1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2020 Facebook 4 * Copyright 2020 Google LLC. 5 */ 6 7 #include <linux/pid.h> 8 #include <linux/sched.h> 9 #include <linux/rculist.h> 10 #include <linux/list.h> 11 #include <linux/hash.h> 12 #include <linux/types.h> 13 #include <linux/spinlock.h> 14 #include <linux/bpf.h> 15 #include <linux/bpf_local_storage.h> 16 #include <linux/filter.h> 17 #include <uapi/linux/btf.h> 18 #include <linux/btf_ids.h> 19 #include <linux/fdtable.h> 20 #include <linux/rcupdate_trace.h> 21 22 DEFINE_BPF_STORAGE_CACHE(task_cache); 23 24 static DEFINE_PER_CPU(int, bpf_task_storage_busy); 25 26 static void bpf_task_storage_lock(void) 27 { 28 migrate_disable(); 29 __this_cpu_inc(bpf_task_storage_busy); 30 } 31 32 static void bpf_task_storage_unlock(void) 33 { 34 __this_cpu_dec(bpf_task_storage_busy); 35 migrate_enable(); 36 } 37 38 static bool bpf_task_storage_trylock(void) 39 { 40 migrate_disable(); 41 if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) { 42 __this_cpu_dec(bpf_task_storage_busy); 43 migrate_enable(); 44 return false; 45 } 46 return true; 47 } 48 49 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner) 50 { 51 struct task_struct *task = owner; 52 53 return &task->bpf_storage; 54 } 55 56 static struct bpf_local_storage_data * 57 task_storage_lookup(struct task_struct *task, struct bpf_map *map, 58 bool cacheit_lockit) 59 { 60 struct bpf_local_storage *task_storage; 61 struct bpf_local_storage_map *smap; 62 63 task_storage = 64 rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); 65 if (!task_storage) 66 return NULL; 67 68 smap = (struct bpf_local_storage_map *)map; 69 return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit); 70 } 71 72 void bpf_task_storage_free(struct task_struct *task) 73 { 74 struct bpf_local_storage_elem *selem; 75 struct bpf_local_storage *local_storage; 76 bool free_task_storage = false; 77 struct hlist_node *n; 78 unsigned long flags; 79 80 rcu_read_lock(); 81 82 local_storage = rcu_dereference(task->bpf_storage); 83 if (!local_storage) { 84 rcu_read_unlock(); 85 return; 86 } 87 88 /* Neither the bpf_prog nor the bpf-map's syscall 89 * could be modifying the local_storage->list now. 90 * Thus, no elem can be added-to or deleted-from the 91 * local_storage->list by the bpf_prog or by the bpf-map's syscall. 92 * 93 * It is racing with bpf_local_storage_map_free() alone 94 * when unlinking elem from the local_storage->list and 95 * the map's bucket->list. 96 */ 97 bpf_task_storage_lock(); 98 raw_spin_lock_irqsave(&local_storage->lock, flags); 99 hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) { 100 /* Always unlink from map before unlinking from 101 * local_storage. 102 */ 103 bpf_selem_unlink_map(selem); 104 free_task_storage = bpf_selem_unlink_storage_nolock( 105 local_storage, selem, false); 106 } 107 raw_spin_unlock_irqrestore(&local_storage->lock, flags); 108 bpf_task_storage_unlock(); 109 rcu_read_unlock(); 110 111 /* free_task_storage should always be true as long as 112 * local_storage->list was non-empty. 113 */ 114 if (free_task_storage) 115 kfree_rcu(local_storage, rcu); 116 } 117 118 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) 119 { 120 struct bpf_local_storage_data *sdata; 121 struct task_struct *task; 122 unsigned int f_flags; 123 struct pid *pid; 124 int fd, err; 125 126 fd = *(int *)key; 127 pid = pidfd_get_pid(fd, &f_flags); 128 if (IS_ERR(pid)) 129 return ERR_CAST(pid); 130 131 /* We should be in an RCU read side critical section, it should be safe 132 * to call pid_task. 133 */ 134 WARN_ON_ONCE(!rcu_read_lock_held()); 135 task = pid_task(pid, PIDTYPE_PID); 136 if (!task) { 137 err = -ENOENT; 138 goto out; 139 } 140 141 bpf_task_storage_lock(); 142 sdata = task_storage_lookup(task, map, true); 143 bpf_task_storage_unlock(); 144 put_pid(pid); 145 return sdata ? sdata->data : NULL; 146 out: 147 put_pid(pid); 148 return ERR_PTR(err); 149 } 150 151 static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key, 152 void *value, u64 map_flags) 153 { 154 struct bpf_local_storage_data *sdata; 155 struct task_struct *task; 156 unsigned int f_flags; 157 struct pid *pid; 158 int fd, err; 159 160 fd = *(int *)key; 161 pid = pidfd_get_pid(fd, &f_flags); 162 if (IS_ERR(pid)) 163 return PTR_ERR(pid); 164 165 /* We should be in an RCU read side critical section, it should be safe 166 * to call pid_task. 167 */ 168 WARN_ON_ONCE(!rcu_read_lock_held()); 169 task = pid_task(pid, PIDTYPE_PID); 170 if (!task) { 171 err = -ENOENT; 172 goto out; 173 } 174 175 bpf_task_storage_lock(); 176 sdata = bpf_local_storage_update( 177 task, (struct bpf_local_storage_map *)map, value, map_flags); 178 bpf_task_storage_unlock(); 179 180 err = PTR_ERR_OR_ZERO(sdata); 181 out: 182 put_pid(pid); 183 return err; 184 } 185 186 static int task_storage_delete(struct task_struct *task, struct bpf_map *map) 187 { 188 struct bpf_local_storage_data *sdata; 189 190 sdata = task_storage_lookup(task, map, false); 191 if (!sdata) 192 return -ENOENT; 193 194 bpf_selem_unlink(SELEM(sdata)); 195 196 return 0; 197 } 198 199 static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) 200 { 201 struct task_struct *task; 202 unsigned int f_flags; 203 struct pid *pid; 204 int fd, err; 205 206 fd = *(int *)key; 207 pid = pidfd_get_pid(fd, &f_flags); 208 if (IS_ERR(pid)) 209 return PTR_ERR(pid); 210 211 /* We should be in an RCU read side critical section, it should be safe 212 * to call pid_task. 213 */ 214 WARN_ON_ONCE(!rcu_read_lock_held()); 215 task = pid_task(pid, PIDTYPE_PID); 216 if (!task) { 217 err = -ENOENT; 218 goto out; 219 } 220 221 bpf_task_storage_lock(); 222 err = task_storage_delete(task, map); 223 bpf_task_storage_unlock(); 224 out: 225 put_pid(pid); 226 return err; 227 } 228 229 BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, 230 task, void *, value, u64, flags) 231 { 232 struct bpf_local_storage_data *sdata; 233 234 WARN_ON_ONCE(!bpf_rcu_lock_held()); 235 if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) 236 return (unsigned long)NULL; 237 238 if (!task) 239 return (unsigned long)NULL; 240 241 if (!bpf_task_storage_trylock()) 242 return (unsigned long)NULL; 243 244 sdata = task_storage_lookup(task, map, true); 245 if (sdata) 246 goto unlock; 247 248 /* only allocate new storage, when the task is refcounted */ 249 if (refcount_read(&task->usage) && 250 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) 251 sdata = bpf_local_storage_update( 252 task, (struct bpf_local_storage_map *)map, value, 253 BPF_NOEXIST); 254 255 unlock: 256 bpf_task_storage_unlock(); 257 return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : 258 (unsigned long)sdata->data; 259 } 260 261 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, 262 task) 263 { 264 int ret; 265 266 WARN_ON_ONCE(!bpf_rcu_lock_held()); 267 if (!task) 268 return -EINVAL; 269 270 if (!bpf_task_storage_trylock()) 271 return -EBUSY; 272 273 /* This helper must only be called from places where the lifetime of the task 274 * is guaranteed. Either by being refcounted or by being protected 275 * by an RCU read-side critical section. 276 */ 277 ret = task_storage_delete(task, map); 278 bpf_task_storage_unlock(); 279 return ret; 280 } 281 282 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key) 283 { 284 return -ENOTSUPP; 285 } 286 287 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) 288 { 289 struct bpf_local_storage_map *smap; 290 291 smap = bpf_local_storage_map_alloc(attr); 292 if (IS_ERR(smap)) 293 return ERR_CAST(smap); 294 295 smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache); 296 return &smap->map; 297 } 298 299 static void task_storage_map_free(struct bpf_map *map) 300 { 301 struct bpf_local_storage_map *smap; 302 303 smap = (struct bpf_local_storage_map *)map; 304 bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx); 305 bpf_local_storage_map_free(smap, &bpf_task_storage_busy); 306 } 307 308 static int task_storage_map_btf_id; 309 const struct bpf_map_ops task_storage_map_ops = { 310 .map_meta_equal = bpf_map_meta_equal, 311 .map_alloc_check = bpf_local_storage_map_alloc_check, 312 .map_alloc = task_storage_map_alloc, 313 .map_free = task_storage_map_free, 314 .map_get_next_key = notsupp_get_next_key, 315 .map_lookup_elem = bpf_pid_task_storage_lookup_elem, 316 .map_update_elem = bpf_pid_task_storage_update_elem, 317 .map_delete_elem = bpf_pid_task_storage_delete_elem, 318 .map_check_btf = bpf_local_storage_map_check_btf, 319 .map_btf_name = "bpf_local_storage_map", 320 .map_btf_id = &task_storage_map_btf_id, 321 .map_owner_storage_ptr = task_storage_ptr, 322 }; 323 324 const struct bpf_func_proto bpf_task_storage_get_proto = { 325 .func = bpf_task_storage_get, 326 .gpl_only = false, 327 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 328 .arg1_type = ARG_CONST_MAP_PTR, 329 .arg2_type = ARG_PTR_TO_BTF_ID, 330 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 331 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 332 .arg4_type = ARG_ANYTHING, 333 }; 334 335 const struct bpf_func_proto bpf_task_storage_delete_proto = { 336 .func = bpf_task_storage_delete, 337 .gpl_only = false, 338 .ret_type = RET_INTEGER, 339 .arg1_type = ARG_CONST_MAP_PTR, 340 .arg2_type = ARG_PTR_TO_BTF_ID, 341 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 342 }; 343