linux/net/core/bpf_sk_storage.c
Andrii Nakryiko 1e0bd5a091 bpf: Switch bpf_map ref counter to atomic64_t so bpf_map_inc() never fails
92117d8443 ("bpf: fix refcnt overflow") turned refcounting of bpf_map into
potentially failing operation, when refcount reaches BPF_MAX_REFCNT limit
(32k). Due to using 32-bit counter, it's possible in practice to overflow
refcounter and make it wrap around to 0, causing erroneous map free, while
there are still references to it, causing use-after-free problems.

But having a failing refcounting operations are problematic in some cases. One
example is mmap() interface. After establishing initial memory-mapping, user
is allowed to arbitrarily map/remap/unmap parts of mapped memory, arbitrarily
splitting it into multiple non-contiguous regions. All this happening without
any control from the users of mmap subsystem. Rather mmap subsystem sends
notifications to original creator of memory mapping through open/close
callbacks, which are optionally specified during initial memory mapping
creation. These callbacks are used to maintain accurate refcount for bpf_map
(see next patch in this series). The problem is that open() callback is not
supposed to fail, because memory-mapped resource is set up and properly
referenced. This is posing a problem for using memory-mapping with BPF maps.

One solution to this is to maintain separate refcount for just memory-mappings
and do single bpf_map_inc/bpf_map_put when it goes from/to zero, respectively.
There are similar use cases in current work on tcp-bpf, necessitating extra
counter as well. This seems like a rather unfortunate and ugly solution that
doesn't scale well to various new use cases.

Another approach to solve this is to use non-failing refcount_t type, which
uses 32-bit counter internally, but, once reaching overflow state at UINT_MAX,
stays there. This utlimately causes memory leak, but prevents use after free.

But given refcounting is not the most performance-critical operation with BPF
maps (it's not used from running BPF program code), we can also just switch to
64-bit counter that can't overflow in practice, potentially disadvantaging
32-bit platforms a tiny bit. This simplifies semantics and allows above
described scenarios to not worry about failing refcount increment operation.

In terms of struct bpf_map size, we are still good and use the same amount of
space:

BEFORE (3 cache lines, 8 bytes of padding at the end):
struct bpf_map {
	const struct bpf_map_ops  * ops __attribute__((__aligned__(64))); /*     0     8 */
	struct bpf_map *           inner_map_meta;       /*     8     8 */
	void *                     security;             /*    16     8 */
	enum bpf_map_type  map_type;                     /*    24     4 */
	u32                        key_size;             /*    28     4 */
	u32                        value_size;           /*    32     4 */
	u32                        max_entries;          /*    36     4 */
	u32                        map_flags;            /*    40     4 */
	int                        spin_lock_off;        /*    44     4 */
	u32                        id;                   /*    48     4 */
	int                        numa_node;            /*    52     4 */
	u32                        btf_key_type_id;      /*    56     4 */
	u32                        btf_value_type_id;    /*    60     4 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	struct btf *               btf;                  /*    64     8 */
	struct bpf_map_memory memory;                    /*    72    16 */
	bool                       unpriv_array;         /*    88     1 */
	bool                       frozen;               /*    89     1 */

	/* XXX 38 bytes hole, try to pack */

	/* --- cacheline 2 boundary (128 bytes) --- */
	atomic_t                   refcnt __attribute__((__aligned__(64))); /*   128     4 */
	atomic_t                   usercnt;              /*   132     4 */
	struct work_struct work;                         /*   136    32 */
	char                       name[16];             /*   168    16 */

	/* size: 192, cachelines: 3, members: 21 */
	/* sum members: 146, holes: 1, sum holes: 38 */
	/* padding: 8 */
	/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));

