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