linux/kernel/bpf/bpf_local_storage.c
Tom Rix c561d11063 bpf: Cleanup comments
Add leading space to spdx tag
Use // for spdx c file comment

Replacements
resereved to reserved
inbetween to in between
everytime to every time
intutivie to intuitive
currenct to current
encontered to encountered
referenceing to referencing
upto to up to
exectuted to executed

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20220220184055.3608317-1-trix@redhat.com
2022-02-23 15:17:51 -08:00

632 lines
18 KiB
C

// 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)
{
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_ATOMIC | __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)
{
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_ATOMIC | __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)
{
struct bpf_local_storage_data *old_sdata = NULL;
struct bpf_local_storage_elem *selem;
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);
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);
if (!selem)
return ERR_PTR(-ENOMEM);
err = bpf_local_storage_alloc(owner, smap, selem);
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;
}
}
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;
}
/* 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);
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);
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;
}