Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Chuanhong Guo <gch981213@gmail.com>
To:     netdev@vger.kernel.org
Cc:     Chuanhong Guo <gch981213@gmail.com>, stable@vger.kernel.org,
        Sean Wang <sean.wang@mediatek.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        =?UTF-8?q?Ren=C3=A9=20van=20Dorst?= <opensource@vdorst.com>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] net: dsa: mt7530: fix null pointer dereferencing in port5 setup
Date:   Fri,  3 Apr 2020 19:28:24 +0800
Message-Id: <20200403112830.505720-1-gch981213@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@gmail.com>
Cc: stable@vger.kernel.org
---

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.

 drivers/net/dsa/mt7530.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 6e91fe2f4b9a..1d53a4ebcd5a 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -1414,6 +1414,9 @@ mt7530_setup(struct dsa_switch *ds)
 				continue;
 
 			phy_node = of_parse_phandle(mac_np, "phy-handle", 0);
+			if (!phy_node)
+				continue;
+
 			if (phy_node->parent == priv->dev->of_node->parent) {
 				ret = of_get_phy_mode(mac_np, &interface);
 				if (ret && ret != -ENODEV)
-- 
2.25.1