Re: [PATCH v9 10/27] resource: harden resource_contains

Dan Williams
2025-01-18T02:04:03Z

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@amd.com>
>
> While resource_contains checks for IORESOURCE_UNSET flag for the
> resources given, if r1 was initialized with 0 size, the function
> returns a false positive. This is so because resource start and
> end fields are unsigned with end initialised to size - 1 by current
> resource macros.
>
> Make the function to check for the resource size for both resources
> since r2 with size 0 should not be considered as valid for the function
> purpose.
>
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Suggested-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> include/linux/ioport.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 5385349f0b8a..7ba31a222536 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -296,6 +296,8 @@ static inline unsigned long resource_ext_type(const struct resource *res)
> /* True iff r1 completely contains r2 */
> static inline bool resource_contains(const struct resource *r1, const struct resource *r2)
> {
> + if (!resource_size(r1) || !resource_size(r2))
> + return false;

I just worry that some code paths expect the opposite, that it is ok to
pass zero size resources and get a true result.

Did you audit existing callers?