[PATCH v2] PCI: kirin: Fix buffer overflow

[Alexandra Diupina]

In kirin_pcie_parse_port() pcie->num_slots is compared to
pcie->gpio_id_reset size (MAX_PCI_SLOTS). Need to fix
condition to pcie->num_slots + 1 >= MAX_PCI_SLOTS and move
pcie->num_slots increment lower to avoid out-of-bounds
array access.

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

Fixes: b22dbbb24571 ("PCI: kirin: Support PERST# GPIOs for HiKey970 external PEX 8606 bridge")
Signed-off-by: Alexandra Diupina <adiupina@xxxxxxxxxxxxx>
---
v2: some changes
 drivers/pci/controller/dwc/pcie-kirin.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-kirin.c b/drivers/pci/controller/dwc/pcie-kirin.c
index d5523f302102..deab1e653b9a 100644
--- a/drivers/pci/controller/dwc/pcie-kirin.c
+++ b/drivers/pci/controller/dwc/pcie-kirin.c
@@ -412,12 +412,12 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
 			if (pcie->gpio_id_reset[i] < 0)
 				continue;
 
-			pcie->num_slots++;
-			if (pcie->num_slots > MAX_PCI_SLOTS) {
+			if (pcie->num_slots + 1 >= MAX_PCI_SLOTS) {
 				dev_err(dev, "Too many PCI slots!\n");
 				ret = -EINVAL;
 				goto put_node;
 			}
+			pcie->num_slots++;
 
 			ret = of_pci_get_devfn(child);
 			if (ret < 0) {
-- 
2.30.2