linux-kernel - Re: Crash on armv7-a using KASAN

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Message-ID: <CACRpkdaMMsHXkgcOtw0aC=SPfJJURCyCgzDq-rEXrBGaM44Sdg@mail.gmail.com>
Date: Tue, 15 Oct 2024 09:55:52 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Clement LE GOFFIC <clement.legoffic@...s.st.com>
Cc: Russell King <linux@...linux.org.uk>, 
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, Kees Cook <kees@...nel.org>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Mark Brown <broonie@...nel.org>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Ard Biesheuvel <ardb@...nel.org>, linux-stm32@...md-mailman.stormreply.com, 
	Antonio Borneo <antonio.borneo@...s.st.com>
Subject: Re: Crash on armv7-a using KASAN

Hi Clement,

thanks for your report! I looked a bit at it:

On Mon, Oct 14, 2024 at 3:21 PM Clement LE GOFFIC
<clement.legoffic@...s.st.com> wrote:

> I have detected a kernel crash in latest kernel on armv7-a when Kasan is
> enabled.
(...)
> Crash log with recent kernel (v6.12-rc3) :
>
> ~ # Insufficient stack space to handle exception!

The crash looks pretty "expected", as you say you start a lot of
parallel processes
and whoops, you run out of memory on the stack. No software can add more
memory to the machine.

KASAN uses a lot of extra memory for intercepting all memory accesses,
nominally one
extra byte per 8 bytes. This is further restricted by the complex
nature of the virtual
memory space on ARM32.

That said, we increase the size of per-thread storage when using KASAN,
THREAD_SIZE_ORDER is 2 instead of 1. Maybe the interrupt stacks need
to be scaled similarly to manage the increased load?

Yours,
Linus Walleij