net: dsa: Remove VLA usage

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case). Link: http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Salvatore Mesoraca <[email protected]> [kees: tweak commit subject and message slightly] Signed-off-by: Kees Cook <[email protected]> Reviewed-by: Andrew Lunn <[email protected]> Signed-off-by: David S. Miller <[email protected]>
zarubaf · Jul 18, 2018 · 0015b80 · 0015b80
1 parent 14260e9
commit 0015b80
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Showing 3 changed files with 27 additions and 12 deletions.
diff --git a/include/net/dsa.h b/include/net/dsa.h
@@ -259,6 +259,9 @@ struct dsa_switch {
 	/* Number of switch port queues */
 	unsigned int		num_tx_queues;
 
+	unsigned long		*bitmap;
+	unsigned long		_bitmap;
+
 	/* Dynamically allocated ports, keep last */
 	size_t num_ports;
 	struct dsa_port ports[];

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
@@ -775,6 +775,20 @@ struct dsa_switch *dsa_switch_alloc(struct device *dev, size_t n)
 	if (!ds)
 		return NULL;
 
+	/* We avoid allocating memory outside dsa_switch
+	 * if it is not needed.
+	 */
+	if (n <= sizeof(ds->_bitmap) * 8) {
+		ds->bitmap = &ds->_bitmap;
+	} else {
+		ds->bitmap = devm_kcalloc(dev,
+					  BITS_TO_LONGS(n),
+					  sizeof(unsigned long),
+					  GFP_KERNEL);
+		if (unlikely(!ds->bitmap))
+			return NULL;
+	}
+
 	ds->dev = dev;
 	ds->num_ports = n;
 

diff --git a/net/dsa/switch.c b/net/dsa/switch.c
@@ -136,21 +136,20 @@ static int dsa_switch_mdb_add(struct dsa_switch *ds,
 {
 	const struct switchdev_obj_port_mdb *mdb = info->mdb;
 	struct switchdev_trans *trans = info->trans;
-	DECLARE_BITMAP(group, ds->num_ports);
 	int port;
 
 	/* Build a mask of Multicast group members */
-	bitmap_zero(group, ds->num_ports);
+	bitmap_zero(ds->bitmap, ds->num_ports);
 	if (ds->index == info->sw_index)
-		set_bit(info->port, group);
+		set_bit(info->port, ds->bitmap);
 	for (port = 0; port < ds->num_ports; port++)
 		if (dsa_is_dsa_port(ds, port))
-			set_bit(port, group);
+			set_bit(port, ds->bitmap);
 
 	if (switchdev_trans_ph_prepare(trans))
-		return dsa_switch_mdb_prepare_bitmap(ds, mdb, group);
+		return dsa_switch_mdb_prepare_bitmap(ds, mdb, ds->bitmap);
 
-	dsa_switch_mdb_add_bitmap(ds, mdb, group);
+	dsa_switch_mdb_add_bitmap(ds, mdb, ds->bitmap);
 
 	return 0;
 }
@@ -204,21 +203,20 @@ static int dsa_switch_vlan_add(struct dsa_switch *ds,
 {
 	const struct switchdev_obj_port_vlan *vlan = info->vlan;
 	struct switchdev_trans *trans = info->trans;
-	DECLARE_BITMAP(members, ds->num_ports);
 	int port;
 
 	/* Build a mask of VLAN members */
-	bitmap_zero(members, ds->num_ports);
+	bitmap_zero(ds->bitmap, ds->num_ports);
 	if (ds->index == info->sw_index)
-		set_bit(info->port, members);
+		set_bit(info->port, ds->bitmap);
 	for (port = 0; port < ds->num_ports; port++)
 		if (dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port))
-			set_bit(port, members);
+			set_bit(port, ds->bitmap);
 
 	if (switchdev_trans_ph_prepare(trans))
-		return dsa_switch_vlan_prepare_bitmap(ds, vlan, members);
+		return dsa_switch_vlan_prepare_bitmap(ds, vlan, ds->bitmap);
 
-	dsa_switch_vlan_add_bitmap(ds, vlan, members);
+	dsa_switch_vlan_add_bitmap(ds, vlan, ds->bitmap);
 
 	return 0;
 }