bpf: introduce cgroup storage maps

This commit introduces BPF_MAP_TYPE_CGROUP_STORAGE maps:
a special type of maps which are implementing the cgroup storage.

>From the userspace point of view it's almost a generic
hash map with the (cgroup inode id, attachment type) pair
used as a key.

The only difference is that some operations are restricted:
  1) a user can't create new entries,
  2) a user can't remove existing entries.

The lookup from userspace is o(log(n)).
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf-cgroup.h

@@ -4,19 +4,39 @@
 
 #include <linux/errno.h>
 #include <linux/jump_label.h>
+#include <linux/rbtree.h>
 #include <uapi/linux/bpf.h>
 
 struct sock;
 struct sockaddr;
 struct cgroup;
 struct sk_buff;
+struct bpf_map;
+struct bpf_prog;
 struct bpf_sock_ops_kern;
+struct bpf_cgroup_storage;
 
 #ifdef CONFIG_CGROUP_BPF
 
 extern struct static_key_false cgroup_bpf_enabled_key;
 #define cgroup_bpf_enabled static_branch_unlikely(&cgroup_bpf_enabled_key)
 
+struct bpf_cgroup_storage_map;
+
+struct bpf_storage_buffer {
+	struct rcu_head rcu;
+	char data[0];
+};
+
+struct bpf_cgroup_storage {
+	struct bpf_storage_buffer *buf;
+	struct bpf_cgroup_storage_map *map;
+	struct bpf_cgroup_storage_key key;
+	struct list_head list;
+	struct rb_node node;
+	struct rcu_head rcu;
+};
+
 struct bpf_prog_list {
 	struct list_head node;
 	struct bpf_prog *prog;
@@ -77,6 +97,15 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
 int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 				      short access, enum bpf_attach_type type);
 
+struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog);
+void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage);
+void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
+			     struct cgroup *cgroup,
+			     enum bpf_attach_type type);
+void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage);
+int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *map);
+void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *map);
+
 /* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */
 #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb)			      \
 ({									      \
@@ -221,6 +250,15 @@ static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
 	return -EINVAL;
 }
 
+static inline int bpf_cgroup_storage_assign(struct bpf_prog *prog,
+					    struct bpf_map *map) { return 0; }
+static inline void bpf_cgroup_storage_release(struct bpf_prog *prog,
+					      struct bpf_map *map) {}
+static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(
+	struct bpf_prog *prog) { return 0; }
+static inline void bpf_cgroup_storage_free(
+	struct bpf_cgroup_storage *storage) {}
+
 #define cgroup_bpf_enabled (0)
 #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (0)
 #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })

include/linux/bpf.h

@@ -282,6 +282,7 @@ struct bpf_prog_aux {
 	struct bpf_prog *prog;
 	struct user_struct *user;
 	u64 load_time; /* ns since boottime */
+	struct bpf_map *cgroup_storage;
 	char name[BPF_OBJ_NAME_LEN];
 #ifdef CONFIG_SECURITY
 	void *security;

include/linux/bpf_types.h

@@ -37,6 +37,9 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_PERF_EVENT_ARRAY, perf_event_array_map_ops)
 #ifdef CONFIG_CGROUPS
 BPF_MAP_TYPE(BPF_MAP_TYPE_CGROUP_ARRAY, cgroup_array_map_ops)
 #endif
+#ifdef CONFIG_CGROUP_BPF
+BPF_MAP_TYPE(BPF_MAP_TYPE_CGROUP_STORAGE, cgroup_storage_map_ops)
+#endif
 BPF_MAP_TYPE(BPF_MAP_TYPE_HASH, htab_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_HASH, htab_percpu_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_LRU_HASH, htab_lru_map_ops)

include/uapi/linux/bpf.h

@@ -75,6 +75,11 @@ struct bpf_lpm_trie_key {
 	__u8	data[0];	/* Arbitrary size */
 };
 
