From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relmlie5.idc.renesas.com (relmlor1.renesas.com [210.160.252.171]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 586D726AFA; Tue, 21 Jan 2025 11:35:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.160.252.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737459304; cv=none; b=YQTOig3NjoS0sEWY4mdOWyhAFxjlK5YqawapUZKN3H/vAbrtXW9mIOSWeabudWmLZM3vfWXG5e9CU5f96lY5WnbuIbSd6oIP7JoRQCBjIUUJeJAXScQMeiNbrH1+SwcJzzTM0HcHHP4BVSvMuhr8wRQZkFMkBaOVwG6jUOD6Ldc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737459304; c=relaxed/simple; bh=VmgBtEO/hZF7/Q8mEph8YxAOPRVcWVHVA/Irb9NrhW4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RfaSZ1b/HvEMcN0ZLNx1xuD+uCAEchZvzWnvqZ6RgiM6Ps9czBtHUd5J8cOF3XGjvmXyvGEy9hsgqbmqhqSC3WB1dKlS18Xu84k5YueRoxRJOvZyO7zkJ90LYN3LTv7/eKWtGBGOmvXzDdbNN1I2m/IEKnMF4bRChuRFJSnP1YU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=bp.renesas.com; spf=pass smtp.mailfrom=bp.renesas.com; arc=none smtp.client-ip=210.160.252.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=bp.renesas.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bp.renesas.com X-CSE-ConnectionGUID: e8BJ3OFSRXaXaPpvPHiknQ== X-CSE-MsgGUID: pJSgtUGiQ7+MYwEwyv7krA== Received: from unknown (HELO relmlir5.idc.renesas.com) ([10.200.68.151]) by relmlie5.idc.renesas.com with ESMTP; 21 Jan 2025 20:34:54 +0900 Received: from [10.24.0.69] (unknown [10.24.0.69]) by relmlir5.idc.renesas.com (Postfix) with ESMTP id 62B774002654; Tue, 21 Jan 2025 20:34:50 +0900 (JST) Message-ID: <134f69de-64f9-4d36-94ff-22b93cb32f2e@bp.renesas.com> Date: Tue, 21 Jan 2025 11:34:48 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v3] net: phy: Fix suspicious rcu_dereference usage Content-Language: en-GB To: Kory Maincent , Jakub Kicinski Cc: "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Claudiu Beznea , thomas.petazzoni@bootlin.com, Andrew Lunn , Heiner Kallweit , Russell King , Eric Dumazet , Paolo Abeni , =?UTF-8?Q?Niklas_S=C3=B6derlund?= , Sergey Shtylyov References: <20250120141926.1290763-1-kory.maincent@bootlin.com> <20250120111228.6bd61673@kernel.org> <20250121103845.6e135477@kmaincent-XPS-13-7390> From: Paul Barker In-Reply-To: <20250121103845.6e135477@kmaincent-XPS-13-7390> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------0Shbx1Wbb9cDU9JEO6JOcSx0" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------0Shbx1Wbb9cDU9JEO6JOcSx0 Content-Type: multipart/mixed; boundary="------------8K1gzAb0cEheIUiNfL8FS00o"; protected-headers="v1" From: Paul Barker To: Kory Maincent , Jakub Kicinski Cc: "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Claudiu Beznea , thomas.petazzoni@bootlin.com, Andrew Lunn , Heiner Kallweit , Russell King , Eric Dumazet , Paolo Abeni , =?UTF-8?Q?Niklas_S=C3=B6derlund?= , Sergey Shtylyov Message-ID: <134f69de-64f9-4d36-94ff-22b93cb32f2e@bp.renesas.com> Subject: Re: [PATCH net-next v3] net: phy: Fix suspicious rcu_dereference usage References: <20250120141926.1290763-1-kory.maincent@bootlin.com> <20250120111228.6bd61673@kernel.org> <20250121103845.6e135477@kmaincent-XPS-13-7390> In-Reply-To: <20250121103845.6e135477@kmaincent-XPS-13-7390> --------------8K1gzAb0cEheIUiNfL8FS00o Content-Type: multipart/mixed; boundary="------------aPGWf5SQgvaWSLEUfnIF2Bcj" --------------aPGWf5SQgvaWSLEUfnIF2Bcj Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 21/01/2025 09:38, Kory Maincent wrote: > On Mon, 20 Jan 2025 11:12:28 -0800 > Jakub Kicinski wrote: >=20 >> On Mon, 20 Jan 2025 15:19:25 +0100 Kory Maincent wrote: >>> The path reported to not having RTNL lock acquired is the suspend pat= h of >>> the ravb MAC driver. Without this fix we got this warning: =20 >> >> I maintain that ravb is buggy, plenty of drivers take rtnl_lock=20 >> from the .suspend callback. We need _some_ write protection here, >> the patch as is only silences a legitimate warning. >=20 > Indeed if the suspend path is buggy we should fix it. Still there is lo= ts of > ethernet drivers calling phy_disconnect without rtnl (IIUC) if probe re= turn an > error or in the remove path. What should we do about it? >=20 > About ravb suspend, I don't have the board, Claudiu could you try this = instead > of the current fix: >=20 > diff --git a/drivers/net/ethernet/renesas/ravb_main.c > b/drivers/net/ethernet/renesas/ravb_main.c index bc395294a32d..c9a0d2d6= f371 > 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c > +++ b/drivers/net/ethernet/renesas/ravb_main.c > @@ -3215,15 +3215,22 @@ static int ravb_suspend(struct device *dev) > if (!netif_running(ndev)) > goto reset_assert; > =20 > + rtnl_lock(); > netif_device_detach(ndev); > =20 > - if (priv->wol_enabled) > - return ravb_wol_setup(ndev); > + if (priv->wol_enabled) { > + ret =3D ravb_wol_setup(ndev); > + rtnl_unlock(); > + return ret; > + } > =20 > ret =3D ravb_close(ndev); > - if (ret) > + if (ret) { > + rtnl_unlock(); > return ret; > + } > =20 > + rtnl_unlock(); > ret =3D pm_runtime_force_suspend(&priv->pdev->dev); > if (ret) > return ret; >=20 > Regards, (Cc'ing Niklas and Sergey as this relates to the ravb driver) Why do we need to hold the rtnl mutex across the calls to netif_device_detach() and ravb_wol_setup()? My reading of Documentation/networking/netdevices.rst is that the rtnl mutex is held when the net subsystem calls the driver's ndo_stop method, which in our case is ravb_close(). So, we should take the rtnl mutex when we call ravb_close() directly, in both ravb_suspend() and ravb_wol_restore(). That would ensure that we do not call phy_disconnect() without holding the rtnl mutex and should fix this issue. Commit 35f7cad1743e ("net: Add the possibility to support a selected hwtstamp in netdevice") may have unearthed the issue, but the fixes tag should point to the commits adding those unlocked calls to ravb_close(). I am not super familiar with the rtnl lock so let me know if I've missed something. 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