linux-kernel - Re: [PATCH] PCI/pwrctl: Do not assume device node presence

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Message-ID: <20241121120637.76ircbsfayjebdvr@thinkpad>
Date: Thu, 21 Nov 2024 17:36:37 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Klara Modin <klarasmodin@...il.com>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	stable+noautosel@...nel.org
Subject: Re: [PATCH] PCI/pwrctl: Do not assume device node presence

On Thu, Nov 21, 2024 at 05:40:19PM +0800, Chen-Yu Tsai wrote:
> A PCI device normally does not have a device node, since the bus is
> fully enumerable. Assuming that a device node is presence is likely
> bad.
> 

I missed the fact that NULL ptr check is removed from of_pci_supply_present().

> The newly added pwrctl code assumes such and crashes with a NULL
> pointer dereference. Besides that, of_find_device_by_node(NULL)
> is likely going to return some random device.
> 

Yeah, good catch.

> Reported-by: Klara Modin <klarasmodin@...il.com>
> Closes: https://lore.kernel.org/linux-pci/a7b8f84d-efa6-490c-8594-84c1de9a7031@gmail.com/
> Fixes: cc70852b0962 ("PCI/pwrctl: Ensure that pwrctl drivers are probed before PCI client drivers")
> Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Cc: Krzysztof Wilczyński <kwilczynski@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> Cc: stable+noautosel@...nel.org         # Depends on power supply check
> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>

Thanks for the fix!

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
>  drivers/pci/bus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 98910bc0fcc4..eca72e0c3b6c 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -405,7 +405,7 @@ void pci_bus_add_device(struct pci_dev *dev)
>  	 * before PCI client drivers.
>  	 */
>  	pdev = of_find_device_by_node(dn);
> -	if (pdev && of_pci_supply_present(dn)) {
> +	if (dn && pdev && of_pci_supply_present(dn)) {
>  		if (!device_link_add(&dev->dev, &pdev->dev,
>  				     DL_FLAG_AUTOREMOVE_CONSUMER))
>  			pci_err(dev, "failed to add device link to power control device %s\n",
> -- 
> 2.47.0.338.g60cca15819-goog
> 

-- 
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