+struct bpf_cgroup_storage_key {
+	__u64	cgroup_inode_id;	/* cgroup inode id */
+	__u32	attach_type;		/* program attach type */
+};
+
 /* BPF syscall commands, see bpf(2) man-page for details. */
 enum bpf_cmd {
 	BPF_MAP_CREATE,
@@ -120,6 +125,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_CPUMAP,
 	BPF_MAP_TYPE_XSKMAP,
 	BPF_MAP_TYPE_SOCKHASH,
+	BPF_MAP_TYPE_CGROUP_STORAGE,
 };
 
 enum bpf_prog_type {

kernel/bpf/Makefile

@@ -3,6 +3,7 @@ obj-y := core.o
 
 obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
+obj-$(CONFIG_BPF_SYSCALL) += local_storage.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o
 obj-$(CONFIG_BPF_SYSCALL) += btf.o
 ifeq ($(CONFIG_NET),y)

kernel/bpf/local_storage.c

+//SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf-cgroup.h>
+#include <linux/bpf.h>
+#include <linux/bug.h>
+#include <linux/filter.h>
+#include <linux/mm.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+
+#ifdef CONFIG_CGROUP_BPF
+
+#define LOCAL_STORAGE_CREATE_FLAG_MASK					\
+	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+
+struct bpf_cgroup_storage_map {
+	struct bpf_map map;
+
+	spinlock_t lock;
+	struct bpf_prog *prog;
+	struct rb_root root;
+	struct list_head list;
+};
+
+static struct bpf_cgroup_storage_map *map_to_storage(struct bpf_map *map)
+{
+	return container_of(map, struct bpf_cgroup_storage_map, map);
+}
+
+static int bpf_cgroup_storage_key_cmp(
+	const struct bpf_cgroup_storage_key *key1,
+	const struct bpf_cgroup_storage_key *key2)
+{
+	if (key1->cgroup_inode_id < key2->cgroup_inode_id)
+		return -1;
+	else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
+		return 1;
+	else if (key1->attach_type < key2->attach_type)
+		return -1;
+	else if (key1->attach_type > key2->attach_type)
+		return 1;
+	return 0;
+}
+
+static struct bpf_cgroup_storage *cgroup_storage_lookup(
+	struct bpf_cgroup_storage_map *map, struct bpf_cgroup_storage_key *key,
+	bool locked)
+{
+	struct rb_root *root = &map->root;
+	struct rb_node *node;
+
+	if (!locked)
+		spin_lock_bh(&map->lock);
+
+	node = root->rb_node;
+	while (node) {
+		struct bpf_cgroup_storage *storage;
+
+		storage = container_of(node, struct bpf_cgroup_storage, node);
+
+		switch (bpf_cgroup_storage_key_cmp(key, &storage->key)) {
+		case -1:
+			node = node->rb_left;
+			break;
+		case 1:
+			node = node->rb_right;
+			break;
+		default:
+			if (!locked)
+				spin_unlock_bh(&map->lock);
+			return storage;
+		}
+	}
+
+	if (!locked)
+		spin_unlock_bh(&map->lock);
+
+	return NULL;
+}
+
+static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
+				 struct bpf_cgroup_storage *storage)
+{
+	struct rb_root *root = &map->root;
+	struct rb_node **new = &(root->rb_node), *parent = NULL;
+
+	while (*new) {
+		struct bpf_cgroup_storage *this;
+
+		this = container_of(*new, struct bpf_cgroup_storage, node);
+
+		parent = *new;
+		switch (bpf_cgroup_storage_key_cmp(&storage->key, &this->key)) {
+		case -1:
+			new = &((*new)->rb_left);
+			break;
+		case 1:
+			new = &((*new)->rb_right);
+			break;
+		default:
+			return -EEXIST;
+		}
+	}
+
+	rb_link_node(&storage->node, parent, new);
+	rb_insert_color(&storage->node, root);
+
+	return 0;
+}
+
+static void *cgroup_storage_lookup_elem(struct bpf_map *_map, void *_key)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage *storage;
+
+	storage = cgroup_storage_lookup(map, key, false);
+	if (!storage)
+		return NULL;
+
+	return &READ_ONCE(storage->buf)->data[0];
