// 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_lockless(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed_lockless(&selem->snode);
}
static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed(&selem->snode);
}
static bool selem_linked_to_map_lockless(const struct bpf_local_storage_elem *selem)
{
return !hlist_unhashed_lockless(&selem->map_node);
}
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;
if (smap->bpf_ma) {
migrate_disable();
selem = bpf_mem_cache_alloc_flags(&smap->selem_ma, gfp_flags);
migrate_enable();
if (selem)
/* Keep the original bpf_map_kzalloc behavior
* before started using the bpf_mem_cache_alloc.
*
* No need to use zero_map_value. The bpf_selem_free()
* only does bpf_mem_cache_free when there is
* no other bpf prog is using the selem.
*/
memset(SDATA(selem)->data, 0, smap->map.value_size);
} else {
selem = bpf_map_kzalloc(&smap->map, smap->elem_size,
gfp_flags | __GFP_NOWARN);
}
if (selem) {
if (value)
copy_map_value(&smap->map, SDATA(selem)->data, value);
/* No need to call check_and_init_map_value as memory is zero init */
return selem;
}
if (charge_mem)
mem_uncharge(smap, owner, smap->elem_size);
return NULL;
}
/* rcu tasks trace callback for bpf_ma == false */
static void __bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
{
struct bpf_local_storage *local_storage;
/* If RCU Tasks Trace grace period implies RCU grace period, do
* kfree(), else do kfree_rcu().
*/
local_storage = container_of(rcu, struct bpf_local_storage, rcu);
if (rcu_trace_implies_rcu_gp())
kfree(local_storage);
else
kfree_rcu(local_storage, rcu);
}
static 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);
bpf_mem_cache_raw_free(local_storage);
}
static void bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
{
if (rcu_trace_implies_rcu_gp())
bpf_local_storage_free_rcu(rcu);
else
call_rcu(rcu, bpf_local_storage_free_rcu);
}
/* Handle bpf_ma == false */
static void __bpf_local_storage_free(struct bpf_local_storage *local_storage,
bool vanilla_rcu)
{
if (vanilla_rcu)
kfree_rcu(local_storage, rcu);
else
call_rcu_tasks_trace(&local_storage->rcu,
__bpf_local_storage_free_trace_rcu);
}
static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
struct bpf_local_storage_map *smap,
bool bpf_ma, bool reuse_now)
{
if (!local_storage)
return;
if (!bpf_ma) {
__bpf_local_storage_free(local_storage, reuse_now);
return;
}
if (!reuse_now) {
call_rcu_tasks_trace(&local_storage->rcu,
bpf_local_storage_free_trace_rcu);
return;
}
if (smap) {
migrate_disable();
bpf_mem_cache_free(&smap->storage_ma, local_storage);
migrate_enable();
} else {
/* smap could be NULL if the selem that triggered
* this 'local_storage' creation had been long gone.
* In this case, directly do call_rcu().
*/
call_rcu(&local_storage->rcu, bpf_local_storage_free_rcu);
}
}
/* rcu tasks trace callback for bpf_ma == false */
static void __bpf_selem_free_trace_rcu(struct rcu_head *rcu)
{
struct bpf_local_storage_elem *selem;
selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
if (rcu_trace_implies_rcu_gp())
kfree(selem);
else
kfree_rcu(selem, rcu);
}
/* Handle bpf_ma == false */
static void __bpf_selem_free(struct bpf_local_storage_elem *selem,
bool vanilla_rcu)
{
if (vanilla_rcu)
kfree_rcu(selem, rcu);
else
call_rcu_tasks_trace(&selem->rcu, __bpf_selem_free_trace_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);
bpf_mem_cache_raw_free(selem);
}
static void bpf_selem_free_trace_rcu(struct rcu_head *rcu)
{
if (rcu_trace_implies_rcu_gp())
bpf_selem_free_rcu(rcu);
else
call_rcu(rcu, bpf_selem_free_rcu);
}
void bpf_selem_free(struct bpf_local_storage_elem *selem,
struct bpf_local_storage_map *smap,
bool reuse_now)
{
bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
if (!smap->bpf_ma) {
__bpf_selem_free(selem, reuse_now);
return;
}
if (!reuse_now) {
call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
} else {
/* Instead of using the vanilla call_rcu(),
* bpf_mem_cache_free will be able to reuse selem
* immediately.
