kernel/bpf/bpf_task_storage.c

   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 *local_storage;
  75         bool free_task_storage = false;
  76         unsigned long flags;
  77
  78         rcu_read_lock();
  79
  80         local_storage = rcu_dereference(task->bpf_storage);
  81         if (!local_storage) {
  82                 rcu_read_unlock();
  83                 return;
  84         }
  85
  86         bpf_task_storage_lock();
  87         raw_spin_lock_irqsave(&local_storage->lock, flags);
  88         free_task_storage = bpf_local_storage_unlink_nolock(local_storage);
  89         raw_spin_unlock_irqrestore(&local_storage->lock, flags);
  90         bpf_task_storage_unlock();
  91         rcu_read_unlock();
  92
  93         if (free_task_storage)
  94                 kfree_rcu(local_storage, rcu);
  95 }
  96
  97 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
  98 {
  99         struct bpf_local_storage_data *sdata;
 100         struct task_struct *task;
 101         unsigned int f_flags;
 102         struct pid *pid;
 103         int fd, err;
 104
 105         fd = *(int *)key;
 106         pid = pidfd_get_pid(fd, &f_flags);
 107         if (IS_ERR(pid))
 108                 return ERR_CAST(pid);
 109
 110         /* We should be in an RCU read side critical section, it should be safe
 111          * to call pid_task.
 112          */
 113         WARN_ON_ONCE(!rcu_read_lock_held());
 114         task = pid_task(pid, PIDTYPE_PID);
 115         if (!task) {
 116                 err = -ENOENT;
 117                 goto out;
 118         }
 119
 120         bpf_task_storage_lock();
 121         sdata = task_storage_lookup(task, map, true);
 122         bpf_task_storage_unlock();
 123         put_pid(pid);
 124         return sdata ? sdata->data : NULL;
 125 out:
 126         put_pid(pid);
 127         return ERR_PTR(err);
 128 }
 129
 130 static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 131                                             void *value, u64 map_flags)
 132 {
 133         struct bpf_local_storage_data *sdata;
 134         struct task_struct *task;
 135         unsigned int f_flags;
 136         struct pid *pid;
 137         int fd, err;
 138
 139         fd = *(int *)key;
 140         pid = pidfd_get_pid(fd, &f_flags);
 141         if (IS_ERR(pid))
 142                 return PTR_ERR(pid);
 143
 144         /* We should be in an RCU read side critical section, it should be safe
 145          * to call pid_task.
 146          */
 147         WARN_ON_ONCE(!rcu_read_lock_held());
 148         task = pid_task(pid, PIDTYPE_PID);
 149         if (!task) {
 150                 err = -ENOENT;
 151                 goto out;
 152         }
 153
 154         bpf_task_storage_lock();
 155         sdata = bpf_local_storage_update(
 156                 task, (struct bpf_local_storage_map *)map, value, map_flags,
 157                 GFP_ATOMIC);
 158         bpf_task_storage_unlock();
 159
 160         err = PTR_ERR_OR_ZERO(sdata);
 161 out:
 162         put_pid(pid);
 163         return err;
 164 }
 165
 166 static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
 167                                bool nobusy)
 168 {
 169         struct bpf_local_storage_data *sdata;
 170
 171         sdata = task_storage_lookup(task, map, false);
 172         if (!sdata)
 173                 return -ENOENT;
 174
 175         if (!nobusy)
 176                 return -EBUSY;
 177
 178         bpf_selem_unlink(SELEM(sdata), true);
 179
 180         return 0;
 181 }
 182
 183 static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
 184 {
 185         struct task_struct *task;
 186         unsigned int f_flags;
 187         struct pid *pid;
 188         int fd, err;
 189
 190         fd = *(int *)key;
 191         pid = pidfd_get_pid(fd, &f_flags);
 192         if (IS_ERR(pid))
 193                 return PTR_ERR(pid);
 194
 195         /* We should be in an RCU read side critical section, it should be safe
 196          * to call pid_task.
