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/20180505185145.GB32630@lunn.ch
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
[kees: tweak commit subject and message slightly]
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/dsa.h b/include/net/dsa.h
index fdbd608..461e8a7 100644 (file)
--- 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
index dc5d9af..a191702 100644 (file)
--- 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
index b935117..142b294 100644 (file)
--- 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;
 }