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 11 struct reuseport_array { 12 struct bpf_map map; 13 struct sock __rcu *ptrs[]; 14 }; 15 16 static 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 */ 22 void bpf_sk_reuseport_detach(struct sock *sk) 23 { 24 uintptr_t sk_user_data; 25 26 write_lock_bh(&sk->sk_callback_lock); 27 sk_user_data = (uintptr_t)sk->sk_user_data; 28 if (sk_user_data & SK_USER_DATA_BPF) { 29 struct sock __rcu **socks; 30 31 socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK); 32 WRITE_ONCE(sk->sk_user_data, NULL); 33 /* 34 * Do not move this NULL assignment outside of 35 * sk->sk_callback_lock because there is 36 * a race with reuseport_array_free() 37 * which does not hold the reuseport_lock. 38 */ 39 RCU_INIT_POINTER(*socks, NULL); 40 } 41 write_unlock_bh(&sk->sk_callback_lock); 42 } 43 44 static int reuseport_array_alloc_check(union bpf_attr *attr) 45 { 46 if (attr->value_size != sizeof(u32) && 47 attr->value_size != sizeof(u64)) 48 return -EINVAL; 49 50 return array_map_alloc_check(attr); 51 } 52 53 static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key) 54 { 55 struct reuseport_array *array = reuseport_array(map); 56 u32 index = *(u32 *)key; 57 58 if (unlikely(index >= array->map.max_entries)) 59 return NULL; 60 61 return rcu_dereference(array->ptrs[index]); 62 } 63 64 /* Called from syscall only */ 65 static int reuseport_array_delete_elem(struct bpf_map *map, void *key) 66 { 67 struct reuseport_array *array = reuseport_array(map); 68 u32 index = *(u32 *)key; 69 struct sock *sk; 70 int err; 71 72 if (index >= map->max_entries) 73 return -E2BIG; 74 75 if (!rcu_access_pointer(array->ptrs[index])) 76 return -ENOENT; 77 78 spin_lock_bh(&reuseport_lock); 79 80 sk = rcu_dereference_protected(array->ptrs[index], 81 lockdep_is_held(&reuseport_lock)); 82 if (sk) { 83 write_lock_bh(&sk->sk_callback_lock); 84 WRITE_ONCE(sk->sk_user_data, NULL); 85 RCU_INIT_POINTER(array->ptrs[index], NULL); 86 write_unlock_bh(&sk->sk_callback_lock); 87 err = 0; 88 } else { 89 err = -ENOENT; 90 } 91 92 spin_unlock_bh(&reuseport_lock); 93 94 return err; 95 } 96 97 static void reuseport_array_free(struct bpf_map *map) 98 { 99 struct reuseport_array *array = reuseport_array(map); 100 struct sock *sk; 101 u32 i; 102 103 /* 104 * ops->map_*_elem() will not be able to access this 105 * array now. Hence, this function only races with 106 * bpf_sk_reuseport_detach() which was triggered by 107 * close() or disconnect(). 108 * 109 * This function and bpf_sk_reuseport_detach() are 110 * both removing sk from "array". Who removes it 111 * first does not matter. 112 * 113 * The only concern here is bpf_sk_reuseport_detach() 114 * may access "array" which is being freed here. 115 * bpf_sk_reuseport_detach() access this "array" 116 * through sk->sk_user_data _and_ with sk->sk_callback_lock 117 * held which is enough because this "array" is not freed 118 * until all sk->sk_user_data has stopped referencing this "array". 119 * 120 * Hence, due to the above, taking "reuseport_lock" is not 121 * needed here. 122 */ 123 124 /* 125 * Since reuseport_lock is not taken, sk is accessed under 126 * rcu_read_lock() 127 */ 128 rcu_read_lock(); 129 for (i = 0; i < map->max_entries; i++) { 130 sk = rcu_dereference(array->ptrs[i]); 131 if (sk) { 132 write_lock_bh(&sk->sk_callback_lock); 133 /* 134 * No need for WRITE_ONCE(). At this point, 135 * no one is reading it without taking the 136 * sk->sk_callback_lock. 137 */ 138 sk->sk_user_data = NULL; 139 write_unlock_bh(&sk->sk_callback_lock); 140 RCU_INIT_POINTER(array->ptrs[i], NULL); 141 } 142 } 143 rcu_read_unlock(); 144 145 /* 146 * Once reaching here, all sk->sk_user_data is not 147 * referencing this "array". "array" can be freed now. 148 */ 149 bpf_map_area_free(array); 150 } 151 152 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr) 153 { 154 int numa_node = bpf_map_attr_numa_node(attr); 155 struct reuseport_array *array; 156 157 if (!bpf_capable()) 158 return ERR_PTR(-EPERM); 159 160 /* allocate all map elements and zero-initialize them */ 161 array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node); 162 if (!array) 163 return ERR_PTR(-ENOMEM); 164 165 /* copy mandatory map attributes */ 166 bpf_map_init_from_attr(&array->map, attr); 167 168 return &array->map; 169 } 170 171 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key, 172 void *value) 173 { 174 struct sock *sk; 175 int err; 176 177 if (map->value_size != sizeof(u64)) 178 return -ENOSPC; 179 180 rcu_read_lock(); 181 sk = reuseport_array_lookup_elem(map, key); 