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

Alejandro Lucero Palau
2025-01-20T16:26:49Z

On 1/20/25 16:16, Alejandro Lucero Palau wrote:
> 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.
>>

I forgot to make my strongest point :-). If someone assumes it is or it
should be true a zero-size resource is contained inside a non zero-size
resource, we do not need to call a function since it is always true
regardless of the non zero-size resource ... that headache is starting
again ...

>>
>> 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?