*/
migrate_disable();
bpf_mem_cache_free(&smap->selem_ma, selem);
migrate_enable();
}
}
/* 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.
*/
static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
struct bpf_local_storage_elem *selem,
bool uncharge_mem, bool reuse_now)
{
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);
bpf_selem_free(selem, smap, reuse_now);
if (rcu_access_pointer(local_storage->smap) == smap)
RCU_INIT_POINTER(local_storage->smap, NULL);
return free_local_storage;
}
static bool check_storage_bpf_ma(struct bpf_local_storage *local_storage,
struct bpf_local_storage_map *storage_smap,
struct bpf_local_storage_elem *selem)
{
struct bpf_local_storage_map *selem_smap;
/* local_storage->smap may be NULL. If it is, get the bpf_ma
* from any selem in the local_storage->list. The bpf_ma of all
* local_storage and selem should have the same value
* for the same map type.
*
* If the local_storage->list is already empty, the caller will not
* care about the bpf_ma value also because the caller is not
* responsible to free the local_storage.
*/
if (storage_smap)
return storage_smap->bpf_ma;
if (!selem) {
struct hlist_node *n;
n = rcu_dereference_check(hlist_first_rcu(&local_storage->list),
bpf_rcu_lock_held());
if (!n)
return false;
selem = hlist_entry(n, struct bpf_local_storage_elem, snode);
}
selem_smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
return selem_smap->bpf_ma;
}
static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
bool reuse_now)
{
struct bpf_local_storage_map *storage_smap;
struct bpf_local_storage *local_storage;
bool bpf_ma, free_local_storage = false;
unsigned long flags;
if (unlikely(!selem_linked_to_storage_lockless(selem)))
/* selem has already been unlinked from sk */
return;
local_storage = rcu_dereference_check(selem->local_storage,
bpf_rcu_lock_held());
storage_smap = rcu_dereference_check(local_storage->smap,
bpf_rcu_lock_held());
bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem);
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, reuse_now);
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (free_local_storage)
bpf_local_storage_free(local_storage, storage_smap, bpf_ma, reuse_now);
}
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);
}
static 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_lockless(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, bool reuse_now)
{
/* 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, reuse_now);
}
void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,
struct bpf_local_storage_map *smap,
struct bpf_local_storage_elem *selem)
{
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(selem));
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
}
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;
if (smap->bpf_ma) {
migrate_disable();
storage = bpf_mem_cache_alloc_flags(&smap->storage_ma, gfp_flags);
migrate_enable();
} else {
storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
gfp_flags | __GFP_NOWARN);
}
if (!storage) {
err = -ENOMEM;
goto uncharge;
}
RCU_INIT_POINTER(storage->smap, smap);
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:
bpf_local_storage_free(storage, smap, smap->bpf_ma, true);
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 *alloc_selem, *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) &&
!btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
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) {
bpf_selem_free(selem, smap, true);
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_lockless(SELEM(old_sdata))) {
copy_map_value_locked(&smap->map, old_sdata->data,
value, false);
return old_sdata;
}
}
/* A lookup has just been done before and concluded a new selem is
* needed. The chance of an unnecessary alloc is unlikely.
*/
alloc_selem = selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags);
if (!alloc_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;
}
old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
err = check_flags(old_sdata, map_flags);
if (err)
goto unlock;
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;
}
alloc_selem = NULL;
/* 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),
true, false);
}
unlock:
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (alloc_selem) {
mem_uncharge(smap, owner, smap->elem_size);
bpf_selem_free(alloc_selem, smap, true);
}
return err ? ERR_PTR(err) : SDATA(selem);
}
static 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;
}
static 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);
}
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 (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
return -E2BIG;
return 0;
}
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;
}
void bpf_local_storage_destroy(struct bpf_local_storage *local_storage)
{
struct bpf_local_storage_map *storage_smap;
struct bpf_local_storage_elem *selem;
bool bpf_ma, free_storage = false;
struct hlist_node *n;
unsigned long flags;
storage_smap = rcu_dereference_check(local_storage->smap, bpf_rcu_lock_held());
bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, NULL);
/* Neither the bpf_prog nor the bpf_map's syscall
* could be modifying the local_storage->list now.