AFTER (same 3 cache lines, no extra padding now):
struct bpf_map {
	const struct bpf_map_ops  * ops __attribute__((__aligned__(64))); /*     0     8 */
	struct bpf_map *           inner_map_meta;       /*     8     8 */
	void *                     security;             /*    16     8 */
	enum bpf_map_type  map_type;                     /*    24     4 */
	u32                        key_size;             /*    28     4 */
	u32                        value_size;           /*    32     4 */
	u32                        max_entries;          /*    36     4 */
	u32                        map_flags;            /*    40     4 */
	int                        spin_lock_off;        /*    44     4 */
	u32                        id;                   /*    48     4 */
	int                        numa_node;            /*    52     4 */
	u32                        btf_key_type_id;      /*    56     4 */
	u32                        btf_value_type_id;    /*    60     4 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	struct btf *               btf;                  /*    64     8 */
	struct bpf_map_memory memory;                    /*    72    16 */
	bool                       unpriv_array;         /*    88     1 */
	bool                       frozen;               /*    89     1 */

	/* XXX 38 bytes hole, try to pack */

	/* --- cacheline 2 boundary (128 bytes) --- */
	atomic64_t                 refcnt __attribute__((__aligned__(64))); /*   128     8 */
	atomic64_t                 usercnt;              /*   136     8 */
	struct work_struct work;                         /*   144    32 */
	char                       name[16];             /*   176    16 */

	/* size: 192, cachelines: 3, members: 21 */
	/* sum members: 154, holes: 1, sum holes: 38 */
	/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));

This patch, while modifying all users of bpf_map_inc, also cleans up its
interface to match bpf_map_put with separate operations for bpf_map_inc and
bpf_map_inc_with_uref (to match bpf_map_put and bpf_map_put_with_uref,
respectively). Also, given there are no users of bpf_map_inc_not_zero
specifying uref=true, remove uref flag and default to uref=false internally.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-2-andriin@fb.com
2019-11-18 11:41:59 +01:00

