| // SPDX-License-Identifier: GPL-2.0 |
| /* Copyright (c) 2019 Facebook */ |
| #include <linux/rculist.h> |
| #include <linux/list.h> |
| #include <linux/hash.h> |
| #include <linux/types.h> |
| #include <linux/spinlock.h> |
| #include <linux/bpf.h> |
| #include <linux/btf_ids.h> |
| #include <linux/bpf_local_storage.h> |
| #include <net/sock.h> |
| #include <uapi/linux/sock_diag.h> |
| #include <uapi/linux/btf.h> |
| #include <linux/rcupdate.h> |
| #include <linux/rcupdate_trace.h> |
| #include <linux/rcupdate_wait.h> |
| |
| #define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE) |
| |
| static struct bpf_local_storage_map_bucket * |
| select_bucket(struct bpf_local_storage_map *smap, |
| struct bpf_local_storage_elem *selem) |
| { |
| return &smap->buckets[hash_ptr(selem, smap->bucket_log)]; |
| } |
| |
| static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size) |
| { |
| struct bpf_map *map = &smap->map; |
| |
| if (!map->ops->map_local_storage_charge) |
| return 0; |
| |
| return map->ops->map_local_storage_charge(smap, owner, size); |
| } |
| |
| static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner, |
| u32 size) |
| { |
| struct bpf_map *map = &smap->map; |
| |
| if (map->ops->map_local_storage_uncharge) |
| map->ops->map_local_storage_uncharge(smap, owner, size); |
| } |
| |
| static struct bpf_local_storage __rcu ** |
| owner_storage(struct bpf_local_storage_map *smap, void *owner) |
| { |
| struct bpf_map *map = &smap->map; |
| |
| return map->ops->map_owner_storage_ptr(owner); |
| } |
| |
| static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem) |
| { |
| return !hlist_unhashed(&selem->snode); |
| } |
| |
| static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem) |
| { |
| return !hlist_unhashed(&selem->map_node); |
| } |
| |
| struct bpf_local_storage_elem * |
| bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, |
| void *value, bool charge_mem, gfp_t gfp_flags) |
| { |
| struct bpf_local_storage_elem *selem; |
| |
| if (charge_mem && mem_charge(smap, owner, smap->elem_size)) |
| return NULL; |
| |
| selem = bpf_map_kzalloc(&smap->map, smap->elem_size, |
| gfp_flags | __GFP_NOWARN); |
| if (selem) { |
| if (value) |
| memcpy(SDATA(selem)->data, value, smap->map.value_size); |
| return selem; |
| } |
| |
| if (charge_mem) |
| mem_uncharge(smap, owner, smap->elem_size); |
| |
| return NULL; |
| } |
| |
| void bpf_local_storage_free_rcu(struct rcu_head *rcu) |
| { |
| struct bpf_local_storage *local_storage; |
| |
| local_storage = container_of(rcu, struct bpf_local_storage, rcu); |
| kfree_rcu(local_storage, rcu); |
| } |
| |
| static void bpf_selem_free_rcu(struct rcu_head *rcu) |
| { |
| struct bpf_local_storage_elem *selem; |
| |
| selem = container_of(rcu, struct bpf_local_storage_elem, rcu); |
| kfree_rcu(selem, rcu); |
| } |
| |
| /* local_storage->lock must be held and selem->local_storage == local_storage. |
| * The caller must ensure selem->smap is still valid to be |
| * dereferenced for its smap->elem_size and smap->cache_idx. |
| */ |
| bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, |
| struct bpf_local_storage_elem *selem, |
| bool uncharge_mem) |
| { |
| struct bpf_local_storage_map *smap; |
| bool free_local_storage; |
| void *owner; |
| |
| smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); |
| owner = local_storage->owner; |
| |
| /* All uncharging on the owner must be done first. |
| * The owner may be freed once the last selem is unlinked |
| * from local_storage. |
| */ |
| if (uncharge_mem) |
| mem_uncharge(smap, owner, smap->elem_size); |
| |
| free_local_storage = hlist_is_singular_node(&selem->snode, |
| &local_storage->list); |
| if (free_local_storage) { |
| mem_uncharge(smap, owner, sizeof(struct bpf_local_storage)); |
| local_storage->owner = NULL; |
| |
| /* After this RCU_INIT, owner may be freed and cannot be used */ |
| RCU_INIT_POINTER(*owner_storage(smap, owner), NULL); |
| |