+}
+
+static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
+				      void *value, u64 flags)
+{
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage *storage;
+	struct bpf_storage_buffer *new;
+
+	if (flags & BPF_NOEXIST)
+		return -EINVAL;
+
+	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
+					key, false);
+	if (!storage)
+		return -ENOENT;
+
+	new = kmalloc_node(sizeof(struct bpf_storage_buffer) +
+			   map->value_size, __GFP_ZERO | GFP_USER,
+			   map->numa_node);
+	if (!new)
+		return -ENOMEM;
+
+	memcpy(&new->data[0], value, map->value_size);
+
+	new = xchg(&storage->buf, new);
+	kfree_rcu(new, rcu);
+
+	return 0;
+}
+
+static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
+				       void *_next_key)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage_key *next = _next_key;
+	struct bpf_cgroup_storage *storage;
+
+	spin_lock_bh(&map->lock);
+
+	if (list_empty(&map->list))
+		goto enoent;
+
+	if (key) {
+		storage = cgroup_storage_lookup(map, key, true);
+		if (!storage)
+			goto enoent;
+
+		storage = list_next_entry(storage, list);
+		if (!storage)
+			goto enoent;
+	} else {
+		storage = list_first_entry(&map->list,
+					 struct bpf_cgroup_storage, list);
+	}
+
+	spin_unlock_bh(&map->lock);
+	next->attach_type = storage->key.attach_type;
+	next->cgroup_inode_id = storage->key.cgroup_inode_id;
+	return 0;
+
+enoent:
+	spin_unlock_bh(&map->lock);
+	return -ENOENT;
+}
+
+static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
+{
+	int numa_node = bpf_map_attr_numa_node(attr);
+	struct bpf_cgroup_storage_map *map;
+
+	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key))
+		return ERR_PTR(-EINVAL);
+
+	if (attr->value_size > PAGE_SIZE)
+		return ERR_PTR(-E2BIG);
+
+	if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK)
+		/* reserved bits should not be used */
+		return ERR_PTR(-EINVAL);
+
+	if (attr->max_entries)
+		/* max_entries is not used and enforced to be 0 */
+		return ERR_PTR(-EINVAL);
+
+	map = kmalloc_node(sizeof(struct bpf_cgroup_storage_map),
+			   __GFP_ZERO | GFP_USER, numa_node);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	map->map.pages = round_up(sizeof(struct bpf_cgroup_storage_map),
+				  PAGE_SIZE) >> PAGE_SHIFT;
+
+	/* copy mandatory map attributes */
+	bpf_map_init_from_attr(&map->map, attr);
+
+	spin_lock_init(&map->lock);
+	map->root = RB_ROOT;
+	INIT_LIST_HEAD(&map->list);
+
+	return &map->map;
+}
+
+static void cgroup_storage_map_free(struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+
+	WARN_ON(!RB_EMPTY_ROOT(&map->root));
+	WARN_ON(!list_empty(&map->list));
+
+	kfree(map);
+}
+
+static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
+{
+	return -EINVAL;
+}
+
+const struct bpf_map_ops cgroup_storage_map_ops = {
+	.map_alloc = cgroup_storage_map_alloc,
+	.map_free = cgroup_storage_map_free,
+	.map_get_next_key = cgroup_storage_get_next_key,
+	.map_lookup_elem = cgroup_storage_lookup_elem,
+	.map_update_elem = cgroup_storage_update_elem,
+	.map_delete_elem = cgroup_storage_delete_elem,
+};
+
+int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	int ret = -EBUSY;
+
+	spin_lock_bh(&map->lock);
+
+	if (map->prog && map->prog != prog)
+		goto unlock;
+	if (prog->aux->cgroup_storage && prog->aux->cgroup_storage != _map)
+		goto unlock;
+
+	map->prog = prog;
+	prog->aux->cgroup_storage = _map;
+	ret = 0;
+unlock:
+	spin_unlock_bh(&map->lock);
+
+	return ret;
+}
+
