linux-kernel - Re: [PATCH] net: dsa: mt7530: fix null pointer dereferencing in port5 setup

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Message-ID: <f4e1a06d-75d1-14e3-3075-822e44454bcc@gmail.com>
Date:   Fri, 3 Apr 2020 10:43:22 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Chuanhong Guo <gch981213@...il.com>, netdev@...r.kernel.org
Cc:     stable@...r.kernel.org, Sean Wang <sean.wang@...iatek.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Matthias Brugger <matthias.bgg@...il.com>,
        René van Dorst <opensource@...rst.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dsa: mt7530: fix null pointer dereferencing in port5
 setup



On 4/3/2020 4:28 AM, Chuanhong Guo wrote:
> The 2nd gmac of mediatek soc ethernet may not be connected to a PHY
> and a phy-handle isn't always available.
> Unfortunately, mt7530 dsa driver assumes that the 2nd gmac is always
> connected to switch port 5 and setup mt7530 according to phy address
> of 2nd gmac node, causing null pointer dereferencing when phy-handle
> isn't defined in dts.
> This commit fix this setup code by checking return value of
> of_parse_phandle before using it.
> 
> Fixes: 38f790a80560 ("net: dsa: mt7530: Add support for port 5")
> Signed-off-by: Chuanhong Guo <gch981213@...il.com>
> Cc: stable@...r.kernel.org

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>

> ---
> 
> mt7530 is available as a standalone chip and we should not make it
> tightly coupled with a specific type of ethernet dt binding in the
> first place.
> A proper fix is to replace this port detection logic with a dt
> property under mt7530 node, but that's too much for linux-stable.

Agree, one would also wonder why the driver needs to parse parts of the
Device Tree which should be done by the core DSA layer.
-- 
Florian