[PATCH] Fix NULL ptr dereference in pci_bus_assign_domain_nr() on ARM

[Bjorn Helgaas]

Hi Krzysztof,

On Tue, Mar 01, 2016 at 07:07:18AM +0100, Krzysztof Hałasa wrote:
> Many ARM platforms use a wrapper:
> /*
>  * Compatibility wrapper for older platforms that do not care about
>  * passing the parent device.
>  */
> static inline void pci_common_init(struct hw_pci *hw)
> {
>         pci_common_init_dev(NULL, hw);
> }
> 
> which means that pci_bus_assign_domain_nr() can be called without
> a parent. This patch fixes the NULL pointer dereference.

What exactly is the impact of this?  Does this fix need to be in v4.5?
It sounds like it should be, but I need a little more detailed
justification, e.g., "platforms X, Y, Z don't boot at all without
this change."

> Signed-off-by: Krzysztof Hałasa <khalasa at piap.pl>
> Cc: stable at vger.kernel.org
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 602eb42..f89db3a 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4772,8 +4772,10 @@ int pci_get_new_domain_nr(void)
>  void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
>  {
>  	static int use_dt_domains = -1;
> -	int domain = of_get_pci_domain_nr(parent->of_node);
> +	int domain = -1;
>  
> +	if (parent)
> +		domain = of_get_pci_domain_nr(parent->of_node);
>  	/*
>  	 * Check DT domain and use_dt_domains values.
>  	 *
> 
> -- 
> Krzysztof Halasa
> 
> Industrial Research Institute for Automation and Measurements PIAP
> Al. Jerozolimskie 202, 02-486 Warsaw, Poland