Subject: [RFC PATCH 1/3] drivers: of: fix resources freeing in of_pci_get_host_bridge_resources()

From: [email-masked] (Lorenzo Pieralisi)
Date: Tue, 20 Jan 2015 10:49:22 +0000

On Mon, Jan 19, 2015 at 06:32:29PM +0000, Liviu Dudau wrote:

[...]

> > @@ -146,6 +146,7 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
> >  	struct of_pci_range_parser parser;
> >  	char range_type[4];
> >  	int err;
> > +	struct pci_host_bridge_window *window;
> >  
> >  	if (io_base)
> >  		*io_base = (resource_size_t)OF_BAD_ADDR;
> > @@ -225,7 +226,10 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
> >  conversion_failed:
> >  	kfree(res);
> >  parse_failed:
> > +	list_for_each_entry(window, resources, list)
> > +		kfree(window->res);
> >  	pci_free_resource_list(resources);
> > +	kfree(bus_range);
> >  	return err;
> >  }
> >  EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
> 
> Hi Lorenzo et all,
> 
> Here is my personal view and I am happy to hear from others on the desired
> behaviour:
> 
> When I wrote this function what I had in mind was that it will parse as
> much as possible from the device tree and return a list of resources that
> could be successfully converted. If the entire list of ranges could not
> be converted then an error code will be returned, but the caller still
> had the list as constructed up to the error. It was the job of the caller
> to free the list in either cases, as stated in the comment.

That's what I am questioning. If the function takes an error path, the
windows list is freed, so the resource pointers are gone. There is no
way the caller can grab those resource pointers and free them.

So either way, the function needs patching. Either we do not free the
windows list (we remove pci_free_resource_list) or we apply my fix (or
we refactor the API which is likely to be what I will do).

Lorenzo

> 
> The historical reason why the function was written that way was because at
> some moment after parsing I've had an additional step where arches could
> cleanup / veto the list and they could return an error value to signal
> their discontent. Also I was (am) not sure how lenient we could be with
> the device tree not being sane (at least one host bridge binding lists the
> config space as a range, which was accepted as broken).
> 
> So, from that point of view, I would NAK this patch, as the function works
> as intended. If others find this mode of operation too convoluted, then
> the patch should probably make clear that cleanup only needs to be done on
> function returning success.
> 
> Best regards,
> 
> > -- 
> > 2.2.1
> > 
> > 
> 
> -- 
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ?\_(?)_/?