PCI: pci-bridge-emul: Fix array overruns, improve safety

[ Upstream commit f8ee579 ]

We allow up to PCI_EXP_SLTSTA2 registers to be accessed, but the
pcie_cap_regs_behavior[] array only covers up to PCI_EXP_RTSTA.  Expand
this array to avoid walking off the end of it.

Do the same for pci_regs_behavior for consistency[], and add a
BUILD_BUG_ON() to also check the bridge->conf structure size.

Fixes: 23a5fba ("PCI: Introduce PCI bridge emulated config space common logic")
Link: https://lore.kernel.org/r/E1l6z9W-0006Re-MQ@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/pci/pci-bridge-emul.c

@@ -21,8 +21,9 @@
 #include "pci-bridge-emul.h"
 
 #define PCI_BRIDGE_CONF_END	PCI_STD_HEADER_SIZEOF
+#define PCI_CAP_PCIE_SIZEOF	(PCI_EXP_SLTSTA2 + 2)
 #define PCI_CAP_PCIE_START	PCI_BRIDGE_CONF_END
-#define PCI_CAP_PCIE_END	(PCI_CAP_PCIE_START + PCI_EXP_SLTSTA2 + 2)
+#define PCI_CAP_PCIE_END	(PCI_CAP_PCIE_START + PCI_CAP_PCIE_SIZEOF)
 
 /**
  * struct pci_bridge_reg_behavior - register bits behaviors
@@ -46,7 +47,8 @@ struct pci_bridge_reg_behavior {
 	u32 w1c;
 };
 
-static const struct pci_bridge_reg_behavior pci_regs_behavior[] = {
+static const
+struct pci_bridge_reg_behavior pci_regs_behavior[PCI_STD_HEADER_SIZEOF / 4] = {
 	[PCI_VENDOR_ID / 4] = { .ro = ~0 },
 	[PCI_COMMAND / 4] = {
 		.rw = (PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
@@ -164,7 +166,8 @@ static const struct pci_bridge_reg_behavior pci_regs_behavior[] = {
 	},
 };
 
-static const struct pci_bridge_reg_behavior pcie_cap_regs_behavior[] = {
+static const
+struct pci_bridge_reg_behavior pcie_cap_regs_behavior[PCI_CAP_PCIE_SIZEOF / 4] = {
 	[PCI_CAP_LIST_ID / 4] = {
 		/*
 		 * Capability ID, Next Capability Pointer and
@@ -260,6 +263,8 @@ static const struct pci_bridge_reg_behavior pcie_cap_regs_behavior[] = {
 int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
 			 unsigned int flags)
 {
+	BUILD_BUG_ON(sizeof(bridge->conf) != PCI_BRIDGE_CONF_END);
+
 	bridge->conf.class_revision |= cpu_to_le32(PCI_CLASS_BRIDGE_PCI << 16);
 	bridge->conf.header_type = PCI_HEADER_TYPE_BRIDGE;
 	bridge->conf.cache_line_size = 0x10;