[PATCH v3] PCI: dwc: al: Check IORESOURCE_BUS existence during PCIe config preparation

[Aleksandr Mishin <amishin@t-argos.ru>]

If IORESOURCE_BUS is not provided in Device Tree it will be fabricated
in of_pci_parse_bus_range(). So NULL pointer dereference will not occur.
But other drivers do this check. So it can be added for code consistency.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
---
v1->v2: Add return code processing as suggested by Bjorn
v2->v3: Return -ENODEV instead of -EINVAL

 drivers/pci/controller/dwc/pcie-al.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-al.c b/drivers/pci/controller/dwc/pcie-al.c
index 6dfdda59f328..643115f74092 100644
--- a/drivers/pci/controller/dwc/pcie-al.c
+++ b/drivers/pci/controller/dwc/pcie-al.c
@@ -242,18 +242,24 @@ static struct pci_ops al_child_pci_ops = {
 	.write = pci_generic_config_write,
 };
 
-static void al_pcie_config_prepare(struct al_pcie *pcie)
+static int al_pcie_config_prepare(struct al_pcie *pcie)
 {
 	struct al_pcie_target_bus_cfg *target_bus_cfg;
 	struct dw_pcie_rp *pp = &pcie->pci->pp;
 	unsigned int ecam_bus_mask;
+	struct resource_entry *ft;
 	u32 cfg_control_offset;
+	struct resource *bus;
 	u8 subordinate_bus;
 	u8 secondary_bus;
 	u32 cfg_control;
 	u32 reg;
-	struct resource *bus = resource_list_first_type(&pp->bridge->windows, IORESOURCE_BUS)->res;
 
+	ft = resource_list_first_type(&pp->bridge->windows, IORESOURCE_BUS);
+	if (!ft)
+		return -ENODEV;
+
+	bus = ft->res;
 	target_bus_cfg = &pcie->target_bus_cfg;
 
 	ecam_bus_mask = (pcie->ecam_size >> PCIE_ECAM_BUS_SHIFT) - 1;
@@ -287,6 +293,8 @@ static void al_pcie_config_prepare(struct al_pcie *pcie)
 	       FIELD_PREP(CFG_CONTROL_SEC_BUS_MASK, secondary_bus);
 
 	al_pcie_controller_writel(pcie, cfg_control_offset, reg);
+
+	return 0;
 }
 
 static int al_pcie_host_init(struct dw_pcie_rp *pp)
@@ -305,7 +313,9 @@ static int al_pcie_host_init(struct dw_pcie_rp *pp)
 	if (rc)
 		return rc;
 
-	al_pcie_config_prepare(pcie);
+	rc = al_pcie_config_prepare(pcie);
+	if (rc)
+		return rc;
 
 	return 0;
 }
-- 
2.30.2