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
 10struct reuseport_array {
 11	struct bpf_map map;
 12	struct sock __rcu *ptrs[];
 13};
 14
 15static struct reuseport_array *reuseport_array(struct bpf_map *map)
 16{
 17	return (struct reuseport_array *)map;
 18}
 19
 20/* The caller must hold the reuseport_lock */
 21void bpf_sk_reuseport_detach(struct sock *sk)
 22{
 23	uintptr_t sk_user_data;
 24
 25	write_lock_bh(&sk->sk_callback_lock);
 26	sk_user_data = (uintptr_t)sk->sk_user_data;
 27	if (sk_user_data & SK_USER_DATA_BPF) {
 28		struct sock __rcu **socks;
 29
 30		socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
 31		WRITE_ONCE(sk->sk_user_data, NULL);
 32		/*
 33		 * Do not move this NULL assignment outside of
 34		 * sk->sk_callback_lock because there is
 35		 * a race with reuseport_array_free()
 36		 * which does not hold the reuseport_lock.
 37		 */
 38		RCU_INIT_POINTER(*socks, NULL);
 39	}
 40	write_unlock_bh(&sk->sk_callback_lock);
 41}
 42
 43static int reuseport_array_alloc_check(union bpf_attr *attr)
 44{
 45	if (attr->value_size != sizeof(u32) &&
 46	    attr->value_size != sizeof(u64))
 47		return -EINVAL;
 48
 49	return array_map_alloc_check(attr);
 50}
 51
 52static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
 53{
 54	struct reuseport_array *array = reuseport_array(map);
 55	u32 index = *(u32 *)key;
 56
 57	if (unlikely(index >= array->map.max_entries))
 58		return NULL;
 59
 60	return rcu_dereference(array->ptrs[index]);
 61}
 62
 63/* Called from syscall only */
 64static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
 65{
 66	struct reuseport_array *array = reuseport_array(map);
 67	u32 index = *(u32 *)key;
 68	struct sock *sk;
 69	int err;
 70
 71	if (index >= map->max_entries)
 72		return -E2BIG;
 73
 74	if (!rcu_access_pointer(array->ptrs[index]))
 75		return -ENOENT;
 76
 77	spin_lock_bh(&reuseport_lock);
 78
 79	sk = rcu_dereference_protected(array->ptrs[index],
 80				       lockdep_is_held(&reuseport_lock));
 81	if (sk) {
 82		write_lock_bh(&sk->sk_callback_lock);
 83		WRITE_ONCE(sk->sk_user_data, NULL);
 84		RCU_INIT_POINTER(array->ptrs[index], NULL);
 85		write_unlock_bh(&sk->sk_callback_lock);
 86		err = 0;
 87	} else {
 88		err = -ENOENT;
 89	}
 90
 91	spin_unlock_bh(&reuseport_lock);
 92
 93	return err;
 94}
 95
 96static void reuseport_array_free(struct bpf_map *map)
 97{
 98	struct reuseport_array *array = reuseport_array(map);
 99	struct sock *sk;
100	u32 i;
101
102	/*
103	 * ops->map_*_elem() will not be able to access this
104	 * array now. Hence, this function only races with
105	 * bpf_sk_reuseport_detach() which was triggered by
106	 * close() or disconnect().
107	 *
108	 * This function and bpf_sk_reuseport_detach() are
109	 * both removing sk from "array".  Who removes it
110	 * first does not matter.
111	 *
112	 * The only concern here is bpf_sk_reuseport_detach()
113	 * may access "array" which is being freed here.
114	 * bpf_sk_reuseport_detach() access this "array"
115	 * through sk->sk_user_data _and_ with sk->sk_callback_lock
116	 * held which is enough because this "array" is not freed
117	 * until all sk->sk_user_data has stopped referencing this "array".
118	 *
119	 * Hence, due to the above, taking "reuseport_lock" is not
120	 * needed here.
121	 */
122
123	/*
124	 * Since reuseport_lock is not taken, sk is accessed under
125	 * rcu_read_lock()
126	 */
127	rcu_read_lock();
128	for (i = 0; i < map->max_entries; i++) {
129		sk = rcu_dereference(array->ptrs[i]);
130		if (sk) {
131			write_lock_bh(&sk->sk_callback_lock);
132			/*
133			 * No need for WRITE_ONCE(). At this point,
134			 * no one is reading it without taking the
135			 * sk->sk_callback_lock.
136			 */
137			sk->sk_user_data = NULL;
138			write_unlock_bh(&sk->sk_callback_lock);
139			RCU_INIT_POINTER(array->ptrs[i], NULL);
140		}
141	}
142	rcu_read_unlock();
143
144	/*
145	 * Once reaching here, all sk->sk_user_data is not
146	 * referenceing this "array".  "array" can be freed now.
