PCI: endpoint: epf-mhi: Avoid NULL dereference if DT lacks 'mmio'

If platform_get_resource_byname() fails and returns NULL because DT lacks
an 'mmio' property for the MHI endpoint, dereferencing res->start will
cause a NULL pointer access. Add a check to prevent it.

Fixes: 1bf5f25324f7 ("PCI: endpoint: Add PCI Endpoint function driver for MHI bus")
Link: https://lore.kernel.org/r/20241105120735.1240728-1-quic_zhonhan@quicinc.com
Signed-off-by: Zhongqiu Han <quic_zhonhan@quicinc.com>
[kwilczynski: error message update per the review feedback]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Niklas Cassel <cassel@kernel.org>

diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
index 7d070b1..54286a4 100644 (file)
--- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
+++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
@@ -867,12 +867,18 @@ static int pci_epf_mhi_bind(struct pci_epf *epf)
 {
        struct pci_epf_mhi *epf_mhi = epf_get_drvdata(epf);
        struct pci_epc *epc = epf->epc;
+       struct device *dev = &epf->dev;
        struct platform_device *pdev = to_platform_device(epc->dev.parent);
        struct resource *res;
        int ret;
 
        /* Get MMIO base address from Endpoint controller */
        res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mmio");
+       if (!res) {
+               dev_err(dev, "Failed to get \"mmio\" resource\n");
+               return -ENODEV;
+       }
+
        epf_mhi->mmio_phys = res->start;
        epf_mhi->mmio_size = resource_size(res);