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 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 */ 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 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 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 */ 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 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 } 149 150 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 (!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 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 } 180 181 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 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 */ 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 WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]); 309 rcu_assign_pointer(array->ptrs[index], nsk); 310 free_osk = osk; 311 err = 0; 312 313 put_file_unlock: 314 write_unlock_bh(&nsk->sk_callback_lock); 315 316 if (free_osk) { 317 write_lock_bh(&free_osk->sk_callback_lock); 318 WRITE_ONCE(free_osk->sk_user_data, NULL); 319 write_unlock_bh(&free_osk->sk_callback_lock); 320 } 321 322 spin_unlock_bh(&reuseport_lock); 323 put_file: 324 fput(socket->file); 325 return err; 326 } 327 328 /* Called from syscall */ 329 static int reuseport_array_get_next_key(struct bpf_map *map, void *key, 330 void *next_key) 331 { 332 struct reuseport_array *array = reuseport_array(map); 333 u32 index = key ? *(u32 *)key : U32_MAX; 334 u32 *next = (u32 *)next_key; 335 336 if (index >= array->map.max_entries) { 337 *next = 0; 338 return 0; 339 } 340 341 if (index == array->map.max_entries - 1) 342 return -ENOENT; 343 344 *next = index + 1; 345 return 0; 346 } 347 348 const struct bpf_map_ops reuseport_array_ops = { 349 .map_alloc_check = reuseport_array_alloc_check, 350 .map_alloc = reuseport_array_alloc, 351 .map_free = reuseport_array_free, 352 .map_lookup_elem = reuseport_array_lookup_elem, 353 .map_get_next_key = reuseport_array_get_next_key, 354 .map_delete_elem = reuseport_array_delete_elem, 355 }; 356