Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Rolf Eike Beer <eb@emlix.com>
To:     Manivannan Sadhasivam <mani@kernel.org>
Cc:     Cristian Ciocaltea <cristian.ciocaltea@gmail.com>,
        Lee Jones <lee.jones@linaro.org>,
        linux-actions@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: atc260x has broken locking
Date:   Wed, 23 Feb 2022 12:07:48 +0100
Message-ID: <16136311.TfV2VxeR0u@mobilepool36.emlix.com>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="nextPart1905280.viRWdgczpX"; micalg="pgp-sha256"; protocol="application/pgp-signature"
Precedence: bulk

--nextPart1905280.viRWdgczpX
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="UTF-8"; protected-headers="v1"
From: Rolf Eike Beer <eb@emlix.com>
To: Manivannan Sadhasivam <mani@kernel.org>
Cc: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>, Lee Jones <lee.jones@linaro.org>, linux-actions@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: atc260x has broken locking
Date: Wed, 23 Feb 2022 12:07:48 +0100
Message-ID: <16136311.TfV2VxeR0u@mobilepool36.emlix.com>

When looking at this functions I found the locking to be broken for the ato=
mic=20
case (comments stripped):

static void regmap_lock_mutex(void *__mutex)
{
	struct mutex *mutex =3D __mutex;

	if (system_state > SYSTEM_RUNNING && irqs_disabled())
		mutex_trylock(mutex);
	else
		mutex_lock(mutex);
}

static void regmap_unlock_mutex(void *__mutex)
{
	struct mutex *mutex =3D __mutex;

	mutex_unlock(mutex);
}

When the mutex is already locked and the atomic context is hit then the loc=
k=20
will not be acquired, this is never noticed, and it afterwards is unlocked=
=20
anyway.

The comment says this is inspired from i2c_in_atomic_xfer_mode() to detect =
the=20
atomic case, but the important caller __i2c_lock_bus_helper() actually does=
=20
check and pass on the return value of mutex_trylock(), which is missing her=
e.

Greetings,

Eike
=2D-=20
Rolf Eike Beer, emlix GmbH, https://www.emlix.com
=46on +49 551 30664-0, Fax +49 551 30664-11
Gothaer Platz 3, 37083 G=C3=B6ttingen, Germany
Sitz der Gesellschaft: G=C3=B6ttingen, Amtsgericht G=C3=B6ttingen HR B 3160
Gesch=C3=A4ftsf=C3=BChrung: Heike Jordan, Dr. Uwe Kracke =E2=80=93 Ust-IdNr=
=2E: DE 205 198 055

emlix - smart embedded open source
--nextPart1905280.viRWdgczpX
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: This is a digitally signed message part.
Content-Transfer-Encoding: 7Bit

-----BEGIN PGP SIGNATURE-----

iLMEAAEIAB0WIQQ/Uctzh31xzAxFCLur5FH7Xu2t/AUCYhYVhAAKCRCr5FH7Xu2t
/J+7A/9yyYI6rtw0seE6T+brf2gPxfT8AN1cR6NhpG1fer66+7sZDFPD8Fcohnm1
3kNuHFnOPbArlvbqJES+XRM9l6EUcnHmZYaqwB7bGg+KkzGhAr24qdWdrchhEY/3
mapEPHpRYwIgYsudF/OEcSukQdDpdhrVFckr2GQUGdNIQ5KVoQ==
=2r1T
-----END PGP SIGNATURE-----

--nextPart1905280.viRWdgczpX--