// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2019 Facebook */
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#include <linux/rculist.h>
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#include <linux/list.h>
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#include <linux/hash.h>
|
#include <linux/types.h>
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#include <linux/spinlock.h>
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#include <linux/bpf.h>
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#include <linux/btf_ids.h>
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#include <linux/bpf_local_storage.h>
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#include <net/sock.h>
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#include <uapi/linux/sock_diag.h>
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#include <uapi/linux/btf.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,
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struct bpf_local_storage_elem *selem)
|
{
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return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
|
}
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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);
|
}
|
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static struct bpf_local_storage __rcu **
|
owner_storage(struct bpf_local_storage_map *smap, void *owner)
|
{
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struct bpf_map *map = &smap->map;
|
|
return map->ops->map_owner_storage_ptr(owner);
|
}
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static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
|
{
|
return !hlist_unhashed(&selem->snode);
|
}
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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 = kzalloc(smap->elem_size, GFP_ATOMIC | __GFP_NOWARN);
|
if (selem) {
|
if (value)
|
copy_map_value(&smap->map, SDATA(selem)->data, value);
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return selem;
|
}
|
|
if (charge_mem)
|
mem_uncharge(smap, owner, smap->elem_size);
|
|
return NULL;
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}
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/* local_storage->lock must be held and selem->local_storage == local_storage.
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* The caller must ensure selem->smap is still valid to be
|
* dereferenced for its smap->elem_size and smap->cache_idx.
|
*/
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bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
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struct bpf_local_storage_elem *selem,
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bool uncharge_mem)
|
{
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struct bpf_local_storage_map *smap;
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bool free_local_storage;
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void *owner;
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smap = rcu_dereference(SDATA(selem)->smap);
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owner = local_storage->owner;
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/* All uncharging on the owner must be done first.
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* The owner may be freed once the last selem is unlinked
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* from local_storage.
|
*/
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if (uncharge_mem)
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mem_uncharge(smap, owner, smap->elem_size);
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free_local_storage = hlist_is_singular_node(&selem->snode,
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&local_storage->list);
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if (free_local_storage) {
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mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
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local_storage->owner = NULL;
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/* After this RCU_INIT, owner may be freed and cannot be used */
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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)
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* will be done by the caller.
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*
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* Although the unlock will be done under
|
* rcu_read_lock(), it is more intutivie to
|
* read if kfree_rcu(local_storage, rcu) is done
|
* after the raw_spin_unlock_bh(&local_storage->lock).
|
*
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* Hence, a "bool free_local_storage" is returned
|
* to the caller which then calls the kfree_rcu()
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* after unlock.
|
*/
|
}
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hlist_del_init_rcu(&selem->snode);
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if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
|
SDATA(selem))
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RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
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kfree_rcu(selem, rcu);
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return free_local_storage;
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}
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static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
|
{
|
struct bpf_local_storage *local_storage;
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bool free_local_storage = false;
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if (unlikely(!selem_linked_to_storage(selem)))
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/* selem has already been unlinked from sk */
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return;
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local_storage = rcu_dereference(selem->local_storage);
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raw_spin_lock_bh(&local_storage->lock);
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if (likely(selem_linked_to_storage(selem)))
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free_local_storage = bpf_selem_unlink_storage_nolock(
|
local_storage, selem, true);
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raw_spin_unlock_bh(&local_storage->lock);
|
|
if (free_local_storage)
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kfree_rcu(local_storage, rcu);
|
}
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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);
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hlist_add_head_rcu(&selem->snode, &local_storage->list);
|
}
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void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
|
{
|
struct bpf_local_storage_map *smap;
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struct bpf_local_storage_map_bucket *b;
|
|
if (unlikely(!selem_linked_to_map(selem)))
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/* selem has already be unlinked from smap */
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return;
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smap = rcu_dereference(SDATA(selem)->smap);
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b = select_bucket(smap, selem);
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raw_spin_lock_bh(&b->lock);
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if (likely(selem_linked_to_map(selem)))
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hlist_del_init_rcu(&selem->map_node);
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raw_spin_unlock_bh(&b->lock);
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}
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void bpf_selem_link_map(struct bpf_local_storage_map *smap,
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struct bpf_local_storage_elem *selem)
|
{
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struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
|
|
raw_spin_lock_bh(&b->lock);
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RCU_INIT_POINTER(SDATA(selem)->smap, smap);
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hlist_add_head_rcu(&selem->map_node, &b->list);
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raw_spin_unlock_bh(&b->lock);
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}
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void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
|
{
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/* Always unlink from map before unlinking from local_storage
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* because selem will be freed after successfully unlinked from
|
* the local_storage.
