linux-kernel - [PATCH] net: dsa: mt7530: Add some return-value checks

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Message-Id: <20200916195017.34057-1-alex.dewar90@gmail.com>
Date:   Wed, 16 Sep 2020 20:50:17 +0100
From:   Alex Dewar <alex.dewar90@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Alex Dewar <alex.dewar90@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Landen Chao <landen.chao@...iatek.com>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] net: dsa: mt7530: Add some return-value checks

In mt7531_cpu_port_config(), if the variable port is neither 5 nor 5,
then variable interface will be used uninitialised. Change the function
to return -EINVAL in this case.

As the return value of mt7531_cpu_port_config() is never checked
(even though it returns an int) add a check in the correct place so that
the error can be passed up the call stack. Now that we correctly handle
errors thrown in this function, also check the return value of
mt7531_mac_config() in case an error occurs here.

Addresses-Coverity: 1496993 ("Uninitialized variables")
Fixes: c288575f7810 ("net: dsa: mt7530: Add the support of MT7531 switch")
Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
---

If it is not expected that these functions will throw errors (i.e.
because the parameters passed will always be correct), we could dispense
with the use of EINVAL errors and just use BUG*() macros instead. Let me
know if you'd rather I fix things up in that way.

Best,
Alex

 drivers/net/dsa/mt7530.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 61388945d316..157d0a01faae 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -945,10 +945,14 @@ static int
 mt753x_cpu_port_enable(struct dsa_switch *ds, int port)
 {
 	struct mt7530_priv *priv = ds->priv;
+	int ret;
 
 	/* Setup max capability of CPU port at first */
-	if (priv->info->cpu_port_config)
-		priv->info->cpu_port_config(ds, port);
+	if (priv->info->cpu_port_config) {
+		ret = priv->info->cpu_port_config(ds, port);
+		if (ret)
+			return ret;
+	}
 
 	/* Enable Mediatek header mode on the cpu port */
 	mt7530_write(priv, MT7530_PVC_P(port),
@@ -2275,7 +2279,7 @@ mt7531_cpu_port_config(struct dsa_switch *ds, int port)
 {
 	struct mt7530_priv *priv = ds->priv;
 	phy_interface_t interface;
-	int speed;
+	int ret, speed;
 
 	switch (port) {
 	case 5:
@@ -2293,6 +2297,8 @@ mt7531_cpu_port_config(struct dsa_switch *ds, int port)
 
 		priv->p6_interface = interface;
 		break;
+	default:
+		return -EINVAL;
 	}
 
 	if (interface == PHY_INTERFACE_MODE_2500BASEX)
@@ -2300,7 +2306,9 @@ mt7531_cpu_port_config(struct dsa_switch *ds, int port)
 	else
 		speed = SPEED_1000;
 
-	mt7531_mac_config(ds, port, MLO_AN_FIXED, interface);
+	ret = mt7531_mac_config(ds, port, MLO_AN_FIXED, interface);
+	if (ret)
+		return ret;
 	mt7530_write(priv, MT7530_PMCR_P(port),
 		     PMCR_CPU_PORT_SETTING(priv->id));
 	mt753x_phylink_mac_link_up(ds, port, MLO_AN_FIXED, interface, NULL,
-- 
2.28.0