| /* local_storage is not freed now. local_storage->lock is |
| * still held and raw_spin_unlock_bh(&local_storage->lock) |
| * will be done by the caller. |
| * |
| * Although the unlock will be done under |
| * rcu_read_lock(), it is more intuitive to |
| * read if the freeing of the storage is done |
| * after the raw_spin_unlock_bh(&local_storage->lock). |
| * |
| * Hence, a "bool free_local_storage" is returned |
| * to the caller which then calls then frees the storage after |
| * all the RCU grace periods have expired. |
| */ |
| } |
| hlist_del_init_rcu(&selem->snode); |
| if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) == |
| SDATA(selem)) |
| RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL); |
| |
| call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu); |
| return free_local_storage; |
| } |
| |
| static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem) |
| { |
| struct bpf_local_storage *local_storage; |
| bool free_local_storage = false; |
| unsigned long flags; |
| |
| if (unlikely(!selem_linked_to_storage(selem))) |
| /* selem has already been unlinked from sk */ |
| return; |
| |
| local_storage = rcu_dereference_check(selem->local_storage, |
| bpf_rcu_lock_held()); |
| raw_spin_lock_irqsave(&local_storage->lock, flags); |
| if (likely(selem_linked_to_storage(selem))) |
| free_local_storage = bpf_selem_unlink_storage_nolock( |
| local_storage, selem, true); |
| raw_spin_unlock_irqrestore(&local_storage->lock, flags); |
| |
| if (free_local_storage) |
| call_rcu_tasks_trace(&local_storage->rcu, |
| bpf_local_storage_free_rcu); |
| } |
| |
| void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, |
| struct bpf_local_storage_elem *selem) |
| { |
| RCU_INIT_POINTER(selem->local_storage, local_storage); |
| hlist_add_head_rcu(&selem->snode, &local_storage->list); |
| } |
| |
| void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) |
| { |
| struct bpf_local_storage_map *smap; |
| struct bpf_local_storage_map_bucket *b; |
| unsigned long flags; |
| |
| if (unlikely(!selem_linked_to_map(selem))) |
| /* selem has already be unlinked from smap */ |
| return; |
| |
| smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); |
| b = select_bucket(smap, selem); |
| raw_spin_lock_irqsave(&b->lock, flags); |
| if (likely(selem_linked_to_map(selem))) |
| hlist_del_init_rcu(&selem->map_node); |
| raw_spin_unlock_irqrestore(&b->lock, flags); |
| } |
| |
| void bpf_selem_link_map(struct bpf_local_storage_map *smap, |
| struct bpf_local_storage_elem *selem) |
| { |
| struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem); |
| unsigned long flags; |
| |
| raw_spin_lock_irqsave(&b->lock, flags); |
| RCU_INIT_POINTER(SDATA(selem)->smap, smap); |
| hlist_add_head_rcu(&selem->map_node, &b->list); |
| raw_spin_unlock_irqrestore(&b->lock, flags); |
| } |
| |
| void bpf_selem_unlink(struct bpf_local_storage_elem *selem) |
| { |
| /* Always unlink from map before unlinking from local_storage |
| * because selem will be freed after successfully unlinked from |
| * the local_storage. |
| */ |
| bpf_selem_unlink_map(selem); |
| __bpf_selem_unlink_storage(selem); |
| } |
| |
| struct bpf_local_storage_data * |
| bpf_local_storage_lookup(struct bpf_local_storage *local_storage, |
| struct bpf_local_storage_map *smap, |
| bool cacheit_lockit) |
| { |
| struct bpf_local_storage_data *sdata; |
| struct bpf_local_storage_elem *selem; |
| |
| /* Fast path (cache hit) */ |
| sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx], |
| bpf_rcu_lock_held()); |
| if (sdata && rcu_access_pointer(sdata->smap) == smap) |
| return sdata; |
| |
| /* Slow path (cache miss) */ |
| hlist_for_each_entry_rcu(selem, &local_storage->list, snode, |
| rcu_read_lock_trace_held()) |
| if (rcu_access_pointer(SDATA(selem)->smap) == smap) |
| break; |
| |
| if (!selem) |
| return NULL; |
| |
| sdata = SDATA(selem); |
| if (cacheit_lockit) { |
| unsigned long flags; |
| |
