93f55f8d99c4c643e77304ee Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel ard.biesheuvel@linaro.org Date: Mon, 2 Oct 2017 15:08:40 +0100 Subject: PCI/ASPM: Deal with missing root ports in link state handling
From: Ard Biesheuvel ard.biesheuvel@linaro.org
commit ee8bdfb6568d86bb93f55f8d99c4c643e77304ee upstream.
Even though it is unconventional, some PCIe host implementations omit the root ports entirely, and simply consist of a host bridge (which is not modeled as a device in the PCI hierarchy) and a link.
When the downstream device is an endpoint, our current code does not seem to mind this unusual configuration. However, when PCIe switches are involved, the ASPM code assumes that any downstream switch port has a parent, and blindly dereferences the bus->parent->self field of the pci_dev struct to chain the downstream link state to the link state of the root port. Given that the root port is missing, the link is not modeled at all, and nor is the link state, and attempting to access it results in a NULL pointer dereference and a crash.
Avoid this by allowing the link state chain to terminate at the downstream port if no root port exists.
Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Bjorn Helgaas bhelgaas@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/pci/pcie/aspm.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -526,10 +526,14 @@ static struct pcie_link_state *alloc_pci
/* * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe - * hierarchies. + * hierarchies. Note that some PCIe host implementations omit + * the root ports entirely, in which case a downstream port on + * a switch may become the root of the link state chain for all + * its subordinate endpoints. */ if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT || - pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE) { + pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE || + !pdev->bus->parent->self) { link->root = link; } else { struct pcie_link_state *parent;
Patches currently in stable-queue which might be from ard.biesheuvel@linaro.org are
queue-4.9/pci-aspm-deal-with-missing-root-ports-in-link-state-handling.patch