147	 */
148	bpf_map_area_free(array);
149}
150
151static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
152{
153	int numa_node = bpf_map_attr_numa_node(attr);
154	struct reuseport_array *array;
155	u64 array_size;
156
157	if (!bpf_capable())
158		return ERR_PTR(-EPERM);
159
160	array_size = sizeof(*array);
161	array_size += (u64)attr->max_entries * sizeof(struct sock *);
162
163	/* allocate all map elements and zero-initialize them */
164	array = bpf_map_area_alloc(array_size, numa_node);
165	if (!array)
166		return ERR_PTR(-ENOMEM);
167
168	/* copy mandatory map attributes */
169	bpf_map_init_from_attr(&array->map, attr);
170
171	return &array->map;
172}
173
174int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
175				       void *value)
176{
177	struct sock *sk;
178	int err;
179
180	if (map->value_size != sizeof(u64))
181		return -ENOSPC;
182
183	rcu_read_lock();
184	sk = reuseport_array_lookup_elem(map, key);
185	if (sk) {
186		*(u64 *)value = __sock_gen_cookie(sk);
187		err = 0;
188	} else {
189		err = -ENOENT;
190	}
191	rcu_read_unlock();
192
193	return err;
194}
195
196static int
197reuseport_array_update_check(const struct reuseport_array *array,
198			     const struct sock *nsk,
199			     const struct sock *osk,
200			     const struct sock_reuseport *nsk_reuse,
201			     u32 map_flags)
202{
203	if (osk && map_flags == BPF_NOEXIST)
204		return -EEXIST;
205
206	if (!osk && map_flags == BPF_EXIST)
207		return -ENOENT;
208
209	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
210		return -ENOTSUPP;
211
212	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
213		return -ENOTSUPP;
214
215	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
216		return -ENOTSUPP;
217
218	/*
219	 * sk must be hashed (i.e. listening in the TCP case or binded
220	 * in the UDP case) and
221	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
222	 *
223	 * Also, sk will be used in bpf helper that is protected by
224	 * rcu_read_lock().
225	 */
226	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
227		return -EINVAL;
228
229	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
230	if (READ_ONCE(nsk->sk_user_data))
231		return -EBUSY;
232
233	return 0;
234}
235
236/*
237 * Called from syscall only.
238 * The "nsk" in the fd refcnt.
239 * The "osk" and "reuse" are protected by reuseport_lock.
240 */
241int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
242				       void *value, u64 map_flags)
243{
244	struct reuseport_array *array = reuseport_array(map);
245	struct sock *free_osk = NULL, *osk, *nsk;
246	struct sock_reuseport *reuse;
247	u32 index = *(u32 *)key;
248	uintptr_t sk_user_data;
249	struct socket *socket;
250	int err, fd;
251
252	if (map_flags > BPF_EXIST)
253		return -EINVAL;
254
255	if (index >= map->max_entries)
256		return -E2BIG;
257
258	if (map->value_size == sizeof(u64)) {
259		u64 fd64 = *(u64 *)value;
260
261		if (fd64 > S32_MAX)
262			return -EINVAL;
263		fd = fd64;
264	} else {
265		fd = *(int *)value;
266	}
267
268	socket = sockfd_lookup(fd, &err);
269	if (!socket)
270		return err;
271
272	nsk = socket->sk;
273	if (!nsk) {
274		err = -EINVAL;
275		goto put_file;
276	}
277
278	/* Quick checks before taking reuseport_lock */
279	err = reuseport_array_update_check(array, nsk,
280					   rcu_access_pointer(array->ptrs[index]),
281					   rcu_access_pointer(nsk->sk_reuseport_cb),
282					   map_flags);
283	if (err)
284		goto put_file;
285
286	spin_lock_bh(&reuseport_lock);
287	/*
288	 * Some of the checks only need reuseport_lock
289	 * but it is done under sk_callback_lock also
290	 * for simplicity reason.
291	 */
292	write_lock_bh(&nsk->sk_callback_lock);
293
294	osk = rcu_dereference_protected(array->ptrs[index],
295					lockdep_is_held(&reuseport_lock));
296	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
297					  lockdep_is_held(&reuseport_lock));
298	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
299	if (err)
300		goto put_file_unlock;
301
302	sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
303		SK_USER_DATA_BPF;
304	WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
305	rcu_assign_pointer(array->ptrs[index], nsk);
306	free_osk = osk;
307	err = 0;
308
309put_file_unlock:
310	write_unlock_bh(&nsk->sk_callback_lock);
311
312	if (free_osk) {
313		write_lock_bh(&free_osk->sk_callback_lock);
314		WRITE_ONCE(free_osk->sk_user_data, NULL);
315		write_unlock_bh(&free_osk->sk_callback_lock);
316	}
317
318	spin_unlock_bh(&reuseport_lock);
319put_file:
320	fput(socket->file);
321	return err;
322}
323
324/* Called from syscall */
325static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
326					void *next_key)
327{
328	struct reuseport_array *array = reuseport_array(map);
329	u32 index = key ? *(u32 *)key : U32_MAX;
330	u32 *next = (u32 *)next_key;
331
332	if (index >= array->map.max_entries) {
333		*next = 0;
334		return 0;
335	}
336
337	if (index == array->map.max_entries - 1)
338		return -ENOENT;
339
340	*next = index + 1;
341	return 0;
342}
343
344static int reuseport_array_map_btf_id;
345const struct bpf_map_ops reuseport_array_ops = {
346	.map_meta_equal = bpf_map_meta_equal,
347	.map_alloc_check = reuseport_array_alloc_check,
348	.map_alloc = reuseport_array_alloc,
349	.map_free = reuseport_array_free,
350	.map_lookup_elem = reuseport_array_lookup_elem,
351	.map_get_next_key = reuseport_array_get_next_key,
352	.map_delete_elem = reuseport_array_delete_elem,
353	.map_btf_name = "reuseport_array",
354	.map_btf_id = &reuseport_array_map_btf_id,
355};