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 long 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	/* allocate all map elements and zero-initialize them */
155	array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node);
156	if (!array)
157		return ERR_PTR(-ENOMEM);
158
159	/* copy mandatory map attributes */
160	bpf_map_init_from_attr(&array->map, attr);
161
162	return &array->map;
163}
164
165int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
166				       void *value)
167{
168	struct sock *sk;
169	int err;
170
171	if (map->value_size != sizeof(u64))
172		return -ENOSPC;
173
174	rcu_read_lock();
175	sk = reuseport_array_lookup_elem(map, key);
176	if (sk) {
177		*(u64 *)value = __sock_gen_cookie(sk);
178		err = 0;
179	} else {
180		err = -ENOENT;
181	}
182	rcu_read_unlock();
183
184	return err;
185}
186
187static int
188reuseport_array_update_check(const struct reuseport_array *array,
189			     const struct sock *nsk,
190			     const struct sock *osk,
191			     const struct sock_reuseport *nsk_reuse,
192			     u32 map_flags)
193{
194	if (osk && map_flags == BPF_NOEXIST)
195		return -EEXIST;
196
197	if (!osk && map_flags == BPF_EXIST)
198		return -ENOENT;
199
200	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
201		return -ENOTSUPP;
202
203	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
204		return -ENOTSUPP;
205
206	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
207		return -ENOTSUPP;
208
209	/*
210	 * sk must be hashed (i.e. listening in the TCP case or binded
211	 * in the UDP case) and
212	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
213	 *
214	 * Also, sk will be used in bpf helper that is protected by
215	 * rcu_read_lock().
216	 */
217	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
218		return -EINVAL;
219
220	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
221	if (READ_ONCE(nsk->sk_user_data))
222		return -EBUSY;
223
224	return 0;
225}
226
227/*
228 * Called from syscall only.
229 * The "nsk" in the fd refcnt.
230 * The "osk" and "reuse" are protected by reuseport_lock.
231 */
232int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
233				       void *value, u64 map_flags)
234{
235	struct reuseport_array *array = reuseport_array(map);
236	struct sock *free_osk = NULL, *osk, *nsk;
237	struct sock_reuseport *reuse;
238	u32 index = *(u32 *)key;
239	uintptr_t sk_user_data;
240	struct socket *socket;
241	int err, fd;
242
243	if (map_flags > BPF_EXIST)
244		return -EINVAL;
245
246	if (index >= map->max_entries)
247		return -E2BIG;
248
249	if (map->value_size == sizeof(u64)) {
250		u64 fd64 = *(u64 *)value;
251
252		if (fd64 > S32_MAX)
253			return -EINVAL;
254		fd = fd64;
255	} else {
256		fd = *(int *)value;
257	}
258
259	socket = sockfd_lookup(fd, &err);
260	if (!socket)
261		return err;
262
263	nsk = socket->sk;
264	if (!nsk) {
265		err = -EINVAL;
266		goto put_file;
267	}
268
269	/* Quick checks before taking reuseport_lock */
270	err = reuseport_array_update_check(array, nsk,
271					   rcu_access_pointer(array->ptrs[index]),
272					   rcu_access_pointer(nsk->sk_reuseport_cb),
273					   map_flags);
274	if (err)
275		goto put_file;
276
277	spin_lock_bh(&reuseport_lock);
278	/*
279	 * Some of the checks only need reuseport_lock
280	 * but it is done under sk_callback_lock also
281	 * for simplicity reason.
282	 */
283	write_lock_bh(&nsk->sk_callback_lock);
284
285	osk = rcu_dereference_protected(array->ptrs[index],
286					lockdep_is_held(&reuseport_lock));
287	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
288					  lockdep_is_held(&reuseport_lock));
289	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
290	if (err)
291		goto put_file_unlock;
292
293	sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
294		SK_USER_DATA_BPF;
295	WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
296	rcu_assign_pointer(array->ptrs[index], nsk);
297	free_osk = osk;
298	err = 0;
299
300put_file_unlock:
301	write_unlock_bh(&nsk->sk_callback_lock);
302
303	if (free_osk) {
304		write_lock_bh(&free_osk->sk_callback_lock);
305		WRITE_ONCE(free_osk->sk_user_data, NULL);
306		write_unlock_bh(&free_osk->sk_callback_lock);
307	}
308
309	spin_unlock_bh(&reuseport_lock);
310put_file:
311	fput(socket->file);
312	return err;
313}
314
315/* Called from syscall */
316static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
317					void *next_key)
318{
319	struct reuseport_array *array = reuseport_array(map);
320	u32 index = key ? *(u32 *)key : U32_MAX;
321	u32 *next = (u32 *)next_key;
322
323	if (index >= array->map.max_entries) {
324		*next = 0;
325		return 0;
326	}
327
328	if (index == array->map.max_entries - 1)
329		return -ENOENT;
330
331	*next = index + 1;
332	return 0;
333}
334
335static u64 reuseport_array_mem_usage(const struct bpf_map *map)
336{
337	struct reuseport_array *array;
338
339	return struct_size(array, ptrs, map->max_entries);
340}
341
342BTF_ID_LIST_SINGLE(reuseport_array_map_btf_ids, struct, reuseport_array)
343const struct bpf_map_ops reuseport_array_ops = {
344	.map_meta_equal = bpf_map_meta_equal,
345	.map_alloc_check = reuseport_array_alloc_check,
346	.map_alloc = reuseport_array_alloc,
347	.map_free = reuseport_array_free,
348	.map_lookup_elem = reuseport_array_lookup_elem,
349	.map_get_next_key = reuseport_array_get_next_key,
350	.map_delete_elem = reuseport_array_delete_elem,
351	.map_mem_usage = reuseport_array_mem_usage,
352	.map_btf_id = &reuseport_array_map_btf_ids[0],
353};