1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (c) 2018 Facebook
  4 */
  5#include <linux/bpf.h>
  6#include <linux/err.h>
  7#include <linux/sock_diag.h>
  8#include <net/sock_reuseport.h>
  9#include <linux/btf_ids.h>
 10
 11struct reuseport_array {
 12	struct bpf_map map;
 13	struct sock __rcu *ptrs[];
 14};
 15
 16static struct reuseport_array *reuseport_array(struct bpf_map *map)
 17{
 18	return (struct reuseport_array *)map;
 19}
 20
 21/* The caller must hold the reuseport_lock */
 22void bpf_sk_reuseport_detach(struct sock *sk)
 23{
 24	struct sock __rcu **socks;
 25
 26	write_lock_bh(&sk->sk_callback_lock);
 27	socks = __locked_read_sk_user_data_with_flags(sk, SK_USER_DATA_BPF);
 28	if (socks) {
 29		WRITE_ONCE(sk->sk_user_data, NULL);
 30		/*
 31		 * Do not move this NULL assignment outside of
 32		 * sk->sk_callback_lock because there is
 33		 * a race with reuseport_array_free()
 34		 * which does not hold the reuseport_lock.
 35		 */
 36		RCU_INIT_POINTER(*socks, NULL);
 37	}
 38	write_unlock_bh(&sk->sk_callback_lock);
 39}
 40
 41static int reuseport_array_alloc_check(union bpf_attr *attr)
 42{
 43	if (attr->value_size != sizeof(u32) &&
 44	    attr->value_size != sizeof(u64))
 45		return -EINVAL;
 46
 47	return array_map_alloc_check(attr);
 48}
 49
 50static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
 51{
 52	struct reuseport_array *array = reuseport_array(map);
 53	u32 index = *(u32 *)key;
 54
 55	if (unlikely(index >= array->map.max_entries))
 56		return NULL;
 57
 58	return rcu_dereference(array->ptrs[index]);
 59}
 60
 61/* Called from syscall only */
 62static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
 63{
 64	struct reuseport_array *array = reuseport_array(map);
 65	u32 index = *(u32 *)key;
 66	struct sock *sk;
 67	int err;
 68
 69	if (index >= map->max_entries)
 70		return -E2BIG;
 71
 72	if (!rcu_access_pointer(array->ptrs[index]))
 73		return -ENOENT;
 74
 75	spin_lock_bh(&reuseport_lock);
 76
 77	sk = rcu_dereference_protected(array->ptrs[index],
 78				       lockdep_is_held(&reuseport_lock));
 79	if (sk) {
 80		write_lock_bh(&sk->sk_callback_lock);
 81		WRITE_ONCE(sk->sk_user_data, NULL);
 82		RCU_INIT_POINTER(array->ptrs[index], NULL);
 83		write_unlock_bh(&sk->sk_callback_lock);
 84		err = 0;
 85	} else {
 86		err = -ENOENT;
 87	}
 88
 89	spin_unlock_bh(&reuseport_lock);
 90
 91	return err;
 92}
 93
 94static void reuseport_array_free(struct bpf_map *map)
 95{
 96	struct reuseport_array *array = reuseport_array(map);
 97	struct sock *sk;
 98	u32 i;
 99
100	/*
101	 * ops->map_*_elem() will not be able to access this
102	 * array now. Hence, this function only races with
103	 * bpf_sk_reuseport_detach() which was triggered by
104	 * close() or disconnect().
105	 *
106	 * This function and bpf_sk_reuseport_detach() are
107	 * both removing sk from "array".  Who removes it
108	 * first does not matter.
109	 *
110	 * The only concern here is bpf_sk_reuseport_detach()
111	 * may access "array" which is being freed here.
112	 * bpf_sk_reuseport_detach() access this "array"
113	 * through sk->sk_user_data _and_ with sk->sk_callback_lock
114	 * held which is enough because this "array" is not freed
115	 * until all sk->sk_user_data has stopped referencing this "array".
116	 *
117	 * Hence, due to the above, taking "reuseport_lock" is not
118	 * needed here.
119	 */
120
121	/*
122	 * Since reuseport_lock is not taken, sk is accessed under
123	 * rcu_read_lock()
124	 */
125	rcu_read_lock();
126	for (i = 0; i < map->max_entries; i++) {
127		sk = rcu_dereference(array->ptrs[i]);
128		if (sk) {
129			write_lock_bh(&sk->sk_callback_lock);
130			/*
131			 * No need for WRITE_ONCE(). At this point,
132			 * no one is reading it without taking the
133			 * sk->sk_callback_lock.
134			 */
135			sk->sk_user_data = NULL;
136			write_unlock_bh(&sk->sk_callback_lock);
137			RCU_INIT_POINTER(array->ptrs[i], NULL);
138		}
139	}
140	rcu_read_unlock();
141
142	/*
143	 * Once reaching here, all sk->sk_user_data is not
144	 * referencing this "array". "array" can be freed now.
