Re: [PATCH v6 01/18] kasan: Unpoison pcpu chunks with base address tag

[Maciej Wieczór-Retman]

On 2025-11-10 at 18:32:21 +0100, Alexander Potapenko wrote:
>On Wed, Oct 29, 2025 at 8:05 PM Maciej Wieczor-Retman
><m.wieczorretman@xxxxx> wrote:
>>
>> From: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
>>
>> The problem presented here is related to NUMA systems and tag-based
>> KASAN modes - software and hardware ones. It can be explained in the
>> following points:
>>
>>         1. There can be more than one virtual memory chunk.
>>         2. Chunk's base address has a tag.
>>         3. The base address points at the first chunk and thus inherits
>>            the tag of the first chunk.
>>         4. The subsequent chunks will be accessed with the tag from the
>>            first chunk.
>>         5. Thus, the subsequent chunks need to have their tag set to
>>            match that of the first chunk.
>>
>> Refactor code by moving it into a helper in preparation for the actual
>> fix.
>
>The code in the helper function:
>
>> +void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms)
>> +{
>> +       int area;
>> +
>> +       for (area = 0 ; area < nr_vms ; area++) {
>> +               kasan_poison(vms[area]->addr, vms[area]->size,
>> +                            arch_kasan_get_tag(vms[area]->addr), false);
>> +       }
>> +}
>
>is different from what was originally called:
>
>> -       for (area = 0; area < nr_vms; area++)
>> -               vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
>> -                               vms[area]->size, KASAN_VMALLOC_PROT_NORMAL);
>> +       kasan_unpoison_vmap_areas(vms, nr_vms);
>
>, so the patch description is a bit misleading.
>
>Please also ensure you fix the errors reported by kbuild test robot.

Thanks for looking at the series! Yes, I'll fix these two patches, I've
split them off into a separate 'fixes' series and I'm trying to make
sure it's an acutal refactor this time.