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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 >>>> Suggested-by: Alison Schofield >>>> Reviewed-by: Alison Schofield >>>> Acked-by: Bjorn Helgaas >>>> Reviewed-by: Jonathan Cameron >>>> --- >>>> 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. > The regression risk is not philosophic relative to how long this > function has returned 'true' for the size == 0 case. Would not this regression be a good thing? Because I argue that is not the right thing to do. >> But maybe it is just  my lack of understanding and there exists a good >> reason for this possibility. > Questions like the following are good to answer when changing long > standing behavior: > > Did you look at any other resource_contains() user to get a sense of > that regression risk? > > Is the benefit to changing this higher than that risk? > > Would it be better to just document the expectation that the caller > should only pass non-zero sized resources to this function?