Re: [PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

["Krzysztof Wilczyński" <kwilczynski@kernel.org>]

Hello,

> pci_mmap_resource() does not check IORESOURCE_DISABLED before mapping
> a PCI BAR resource into userspace. This allows new mmaps to succeed
> even after a device has been marked disabled or soft-unplugged by the
> driver to prevent further access.

Which driver disables resources?  Would this be some Amazon-specific thing
you are trying to fix?  Or are you just manually disabling a given device
using sysfs, or something like this?

For "soft-unplugged" device we have pci_dev_set_disconnected(), but this
does not check current flags set.

What is your use case here?

> Add the check to return -ENODEV when the resource is disabled, blocking
> new userspace mmaps of BAR resources after device removal.
> 
> Tested by marking the PCI BAR resource as disabled and verifying that
> a subsequent mmap attempt fails with -ENODEV.

Can you explain how did you do this?

> @@ -1089,6 +1089,9 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
>  	if (ret)
>  		return ret;
>  
> +	if (res->flags & IORESOURCE_DISABLED)
> +		return -ENODEV;
> +

This probably would be better if it checked IORESOURCE_DISABLED and
IORESOURCE_UNSET, but then probably using resource_assigned() would
be even better.

Thank you!

	Krzysztof