kernel/bpf/bpf_cgrp_storage.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
   4  */
   5
   6 #include <linux/types.h>
   7 #include <linux/bpf.h>
   8 #include <linux/bpf_local_storage.h>
   9 #include <uapi/linux/btf.h>
  10 #include <linux/btf_ids.h>
  11
  12 DEFINE_BPF_STORAGE_CACHE(cgroup_cache);
  13
  14 static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy);
  15
  16 static void bpf_cgrp_storage_lock(void)
  17 {
  18         migrate_disable();
  19         this_cpu_inc(bpf_cgrp_storage_busy);
  20 }
  21
  22 static void bpf_cgrp_storage_unlock(void)
  23 {
  24         this_cpu_dec(bpf_cgrp_storage_busy);
  25         migrate_enable();
  26 }
  27
  28 static bool bpf_cgrp_storage_trylock(void)
  29 {
  30         migrate_disable();
  31         if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) {
  32                 this_cpu_dec(bpf_cgrp_storage_busy);
  33                 migrate_enable();
  34                 return false;
  35         }
  36         return true;
  37 }
  38
  39 static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner)
  40 {
  41         struct cgroup *cg = owner;
  42
  43         return &cg->bpf_cgrp_storage;
  44 }
  45
  46 void bpf_cgrp_storage_free(struct cgroup *cgroup)
  47 {
  48         struct bpf_local_storage *local_storage;
  49         bool free_cgroup_storage = false;
  50         unsigned long flags;
  51
  52         rcu_read_lock();
  53         local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
  54         if (!local_storage) {
  55                 rcu_read_unlock();
  56                 return;
  57         }
  58
  59         bpf_cgrp_storage_lock();
  60         raw_spin_lock_irqsave(&local_storage->lock, flags);
  61         free_cgroup_storage = bpf_local_storage_unlink_nolock(local_storage);
  62         raw_spin_unlock_irqrestore(&local_storage->lock, flags);
  63         bpf_cgrp_storage_unlock();
  64         rcu_read_unlock();
  65
  66         if (free_cgroup_storage)
  67                 kfree_rcu(local_storage, rcu);
  68 }
  69
  70 static struct bpf_local_storage_data *
  71 cgroup_storage_lookup(struct cgroup *cgroup, struct bpf_map *map, bool cacheit_lockit)
  72 {
  73         struct bpf_local_storage *cgroup_storage;
  74         struct bpf_local_storage_map *smap;
  75
  76         cgroup_storage = rcu_dereference_check(cgroup->bpf_cgrp_storage,
  77                                                bpf_rcu_lock_held());
  78         if (!cgroup_storage)
  79                 return NULL;
  80
  81         smap = (struct bpf_local_storage_map *)map;
  82         return bpf_local_storage_lookup(cgroup_storage, smap, cacheit_lockit);
  83 }
  84
  85 static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key)
  86 {
  87         struct bpf_local_storage_data *sdata;
  88         struct cgroup *cgroup;
  89         int fd;
  90
  91         fd = *(int *)key;
  92         cgroup = cgroup_get_from_fd(fd);
  93         if (IS_ERR(cgroup))
  94                 return ERR_CAST(cgroup);
  95
  96         bpf_cgrp_storage_lock();
  97         sdata = cgroup_storage_lookup(cgroup, map, true);
  98         bpf_cgrp_storage_unlock();
  99         cgroup_put(cgroup);
 100         return sdata ? sdata->data : NULL;
 101 }
 102
 103 static int bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,
 104                                           void *value, u64 map_flags)
 105 {
 106         struct bpf_local_storage_data *sdata;
 107         struct cgroup *cgroup;
 108         int fd;
 109
 110         fd = *(int *)key;
 111         cgroup = cgroup_get_from_fd(fd);
 112         if (IS_ERR(cgroup))
 113                 return PTR_ERR(cgroup);
 114
 115         bpf_cgrp_storage_lock();
 116         sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
 117                                          value, map_flags, GFP_ATOMIC);
 118         bpf_cgrp_storage_unlock();
 119         cgroup_put(cgroup);
 120         return PTR_ERR_OR_ZERO(sdata);
 121 }
 122
 123 static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map)
 124 {
 125         struct bpf_local_storage_data *sdata;
 126
 127         sdata = cgroup_storage_lookup(cgroup, map, false);
 128         if (!sdata)
 129                 return -ENOENT;
 130
 131         bpf_selem_unlink(SELEM(sdata), true);