* Thus, no elem can be added to or deleted from the
* local_storage->list by the bpf_prog or by the bpf_map's syscall.
*
* It is racing with bpf_local_storage_map_free() alone
* when unlinking elem from the local_storage->list and
* the map's bucket->list.
*/
raw_spin_lock_irqsave(&local_storage->lock, flags);
hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
/* Always unlink from map before unlinking from
* local_storage.
*/
bpf_selem_unlink_map(selem);
/* If local_storage list has only one element, the
* bpf_selem_unlink_storage_nolock() will return true.
* Otherwise, it will return false. The current loop iteration
* intends to remove all local storage. So the last iteration
* of the loop will set the free_cgroup_storage to true.
*/
free_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, true, true);
}
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (free_storage)
bpf_local_storage_free(local_storage, storage_smap, bpf_ma, true);
}
u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map)
{
struct bpf_local_storage_map *smap = (struct bpf_local_storage_map *)map;
u64 usage = sizeof(*smap);
/* The dynamically callocated selems are not counted currently. */
usage += sizeof(*smap->buckets) * (1ULL << smap->bucket_log);
return usage;
}
/* When bpf_ma == true, the bpf_mem_alloc is used to allocate and free memory.
* A deadlock free allocator is useful for storage that the bpf prog can easily
* get a hold of the owner PTR_TO_BTF_ID in any context. eg. bpf_get_current_task_btf.
* The task and cgroup storage fall into this case. The bpf_mem_alloc reuses
* memory immediately. To be reuse-immediate safe, the owner destruction
* code path needs to go through a rcu grace period before calling
* bpf_local_storage_destroy().
*
* When bpf_ma == false, the kmalloc and kfree are used.
*/
struct bpf_map *
bpf_local_storage_map_alloc(union bpf_attr *attr,
struct bpf_local_storage_cache *cache,
bool bpf_ma)
{
struct bpf_local_storage_map *smap;
unsigned int i;
u32 nbuckets;
int err;
smap = bpf_map_area_alloc(sizeof(*smap), NUMA_NO_NODE);
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 = bpf_map_kvcalloc(&smap->map, nbuckets,
sizeof(*smap->buckets), GFP_USER | __GFP_NOWARN);
if (!smap->buckets) {
err = -ENOMEM;
goto free_smap;
}
for (i = 0; i < nbuckets; i++) {
INIT_HLIST_HEAD(&smap->buckets[i].list);
raw_spin_lock_init(&smap->buckets[i].lock);
}
smap->elem_size = offsetof(struct bpf_local_storage_elem,
sdata.data[attr->value_size]);
smap->bpf_ma = bpf_ma;
if (bpf_ma) {
err = bpf_mem_alloc_init(&smap->selem_ma, smap->elem_size, false);
if (err)
goto free_smap;
err = bpf_mem_alloc_init(&smap->storage_ma, sizeof(struct bpf_local_storage), false);
if (err) {
bpf_mem_alloc_destroy(&smap->selem_ma);
goto free_smap;
}
}
smap->cache_idx = bpf_local_storage_cache_idx_get(cache);
return &smap->map;
free_smap:
kvfree(smap->buckets);
bpf_map_area_free(smap);
return ERR_PTR(err);
}
void bpf_local_storage_map_free(struct bpf_map *map,
struct bpf_local_storage_cache *cache,
int __percpu *busy_counter)
{
struct bpf_local_storage_map_bucket *b;
struct bpf_local_storage_elem *selem;
struct bpf_local_storage_map *smap;
unsigned int i;
smap = (struct bpf_local_storage_map *)map;
bpf_local_storage_cache_idx_free(cache, smap->cache_idx);
/* 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, true);
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();
if (smap->bpf_ma) {
bpf_mem_alloc_destroy(&smap->selem_ma);
bpf_mem_alloc_destroy(&smap->storage_ma);
}
kvfree(smap->buckets);
bpf_map_area_free(smap);
}
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