Re: [PATCH 09/15] resource: implement resize_region

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 1/30/26 1:38 PM, Sascha Hauer wrote:
> On Tue, Jan 27, 2026 at 09:39:19AM +0100, Ahmad Fatoum wrote:
>> resize_region allows enlarging or reducing a region end while checking
>> for conflicts. This is less effort than removing a region and
>> reallocating it.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>>  common/resource.c      | 45 ++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/ioport.h |  2 ++
>>  2 files changed, 47 insertions(+)
>>
>> diff --git a/common/resource.c b/common/resource.c
>> index e391d268e0bb..39867da63b69 100644
>> --- a/common/resource.c
>> +++ b/common/resource.c
>> @@ -92,6 +92,51 @@ struct resource *__request_region(struct resource *parent,
>>  	return new;
>>  }
>>  
>> +int resize_region(struct resource *res, resource_size_t size)
>> +{
>> +	struct resource *parent;
>> +	struct resource *next;
>> +	resource_size_t newend;
>> +
>> +	if (!res)
>> +		return 0;
>> +	if (!size)
>> +		return release_region(res);
> 
> This frees the resource itself. I am not sure if this is useful. It's an
> invitation for the caller to reference freed memory. I think the caller
> must distinguish between resizing and releasing the resource anyway, so
> he could equally call resize_region() or release_region() directly.

You're right. I did actually have a use after free for 0 size :D

>> +
>> +	if (size == resource_size(res))
>> +		return 0;
>> +
>> +	if (size < resource_size(res)) {
>> +		res->end = res->start + size - 1;
>> +		return 0;
>> +	}
> 
> A resource can have child resources. For completeness we should check if
> the child resources are still inside the now smaller parent resource.

Ok will do.

Cheers,
Ahmad

> 
> Sascha
> 

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