 132         return 0;
 133 }
 134
 135 static int bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)
 136 {
 137         struct cgroup *cgroup;
 138         int err, fd;
 139
 140         fd = *(int *)key;
 141         cgroup = cgroup_get_from_fd(fd);
 142         if (IS_ERR(cgroup))
 143                 return PTR_ERR(cgroup);
 144
 145         bpf_cgrp_storage_lock();
 146         err = cgroup_storage_delete(cgroup, map);
 147         bpf_cgrp_storage_unlock();
 148         cgroup_put(cgroup);
 149         return err;
 150 }
 151
 152 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
 153 {
 154         return -ENOTSUPP;
 155 }
 156
 157 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
 158 {
 159         return bpf_local_storage_map_alloc(attr, &cgroup_cache);
 160 }
 161
 162 static void cgroup_storage_map_free(struct bpf_map *map)
 163 {
 164         bpf_local_storage_map_free(map, &cgroup_cache, NULL);
 165 }
 166
 167 /* *gfp_flags* is a hidden argument provided by the verifier */
 168 BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup,
 169            void *, value, u64, flags, gfp_t, gfp_flags)
 170 {
 171         struct bpf_local_storage_data *sdata;
 172
 173         WARN_ON_ONCE(!bpf_rcu_lock_held());
 174         if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
 175                 return (unsigned long)NULL;
 176
 177         if (!cgroup)
 178                 return (unsigned long)NULL;
 179
 180         if (!bpf_cgrp_storage_trylock())
 181                 return (unsigned long)NULL;
 182
 183         sdata = cgroup_storage_lookup(cgroup, map, true);
 184         if (sdata)
 185                 goto unlock;
 186
 187         /* only allocate new storage, when the cgroup is refcounted */
 188         if (!percpu_ref_is_dying(&cgroup->self.refcnt) &&
 189             (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
 190                 sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
 191                                                  value, BPF_NOEXIST, gfp_flags);
 192
 193 unlock:
 194         bpf_cgrp_storage_unlock();
 195         return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data;
 196 }
 197
 198 BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup)
 199 {
 200         int ret;
 201
 202         WARN_ON_ONCE(!bpf_rcu_lock_held());
 203         if (!cgroup)
 204                 return -EINVAL;
 205
 206         if (!bpf_cgrp_storage_trylock())
 207                 return -EBUSY;
 208
 209         ret = cgroup_storage_delete(cgroup, map);
 210         bpf_cgrp_storage_unlock();
 211         return ret;
 212 }
 213
 214 BTF_ID_LIST_SINGLE(cgroup_storage_map_btf_ids, struct, bpf_local_storage_map)
 215 const struct bpf_map_ops cgrp_storage_map_ops = {
 216         .map_meta_equal = bpf_map_meta_equal,
 217         .map_alloc_check = bpf_local_storage_map_alloc_check,
 218         .map_alloc = cgroup_storage_map_alloc,
 219         .map_free = cgroup_storage_map_free,
 220         .map_get_next_key = notsupp_get_next_key,
 221         .map_lookup_elem = bpf_cgrp_storage_lookup_elem,
 222         .map_update_elem = bpf_cgrp_storage_update_elem,
 223         .map_delete_elem = bpf_cgrp_storage_delete_elem,
 224         .map_check_btf = bpf_local_storage_map_check_btf,
 225         .map_btf_id = &cgroup_storage_map_btf_ids[0],
 226         .map_owner_storage_ptr = cgroup_storage_ptr,
 227 };
 228
 229 const struct bpf_func_proto bpf_cgrp_storage_get_proto = {
 230         .func           = bpf_cgrp_storage_get,
 231         .gpl_only       = false,
 232         .ret_type       = RET_PTR_TO_MAP_VALUE_OR_NULL,
 233         .arg1_type      = ARG_CONST_MAP_PTR,
 234         .arg2_type      = ARG_PTR_TO_BTF_ID,
 235         .arg2_btf_id    = &bpf_cgroup_btf_id[0],
 236         .arg3_type      = ARG_PTR_TO_MAP_VALUE_OR_NULL,
 237         .arg4_type      = ARG_ANYTHING,
 238 };
 239
 240 const struct bpf_func_proto bpf_cgrp_storage_delete_proto = {
 241         .func           = bpf_cgrp_storage_delete,
 242         .gpl_only       = false,
 243         .ret_type       = RET_INTEGER,
 244         .arg1_type      = ARG_CONST_MAP_PTR,
 245         .arg2_type      = ARG_PTR_TO_BTF_ID,
 246         .arg2_btf_id    = &bpf_cgroup_btf_id[0],
 247 };