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 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 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 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 */ 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 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 } 150 151 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 } 181 182 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 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 */ 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 */ 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_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 .map_btf_name = "reuseport_array", 361 .map_btf_id = &reuseport_array_map_btf_id, 362 }; 363