912 lines
24 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 <net/bpf_sk_storage.h>
#include <net/sock.h>
#include <uapi/linux/btf.h>
static atomic_t cache_idx;
#define SK_STORAGE_CREATE_FLAG_MASK \
(BPF_F_NO_PREALLOC | BPF_F_CLONE)
struct bucket {
struct hlist_head list;
raw_spinlock_t lock;
};
/* Thp map is not the primary owner of a bpf_sk_storage_elem.
* Instead, the sk->sk_bpf_storage is.
*
* The map (bpf_sk_storage_map) is for two purposes
* 1. Define the size of the "sk local storage". It is
* the map's value_size.
*
* 2. Maintain a list to keep track of all elems such
* that they can be cleaned up during the map destruction.
*
* When a bpf local storage is being looked up for a
* particular sk, the "bpf_map" pointer is actually used
* as the "key" to search in the list of elem in
* sk->sk_bpf_storage.
*
* Hence, consider sk->sk_bpf_storage is the mini-map
* with the "bpf_map" pointer as the searching key.
*/
struct bpf_sk_storage_map {
struct bpf_map map;
/* Lookup elem does not require accessing the map.
*
* Updating/Deleting requires a bucket lock to
* link/unlink the elem from the map. Having
* multiple buckets to improve contention.
*/
struct bucket *buckets;
u32 bucket_log;
u16 elem_size;
u16 cache_idx;
};
struct bpf_sk_storage_data {
/* smap is used as the searching key when looking up
* from sk->sk_bpf_storage.
*
* Put it in the same cacheline as the data to minimize
* the number of cachelines access during the cache hit case.
*/
struct bpf_sk_storage_map __rcu *smap;
u8 data[0] __aligned(8);
};
/* Linked to bpf_sk_storage and bpf_sk_storage_map */
struct bpf_sk_storage_elem {
struct hlist_node map_node; /* Linked to bpf_sk_storage_map */
struct hlist_node snode; /* Linked to bpf_sk_storage */
struct bpf_sk_storage __rcu *sk_storage;
struct rcu_head rcu;
/* 8 bytes hole */
/* The data is stored in aother cacheline to minimize
* the number of cachelines access during a cache hit.
*/
struct bpf_sk_storage_data sdata ____cacheline_aligned;
};
#define SELEM(_SDATA) container_of((_SDATA), struct bpf_sk_storage_elem, sdata)
#define SDATA(_SELEM) (&(_SELEM)->sdata)
#define BPF_SK_STORAGE_CACHE_SIZE 16
struct bpf_sk_storage {
struct bpf_sk_storage_data __rcu *cache[BPF_SK_STORAGE_CACHE_SIZE];
struct hlist_head list; /* List of bpf_sk_storage_elem */
struct sock *sk; /* The sk that owns the the above "list" of
* bpf_sk_storage_elem.
*/
struct rcu_head rcu;
raw_spinlock_t lock; /* Protect adding/removing from the "list" */
};
static struct bucket *select_bucket(struct bpf_sk_storage_map *smap,
struct bpf_sk_storage_elem *selem)
{
return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
}
static int omem_charge(struct sock *sk, unsigned int size)
{
/* same check as in sock_kmalloc() */
if (size <= sysctl_optmem_max &&
atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
atomic_add(size, &sk->sk_omem_alloc);
return 0;
}
return -ENOMEM;
}
static bool selem_linked_to_sk(const struct bpf_sk_storage_elem *selem)
{
return !hlist_unhashed(&selem->snode);
}
static bool selem_linked_to_map(const struct bpf_sk_storage_elem *selem)
{
return !hlist_unhashed(&selem->map_node);
}
static struct bpf_sk_storage_elem *selem_alloc(struct bpf_sk_storage_map *smap,
struct sock *sk, void *value,
bool charge_omem)
{
struct bpf_sk_storage_elem *selem;
if (charge_omem && omem_charge(sk, smap->elem_size))
return NULL;
selem = kzalloc(smap->elem_size, GFP_ATOMIC | __GFP_NOWARN);
if (selem) {
if (value)
memcpy(SDATA(selem)->data, value, smap->map.value_size);
return selem;
}
if (charge_omem)
atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
return NULL;
}
/* sk_storage->lock must be held and selem->sk_storage == sk_storage.
* The caller must ensure selem->smap is still valid to be
* dereferenced for its smap->elem_size and smap->cache_idx.
*/
static bool __selem_unlink_sk(struct bpf_sk_storage *sk_storage,
struct bpf_sk_storage_elem *selem,
bool uncharge_omem)
{
struct bpf_sk_storage_map *smap;
bool free_sk_storage;
struct sock *sk;
smap = rcu_dereference(SDATA(selem)->smap);
sk = sk_storage->sk;
/* All uncharging on sk->sk_omem_alloc must be done first.
