linux-kernel - Re: [PATCH] PCI: epf-mhi: Fix potential NULL dereference in pci_epf_mhi

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Message-ID: <ZyofRAZoAE5IgCVi@ryzen>
Date: Tue, 5 Nov 2024 14:36:04 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Zhongqiu Han <quic_zhonhan@...cinc.com>
Cc: manivannan.sadhasivam@...aro.org, kw@...ux.com, kishon@...nel.org,
	bhelgaas@...gle.com, lpieralisi@...nel.org, dlemoal@...nel.org,
	mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: epf-mhi: Fix potential NULL dereference in
 pci_epf_mhi_bind()

On Tue, Nov 05, 2024 at 08:07:35PM +0800, Zhongqiu Han wrote:
> If platform_get_resource_byname() fails and returns NULL, 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")
> Signed-off-by: Zhongqiu Han <quic_zhonhan@...cinc.com>
> ---
>  drivers/pci/endpoint/functions/pci-epf-mhi.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> index 7d070b1def11..2712026733ab 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> @@ -873,6 +873,11 @@ static int pci_epf_mhi_bind(struct pci_epf *epf)
>  
>  	/* Get MMIO base address from Endpoint controller */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mmio");
> +	if (!res) {
> +		dev_err(&pdev->dev, "Failed to get MMIO base address\n");

dev_err(&epf->dev, "Failed to get mmio resource\n");
or
dev_err(&epf->dev, "Failed to get \"mmio\" resource\n");

Note: &epf->dev instead of &pdev->dev in order to be consistent with other
EPF ->bind() functions.

With that, feel free to add:
Reviewed-by: Niklas Cassel <cassel@...nel.org>


Kind regards,
Niklas

> +		return -ENODEV;
> +	}
> +
>  	epf_mhi->mmio_phys = res->start;
>  	epf_mhi->mmio_size = resource_size(res);
>  
> -- 
> 2.25.1
>