 197          */
 198         WARN_ON_ONCE(!rcu_read_lock_held());
 199         task = pid_task(pid, PIDTYPE_PID);
 200         if (!task) {
 201                 err = -ENOENT;
 202                 goto out;
 203         }
 204
 205         bpf_task_storage_lock();
 206         err = task_storage_delete(task, map, true);
 207         bpf_task_storage_unlock();
 208 out:
 209         put_pid(pid);
 210         return err;
 211 }
 212
 213 /* Called by bpf_task_storage_get*() helpers */
 214 static void *__bpf_task_storage_get(struct bpf_map *map,
 215                                     struct task_struct *task, void *value,
 216                                     u64 flags, gfp_t gfp_flags, bool nobusy)
 217 {
 218         struct bpf_local_storage_data *sdata;
 219
 220         sdata = task_storage_lookup(task, map, nobusy);
 221         if (sdata)
 222                 return sdata->data;
 223
 224         /* only allocate new storage, when the task is refcounted */
 225         if (refcount_read(&task->usage) &&
 226             (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) {
 227                 sdata = bpf_local_storage_update(
 228                         task, (struct bpf_local_storage_map *)map, value,
 229                         BPF_NOEXIST, gfp_flags);
 230                 return IS_ERR(sdata) ? NULL : sdata->data;
 231         }
 232
 233         return NULL;
 234 }
 235
 236 /* *gfp_flags* is a hidden argument provided by the verifier */
 237 BPF_CALL_5(bpf_task_storage_get_recur, struct bpf_map *, map, struct task_struct *,
 238            task, void *, value, u64, flags, gfp_t, gfp_flags)
 239 {
 240         bool nobusy;
 241         void *data;
 242
 243         WARN_ON_ONCE(!bpf_rcu_lock_held());
 244         if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task)
 245                 return (unsigned long)NULL;
 246
 247         nobusy = bpf_task_storage_trylock();
 248         data = __bpf_task_storage_get(map, task, value, flags,
 249                                       gfp_flags, nobusy);
 250         if (nobusy)
 251                 bpf_task_storage_unlock();
 252         return (unsigned long)data;
 253 }
 254
 255 /* *gfp_flags* is a hidden argument provided by the verifier */
 256 BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
 257            task, void *, value, u64, flags, gfp_t, gfp_flags)
 258 {
 259         void *data;
 260
 261         WARN_ON_ONCE(!bpf_rcu_lock_held());
 262         if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task)
 263                 return (unsigned long)NULL;
 264
 265         bpf_task_storage_lock();
 266         data = __bpf_task_storage_get(map, task, value, flags,
 267                                       gfp_flags, true);
 268         bpf_task_storage_unlock();
 269         return (unsigned long)data;
 270 }
 271
 272 BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *,
 273            task)
 274 {
 275         bool nobusy;
 276         int ret;
 277
 278         WARN_ON_ONCE(!bpf_rcu_lock_held());
 279         if (!task)
 280                 return -EINVAL;
 281
 282         nobusy = bpf_task_storage_trylock();
 283         /* This helper must only be called from places where the lifetime of the task
 284          * is guaranteed. Either by being refcounted or by being protected
 285          * by an RCU read-side critical section.
 286          */
 287         ret = task_storage_delete(task, map, nobusy);
 288         if (nobusy)
 289                 bpf_task_storage_unlock();
 290         return ret;
 291 }
 292
 293 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
 294            task)
 295 {
 296         int ret;
 297
 298         WARN_ON_ONCE(!bpf_rcu_lock_held());
 299         if (!task)
 300                 return -EINVAL;
 301
 302         bpf_task_storage_lock();
 303         /* This helper must only be called from places where the lifetime of the task
 304          * is guaranteed. Either by being refcounted or by being protected
 305          * by an RCU read-side critical section.
 306          */
 307         ret = task_storage_delete(task, map, true);
 308         bpf_task_storage_unlock();
 309         return ret;
 310 }
 311
 312 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
 313 {
 314         return -ENOTSUPP;
 315 }
 316
 317 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
 318 {
 319         return bpf_local_storage_map_alloc(attr, &task_cache);
 320 }
 321
 322 static void task_storage_map_free(struct bpf_map *map)
 323 {
 324         bpf_local_storage_map_free(map, &task_cache, &bpf_task_storage_busy);
 325 }
 326
 327 BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map)
 328 const struct bpf_map_ops task_storage_map_ops = {
 329         .map_meta_equal = bpf_map_meta_equal,
 330         .map_alloc_check = bpf_local_storage_map_alloc_check,
 331         .map_alloc = task_storage_map_alloc,
 332         .map_free = task_storage_map_free,
 333         .map_get_next_key = notsupp_get_next_key,
 334         .map_lookup_elem = bpf_pid_task_storage_lookup_elem,
 335         .map_update_elem = bpf_pid_task_storage_update_elem,
 336         .map_delete_elem = bpf_pid_task_storage_delete_elem,
 337         .map_check_btf = bpf_local_storage_map_check_btf,
 338         .map_btf_id = &bpf_local_storage_map_btf_id[0],
 339         .map_owner_storage_ptr = task_storage_ptr,
 340 };
 341
 342 const struct bpf_func_proto bpf_task_storage_get_recur_proto = {
 343         .func = bpf_task_storage_get_recur,
 344         .gpl_only = false,
 345         .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
 346         .arg1_type = ARG_CONST_MAP_PTR,
 347         .arg2_type = ARG_PTR_TO_BTF_ID,
 348         .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
 349         .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
 350         .arg4_type = ARG_ANYTHING,
 351 };
 352
 353 const struct bpf_func_proto bpf_task_storage_get_proto = {
 354         .func = bpf_task_storage_get,
 355         .gpl_only = false,
 356         .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
 357         .arg1_type = ARG_CONST_MAP_PTR,
 358         .arg2_type = ARG_PTR_TO_BTF_ID,
 359         .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
 360         .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
 361         .arg4_type = ARG_ANYTHING,
 362 };
 363
 364 const struct bpf_func_proto bpf_task_storage_delete_recur_proto = {
 365         .func = bpf_task_storage_delete_recur,
 366         .gpl_only = false,
 367         .ret_type = RET_INTEGER,
 368         .arg1_type = ARG_CONST_MAP_PTR,
 369         .arg2_type = ARG_PTR_TO_BTF_ID,
 370         .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
 371 };
 372
 373 const struct bpf_func_proto bpf_task_storage_delete_proto = {
 374         .func = bpf_task_storage_delete,
 375         .gpl_only = false,
 376         .ret_type = RET_INTEGER,
 377         .arg1_type = ARG_CONST_MAP_PTR,
 378         .arg2_type = ARG_PTR_TO_BTF_ID,
 379         .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
 380 };