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

Alejandro Lucero Palau
2025-01-20T16:16:51Z

Adding Bjorn to the thread. Not sure if he just gets the email being in
an Acked-by line.

On 1/20/25 16:10, Alejandro Lucero Palau wrote:
>
> On 1/18/25 02:03, Dan Williams wrote:
>> 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.
>
>
> That is an interesting point, I would say close to philosophic
> arguments. I guess you mean the zero size resource being the one that
> is contained inside the non-zero one, because the other option is
> making my vision blurry. In fact, even that one makes me feel trapped
> in a window-less room, in summer, with a bunch of economists, I mean
> philosophers, and my phone without signal for emergency calls.
>
>
> But maybe it is just  my lack of understanding and there exists a good
> reason for this possibility.
>
>
> Bjorn, I guess the ball is in your side ...
>
>> Did you audit existing callers?