linux-kernel - Re: [PATCH net-next 06/30] net: dsa: mt7530: improve code path for setting up port 5

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230524173510.xvq434ekaee4664m@skbuf>
Date:   Wed, 24 May 2023 20:35:10 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     arinc9.unal@...il.com
Cc:     Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Daniel Golle <daniel@...rotopia.org>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Russell King <linux@...linux.org.uk>,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        Richard van Schagen <richard@...terhints.com>,
        Richard van Schagen <vschagen@...com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Bartel Eerdekens <bartel.eerdekens@...stell8.be>,
        erkin.bozoglu@...ont.com, mithat.guner@...ont.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next 06/30] net: dsa: mt7530: improve code path for
 setting up port 5

On Mon, May 22, 2023 at 03:15:08PM +0300, arinc9.unal@...il.com wrote:
> From: Arınç ÜNAL <arinc.unal@...nc9.com>
> 
> There're two code paths for setting up port 5:
> 
> mt7530_setup()
> -> mt7530_setup_port5()
> 
> mt753x_phylink_mac_config()
> -> mt753x_mac_config()
>    -> mt7530_mac_config()
>       -> mt7530_setup_port5()
> 
> Currently mt7530_setup_port5() from mt7530_setup() always runs. If port 5
> is used as a CPU, DSA, or user port, mt7530_setup_port5() from
> mt753x_phylink_mac_config() won't run. That is because priv->p5_interface
> set on mt7530_setup_port5() will match state->interface on
> mt753x_phylink_mac_config() which will stop running mt7530_setup_port5()
> again.
> 
> mt7530_setup_port5() from mt753x_phylink_mac_config() won't run when port 5
> is disabled or used for PHY muxing as port 5 won't be defined on the
> devicetree.
> 
> Therefore, mt7530_setup_port5() will never run from
> mt753x_phylink_mac_config().
> 
> Address this by not running mt7530_setup_port5() from mt7530_setup() if
> port 5 is used as a CPU, DSA, or user port. For the cases of PHY muxing or
> the port being disabled, call mt7530_setup_port5() from mt7530_setup().

So TL;DR: mt7530_setup() -> mt7530_setup_port5() short-circuits
mt753x_phylink_mac_config() -> ... -> mt7530_setup_port5() through the
stateful variable priv->p5_interface, such that port 5 is effectively
never configured by phylink, but statically at probe time. The main goal of
the patch is to undo the short-circuit, and let phylink configure port 5.

It is worth stating that we know phylink will always be present, because
mt7530 isn't in the dsa_switches_apply_workarounds[] array. Otherwise
this strategy would have been problematic with some device trees.

> Do not set priv->p5_interface on mt7530_setup_port5(). There won't be a
> case where mt753x_phylink_mac_config() runs after mt7530_setup_port5()
> anymore.

The bulk of the change is difficult enough to follow. I believe this
part could be done through a separate patch, and the rest would still
work.