linux-kernel - Re: [PATCH 2/2] kasan: apply store-only mode in kasan kunit testcases

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Message-ID: <aJwuwBL+Egh3Fivv@e129823.arm.com>
Date: Wed, 13 Aug 2025 07:20:48 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Andrey Konovalov <andreyknvl@...il.com>
Cc: ryabinin.a.a@...il.com, glider@...gle.com, dvyukov@...gle.com,
	vincenzo.frascino@....com, corbet@....net, catalin.marinas@....com,
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	james.morse@....com, ardb@...nel.org,
	hardevsinh.palaniya@...iconsignals.io, david@...hat.com,
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Subject: Re: [PATCH 2/2] kasan: apply store-only mode in kasan kunit testcases

Hi Andrey,

> > > > But in case of sync, when the MTE fault happens, it doesn't
> > > > write to memory so, I think it's fine.
> > >
> > > Does it not? I thought MTE gets disabled and we return from the fault
> > > handler and let the write instruction execute. But my memory on this
> > > is foggy. And I don't have a setup right now to test.
> >
> > Right. when fault is hit the MTE gets disabled.
> > But in kasan_test_c.c -- See the KUNIT_EXPECT_KASAN_FAIL,
> > It re-enables for next test by calling kasan_enable_hw_tags().
>
> But before that, does the faulting instruction get executed? After MTE
> gets disabled in the fault handler.

Right. in case of tag check fault, the preferred excecption return
address is the instruction where TCF happen.
I was lucky when running the test :\

Okay then I'll remove the invalid write in test,
But I want to keep the if/else on each case with the reason I said.

Thank you.

--
Sincerely,
Yeoreum Yun