On Thu, Jul 09, 2020 at 12:12:37PM +0200, KP Singh wrote:

From: KP Singh <redacted>

Similar to bpf_local_storage for sockets, add local storage for inodes.
The life-cycle of storage is managed with the life-cycle of the inode.
i.e. the storage is destroyed along with the owning inode.

The BPF LSM allocates an __rcu pointer to the bpf_local_storage in the
security blob which are now stackable and can co-exist with other LSMs.

Signed-off-by: KP Singh <redacted>

[ ... ]

+static void *bpf_inode_storage_lookup_elem(struct bpf_map *map, void *key)
+{
+	struct bpf_local_storage_data *sdata;
+	struct inode *inode;
+	int err = -EINVAL;
+
+	if (key) {
+		inode = *(struct inode **)(key);

The bpf_inode_storage_lookup_elem() here and the (update|delete)_elem() below
are called from the userspace syscall.  How the userspace may provide this key?

+		sdata = inode_storage_lookup(inode, map, true);
+		return sdata ? sdata->data : NULL;
+	}
+
+	return ERR_PTR(err);
+}
+
+static int bpf_inode_storage_update_elem(struct bpf_map *map, void *key,
+					 void *value, u64 map_flags)
+{
+	struct bpf_local_storage_data *sdata;
+	struct inode *inode;
+	int err = -EINVAL;
+
+	if (key) {
+		inode = *(struct inode **)(key);
+		sdata = map->ops->map_local_storage_update(inode, map, value,
+							   map_flags);
+		return PTR_ERR_OR_ZERO(sdata);
+	}
+	return err;
+}
+
+static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
+{
+	struct bpf_local_storage_data *sdata;
+
+	sdata = inode_storage_lookup(inode, map, false);
+	if (!sdata)
+		return -ENOENT;
+
+	bpf_selem_unlink_map_elem(SELEM(sdata));
+
+	return 0;
+}
+
+static int bpf_inode_storage_delete_elem(struct bpf_map *map, void *key)
+{
+	struct inode *inode;
+	int err = -EINVAL;
+
+	if (key) {
+		inode = *(struct inode **)(key);
+		err = inode_storage_delete(inode, map);
+	}
+
+	return err;
+}
+

[ ... ]

+static int inode_storage_map_btf_id;
+const struct bpf_map_ops inode_storage_map_ops = {
+	.map_alloc_check = bpf_local_storage_map_alloc_check,
+	.map_alloc = inode_storage_map_alloc,
+	.map_free = inode_storage_map_free,
+	.map_get_next_key = notsupp_get_next_key,
+	.map_lookup_elem = bpf_inode_storage_lookup_elem,
+	.map_update_elem = bpf_inode_storage_update_elem,
+	.map_delete_elem = bpf_inode_storage_delete_elem,
+	.map_check_btf = bpf_local_storage_map_check_btf,
+	.map_btf_name = "bpf_local_storage_map",
+	.map_btf_id = &inode_storage_map_btf_id,
+	.map_local_storage_alloc = inode_storage_alloc,
+	.map_selem_alloc = inode_selem_alloc,
+	.map_local_storage_update = inode_storage_update,
+	.map_local_storage_unlink = unlink_inode_storage,
+};
+