| /* spinlock is needed to avoid racing with the |
| * parallel delete. Otherwise, publishing an already |
| * deleted sdata to the cache will become a use-after-free |
| * problem in the next bpf_local_storage_lookup(). |
| */ |
| raw_spin_lock_irqsave(&local_storage->lock, flags); |
| if (selem_linked_to_storage(selem)) |
| rcu_assign_pointer(local_storage->cache[smap->cache_idx], |
| sdata); |
| raw_spin_unlock_irqrestore(&local_storage->lock, flags); |
| } |
| |
| return sdata; |
| } |
| |
| static int check_flags(const struct bpf_local_storage_data *old_sdata, |
| u64 map_flags) |
| { |
| if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST) |
| /* elem already exists */ |
| return -EEXIST; |
| |
| if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST) |
| /* elem doesn't exist, cannot update it */ |
| return -ENOENT; |
| |
| return 0; |
| } |
| |
| int bpf_local_storage_alloc(void *owner, |
| struct bpf_local_storage_map *smap, |
| struct bpf_local_storage_elem *first_selem, |
| gfp_t gfp_flags) |
| { |
| struct bpf_local_storage *prev_storage, *storage; |
| struct bpf_local_storage **owner_storage_ptr; |
| int err; |
| |
| err = mem_charge(smap, owner, sizeof(*storage)); |
| if (err) |
| return err; |
| |
| storage = bpf_map_kzalloc(&smap->map, sizeof(*storage), |
| gfp_flags | __GFP_NOWARN); |
| if (!storage) { |
| err = -ENOMEM; |
| goto uncharge; |
| } |
| |
| INIT_HLIST_HEAD(&storage->list); |
| raw_spin_lock_init(&storage->lock); |
| storage->owner = owner; |
| |
| bpf_selem_link_storage_nolock(storage, first_selem); |
| bpf_selem_link_map(smap, first_selem); |
| |
| owner_storage_ptr = |
| (struct bpf_local_storage **)owner_storage(smap, owner); |
| /* Publish storage to the owner. |
| * Instead of using any lock of the kernel object (i.e. owner), |
| * cmpxchg will work with any kernel object regardless what |
| * the running context is, bh, irq...etc. |
| * |
| * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage) |
| * is protected by the storage->lock. Hence, when freeing |
| * the owner->storage, the storage->lock must be held before |
| * setting owner->storage ptr to NULL. |
| */ |
| prev_storage = cmpxchg(owner_storage_ptr, NULL, storage); |
| if (unlikely(prev_storage)) { |
| bpf_selem_unlink_map(first_selem); |
| err = -EAGAIN; |
| goto uncharge; |
| |
| /* Note that even first_selem was linked to smap's |
| * bucket->list, first_selem can be freed immediately |
| * (instead of kfree_rcu) because |
| * bpf_local_storage_map_free() does a |
| * synchronize_rcu_mult (waiting for both sleepable and |
| * normal programs) before walking the bucket->list. |
| * Hence, no one is accessing selem from the |
| * bucket->list under rcu_read_lock(). |
| */ |
| } |
| |
| return 0; |
| |
| uncharge: |
| kfree(storage); |
| mem_uncharge(smap, owner, sizeof(*storage)); |
| return err; |
| } |
| |
| /* sk cannot be going away because it is linking new elem |
| * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0). |
| * Otherwise, it will become a leak (and other memory issues |
| * during map destruction). |
| */ |
| struct bpf_local_storage_data * |
| bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, |
| void *value, u64 map_flags, gfp_t gfp_flags) |
| { |
| struct bpf_local_storage_data *old_sdata = NULL; |
| struct bpf_local_storage_elem *selem = NULL; |
| struct bpf_local_storage *local_storage; |
| unsigned long flags; |
| int err; |
| |
| /* BPF_EXIST and BPF_NOEXIST cannot be both set */ |
| if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) || |
| /* BPF_F_LOCK can only be used in a value with spin_lock */ |
| unlikely((map_flags & BPF_F_LOCK) && |
| !map_value_has_spin_lock(&smap->map))) |
| return ERR_PTR(-EINVAL); |
| |
| if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST) |
| return ERR_PTR(-EINVAL); |
| |
| local_storage = rcu_dereference_check(*owner_storage(smap, owner), |
| bpf_rcu_lock_held()); |
| if (!local_storage || hlist_empty(&local_storage->list)) { |
