devmap: Formalize map value as a named struct

Add 'struct bpf_devmap_val' to formalize the expected values that can
be passed in for a DEVMAP. Update devmap code to use the struct.

Signed-off-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200529220716.75383-2-dsahern@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a51d9fb7a359c0d9874594902cc38bfad6d2e75f..a1459de0914e8d92a2697461d728142707a1346f 100644 (file)
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -60,12 +60,18 @@ struct xdp_dev_bulk_queue {
        unsigned int count;
 };
 
+/* DEVMAP values */
+struct bpf_devmap_val {
+       u32 ifindex;   /* device index */
+};
+
 struct bpf_dtab_netdev {
        struct net_device *dev; /* must be first member, due to tracepoint */
        struct hlist_node index_hlist;
        struct bpf_dtab *dtab;
        struct rcu_head rcu;
        unsigned int idx;
+       struct bpf_devmap_val val;
 };
 
 struct bpf_dtab {
@@ -472,18 +478,15 @@ int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
        struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
-       struct net_device *dev = obj ? obj->dev : NULL;
 
-       return dev ? &dev->ifindex : NULL;
+       return obj ? &obj->val : NULL;
 }
 
 static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
 {
        struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
                                                                *(u32 *)key);
-       struct net_device *dev = obj ? obj->dev : NULL;
-
-       return dev ? &dev->ifindex : NULL;
+       return obj ? &obj->val : NULL;
 }
 
 static void __dev_map_entry_free(struct rcu_head *rcu)
@@ -541,7 +544,7 @@ static int dev_map_hash_delete_elem(struct bpf_map *map, void *key)
 
 static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
                                                    struct bpf_dtab *dtab,
-                                                   u32 ifindex,
+                                                   struct bpf_devmap_val *val,
                                                    unsigned int idx)
 {
        struct bpf_dtab_netdev *dev;
@@ -551,16 +554,18 @@ static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
        if (!dev)
                return ERR_PTR(-ENOMEM);
 
-       dev->dev = dev_get_by_index(net, ifindex);
-       if (!dev->dev) {
-               kfree(dev);
-               return ERR_PTR(-EINVAL);
-       }
+       dev->dev = dev_get_by_index(net, val->ifindex);
+       if (!dev->dev)
+               goto err_out;
 
        dev->idx = idx;
        dev->dtab = dtab;
+       dev->val.ifindex = val->ifindex;
 
        return dev;
+err_out:
+       kfree(dev);
+       return ERR_PTR(-EINVAL);
 }
 
 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
@@ -568,7 +573,7 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 {
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dev, *old_dev;
-       u32 ifindex = *(u32 *)value;
+       struct bpf_devmap_val val = { };
        u32 i = *(u32 *)key;
 
        if (unlikely(map_flags > BPF_EXIST))
@@ -578,10 +583,13 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
        if (unlikely(map_flags == BPF_NOEXIST))
                return -EEXIST;
 
-       if (!ifindex) {
+       /* already verified value_size <= sizeof val */
+       memcpy(&val, value, map->value_size);
+
+       if (!val.ifindex) {
                dev = NULL;
        } else {
-               dev = __dev_map_alloc_node(net, dtab, ifindex, i);
+               dev = __dev_map_alloc_node(net, dtab, &val, i);
                if (IS_ERR(dev))
                        return PTR_ERR(dev);
        }
@@ -609,12 +617,15 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
 {
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dev, *old_dev;
-       u32 ifindex = *(u32 *)value;
+       struct bpf_devmap_val val = { };
        u32 idx = *(u32 *)key;
        unsigned long flags;
        int err = -EEXIST;
 
-       if (unlikely(map_flags > BPF_EXIST || !ifindex))
+       /* already verified value_size <= sizeof val */
+       memcpy(&val, value, map->value_size);
+
+       if (unlikely(map_flags > BPF_EXIST || !val.ifindex))
                return -EINVAL;
 
        spin_lock_irqsave(&dtab->index_lock, flags);
@@ -623,7 +634,7 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
        if (old_dev && (map_flags & BPF_NOEXIST))
                goto out_err;
 
-       dev = __dev_map_alloc_node(net, dtab, ifindex, idx);
+       dev = __dev_map_alloc_node(net, dtab, &val, idx);
        if (IS_ERR(dev)) {
                err = PTR_ERR(dev);
                goto out_err;