linux-kernel - Re: [PATCH 1/2] mm/kasan: Fix KASAN poisoning in vrealloc()

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Message-ID: <CA+fCnZcFcpbME+a34L49pk2Z-WLbT_L25bSzZFixUiNFevJXzA@mail.gmail.com>
Date: Sat, 17 Jan 2026 18:08:36 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Maciej Żenczykowski <maze@...gle.com>, 
	Maciej Wieczor-Retman <m.wieczorretman@...me>, Alexander Potapenko <glider@...gle.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, 
	kasan-dev@...glegroups.com, Uladzislau Rezki <urezki@...il.com>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, joonki.min@...sung-slsi.corp-partner.google.com, 
	stable@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/kasan: Fix KASAN poisoning in vrealloc()

On Sat, Jan 17, 2026 at 2:16 AM Andrey Konovalov <andreyknvl@...il.com> wrote:
>
> On Fri, Jan 16, 2026 at 2:26 PM Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
> >
> > So something like bellow I guess.
>
> Yeah, looks good.
>
> > I think this would actually have the opposite effect and make the code harder to follow.
> > Introducing an extra wrapper adds another layer of indirection and more boilerplate, which
> > makes the control flow less obvious and the code harder to navigate and grep.
> >
> > And what's the benefit here? I don't clearly see it.
>
> One functional benefit is when HW_TAGS mode enabled in .config but
> disabled via command-line, we avoid a function call into KASAN
> runtime.

Ah, and I just realized than kasan_vrealloc should go into common.c -
we also need it for HW_TAGS.


>
> From the readability perspective, what we had before the recent
> clean-up was an assortment of kasan_enabled/kasan_arch_ready checks in
> lower-level KASAN functions, which made it hard to figure out what
> actually happens when KASAN is not enabled. And these high-level
> checks make it more clear. At least in my opinion.