182 if (sk) { 183 *(u64 *)value = __sock_gen_cookie(sk); 184 err = 0; 185 } else { 186 err = -ENOENT; 187 } 188 rcu_read_unlock(); 189 190 return err; 191 } 192 193 static int 194 reuseport_array_update_check(const struct reuseport_array *array, 195 const struct sock *nsk, 196 const struct sock *osk, 197 const struct sock_reuseport *nsk_reuse, 198 u32 map_flags) 199 { 200 if (osk && map_flags == BPF_NOEXIST) 201 return -EEXIST; 202 203 if (!osk && map_flags == BPF_EXIST) 204 return -ENOENT; 205 206 if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP) 207 return -ENOTSUPP; 208 209 if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6) 210 return -ENOTSUPP; 211 212 if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM) 213 return -ENOTSUPP; 214 215 /* 216 * sk must be hashed (i.e. listening in the TCP case or binded 217 * in the UDP case) and 218 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL). 219 * 220 * Also, sk will be used in bpf helper that is protected by 221 * rcu_read_lock(). 222 */ 223 if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse) 224 return -EINVAL; 225 226 /* READ_ONCE because the sk->sk_callback_lock may not be held here */ 227 if (READ_ONCE(nsk->sk_user_data)) 228 return -EBUSY; 229 230 return 0; 231 } 232 233 /* 234 * Called from syscall only. 235 * The "nsk" in the fd refcnt. 236 * The "osk" and "reuse" are protected by reuseport_lock. 237 */ 238 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key, 239 void *value, u64 map_flags) 240 { 241 struct reuseport_array *array = reuseport_array(map); 242 struct sock *free_osk = NULL, *osk, *nsk; 243 struct sock_reuseport *reuse; 244 u32 index = *(u32 *)key; 245 uintptr_t sk_user_data; 246 struct socket *socket; 247 int err, fd; 248 249 if (map_flags > BPF_EXIST) 250 return -EINVAL; 251 252 if (index >= map->max_entries) 253 return -E2BIG; 254 255 if (map->value_size == sizeof(u64)) { 256 u64 fd64 = *(u64 *)value; 257 258 if (fd64 > S32_MAX) 259 return -EINVAL; 260 fd = fd64; 261 } else { 262 fd = *(int *)value; 263 } 264 265 socket = sockfd_lookup(fd, &err); 266 if (!socket) 267 return err; 268 269 nsk = socket->sk; 270 if (!nsk) { 271 err = -EINVAL; 272 goto put_file; 273 } 274 275 /* Quick checks before taking reuseport_lock */ 276 err = reuseport_array_update_check(array, nsk, 277 rcu_access_pointer(array->ptrs[index]), 278 rcu_access_pointer(nsk->sk_reuseport_cb), 279 map_flags); 280 if (err) 281 goto put_file; 282 283 spin_lock_bh(&reuseport_lock); 284 /* 285 * Some of the checks only need reuseport_lock 286 * but it is done under sk_callback_lock also 287 * for simplicity reason. 288 */ 289 write_lock_bh(&nsk->sk_callback_lock); 290 291 osk = rcu_dereference_protected(array->ptrs[index], 292 lockdep_is_held(&reuseport_lock)); 293 reuse = rcu_dereference_protected(nsk->sk_reuseport_cb, 294 lockdep_is_held(&reuseport_lock)); 295 err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags); 296 if (err) 297 goto put_file_unlock; 298 299 sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY | 300 SK_USER_DATA_BPF; 301 WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data); 302 rcu_assign_pointer(array->ptrs[index], nsk); 303 free_osk = osk; 304 err = 0; 305 306 put_file_unlock: 307 write_unlock_bh(&nsk->sk_callback_lock); 308 309 if (free_osk) { 310 write_lock_bh(&free_osk->sk_callback_lock); 311 WRITE_ONCE(free_osk->sk_user_data, NULL); 312 write_unlock_bh(&free_osk->sk_callback_lock); 313 } 314 315 spin_unlock_bh(&reuseport_lock); 316 put_file: 317 fput(socket->file); 318 return err; 319 } 320 321 /* Called from syscall */ 322 static int reuseport_array_get_next_key(struct bpf_map *map, void *key, 323 void *next_key) 324 { 325 struct reuseport_array *array = reuseport_array(map); 326 u32 index = key ? *(u32 *)key : U32_MAX; 327 u32 *next = (u32 *)next_key; 328 329 if (index >= array->map.max_entries) { 330 *next = 0; 331 return 0; 332 } 333 334 if (index == array->map.max_entries - 1) 335 return -ENOENT; 336 337 *next = index + 1; 338 return 0; 339 } 340 341 BTF_ID_LIST_SINGLE(reuseport_array_map_btf_ids, struct, reuseport_array) 342 const struct bpf_map_ops reuseport_array_ops = { 343 .map_meta_equal = bpf_map_meta_equal, 344 .map_alloc_check = reuseport_array_alloc_check, 345 .map_alloc = reuseport_array_alloc, 346 .map_free = reuseport_array_free, 347 .map_lookup_elem = reuseport_array_lookup_elem, 348 .map_get_next_key = reuseport_array_get_next_key, 349 .map_delete_elem = reuseport_array_delete_elem, 350 .map_btf_id = &reuseport_array_map_btf_ids[0], 351 }; 352