net: dsa: Introduce dsa_is_port_initialized

To avoid race conditions when using the ds->ports[] array,
we need to check if the accessed port has been initialized.
Introduce and use helper function dsa_is_port_initialized
for that purpose and use it where needed.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -165,6 +165,11 @@ static inline bool dsa_is_cpu_port(struct dsa_switch *ds, int p)
 	return !!(ds->index == ds->dst->cpu_switch && p == ds->dst->cpu_port);
 }
 
+static inline bool dsa_is_port_initialized(struct dsa_switch *ds, int p)
+{
+	return ds->phys_port_mask & (1 << p) && ds->ports[p];
+}
+
 static inline u8 dsa_upstream_port(struct dsa_switch *ds)
 {
 	struct dsa_switch_tree *dst = ds->dst;

net/dsa/dsa.c

@@ -374,7 +374,7 @@ static int dsa_switch_suspend(struct dsa_switch *ds)
 
 	/* Suspend slave network devices */
 	for (i = 0; i < DSA_MAX_PORTS; i++) {
-		if (!(ds->phys_port_mask & (1 << i)))
+		if (!dsa_is_port_initialized(ds, i))
 			continue;
 
 		ret = dsa_slave_suspend(ds->ports[i]);
@@ -400,7 +400,7 @@ static int dsa_switch_resume(struct dsa_switch *ds)
 
 	/* Resume slave network devices */
 	for (i = 0; i < DSA_MAX_PORTS; i++) {
-		if (!(ds->phys_port_mask & (1 << i)))
+		if (!dsa_is_port_initialized(ds, i))
 			continue;
 
 		ret = dsa_slave_resume(ds->ports[i]);

net/dsa/slave.c

@@ -222,10 +222,7 @@ static u32 dsa_slave_br_port_mask(struct dsa_switch *ds,
 	u32 mask = 0;
 
 	for (port = 0; port < DSA_MAX_PORTS; port++) {
-		if (!((1 << port) & ds->phys_port_mask))
-			continue;
-
-		if (!ds->ports[port])
+		if (!dsa_is_port_initialized(ds, port))
 			continue;
 
 		p = netdev_priv(ds->ports[port]);