From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934454AbcKPSOP (ORCPT ); Wed, 16 Nov 2016 13:14:15 -0500 Received: from mail-pg0-f67.google.com ([74.125.83.67]:35232 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932361AbcKPSON (ORCPT ); Wed, 16 Nov 2016 13:14:13 -0500 Subject: Re: [PATCH] net: dsa: fix fixed-link-phy device leaks To: Johan Hovold References: <1479307664-32428-1-git-send-email-johan@kernel.org> <42af57ed-df84-f628-659d-c982d30da7d5@gmail.com> <20161116171145.GE4864@localhost> Cc: Andrew Lunn , Vivien Didelot , "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org From: Florian Fainelli Message-ID: <8387696c-813a-4c88-5f10-7d2e5fdae6b8@gmail.com> Date: Wed, 16 Nov 2016 10:14:10 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20161116171145.GE4864@localhost> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/16/2016 09:11 AM, Johan Hovold wrote: > On Wed, Nov 16, 2016 at 09:06:26AM -0800, Florian Fainelli wrote: >> On 11/16/2016 06:47 AM, Johan Hovold wrote: >>> Make sure to drop the reference taken by of_phy_find_device() when >>> registering and deregistering the fixed-link PHY-device. >>> >>> Note that we need to put both references held at deregistration. >>> >>> Fixes: 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port >>> speeds/duplex") >>> Signed-off-by: Johan Hovold >>> --- >>> >>> Hi, >>> >>> This is one has been compile tested only, but fixes a couple of leaks >>> similar to one that was found in the cpsw driver for which I just posted >>> a patch. >>> >>> It turns out all drivers but DSA fail to deregister the fixed-link PHYs >>> registered by of_phy_register_fixed_link(). Due to the way this >>> interface was designed, deregistering such a PHY is a bit cumbersome and >>> looks like it would benefit from a common helper. >>> >>> However, perhaps the interface should instead be changed so that the PHY >>> device is returned so that drivers do not need to use >>> of_phy_find_device() when they need to access properties of the fixed >>> link (e.g. as in dsu_cpu_dsa_setup below). >>> >>> Thoughts? >>> >>> Thanks, >>> Johan >>> >>> >>> net/dsa/dsa.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c >>> index a6902c1e2f28..798a6a776a5f 100644 >>> --- a/net/dsa/dsa.c >>> +++ b/net/dsa/dsa.c >>> @@ -233,6 +233,8 @@ int dsa_cpu_dsa_setup(struct dsa_switch *ds, struct device *dev, >>> genphy_read_status(phydev); >>> if (ds->ops->adjust_link) >>> ds->ops->adjust_link(ds, port, phydev); >>> + >>> + phy_device_free(phydev); /* of_phy_find_device */ >>> } >>> >>> return 0; >>> @@ -509,8 +511,12 @@ void dsa_cpu_dsa_destroy(struct device_node *port_dn) >>> if (of_phy_is_fixed_link(port_dn)) { >>> phydev = of_phy_find_device(port_dn); >>> if (phydev) { >>> - phy_device_free(phydev); >>> fixed_phy_unregister(phydev); >>> + /* Put references taken by of_phy_find_device() and >>> + * of_phy_register_fixed_link(). >>> + */ >>> + phy_device_free(phydev); >>> + phy_device_free(phydev); >> >> Double free, this looks bogus here. Actually would not this mean a >> triple free since you already free in dsa_cpu_dsa_setup() which is >> paired with dsa_cpu_dsa_destroy()? > > The naming of phy_device_free() is unfortunate when it's really a put(): > > void phy_device_free(struct phy_device *phydev) > { > put_device(&phydev->mdio.dev); > } Indeed, should have looked a little harder. > > which may need to be called multiple times, specifically after a call to > of_phy_find_device() which takes another reference. > > With this patch the refcounts are properly balanced. The intent of your patch is good, but it still feels like having to double imbalance the refcount is symptomatic of a larger issue here, it does not seem like having several refcounts are necessary, so we may really want to rework the API. -- Florian