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
10 struct reuseport_array {
11 struct bpf_map map;
12 struct sock __rcu *ptrs[];
13 };
14
reuseport_array(struct bpf_map * map)15 static 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 */
bpf_sk_reuseport_detach(struct sock * sk)21 void 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
reuseport_array_alloc_check(union bpf_attr * attr)43 static 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
reuseport_array_lookup_elem(struct bpf_map * map,void * key)52 static 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 */
reuseport_array_delete_elem(struct bpf_map * map,void * key)64 static 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
reuseport_array_free(struct bpf_map * map)96 static 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 triggerred 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
reuseport_array_alloc(union bpf_attr * attr)151 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
152 {
153 int err, numa_node = bpf_map_attr_numa_node(attr);
154 struct reuseport_array *array;
155 struct bpf_map_memory mem;
156 u64 array_size;
157
158 if (!bpf_capable())
159 return ERR_PTR(-EPERM);
160
161 array_size = sizeof(*array);
162 array_size += (u64)attr->max_entries * sizeof(struct sock *);
163
164 err = bpf_map_charge_init(&mem, array_size);
165 if (err)
166 return ERR_PTR(err);
167
168 /* allocate all map elements and zero-initialize them */
169 array = bpf_map_area_alloc(array_size, numa_node);
170 if (!array) {
171 bpf_map_charge_finish(&mem);
172 return ERR_PTR(-ENOMEM);
173 }
174
175 /* copy mandatory map attributes */
176 bpf_map_init_from_attr(&array->map, attr);
177 bpf_map_charge_move(&array->map.memory, &mem);
178
179 return &array->map;
180 }
181
bpf_fd_reuseport_array_lookup_elem(struct bpf_map * map,void * key,void * value)182 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
183 void *value)
184 {
185 struct sock *sk;
186 int err;
187
188 if (map->value_size != sizeof(u64))
189 return -ENOSPC;
190
191 rcu_read_lock();
192 sk = reuseport_array_lookup_elem(map, key);
193 if (sk) {
194 *(u64 *)value = __sock_gen_cookie(sk);
195 err = 0;
196 } else {
197 err = -ENOENT;
198 }
199 rcu_read_unlock();
200
201 return err;
202 }
203
204 static int
reuseport_array_update_check(const struct reuseport_array * array,const struct sock * nsk,const struct sock * osk,const struct sock_reuseport * nsk_reuse,u32 map_flags)205 reuseport_array_update_check(const struct reuseport_array *array,
206 const struct sock *nsk,
207 const struct sock *osk,
208 const struct sock_reuseport *nsk_reuse,
209 u32 map_flags)
210 {
211 if (osk && map_flags == BPF_NOEXIST)
212 return -EEXIST;
213
214 if (!osk && map_flags == BPF_EXIST)
215 return -ENOENT;
216
217 if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
218 return -ENOTSUPP;
219
220 if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
221 return -ENOTSUPP;
222
223 if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
224 return -ENOTSUPP;
225
226 /*
227 * sk must be hashed (i.e. listening in the TCP case or binded
228 * in the UDP case) and
229 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
230 *
231 * Also, sk will be used in bpf helper that is protected by
232 * rcu_read_lock().
233 */
234 if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
235 return -EINVAL;
236
237 /* READ_ONCE because the sk->sk_callback_lock may not be held here */
238 if (READ_ONCE(nsk->sk_user_data))
239 return -EBUSY;
240
241 return 0;
242 }
243
244 /*
245 * Called from syscall only.
246 * The "nsk" in the fd refcnt.
247 * The "osk" and "reuse" are protected by reuseport_lock.
248 */
bpf_fd_reuseport_array_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)249 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
250 void *value, u64 map_flags)
251 {
252 struct reuseport_array *array = reuseport_array(map);
253 struct sock *free_osk = NULL, *osk, *nsk;
254 struct sock_reuseport *reuse;
255 u32 index = *(u32 *)key;
256 uintptr_t sk_user_data;
257 struct socket *socket;
258 int err, fd;
259
260 if (map_flags > BPF_EXIST)
261 return -EINVAL;
262
263 if (index >= map->max_entries)
264 return -E2BIG;
265
266 if (map->value_size == sizeof(u64)) {
267 u64 fd64 = *(u64 *)value;
268
269 if (fd64 > S32_MAX)
270 return -EINVAL;
271 fd = fd64;
272 } else {
273 fd = *(int *)value;
274 }
275
276 socket = sockfd_lookup(fd, &err);
277 if (!socket)
278 return err;
279
280 nsk = socket->sk;
281 if (!nsk) {
282 err = -EINVAL;
283 goto put_file;
284 }
285
286 /* Quick checks before taking reuseport_lock */
287 err = reuseport_array_update_check(array, nsk,
288 rcu_access_pointer(array->ptrs[index]),
289 rcu_access_pointer(nsk->sk_reuseport_cb),
290 map_flags);
291 if (err)
292 goto put_file;
293
294 spin_lock_bh(&reuseport_lock);
295 /*
296 * Some of the checks only need reuseport_lock
297 * but it is done under sk_callback_lock also
298 * for simplicity reason.
299 */
300 write_lock_bh(&nsk->sk_callback_lock);
301
302 osk = rcu_dereference_protected(array->ptrs[index],
303 lockdep_is_held(&reuseport_lock));
304 reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
305 lockdep_is_held(&reuseport_lock));
306 err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
307 if (err)
308 goto put_file_unlock;
309
310 sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
311 SK_USER_DATA_BPF;
312 WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
313 rcu_assign_pointer(array->ptrs[index], nsk);
314 free_osk = osk;
315 err = 0;
316
317 put_file_unlock:
318 write_unlock_bh(&nsk->sk_callback_lock);
319
320 if (free_osk) {
321 write_lock_bh(&free_osk->sk_callback_lock);
322 WRITE_ONCE(free_osk->sk_user_data, NULL);
323 write_unlock_bh(&free_osk->sk_callback_lock);
324 }
325
326 spin_unlock_bh(&reuseport_lock);
327 put_file:
328 fput(socket->file);
329 return err;
330 }
331
332 /* Called from syscall */
reuseport_array_get_next_key(struct bpf_map * map,void * key,void * next_key)333 static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
334 void *next_key)
335 {
336 struct reuseport_array *array = reuseport_array(map);
337 u32 index = key ? *(u32 *)key : U32_MAX;
338 u32 *next = (u32 *)next_key;
339
340 if (index >= array->map.max_entries) {
341 *next = 0;
342 return 0;
343 }
344
345 if (index == array->map.max_entries - 1)
346 return -ENOENT;
347
348 *next = index + 1;
349 return 0;
350 }
351
352 static int reuseport_array_map_btf_id;
353 const struct bpf_map_ops reuseport_array_ops = {
354 .map_meta_equal = bpf_map_meta_equal,
355 .map_alloc_check = reuseport_array_alloc_check,
356 .map_alloc = reuseport_array_alloc,
357 .map_free = reuseport_array_free,
358 .map_lookup_elem = reuseport_array_lookup_elem,
359 .map_get_next_key = reuseport_array_get_next_key,
360 .map_delete_elem = reuseport_array_delete_elem,
361 .map_btf_name = "reuseport_array",
362 .map_btf_id = &reuseport_array_map_btf_id,
363 };
364