Re: [PATCH] PCI: kirin: fix memory leak in kirin_pcie_parse_port()

[Bjorn Helgaas <helgaas@kernel.org>]

On Sun, Jun 09, 2024 at 12:56:14PM +0200, Javier Carrasco wrote:
> The conversion of this file to use the agnostic GPIO API has introduced
> a new early return where the refcounts of two device nodes (parent and
> child) are not decremented.
> 
> Given that the device nodes are not required outside the loops where
> they are used, and to avoid potential bugs every time a new error path
> is introduced to the loop, the _scoped() versions of the macros have
> been applied. The bug was introduced recently, and the fix is not
> relevant for old stable kernels that might not support the scoped()
> variant.
> 
> Fixes: 1d38f9d89f85 ("PCI: kirin: Convert to use agnostic GPIO API")
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>

FYI, I moved this to the pci/controller/gpio patch just before
1d38f9d89f85.  That way there's no bisection hole and we don't need to
complicate this commit log with details about the bug because the bug
never exists.

> ---
> This bug was found while analyzing the code and I don't have hardware to
> validate it beyond compilation and static analysis. Any test with real
> hardware to make sure there are no regressions is always welcome.
> 
> The dev_err() messages have not been converted into dev_err_probe() to
> keep the current format, but I am open to convert them if preferred.
> ---
>  drivers/pci/controller/dwc/pcie-kirin.c | 21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-kirin.c b/drivers/pci/controller/dwc/pcie-kirin.c
> index d1f54f188e71..0a29136491b8 100644
> --- a/drivers/pci/controller/dwc/pcie-kirin.c
> +++ b/drivers/pci/controller/dwc/pcie-kirin.c
> @@ -403,11 +403,10 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
>  				 struct device_node *node)
>  {
>  	struct device *dev = &pdev->dev;
> -	struct device_node *parent, *child;
>  	int ret, slot, i;
>  
> -	for_each_available_child_of_node(node, parent) {
> -		for_each_available_child_of_node(parent, child) {
> +	for_each_available_child_of_node_scoped(node, parent) {
> +		for_each_available_child_of_node_scoped(parent, child) {
>  			i = pcie->num_slots;
>  
>  			pcie->id_reset_gpio[i] = devm_fwnode_gpiod_get_index(dev,
> @@ -424,14 +423,13 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
>  			pcie->num_slots++;
>  			if (pcie->num_slots > MAX_PCI_SLOTS) {
>  				dev_err(dev, "Too many PCI slots!\n");
> -				ret = -EINVAL;
> -				goto put_node;
> +				return -EINVAL;
>  			}
>  
>  			ret = of_pci_get_devfn(child);
>  			if (ret < 0) {
>  				dev_err(dev, "failed to parse devfn: %d\n", ret);
> -				goto put_node;
> +				return ret;
>  			}
>  
>  			slot = PCI_SLOT(ret);
> @@ -439,10 +437,8 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
>  			pcie->reset_names[i] = devm_kasprintf(dev, GFP_KERNEL,
>  							      "pcie_perst_%d",
>  							      slot);
> -			if (!pcie->reset_names[i]) {
> -				ret = -ENOMEM;
> -				goto put_node;
> -			}
> +			if (!pcie->reset_names[i])
> +				return -ENOMEM;
>  
>  			gpiod_set_consumer_name(pcie->id_reset_gpio[i],
>  						pcie->reset_names[i]);
> @@ -450,11 +446,6 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
>  	}
>  
>  	return 0;
> -
> -put_node:
> -	of_node_put(child);
> -	of_node_put(parent);
> -	return ret;
>  }
>  
>  static long kirin_pcie_get_resource(struct kirin_pcie *kirin_pcie,
> 
> ---
> base-commit: d35b2284e966c0bef3e2182a5c5ea02177dd32e4
> change-id: 20240609-pcie-kirin-memleak-18c83a31d111
> 
> Best regards,
> -- 
> Javier Carrasco <javier.carrasco.cruz@gmail.com>
>