+void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+
+	spin_lock_bh(&map->lock);
+	if (map->prog == prog) {
+		WARN_ON(prog->aux->cgroup_storage != _map);
+		map->prog = NULL;
+		prog->aux->cgroup_storage = NULL;
+	}
+	spin_unlock_bh(&map->lock);
+}
+
+struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog)
+{
+	struct bpf_cgroup_storage *storage;
+	struct bpf_map *map;
+	u32 pages;
+
+	map = prog->aux->cgroup_storage;
+	if (!map)
+		return NULL;
+
+	pages = round_up(sizeof(struct bpf_cgroup_storage) +
+			 sizeof(struct bpf_storage_buffer) +
+			 map->value_size, PAGE_SIZE) >> PAGE_SHIFT;
+	if (bpf_map_charge_memlock(map, pages))
+		return ERR_PTR(-EPERM);
+
+	storage = kmalloc_node(sizeof(struct bpf_cgroup_storage),
+			       __GFP_ZERO | GFP_USER, map->numa_node);
+	if (!storage) {
+		bpf_map_uncharge_memlock(map, pages);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	storage->buf = kmalloc_node(sizeof(struct bpf_storage_buffer) +
+				    map->value_size, __GFP_ZERO | GFP_USER,
+				    map->numa_node);
+	if (!storage->buf) {
+		bpf_map_uncharge_memlock(map, pages);
+		kfree(storage);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	storage->map = (struct bpf_cgroup_storage_map *)map;
+
+	return storage;
+}
+
+void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
+{
+	u32 pages;
+	struct bpf_map *map;
+
+	if (!storage)
+		return;
+
+	map = &storage->map->map;
+	pages = round_up(sizeof(struct bpf_cgroup_storage) +
+			 sizeof(struct bpf_storage_buffer) +
+			 map->value_size, PAGE_SIZE) >> PAGE_SHIFT;
+	bpf_map_uncharge_memlock(map, pages);
+
+	kfree_rcu(storage->buf, rcu);
+	kfree_rcu(storage, rcu);
+}
+
+void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
+			     struct cgroup *cgroup,
+			     enum bpf_attach_type type)
+{
+	struct bpf_cgroup_storage_map *map;
+
+	if (!storage)
+		return;
+
+	storage->key.attach_type = type;
+	storage->key.cgroup_inode_id = cgroup->kn->id.id;
+
+	map = storage->map;
+
+	spin_lock_bh(&map->lock);
+	WARN_ON(cgroup_storage_insert(map, storage));
+	list_add(&storage->list, &map->list);
+	spin_unlock_bh(&map->lock);
+}
+
+void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
+{
+	struct bpf_cgroup_storage_map *map;
+	struct rb_root *root;
+
+	if (!storage)
+		return;
+
+	map = storage->map;
+
+	spin_lock_bh(&map->lock);
+	root = &map->root;
+	rb_erase(&storage->node, root);
+
+	list_del(&storage->list);
+	spin_unlock_bh(&map->lock);
+}
+
+#endif

kernel/bpf/syscall.c

@@ -957,6 +957,9 @@ static void free_used_maps(struct bpf_prog_aux *aux)
 {
 	int i;
 
+	if (aux->cgroup_storage)
+		bpf_cgroup_storage_release(aux->prog, aux->cgroup_storage);
+
 	for (i = 0; i < aux->used_map_cnt; i++)
 		bpf_map_put(aux->used_maps[i]);
 

kernel/bpf/verifier.c

@@ -5154,6 +5154,14 @@ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
 			}
 			env->used_maps[env->used_map_cnt++] = map;
 
+			if (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE &&
+			    bpf_cgroup_storage_assign(env->prog, map)) {
+				verbose(env,
+					"only one cgroup storage is allowed\n");
+				fdput(f);
+				return -EBUSY;
+			}
+
 			fdput(f);
 next_insn:
 			insn++;
@@ -5180,6 +5188,10 @@ static void release_maps(struct bpf_verifier_env *env)
 {
 	int i;
 
+	if (env->prog->aux->cgroup_storage)
+		bpf_cgroup_storage_release(env->prog,
+					   env->prog->aux->cgroup_storage);
+
 	for (i = 0; i < env->used_map_cnt; i++)
 		bpf_map_put(env->used_maps[i]);
 }