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	struct sock __rcu **socks;
 24
 25	write_lock_bh(&sk->sk_callback_lock);
 26	socks = sk->sk_user_data;
 27	if (socks) {
 28		WRITE_ONCE(sk->sk_user_data, NULL);
 29		/*
 30		 * Do not move this NULL assignment outside of
 31		 * sk->sk_callback_lock because there is
 32		 * a race with reuseport_array_free()
 33		 * which does not hold the reuseport_lock.
 34		 */
 35		RCU_INIT_POINTER(*socks, NULL);
 36	}
 37	write_unlock_bh(&sk->sk_callback_lock);
 38}
 39
 40static int reuseport_array_alloc_check(union bpf_attr *attr)
 41{
 42	if (attr->value_size != sizeof(u32) &&
 43	    attr->value_size != sizeof(u64))
 44		return -EINVAL;
 45
 46	return array_map_alloc_check(attr);
 47}
 48
 49static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
 50{
 51	struct reuseport_array *array = reuseport_array(map);
 52	u32 index = *(u32 *)key;
 53
 54	if (unlikely(index >= array->map.max_entries))
 55		return NULL;
 56
 57	return rcu_dereference(array->ptrs[index]);
 58}
 59
 60/* Called from syscall only */
 61static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
 62{
 63	struct reuseport_array *array = reuseport_array(map);
 64	u32 index = *(u32 *)key;
 65	struct sock *sk;
 66	int err;
 67
 68	if (index >= map->max_entries)
 69		return -E2BIG;
 70
 71	if (!rcu_access_pointer(array->ptrs[index]))
 72		return -ENOENT;
 73
 74	spin_lock_bh(&reuseport_lock);
 75
 76	sk = rcu_dereference_protected(array->ptrs[index],
 77				       lockdep_is_held(&reuseport_lock));
 78	if (sk) {
 79		write_lock_bh(&sk->sk_callback_lock);
 80		WRITE_ONCE(sk->sk_user_data, NULL);
 81		RCU_INIT_POINTER(array->ptrs[index], NULL);
 82		write_unlock_bh(&sk->sk_callback_lock);
 83		err = 0;
 84	} else {
 85		err = -ENOENT;
 86	}
 87
 88	spin_unlock_bh(&reuseport_lock);
 89
 90	return err;
 91}
 92
 93static void reuseport_array_free(struct bpf_map *map)
 94{
 95	struct reuseport_array *array = reuseport_array(map);
 96	struct sock *sk;
 97	u32 i;
 98
 99	synchronize_rcu();
100
101	/*
102	 * ops->map_*_elem() will not be able to access this
103	 * array now. Hence, this function only races with
104	 * bpf_sk_reuseport_detach() which was triggerred by
105	 * close() or disconnect().
106	 *
107	 * This function and bpf_sk_reuseport_detach() are
108	 * both removing sk from "array".  Who removes it
109	 * first does not matter.
110	 *
111	 * The only concern here is bpf_sk_reuseport_detach()
112	 * may access "array" which is being freed here.
113	 * bpf_sk_reuseport_detach() access this "array"
114	 * through sk->sk_user_data _and_ with sk->sk_callback_lock
115	 * held which is enough because this "array" is not freed
116	 * until all sk->sk_user_data has stopped referencing this "array".
117	 *
118	 * Hence, due to the above, taking "reuseport_lock" is not
119	 * needed here.
120	 */
121
122	/*
123	 * Since reuseport_lock is not taken, sk is accessed under
124	 * rcu_read_lock()
125	 */
126	rcu_read_lock();
127	for (i = 0; i < map->max_entries; i++) {
128		sk = rcu_dereference(array->ptrs[i]);
129		if (sk) {
130			write_lock_bh(&sk->sk_callback_lock);
131			/*
132			 * No need for WRITE_ONCE(). At this point,
133			 * no one is reading it without taking the
134			 * sk->sk_callback_lock.
135			 */
136			sk->sk_user_data = NULL;
137			write_unlock_bh(&sk->sk_callback_lock);
138			RCU_INIT_POINTER(array->ptrs[i], NULL);
139		}
140	}
141	rcu_read_unlock();
142
143	/*
144	 * Once reaching here, all sk->sk_user_data is not
145	 * referenceing this "array".  "array" can be freed now.
