linux-kernel - Re: [PATCH v2 01/14] kasan: sw_tags: Use arithmetic shift for shadow computation

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Message-ID: <CA+fCnZd2xPEwMGP7QRSyqHAJEbs_TY8Pg1ijG0iDFojMzphnfg@mail.gmail.com>
Date: Tue, 18 Mar 2025 16:32:46 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: Re: [PATCH v2 01/14] kasan: sw_tags: Use arithmetic shift for shadow computation

On Fri, Mar 14, 2025 at 4:58 PM Maciej Wieczor-Retman
<maciej.wieczor-retman@...el.com> wrote:
>
> >KASAN does nothing to deliberately prevent or detect races. Even if
> >the race leads to an OOB or UAF, KASAN might not be able to detect it.
> >But sometimes it does: if poisoned shadow memory values become visible
> >to the other thread/CPU before it makes a shadow memory value check.
>
> Thanks :)
>
> I've came up with a theoretical issue for the following dense series that might
> happen if there is some racing but I'll have to experiment if it actually
> happens.

As long as it doesn't lead to false positive reports or crashes in the
KASAN runtime - I think it should fine.