145	 */
146	bpf_map_area_free(array);
147}
148
149static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
150{
151	int numa_node = bpf_map_attr_numa_node(attr);
152	struct reuseport_array *array;
153
154	if (!bpf_capable())
155		return ERR_PTR(-EPERM);
156
157	/* allocate all map elements and zero-initialize them */
158	array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node);
159	if (!array)
160		return ERR_PTR(-ENOMEM);
161
162	/* copy mandatory map attributes */
163	bpf_map_init_from_attr(&array->map, attr);
164
165	return &array->map;
166}
167
168int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
169				       void *value)
170{
171	struct sock *sk;
172	int err;
173
174	if (map->value_size != sizeof(u64))
175		return -ENOSPC;
176
177	rcu_read_lock();
178	sk = reuseport_array_lookup_elem(map, key);
179	if (sk) {
180		*(u64 *)value = __sock_gen_cookie(sk);
181		err = 0;
182	} else {
183		err = -ENOENT;
184	}
185	rcu_read_unlock();
186
187	return err;
188}
189
190static int
191reuseport_array_update_check(const struct reuseport_array *array,
192			     const struct sock *nsk,
193			     const struct sock *osk,
194			     const struct sock_reuseport *nsk_reuse,
195			     u32 map_flags)
196{
197	if (osk && map_flags == BPF_NOEXIST)
198		return -EEXIST;
199
200	if (!osk && map_flags == BPF_EXIST)
201		return -ENOENT;
202
203	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
204		return -ENOTSUPP;
205
206	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
207		return -ENOTSUPP;
208
209	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
210		return -ENOTSUPP;
211
212	/*
213	 * sk must be hashed (i.e. listening in the TCP case or binded
214	 * in the UDP case) and
215	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
216	 *
217	 * Also, sk will be used in bpf helper that is protected by
218	 * rcu_read_lock().
219	 */
220	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
221		return -EINVAL;
222
223	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
224	if (READ_ONCE(nsk->sk_user_data))
225		return -EBUSY;
226
227	return 0;
228}
229
230/*
231 * Called from syscall only.
232 * The "nsk" in the fd refcnt.
233 * The "osk" and "reuse" are protected by reuseport_lock.
234 */
235int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
236				       void *value, u64 map_flags)
237{
238	struct reuseport_array *array = reuseport_array(map);
239	struct sock *free_osk = NULL, *osk, *nsk;
240	struct sock_reuseport *reuse;
241	u32 index = *(u32 *)key;
242	uintptr_t sk_user_data;
243	struct socket *socket;
244	int err, fd;
245
246	if (map_flags > BPF_EXIST)
247		return -EINVAL;
248
249	if (index >= map->max_entries)
250		return -E2BIG;
251
252	if (map->value_size == sizeof(u64)) {
253		u64 fd64 = *(u64 *)value;
254
255		if (fd64 > S32_MAX)
256			return -EINVAL;
257		fd = fd64;
258	} else {
259		fd = *(int *)value;
260	}
261
262	socket = sockfd_lookup(fd, &err);
263	if (!socket)
264		return err;
265
266	nsk = socket->sk;
267	if (!nsk) {
268		err = -EINVAL;
269		goto put_file;
270	}
271
272	/* Quick checks before taking reuseport_lock */
273	err = reuseport_array_update_check(array, nsk,
274					   rcu_access_pointer(array->ptrs[index]),
275					   rcu_access_pointer(nsk->sk_reuseport_cb),
276					   map_flags);
277	if (err)
278		goto put_file;
279
280	spin_lock_bh(&reuseport_lock);
281	/*
282	 * Some of the checks only need reuseport_lock
283	 * but it is done under sk_callback_lock also
284	 * for simplicity reason.
285	 */
286	write_lock_bh(&nsk->sk_callback_lock);
287
288	osk = rcu_dereference_protected(array->ptrs[index],
289					lockdep_is_held(&reuseport_lock));
290	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
291					  lockdep_is_held(&reuseport_lock));
292	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
293	if (err)
294		goto put_file_unlock;
295
296	sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
297		SK_USER_DATA_BPF;
298	WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
299	rcu_assign_pointer(array->ptrs[index], nsk);
300	free_osk = osk;
301	err = 0;
302
303put_file_unlock:
304	write_unlock_bh(&nsk->sk_callback_lock);
305
306	if (free_osk) {
307		write_lock_bh(&free_osk->sk_callback_lock);
308		WRITE_ONCE(free_osk->sk_user_data, NULL);
309		write_unlock_bh(&free_osk->sk_callback_lock);
310	}
311
312	spin_unlock_bh(&reuseport_lock);
313put_file:
314	fput(socket->file);
315	return err;
316}
317
318/* Called from syscall */
319static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
320					void *next_key)
321{
322	struct reuseport_array *array = reuseport_array(map);
323	u32 index = key ? *(u32 *)key : U32_MAX;
324	u32 *next = (u32 *)next_key;
325
326	if (index >= array->map.max_entries) {
327		*next = 0;
328		return 0;
329	}
330
331	if (index == array->map.max_entries - 1)
332		return -ENOENT;
333
334	*next = index + 1;
335	return 0;
336}
337
338BTF_ID_LIST_SINGLE(reuseport_array_map_btf_ids, struct, reuseport_array)
339const struct bpf_map_ops reuseport_array_ops = {
340	.map_meta_equal = bpf_map_meta_equal,
341	.map_alloc_check = reuseport_array_alloc_check,
342	.map_alloc = reuseport_array_alloc,
343	.map_free = reuseport_array_free,
344	.map_lookup_elem = reuseport_array_lookup_elem,
345	.map_get_next_key = reuseport_array_get_next_key,
346	.map_delete_elem = reuseport_array_delete_elem,
347	.map_btf_id = &reuseport_array_map_btf_ids[0],
348};