commit 9d36a93af8fe ("PCI: j721e: Initialize pcie->cdns_pcie before using it")
Author: Bjorn Helgaas [off-list ref]
Date:   Thu Jan 27 15:49:49 2022 -0600

    PCI: j721e: Initialize pcie->cdns_pcie before using it

    Christian reported a NULL pointer dereference in j721e_pcie_probe() caused
    by 19e863828acf ("PCI: j721e: Drop redundant struct device *"), which
    removed struct j721e_pcie.dev since there's another copy in struct
    cdns_pcie.dev reachable via j721e_pcie->cdns_pcie->dev.

    The problem is that j721e_pcie->cdns_pcie was dereferenced before being
    initialized:

      j721e_pcie_probe
        pcie = devm_kzalloc()             # struct j721e_pcie
        j721e_pcie_ctrl_init(pcie)
          dev = pcie->cdns_pcie->dev      <-- dereference cdns_pcie
        switch (mode) {
        case PCI_MODE_RC:
          cdns_pcie = ...                 # alloc as part of pci_host_bridge
          pcie->cdns_pcie = cdns_pcie     <-- initialize pcie->cdns_pcie

    Initialize pcie->cdns_pcie before it is used.

    Fixes: 19e863828acf ("PCI: j721e: Drop redundant struct device *")
    Reported-by: Christian Gmeiner [off-list ref]
    Link: https://lore.kernel.org/r/20220124122132.435743-1-christian.gmeiner@gmail.com (local)
    Signed-off-by: Bjorn Helgaas [off-list ref]

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index 489586a4cdc7..5d950c1d9fd0 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c

@@ -372,10 +372,48 @@ static int j721e_pcie_probe(struct platform_device *pdev)

        mode = (u32)data->mode;

+       switch (mode) {
+       case PCI_MODE_RC:
+               if (!IS_ENABLED(CONFIG_PCIE_CADENCE_HOST))
+                       return -ENODEV;
+
+               bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
+               if (!bridge)
+                       return -ENOMEM;
+
+               if (!data->byte_access_allowed)
+                       bridge->ops = &cdns_ti_pcie_host_ops;
+               rc = pci_host_bridge_priv(bridge);
+               rc->quirk_retrain_flag = data->quirk_retrain_flag;
+               rc->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
+
+               cdns_pcie = &rc->pcie;
+               break;
+       case PCI_MODE_EP:
+               if (!IS_ENABLED(CONFIG_PCIE_CADENCE_EP))
+                       return -ENODEV;
+
+               ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
+               if (!ep)
+                       return -ENOMEM;
+
+               ep->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
+
+               cdns_pcie = &ep->pcie;
+               break;
+       default:
+               dev_err(dev, "INVALID device type %d\n", mode);
+               return 0;
+       }
+
+       cdns_pcie->dev = dev;
+       cdns_pcie->ops = &j721e_pcie_ops;
+
        pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
        if (!pcie)
                return -ENOMEM;

+       pcie->cdns_pcie = cdns_pcie;
        pcie->mode = mode;
        pcie->linkdown_irq_regfield = data->linkdown_irq_regfield;

@@ -426,28 +464,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)

        switch (mode) {
        case PCI_MODE_RC:
-               if (!IS_ENABLED(CONFIG_PCIE_CADENCE_HOST)) {
-                       ret = -ENODEV;
-                       goto err_get_sync;
-               }
-
-               bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
-               if (!bridge) {
-                       ret = -ENOMEM;
-                       goto err_get_sync;
-               }
-
-               if (!data->byte_access_allowed)
-                       bridge->ops = &cdns_ti_pcie_host_ops;
-               rc = pci_host_bridge_priv(bridge);
-               rc->quirk_retrain_flag = data->quirk_retrain_flag;
-               rc->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
-
-               cdns_pcie = &rc->pcie;
-               cdns_pcie->dev = dev;
-               cdns_pcie->ops = &j721e_pcie_ops;
-               pcie->cdns_pcie = cdns_pcie;
-
                gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
                if (IS_ERR(gpiod)) {
                        ret = PTR_ERR(gpiod);

@@ -497,23 +513,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)

                break;
        case PCI_MODE_EP:
-               if (!IS_ENABLED(CONFIG_PCIE_CADENCE_EP)) {
-                       ret = -ENODEV;
-                       goto err_get_sync;
-               }
-
-               ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
-               if (!ep) {
-                       ret = -ENOMEM;
-                       goto err_get_sync;
-               }
-               ep->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
-
-               cdns_pcie = &ep->pcie;
-               cdns_pcie->dev = dev;
-               cdns_pcie->ops = &j721e_pcie_ops;
-               pcie->cdns_pcie = cdns_pcie;
-
                ret = cdns_pcie_init_phy(dev, cdns_pcie);
                if (ret) {
                        dev_err(dev, "Failed to init phy\n");

@@ -525,8 +524,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)
                        goto err_pcie_setup;

                break;
-       default:
-               dev_err(dev, "INVALID device type %d\n", mode);
        }

        return 0;