* sk may be freed once the last selem is unlinked from sk_storage.
*/
if (uncharge_omem)
atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
free_sk_storage = hlist_is_singular_node(&selem->snode,
&sk_storage->list);
if (free_sk_storage) {
atomic_sub(sizeof(struct bpf_sk_storage), &sk->sk_omem_alloc);
sk_storage->sk = NULL;
/* After this RCU_INIT, sk may be freed and cannot be used */
RCU_INIT_POINTER(sk->sk_bpf_storage, NULL);
/* sk_storage is not freed now. sk_storage->lock is
* still held and raw_spin_unlock_bh(&sk_storage->lock)
* will be done by the caller.
*
* Although the unlock will be done under
* rcu_read_lock(), it is more intutivie to
* read if kfree_rcu(sk_storage, rcu) is done
* after the raw_spin_unlock_bh(&sk_storage->lock).
*
* Hence, a "bool free_sk_storage" is returned
* to the caller which then calls the kfree_rcu()
* after unlock.
*/
}
hlist_del_init_rcu(&selem->snode);
if (rcu_access_pointer(sk_storage->cache[smap->cache_idx]) ==
SDATA(selem))
RCU_INIT_POINTER(sk_storage->cache[smap->cache_idx], NULL);
kfree_rcu(selem, rcu);
return free_sk_storage;
}
static void selem_unlink_sk(struct bpf_sk_storage_elem *selem)
{
struct bpf_sk_storage *sk_storage;
bool free_sk_storage = false;
if (unlikely(!selem_linked_to_sk(selem)))
/* selem has already been unlinked from sk */
return;
sk_storage = rcu_dereference(selem->sk_storage);
raw_spin_lock_bh(&sk_storage->lock);
if (likely(selem_linked_to_sk(selem)))
free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
raw_spin_unlock_bh(&sk_storage->lock);
if (free_sk_storage)
kfree_rcu(sk_storage, rcu);
}
static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
struct bpf_sk_storage_elem *selem)
{
RCU_INIT_POINTER(selem->sk_storage, sk_storage);
hlist_add_head(&selem->snode, &sk_storage->list);
}
static void selem_unlink_map(struct bpf_sk_storage_elem *selem)
{
struct bpf_sk_storage_map *smap;
struct bucket *b;
if (unlikely(!selem_linked_to_map(selem)))
/* selem has already be unlinked from smap */
return;
smap = rcu_dereference(SDATA(selem)->smap);
b = select_bucket(smap, selem);
raw_spin_lock_bh(&b->lock);
if (likely(selem_linked_to_map(selem)))
hlist_del_init_rcu(&selem->map_node);
raw_spin_unlock_bh(&b->lock);
}
static void selem_link_map(struct bpf_sk_storage_map *smap,
struct bpf_sk_storage_elem *selem)
{
struct bucket *b = select_bucket(smap, selem);
raw_spin_lock_bh(&b->lock);
RCU_INIT_POINTER(SDATA(selem)->smap, smap);
hlist_add_head_rcu(&selem->map_node, &b->list);
raw_spin_unlock_bh(&b->lock);
}
static void selem_unlink(struct bpf_sk_storage_elem *selem)
{
/* Always unlink from map before unlinking from sk_storage
* because selem will be freed after successfully unlinked from
* the sk_storage.
*/
selem_unlink_map(selem);
selem_unlink_sk(selem);
}
static struct bpf_sk_storage_data *
__sk_storage_lookup(struct bpf_sk_storage *sk_storage,
struct bpf_sk_storage_map *smap,
bool cacheit_lockit)
{
struct bpf_sk_storage_data *sdata;
struct bpf_sk_storage_elem *selem;
/* Fast path (cache hit) */
sdata = rcu_dereference(sk_storage->cache[smap->cache_idx]);
if (sdata && rcu_access_pointer(sdata->smap) == smap)
return sdata;
/* Slow path (cache miss) */
hlist_for_each_entry_rcu(selem, &sk_storage->list, snode)
if (rcu_access_pointer(SDATA(selem)->smap) == smap)
break;
if (!selem)
return NULL;
sdata = SDATA(selem);
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 __sk_storage_lookup().
*/
raw_spin_lock_bh(&sk_storage->lock);
if (selem_linked_to_sk(selem))
rcu_assign_pointer(sk_storage->cache[smap->cache_idx],
sdata);
raw_spin_unlock_bh(&sk_storage->lock);
}
return sdata;
}
static struct bpf_sk_storage_data *
sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit)
{
struct bpf_sk_storage *sk_storage;
struct bpf_sk_storage_map *smap;
sk_storage = rcu_dereference(sk->sk_bpf_storage);
if (!sk_storage)
return NULL;
smap = (struct bpf_sk_storage_map *)map;
return __sk_storage_lookup(sk_storage, smap, cacheit_lockit);
}
static int check_flags(const struct bpf_sk_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;
}
static int sk_storage_alloc(struct sock *sk,
struct bpf_sk_storage_map *smap,