| /* Very first elem for the owner */ |
| err = check_flags(NULL, map_flags); |
| if (err) |
| return ERR_PTR(err); |
| |
| selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); |
| if (!selem) |
| return ERR_PTR(-ENOMEM); |
| |
| err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags); |
| if (err) { |
| kfree(selem); |
| mem_uncharge(smap, owner, smap->elem_size); |
| return ERR_PTR(err); |
| } |
| |
| return SDATA(selem); |
| } |
| |
| if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) { |
| /* Hoping to find an old_sdata to do inline update |
| * such that it can avoid taking the local_storage->lock |
| * and changing the lists. |
| */ |
| old_sdata = |
| bpf_local_storage_lookup(local_storage, smap, false); |
| err = check_flags(old_sdata, map_flags); |
| if (err) |
| return ERR_PTR(err); |
| if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) { |
| copy_map_value_locked(&smap->map, old_sdata->data, |
| value, false); |
| return old_sdata; |
| } |
| } |
| |
| if (gfp_flags == GFP_KERNEL) { |
| selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); |
| if (!selem) |
| return ERR_PTR(-ENOMEM); |
| } |
| |
| raw_spin_lock_irqsave(&local_storage->lock, flags); |
| |
| /* Recheck local_storage->list under local_storage->lock */ |
| if (unlikely(hlist_empty(&local_storage->list))) { |
| /* A parallel del is happening and local_storage is going |
| * away. It has just been checked before, so very |
| * unlikely. Return instead of retry to keep things |
| * simple. |
| */ |
| err = -EAGAIN; |
| goto unlock_err; |
| } |
| |
| old_sdata = bpf_local_storage_lookup(local_storage, smap, false); |
| err = check_flags(old_sdata, map_flags); |
| if (err) |
| goto unlock_err; |
| |
| if (old_sdata && (map_flags & BPF_F_LOCK)) { |
| copy_map_value_locked(&smap->map, old_sdata->data, value, |
| false); |
| selem = SELEM(old_sdata); |
| goto unlock; |
| } |
| |
| if (gfp_flags != GFP_KERNEL) { |
| /* local_storage->lock is held. Hence, we are sure |
| * we can unlink and uncharge the old_sdata successfully |
| * later. Hence, instead of charging the new selem now |
| * and then uncharge the old selem later (which may cause |
| * a potential but unnecessary charge failure), avoid taking |
| * a charge at all here (the "!old_sdata" check) and the |
| * old_sdata will not be uncharged later during |
| * bpf_selem_unlink_storage_nolock(). |
| */ |
| selem = bpf_selem_alloc(smap, owner, value, !old_sdata, gfp_flags); |
| if (!selem) { |
| err = -ENOMEM; |
| goto unlock_err; |
| } |
| } |
| |
| /* First, link the new selem to the map */ |
| bpf_selem_link_map(smap, selem); |
| |
| /* Second, link (and publish) the new selem to local_storage */ |
| bpf_selem_link_storage_nolock(local_storage, selem); |
| |
| /* Third, remove old selem, SELEM(old_sdata) */ |
| if (old_sdata) { |
| bpf_selem_unlink_map(SELEM(old_sdata)); |
| bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata), |
| false); |
| } |
| |
| unlock: |
| raw_spin_unlock_irqrestore(&local_storage->lock, flags); |
| return SDATA(selem); |
| |
| unlock_err: |
| raw_spin_unlock_irqrestore(&local_storage->lock, flags); |
| if (selem) { |
| mem_uncharge(smap, owner, smap->elem_size); |
| kfree(selem); |
| } |
| return ERR_PTR(err); |
| } |
| |
| u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache) |
| { |
| u64 min_usage = U64_MAX; |
| u16 i, res = 0; |
| |
| spin_lock(&cache->idx_lock); |
| |
| for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) { |
| if (cache->idx_usage_counts[i] < min_usage) { |
| min_usage = cache->idx_usage_counts[i]; |
| res = i; |
| |
| /* Found a free cache_idx */ |
| if (!min_usage) |
| break; |
| } |
| } |
| cache->idx_usage_counts[res]++; |
| |
| spin_unlock(&cache->idx_lock); |
| |
| return res; |
| } |
| |
| void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache, |
| u16 idx) |
| { |
| spin_lock(&cache->idx_lock); |
| cache->idx_usage_counts[idx]--; |
