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@pm.me wrote:

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From: Maciej Wieczor-Retman maciej.wieczor-retman@intel.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

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