netdev - Re: [PATCH v9 10/27] resource: harden resource

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Message-ID: <fe48e2e9-5a13-78fe-d8f6-6c3faeecebcc@amd.com>
Date: Mon, 20 Jan 2025 16:10:05 +0000
From: Alejandro Lucero Palau <alucerop@....com>
To: Dan Williams <dan.j.williams@...el.com>, alejandro.lucero-palau@....com,
 linux-cxl@...r.kernel.org, netdev@...r.kernel.org, edward.cree@....com,
 davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
 edumazet@...gle.com, dave.jiang@...el.com
Subject: Re: [PATCH v9 10/27] resource: harden resource_contains


On 1/18/25 02:03, Dan Williams wrote:
> alejandro.lucero-palau@ wrote:
>> From: Alejandro Lucero <alucerop@....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@....com>
>> Suggested-by: Alison Schofield <alison.schofield@...el.com>
>> Reviewed-by: Alison Schofield <alison.schofield@...el.com>
>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.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?