linux-kernel - Re: [PATCH v2 1/4] PCI: s390: Fix use-after-free of PCI resources with per-function hotplug

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Date:   Mon, 17 Apr 2023 09:46:33 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v2 1/4] PCI: s390: Fix use-after-free of PCI resources
 with per-function hotplug

On Mon, Mar 06, 2023 at 04:10:11PM +0100, Niklas Schnelle wrote:
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -76,6 +76,27 @@ struct resource *pci_bus_resource_n(const struct pci_bus *bus, int n)
>  }
>  EXPORT_SYMBOL_GPL(pci_bus_resource_n);
>  
> +void pci_bus_remove_resource(struct pci_bus *bus, struct resource *res)
> +{
> +	struct pci_bus_resource *bus_res, *tmp;
> +	int i;
> +
> +	for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++) {
> +		if (bus->resource[i] == res) {
> +			bus->resource[i] = NULL;
> +			return;
> +		}
> +	}
> +
> +	list_for_each_entry_safe(bus_res, tmp, &bus->resources, list) {
> +		if (bus_res->res == res) {
> +			list_del(&bus_res->list);
> +			kfree(bus_res);
> +			return;
> +		}
> +	}
> +}

I realize this has already been applied so s390.git/master,
but nevertheless would like to point out there's a handy
pci_bus_for_each_resource() helper which could have been
used here instead of the for-loop.

Sorry for chiming in late, I just spotted this while flushing out
my inbox.

Adding Andy to cc: who's been active in this area recently.

Thanks,

Lukas