linux-kernel - Re: arm64: fp-stress: BUG: KFENCE: memory corruption in fpsimd_release

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Message-ID: <a174b99c-3b60-410d-b6b3-67e8e792354c@sirena.org.uk>
Date:   Tue, 23 May 2023 11:49:38 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Will Deacon <will@...nel.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-stable <stable@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        lkft-triage@...ts.linaro.org,
        Catalin Marinas <catalin.marinas@....com>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Shuah Khan <shuah@...nel.org>,
        Anders Roxell <anders.roxell@...aro.org>
Subject: Re: arm64: fp-stress: BUG: KFENCE: memory corruption in
 fpsimd_release_task

On Mon, May 22, 2023 at 05:41:17PM +0100, Will Deacon wrote:
> On Tue, May 16, 2023 at 02:44:49PM +0100, Will Deacon wrote:
> > On Tue, May 16, 2023 at 11:58:40AM +0530, Naresh Kamboju wrote:

> > > Following kernel BUG noticed while running selftests arm64 fp-stress
> > > running stable rc kernel versions 6.1.29-rc1 and 6.3.3-rc1.

> > Is there a known-good build so that we could attempt a bisection?

> FWIW, I've been trying (and failing) all day to reproduce this in QEMU.
> I matched the same VL configuration as you have in the fastmodel and
> tried enabling additional memory debugging options too, but I'm yet to
> see a kfence splat (or any other splat fwiw).

> How often do you see this?

As I said in another mail I've also been unable to reproduce this.  FWIW
I *suspect* that it might need to be run in the context of a full
kselftest run to manifest rather than just running fp-stress in
isolation, that's mostly a guess but given that the kfence trap appeared
to be happening on free at a point where the test program shouldn't be
exiting any tasks and should not be changing vector lengths on tasks
that have used either of the vector extensions.

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