From 6f6f42466d902c92f21b46a45e6af22d1d663607 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Mon, 25 Jun 2018 08:17:33 -0500 Subject: [PATCH] PCI: shpchp: Manage SHPC unconditionally on non-ACPI systems An SHPC can be operated either by platform firmware or by the OS. The OS uses a host bridge ACPI _OSC method to negotiate for control of SHPC. If firmware wants to prevent an OS from operating an SHPC, it must supply an _OSC method that declines to grant SHPC ownership to the OS. If acpi_pci_find_root() returns NULL, it means there's no ACPI host bridge device (PNP0A03 or PNP0A08) and hence no _OSC method, so the OS is always allowed to manage the SHPC. Fix a NULL pointer dereference when CONFIG_ACPI=y but the current hardware/firmware platform doesn't support ACPI. In that case, acpi_get_hp_hw_control_from_firmware() is implemented but acpi_pci_find_root() returns NULL. Fixes: 90cc0c3cc709 ("PCI: shpchp: Add shpchp_is_native()") Link: https://lkml.kernel.org/r/20180621164715.28160-1-marc.zyngier@arm.com Reported-by: Marc Zyngier Tested-by: Marc Zyngier Signed-off-by: Bjorn Helgaas Reviewed-by: Mika Westerberg --- drivers/pci/hotplug/acpi_pcihp.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/pci/hotplug/acpi_pcihp.c b/drivers/pci/hotplug/acpi_pcihp.c index 3979f89b250a..5bd6c1573295 100644 --- a/drivers/pci/hotplug/acpi_pcihp.c +++ b/drivers/pci/hotplug/acpi_pcihp.c @@ -7,7 +7,6 @@ * All rights reserved. * * Send feedback to - * */ #include @@ -87,8 +86,17 @@ int acpi_get_hp_hw_control_from_firmware(struct pci_dev *pdev) return 0; /* If _OSC exists, we should not evaluate OSHP */ + + /* + * If there's no ACPI host bridge (i.e., ACPI support is compiled + * into the kernel but the hardware platform doesn't support ACPI), + * there's nothing to do here. + */ host = pci_find_host_bridge(pdev->bus); root = acpi_pci_find_root(ACPI_HANDLE(&host->dev)); + if (!root) + return 0; + if (root->osc_support_set) goto no_control; -- 2.30.2