linux-kernel - Re: [PATCH v3 2/3] kasan: Refactor pcpu kasan vmalloc unpoison

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Message-ID: <mtfitb3vqbcqzezrckjlo2vyszb3ufqgimmpmfhnybrkjt7m6f@3ovjldsuitwc>
Date: Fri, 05 Dec 2025 08:01:34 +0000
From: Maciej Wieczór-Retman <m.wieczorretman@...me>
To: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, Andrew Morton <akpm@...ux-foundation.org>, Uladzislau Rezki <urezki@...il.com>, Marco Elver <elver@...gle.com>, jiayuan.chen@...ux.dev, stable@...r.kernel.org, Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 2/3] kasan: Refactor pcpu kasan vmalloc unpoison

On 2025-12-05 at 02:09:02 +0100, Andrey Konovalov wrote:
>On Thu, Dec 4, 2025 at 8:00 PM Maciej Wieczor-Retman
><m.wieczorretman@...me> wrote:
>>
>> From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>>
>> A KASAN tag mismatch, possibly causing a kernel panic, can be observed
>> on systems with a tag-based KASAN enabled and with multiple NUMA nodes.
>> It was reported on arm64 and reproduced on x86. 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 reusing __kasan_unpoison_vmalloc in a new helper in
>> preparation for the actual fix.
>>
>> Changelog v1 (after splitting of from the KASAN series):
>> - Rewrite first paragraph of the patch message to point at the user
>>   impact of the issue.
>> - Move helper to common.c so it can be compiled in all KASAN modes.
>
>Nit: Can put this part after ---.

Thanks for noticing that, guess I need to revise my script that moves
these under the three dashes

...

-- 
Kind regards
Maciej Wieczór-Retman