Re: [PATCH v2] PCI: endpoint: Fix NULL pointer dereference for ->get_features()

From: Bjorn Helgaas
Date: Wed Dec 23 2020 - 15:35:02 EST


On Fri, Dec 18, 2020 at 09:15:16PM +0530, Shradha Todi wrote:
> get_features ops of pci_epc_ops may return NULL, causing NULL pointer
> dereference in pci_epf_test_bind function. Let us add a check for
> pci_epc_feature pointer in pci_epf_test_bind before we access it to
> avoid any such NULL pointer dereference and return -ENOTSUPP in case
> pci_epc_feature is not found.

Can you add a Fixes: tag to identify where this broke to help people
decide where to backport the fix?

> Reviewed-by: Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx>
> Signed-off-by: Sriram Dash <sriram.dash@xxxxxxxxxxx>
> Signed-off-by: Shradha Todi <shradha.t@xxxxxxxxxxx>
> ---
> v2:
> rebase on v1
> v1: https://lore.kernel.org/patchwork/patch/1208269/
>
> drivers/pci/endpoint/functions/pci-epf-test.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 66723d5..f1842e6 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -835,13 +835,16 @@ static int pci_epf_test_bind(struct pci_epf *epf)
> return -EINVAL;
>
> epc_features = pci_epc_get_features(epc, epf->func_no);
> - if (epc_features) {
> - linkup_notifier = epc_features->linkup_notifier;
> - core_init_notifier = epc_features->core_init_notifier;
> - test_reg_bar = pci_epc_get_first_free_bar(epc_features);
> - pci_epf_configure_bar(epf, epc_features);
> + if (!epc_features) {
> + dev_err(&epf->dev, "epc_features not implemented\n");
> + return -EOPNOTSUPP;
> }
>
> + linkup_notifier = epc_features->linkup_notifier;
> + core_init_notifier = epc_features->core_init_notifier;
> + test_reg_bar = pci_epc_get_first_free_bar(epc_features);
> + pci_epf_configure_bar(epf, epc_features);
> +
> epf_test->test_reg_bar = test_reg_bar;
> epf_test->epc_features = epc_features;
>
> --
> 2.7.4
>