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 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
reuseport_array_alloc_check(union bpf_attr * attr)40 static 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
reuseport_array_lookup_elem(struct bpf_map * map,void * key)49 static 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 */
reuseport_array_delete_elem(struct bpf_map * map,void * key)61 static 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
reuseport_array_free(struct bpf_map * map)93 static 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
reuseport_array_alloc(union bpf_attr * attr)150 static 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
bpf_fd_reuseport_array_lookup_elem(struct bpf_map * map,void * key,void * value)181 int 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
203 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)204 reuseport_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 */
bpf_fd_reuseport_array_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)248 int 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
318 put_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);
328 put_file:
329 fput(socket->file);
330 return err;
331 }
332
333 /* Called from syscall */
reuseport_array_get_next_key(struct bpf_map * map,void * key,void * next_key)334 static 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
353 const 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 };
361