146	 */
147	bpf_map_area_free(array);
148}
149
150static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
151{
152	int err, numa_node = bpf_map_attr_numa_node(attr);
153	struct reuseport_array *array;
154	struct bpf_map_memory mem;
155	u64 array_size;
156
157	if (!capable(CAP_SYS_ADMIN))
158		return ERR_PTR(-EPERM);
159
160	array_size = sizeof(*array);
161	array_size += (u64)attr->max_entries * sizeof(struct sock *);
162
163	err = bpf_map_charge_init(&mem, array_size);
164	if (err)
165		return ERR_PTR(err);
166
167	/* allocate all map elements and zero-initialize them */
168	array = bpf_map_area_alloc(array_size, numa_node);
169	if (!array) {
170		bpf_map_charge_finish(&mem);
171		return ERR_PTR(-ENOMEM);
172	}
173
174	/* copy mandatory map attributes */
175	bpf_map_init_from_attr(&array->map, attr);
176	bpf_map_charge_move(&array->map.memory, &mem);
177
178	return &array->map;
179}
180
181int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
182				       void *value)
183{
184	struct sock *sk;
185	int err;
186
187	if (map->value_size != sizeof(u64))
188		return -ENOSPC;
189
190	rcu_read_lock();
191	sk = reuseport_array_lookup_elem(map, key);
192	if (sk) {
193		*(u64 *)value = sock_gen_cookie(sk);
194		err = 0;
195	} else {
196		err = -ENOENT;
197	}
198	rcu_read_unlock();
199
200	return err;
201}
202
203static int
204reuseport_array_update_check(const struct reuseport_array *array,
205			     const struct sock *nsk,
206			     const struct sock *osk,
207			     const struct sock_reuseport *nsk_reuse,
208			     u32 map_flags)
209{
210	if (osk && map_flags == BPF_NOEXIST)
211		return -EEXIST;
212
213	if (!osk && map_flags == BPF_EXIST)
214		return -ENOENT;
215
216	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
217		return -ENOTSUPP;
218
219	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
220		return -ENOTSUPP;
221
222	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
223		return -ENOTSUPP;
224
225	/*
226	 * sk must be hashed (i.e. listening in the TCP case or binded
227	 * in the UDP case) and
228	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
229	 *
230	 * Also, sk will be used in bpf helper that is protected by
231	 * rcu_read_lock().
232	 */
233	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
234		return -EINVAL;
235
236	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
237	if (READ_ONCE(nsk->sk_user_data))
238		return -EBUSY;
239
240	return 0;
241}
242
243/*
244 * Called from syscall only.
245 * The "nsk" in the fd refcnt.
246 * The "osk" and "reuse" are protected by reuseport_lock.
247 */
248int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
249				       void *value, u64 map_flags)
250{
251	struct reuseport_array *array = reuseport_array(map);
252	struct sock *free_osk = NULL, *osk, *nsk;
253	struct sock_reuseport *reuse;
254	u32 index = *(u32 *)key;
255	struct socket *socket;
256	int err, fd;
257
258	if (map_flags > BPF_EXIST)
259		return -EINVAL;
260
261	if (index >= map->max_entries)
262		return -E2BIG;
263
264	if (map->value_size == sizeof(u64)) {
265		u64 fd64 = *(u64 *)value;
266
267		if (fd64 > S32_MAX)
268			return -EINVAL;
269		fd = fd64;
270	} else {
271		fd = *(int *)value;
272	}
273
274	socket = sockfd_lookup(fd, &err);
275	if (!socket)
276		return err;
277
278	nsk = socket->sk;
279	if (!nsk) {
280		err = -EINVAL;
281		goto put_file;
282	}
283
284	/* Quick checks before taking reuseport_lock */
285	err = reuseport_array_update_check(array, nsk,
286					   rcu_access_pointer(array->ptrs[index]),
287					   rcu_access_pointer(nsk->sk_reuseport_cb),
288					   map_flags);
289	if (err)
290		goto put_file;
291
292	spin_lock_bh(&reuseport_lock);
293	/*
294	 * Some of the checks only need reuseport_lock
295	 * but it is done under sk_callback_lock also
296	 * for simplicity reason.
297	 */
298	write_lock_bh(&nsk->sk_callback_lock);
299
300	osk = rcu_dereference_protected(array->ptrs[index],
301					lockdep_is_held(&reuseport_lock));
302	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
303					  lockdep_is_held(&reuseport_lock));
304	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
305	if (err)
306		goto put_file_unlock;
307
308	/* Ensure reuse->reuseport_id is set */
309	err = reuseport_get_id(reuse);
310	if (err < 0)
311		goto put_file_unlock;
312
313	WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
314	rcu_assign_pointer(array->ptrs[index], nsk);
315	free_osk = osk;
316	err = 0;
317
318put_file_unlock:
319	write_unlock_bh(&nsk->sk_callback_lock);
320
321	if (free_osk) {
322		write_lock_bh(&free_osk->sk_callback_lock);
323		WRITE_ONCE(free_osk->sk_user_data, NULL);
324		write_unlock_bh(&free_osk->sk_callback_lock);
325	}
326
327	spin_unlock_bh(&reuseport_lock);
328put_file:
329	fput(socket->file);
330	return err;
331}
332
333/* Called from syscall */
334static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
335					void *next_key)
336{
337	struct reuseport_array *array = reuseport_array(map);
338	u32 index = key ? *(u32 *)key : U32_MAX;
339	u32 *next = (u32 *)next_key;
340
341	if (index >= array->map.max_entries) {
342		*next = 0;
343		return 0;
344	}
345
346	if (index == array->map.max_entries - 1)
347		return -ENOENT;
348
349	*next = index + 1;
350	return 0;
351}
352
353const struct bpf_map_ops reuseport_array_ops = {
354	.map_alloc_check = reuseport_array_alloc_check,
355	.map_alloc = reuseport_array_alloc,
356	.map_free = reuseport_array_free,
357	.map_lookup_elem = reuseport_array_lookup_elem,
358	.map_get_next_key = reuseport_array_get_next_key,
359	.map_delete_elem = reuseport_array_delete_elem,
360};