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, 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 GFP_ATOMIC); 179 bpf_task_storage_unlock(); 180 181 err = PTR_ERR_OR_ZERO(sdata); 182 out: 183 put_pid(pid); 184 return err; 185 } 186 187 static int task_storage_delete(struct task_struct *task, struct bpf_map *map) 188 { 189 struct bpf_local_storage_data *sdata; 190 191 sdata = task_storage_lookup(task, map, false); 192 if (!sdata) 193 return -ENOENT; 194 195 bpf_selem_unlink(SELEM(sdata), true); 196 197 return 0; 198 } 199 200 static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) 201 { 202 struct task_struct *task; 203 unsigned int f_flags; 204 struct pid *pid; 205 int fd, err; 206 207 fd = *(int *)key; 208 pid = pidfd_get_pid(fd, &f_flags); 209 if (IS_ERR(pid)) 210 return PTR_ERR(pid); 211 212 /* We should be in an RCU read side critical section, it should be safe 213 * to call pid_task. 214 */ 215 WARN_ON_ONCE(!rcu_read_lock_held()); 216 task = pid_task(pid, PIDTYPE_PID); 217 if (!task) { 218 err = -ENOENT; 219 goto out; 220 } 221 222 bpf_task_storage_lock(); 223 err = task_storage_delete(task, map); 224 bpf_task_storage_unlock(); 225 out: 226 put_pid(pid); 227 return err; 228 } 229 230 /* *gfp_flags* is a hidden argument provided by the verifier */ 231 BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, 232 task, void *, value, u64, flags, gfp_t, gfp_flags) 233 { 234 struct bpf_local_storage_data *sdata; 235 236 WARN_ON_ONCE(!bpf_rcu_lock_held()); 237 if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) 238 return (unsigned long)NULL; 239 240 if (!task) 241 return (unsigned long)NULL; 242 243 if (!bpf_task_storage_trylock()) 244 return (unsigned long)NULL; 245 246 sdata = task_storage_lookup(task, map, true); 247 if (sdata) 248 goto unlock; 249 250 /* only allocate new storage, when the task is refcounted */ 251 if (refcount_read(&task->usage) && 252 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) 253 sdata = bpf_local_storage_update( 254 task, (struct bpf_local_storage_map *)map, value, 255 BPF_NOEXIST, gfp_flags); 256 257 unlock: 258 bpf_task_storage_unlock(); 259 return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : 260 (unsigned long)sdata->data; 261 } 262 263 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, 264 task) 265 { 266 int ret; 267 268 WARN_ON_ONCE(!bpf_rcu_lock_held()); 269 if (!task) 270 return -EINVAL; 271 272 if (!bpf_task_storage_trylock()) 273 return -EBUSY; 274 275 /* This helper must only be called from places where the lifetime of the task 276 * is guaranteed. Either by being refcounted or by being protected 277 * by an RCU read-side critical section. 278 */ 279 ret = task_storage_delete(task, map); 280 bpf_task_storage_unlock(); 281 return ret; 282 } 283 284 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key) 285 { 286 return -ENOTSUPP; 287 } 288 289 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) 290 { 291 struct bpf_local_storage_map *smap; 292 293 smap = bpf_local_storage_map_alloc(attr); 294 if (IS_ERR(smap)) 295 return ERR_CAST(smap); 296 297 smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache); 298 return &smap->map; 299 } 300 301 static void task_storage_map_free(struct bpf_map *map) 302 { 303 struct bpf_local_storage_map *smap; 304 305 smap = (struct bpf_local_storage_map *)map; 306 bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx); 307 bpf_local_storage_map_free(smap, &bpf_task_storage_busy); 308 } 309 310 BTF_ID_LIST_SINGLE(task_storage_map_btf_ids, struct, bpf_local_storage_map) 311 const struct bpf_map_ops task_storage_map_ops = { 312 .map_meta_equal = bpf_map_meta_equal, 313 .map_alloc_check = bpf_local_storage_map_alloc_check, 314 .map_alloc = task_storage_map_alloc, 315 .map_free = task_storage_map_free, 316 .map_get_next_key = notsupp_get_next_key, 317 .map_lookup_elem = bpf_pid_task_storage_lookup_elem, 318 .map_update_elem = bpf_pid_task_storage_update_elem, 319 .map_delete_elem = bpf_pid_task_storage_delete_elem, 320 .map_check_btf = bpf_local_storage_map_check_btf, 321 .map_btf_id = &task_storage_map_btf_ids[0], 322 .map_owner_storage_ptr = task_storage_ptr, 323 }; 324 325 const struct bpf_func_proto bpf_task_storage_get_proto = { 326 .func = bpf_task_storage_get, 327 .gpl_only = false, 328 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 329 .arg1_type = ARG_CONST_MAP_PTR, 330 .arg2_type = ARG_PTR_TO_BTF_ID, 331 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 332 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 333 .arg4_type = ARG_ANYTHING, 334 }; 335 336 const struct bpf_func_proto bpf_task_storage_delete_proto = { 337 .func = bpf_task_storage_delete, 338 .gpl_only = false, 339 .ret_type = RET_INTEGER, 340 .arg1_type = ARG_CONST_MAP_PTR, 341 .arg2_type = ARG_PTR_TO_BTF_ID, 342 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 343 }; 344