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

Alejandro Lucero Palau
2025-01-20T16:10:28Z

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?