From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Horia =?utf-8?Q?Geant=C4=83?= <horia.geanta@nxp.com>,
        Pankaj Gupta <pankaj.gupta@nxp.com>,
        Gaurav Jain <gaurav.jain@nxp.com>,
        Mathew McBride <matt@traverse.com.au>,
        linux-crypto@vger.kernel.org
Subject: Re: Hitting BUG_ON in crypto_unregister_alg() on reboot with
 caamalg_qi2 driver
In-Reply-To: <ZAqwTqw3lR+dnImO@gondor.apana.org.au>
References: <87r0tyq8ph.fsf@toke.dk> <ZAqwTqw3lR+dnImO@gondor.apana.org.au>
Date:   Fri, 10 Mar 2023 14:37:57 +0100
Message-ID: <87ilf8rakq.fsf@toke.dk>
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Herbert Xu <herbert@gondor.apana.org.au> writes:

> On Thu, Mar 09, 2023 at 03:51:22PM +0100, Toke H=C3=B8iland-J=C3=B8rgense=
n wrote:
>> Hi folks
>>=20
>> I'm hitting what appears to be a deliberate BUG_ON() in
>> crypto_unregister_alg() when rebooting my traverse ten64 device on a
>> 6.2.2 kernel (using the Arch linux-aarch64 build, which is basically an
>> upstream kernel).
>>=20
>> Any idea what might be causing this? It does not appear on an older
>> (5.17, which is the newest kernel that works reliably, for unrelated
>> reasons).
>
> On the face of it this looks like a generic issue with drivers
> and the Crypto API.  Historically crypto modules weren't meant
> to be removed/unregistered until the last user has freed the tfm.
>
> Obviously with drivers that start unregistering the algorithms when
> the hardware goes away this paradigm breaks.  What should happen is
> that the driver continues to hold onto the crypto algorithm registration
> even when the hardware has gone away.
>
> Some work has to be done in the driver to actually make this safe
> (all the drivers I've looked at are broken in this way).

Hmm, okay; any idea why this started happening with the newer kernel
version? I don't see any changes to the driver that could have caused
this; so is it some core-kernel change that has changed the
order of driver removal on shutdown or something?

Also, absent of a fixed driver (which doesn't sound like it's a trivial
fix?), how do I prevent the system from crashing on shutdown? The
BUG_ON() seems a bit heavy-handed, could it be replaced with a WARN_ON?

-Toke