| spin_unlock(&cache->idx_lock); |
| } |
| |
| void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, |
| int __percpu *busy_counter) |
| { |
| struct bpf_local_storage_elem *selem; |
| struct bpf_local_storage_map_bucket *b; |
| unsigned int i; |
| |
| /* Note that this map might be concurrently cloned from |
| * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone |
| * RCU read section to finish before proceeding. New RCU |
| * read sections should be prevented via bpf_map_inc_not_zero. |
| */ |
| synchronize_rcu(); |
| |
| /* bpf prog and the userspace can no longer access this map |
| * now. No new selem (of this map) can be added |
| * to the owner->storage or to the map bucket's list. |
| * |
| * The elem of this map can be cleaned up here |
| * or when the storage is freed e.g. |
| * by bpf_sk_storage_free() during __sk_destruct(). |
| */ |
| for (i = 0; i < (1U << smap->bucket_log); i++) { |
| b = &smap->buckets[i]; |
| |
| rcu_read_lock(); |
| /* No one is adding to b->list now */ |
| while ((selem = hlist_entry_safe( |
| rcu_dereference_raw(hlist_first_rcu(&b->list)), |
| struct bpf_local_storage_elem, map_node))) { |
| if (busy_counter) { |
| migrate_disable(); |
| __this_cpu_inc(*busy_counter); |
| } |
| bpf_selem_unlink(selem); |
| if (busy_counter) { |
| __this_cpu_dec(*busy_counter); |
| migrate_enable(); |
| } |
| cond_resched_rcu(); |
| } |
| rcu_read_unlock(); |
| } |
| |
| /* While freeing the storage we may still need to access the map. |
| * |
| * e.g. when bpf_sk_storage_free() has unlinked selem from the map |
| * which then made the above while((selem = ...)) loop |
| * exit immediately. |
| * |
| * However, while freeing the storage one still needs to access the |
| * smap->elem_size to do the uncharging in |
| * bpf_selem_unlink_storage_nolock(). |
| * |
| * Hence, wait another rcu grace period for the storage to be freed. |
| */ |
| synchronize_rcu(); |
| |
| kvfree(smap->buckets); |
| kfree(smap); |
| } |
| |
| int bpf_local_storage_map_alloc_check(union bpf_attr *attr) |
| { |
| if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK || |
| !(attr->map_flags & BPF_F_NO_PREALLOC) || |
| attr->max_entries || |
| attr->key_size != sizeof(int) || !attr->value_size || |
| /* Enforce BTF for userspace sk dumping */ |
| !attr->btf_key_type_id || !attr->btf_value_type_id) |
| return -EINVAL; |
| |
| if (!bpf_capable()) |
| return -EPERM; |
| |
| if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE) |
| return -E2BIG; |
| |
| return 0; |
| } |
| |
| struct bpf_local_storage_map *bpf_local_storage_map_alloc(union bpf_attr *attr) |
| { |
| struct bpf_local_storage_map *smap; |
| unsigned int i; |
| u32 nbuckets; |
| |
| smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT); |
| if (!smap) |
| return ERR_PTR(-ENOMEM); |
| bpf_map_init_from_attr(&smap->map, attr); |
| |
| nbuckets = roundup_pow_of_two(num_possible_cpus()); |
| /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */ |
| nbuckets = max_t(u32, 2, nbuckets); |
| smap->bucket_log = ilog2(nbuckets); |
| |
| smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets, |
| GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT); |
| if (!smap->buckets) { |
| kfree(smap); |
| return ERR_PTR(-ENOMEM); |
| } |
| |
| for (i = 0; i < nbuckets; i++) { |
| INIT_HLIST_HEAD(&smap->buckets[i].list); |
| raw_spin_lock_init(&smap->buckets[i].lock); |
| } |
| |
| smap->elem_size = |
| sizeof(struct bpf_local_storage_elem) + attr->value_size; |
| |
| return smap; |
| } |
| |
| int bpf_local_storage_map_check_btf(const struct bpf_map *map, |
| const struct btf *btf, |
| const struct btf_type *key_type, |
| const struct btf_type *value_type) |
| { |
| u32 int_data; |
| |
| if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT) |
| return -EINVAL; |
| |
| int_data = *(u32 *)(key_type + 1); |
| if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data)) |
| return -EINVAL; |
| |
| return 0; |
| } |