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

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Message-ID: <ha5gz3hfjtfrmldzbscrbbtptecyqkwzkwdkjxnc2puqzquurl@nthv7frvqatw>
Date: Mon, 17 Nov 2025 17:51:13 +0000
From: Maciej Wieczór-Retman <m.wieczorretman@...me>
To: Alexander Potapenko <glider@...gle.com>
Cc: xin@...or.com, peterz@...radead.org, kaleshsingh@...gle.com, kbingham@...nel.org, akpm@...ux-foundation.org, nathan@...nel.org, ryabinin.a.a@...il.com, dave.hansen@...ux.intel.com, bp@...en8.de, morbo@...gle.com, jeremy.linton@....com, smostafa@...gle.com, kees@...nel.org, baohua@...nel.org, vbabka@...e.cz, justinstitt@...gle.com, wangkefeng.wang@...wei.com, leitao@...ian.org, jan.kiszka@...mens.com, fujita.tomonori@...il.com, hpa@...or.com, urezki@...il.com, ubizjak@...il.com, ada.coupriediaz@....com, nick.desaulniers+lkml@...il.com, ojeda@...nel.org, brgerst@...il.com, elver@...gle.com, pankaj.gupta@....com, mark.rutland@....com, trintaeoitogc@...il.com, jpoimboe@...nel.org, thuth@...hat.com, pasha.tatashin@...een.com, dvyukov@...gle.com, jhubbard@...dia.com, catalin.marinas@....com, yeoreum.yun@....com, mhocko@...e.com, lorenzo.stoakes@...cle.com, samuel.holland@...ive.com, vincenzo.frascino@....com, bigeasy@...utronix.de, surenb@...gle.com, ardb@...nel.org,
	Liam.Howlett@...cle.com, nicolas.schier@...ux.dev, ziy@...dia.com, kas@...nel.org, tglx@...utronix.de, mingo@...hat.com, broonie@...nel.org, corbet@....net, andreyknvl@...il.com, maciej.wieczor-retman@...el.com, david@...hat.com, maz@...nel.org, rppt@...nel.org, will@...nel.org, luto@...nel.org, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, x86@...nel.org, linux-kbuild@...r.kernel.org, linux-mm@...ck.org, llvm@...ts.linux.dev, linux-doc@...r.kernel.org, stable@...r.kernel.org, Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v6 01/18] kasan: Unpoison pcpu chunks with base address tag

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@...me> wrote:
>>
>> From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>>
>> 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.