|
*/
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bpf_selem_unlink_map(selem);
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__bpf_selem_unlink_storage(selem);
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}
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struct bpf_local_storage_data *
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bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
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struct bpf_local_storage_map *smap,
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bool cacheit_lockit)
|
{
|
struct bpf_local_storage_data *sdata;
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struct bpf_local_storage_elem *selem;
|
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/* Fast path (cache hit) */
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sdata = rcu_dereference(local_storage->cache[smap->cache_idx]);
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if (sdata && rcu_access_pointer(sdata->smap) == smap)
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return sdata;
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/* Slow path (cache miss) */
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hlist_for_each_entry_rcu(selem, &local_storage->list, snode)
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if (rcu_access_pointer(SDATA(selem)->smap) == smap)
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break;
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|
if (!selem)
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return NULL;
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sdata = SDATA(selem);
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if (cacheit_lockit) {
|
/* 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_bh(&local_storage->lock);
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if (selem_linked_to_storage(selem))
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rcu_assign_pointer(local_storage->cache[smap->cache_idx],
|
sdata);
|
raw_spin_unlock_bh(&local_storage->lock);
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}
|
|
return sdata;
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}
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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)
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/* elem already exists */
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return -EEXIST;
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if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
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/* elem doesn't exist, cannot update it */
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return -ENOENT;
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return 0;
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}
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int bpf_local_storage_alloc(void *owner,
|
struct bpf_local_storage_map *smap,
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struct bpf_local_storage_elem *first_selem)
|
{
|
struct bpf_local_storage *prev_storage, *storage;
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struct bpf_local_storage **owner_storage_ptr;
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int err;
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err = mem_charge(smap, owner, sizeof(*storage));
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if (err)
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return err;
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storage = kzalloc(sizeof(*storage), GFP_ATOMIC | __GFP_NOWARN);
|
if (!storage) {
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err = -ENOMEM;
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goto uncharge;
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}
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INIT_HLIST_HEAD(&storage->list);
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raw_spin_lock_init(&storage->lock);
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storage->owner = owner;
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bpf_selem_link_storage_nolock(storage, first_selem);
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bpf_selem_link_map(smap, first_selem);
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owner_storage_ptr =
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(struct bpf_local_storage **)owner_storage(smap, owner);
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/* Publish storage to the owner.
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* Instead of using any lock of the kernel object (i.e. owner),
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* cmpxchg will work with any kernel object regardless what
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* 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
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* setting owner->storage ptr to NULL.
|
*/
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prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
|
if (unlikely(prev_storage)) {
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bpf_selem_unlink_map(first_selem);
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err = -EAGAIN;
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goto uncharge;
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|
/* Note that even first_selem was linked to smap's
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* bucket->list, first_selem can be freed immediately
|
* (instead of kfree_rcu) because
|
* bpf_local_storage_map_free() does a
|
* synchronize_rcu() before walking the bucket->list.
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* Hence, no one is accessing selem from the
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* bucket->list under rcu_read_lock().
|
*/
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}
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return 0;
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uncharge:
|
kfree(storage);
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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).
|
*/
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struct bpf_local_storage_data *
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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;
|
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(*owner_storage(smap, owner));
|
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_bh(&local_storage->lock);
|
|
/* 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_bh(&local_storage->lock);
|
return SDATA(selem);
|
|
unlock_err:
|
raw_spin_unlock_bh(&local_storage->lock);
|
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)
|
{
|
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))) {
|
bpf_selem_unlink(selem);
|
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;
|
u64 cost;
|
int ret;
|
|
smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN);
|
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);
|
cost = sizeof(*smap->buckets) * nbuckets + sizeof(*smap);
|
|
ret = bpf_map_charge_init(&smap->map.memory, cost);
|
if (ret < 0) {
|
kfree(smap);
|
return ERR_PTR(ret);
|
}
|
|
smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
|
GFP_USER | __GFP_NOWARN);
|
if (!smap->buckets) {
|
bpf_map_charge_finish(&smap->map.memory);
|
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;
|
}
|
