linux-kernel - Re: [PATCH v2] PCI: endpoint: Fix NULL pointer dereference for ->get

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Date:   Wed, 23 Dec 2020 14:34:03 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Shradha Todi <shradha.t@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        kishon@...com, lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        pankaj.dubey@...sung.com, Sriram Dash <sriram.dash@...sung.com>
Subject: Re: [PATCH v2] PCI: endpoint: Fix NULL pointer dereference for
 ->get_features()

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@...sung.com>
> Signed-off-by: Sriram Dash <sriram.dash@...sung.com>
> Signed-off-by: Shradha Todi <shradha.t@...sung.com>
> ---
> 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
>