struct bpf_sk_storage_elem *first_selem)
{
struct bpf_sk_storage *prev_sk_storage, *sk_storage;
int err;
err = omem_charge(sk, sizeof(*sk_storage));
if (err)
return err;
sk_storage = kzalloc(sizeof(*sk_storage), GFP_ATOMIC | __GFP_NOWARN);
if (!sk_storage) {
err = -ENOMEM;
goto uncharge;
}
INIT_HLIST_HEAD(&sk_storage->list);
raw_spin_lock_init(&sk_storage->lock);
sk_storage->sk = sk;
__selem_link_sk(sk_storage, first_selem);
selem_link_map(smap, first_selem);
/* Publish sk_storage to sk. sk->sk_lock cannot be acquired.
* Hence, atomic ops is used to set sk->sk_bpf_storage
* from NULL to the newly allocated sk_storage ptr.
*
* From now on, the sk->sk_bpf_storage pointer is protected
* by the sk_storage->lock. Hence, when freeing
* the sk->sk_bpf_storage, the sk_storage->lock must
* be held before setting sk->sk_bpf_storage to NULL.
*/
prev_sk_storage = cmpxchg((struct bpf_sk_storage **)&sk->sk_bpf_storage,
NULL, sk_storage);
if (unlikely(prev_sk_storage)) {
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_sk_storage_map_free() does a
* synchronize_rcu() before walking the bucket->list.
* Hence, no one is accessing selem from the
* bucket->list under rcu_read_lock().
*/
}
return 0;
uncharge:
kfree(sk_storage);
atomic_sub(sizeof(*sk_storage), &sk->sk_omem_alloc);
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).
*/
static struct bpf_sk_storage_data *sk_storage_update(struct sock *sk,
struct bpf_map *map,
void *value,
u64 map_flags)
{
struct bpf_sk_storage_data *old_sdata = NULL;
struct bpf_sk_storage_elem *selem;
struct bpf_sk_storage *sk_storage;
struct bpf_sk_storage_map *smap;
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(map)))
return ERR_PTR(-EINVAL);
smap = (struct bpf_sk_storage_map *)map;
sk_storage = rcu_dereference(sk->sk_bpf_storage);
if (!sk_storage || hlist_empty(&sk_storage->list)) {
/* Very first elem for this sk */
err = check_flags(NULL, map_flags);
if (err)
return ERR_PTR(err);
selem = selem_alloc(smap, sk, value, true);
if (!selem)
return ERR_PTR(-ENOMEM);
err = sk_storage_alloc(sk, smap, selem);
if (err) {
kfree(selem);
atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
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 sk_storage->lock
* and changing the lists.
*/
old_sdata = __sk_storage_lookup(sk_storage, smap, false);
err = check_flags(old_sdata, map_flags);
if (err)
return ERR_PTR(err);
if (old_sdata && selem_linked_to_sk(SELEM(old_sdata))) {
copy_map_value_locked(map, old_sdata->data,
value, false);
return old_sdata;
}
}
raw_spin_lock_bh(&sk_storage->lock);
/* Recheck sk_storage->list under sk_storage->lock */
if (unlikely(hlist_empty(&sk_storage->list))) {
/* A parallel del is happening and sk_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 = __sk_storage_lookup(sk_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(map, old_sdata->data, value, false);
selem = SELEM(old_sdata);
goto unlock;
}
/* sk_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 __selem_unlink_sk().
*/
selem = selem_alloc(smap, sk, value, !old_sdata);
if (!selem) {
err = -ENOMEM;
goto unlock_err;
}
/* First, link the new selem to the map */
selem_link_map(smap, selem);
/* Second, link (and publish) the new selem to sk_storage */
__selem_link_sk(sk_storage, selem);
/* Third, remove old selem, SELEM(old_sdata) */
if (old_sdata) {
selem_unlink_map(SELEM(old_sdata));
__selem_unlink_sk(sk_storage, SELEM(old_sdata), false);
}
unlock:
raw_spin_unlock_bh(&sk_storage->lock);
return SDATA(selem);
unlock_err:
raw_spin_unlock_bh(&sk_storage->lock);
return ERR_PTR(err);
}
static int sk_storage_delete(struct sock *sk, struct bpf_map *map)
{
struct bpf_sk_storage_data *sdata;
sdata = sk_storage_lookup(sk, map, false);
if (!sdata)
return -ENOENT;
selem_unlink(SELEM(sdata));
return 0;
}
/* Called by __sk_destruct() & bpf_sk_storage_clone() */
void bpf_sk_storage_free(struct sock *sk)
{
struct bpf_sk_storage_elem *selem;
struct bpf_sk_storage *sk_storage;
bool free_sk_storage = false;
struct hlist_node *n;
rcu_read_lock();
sk_storage = rcu_dereference(sk->sk_bpf_storage);
if (!sk_storage) {
rcu_read_unlock();
return;
}
/* Netiher the bpf_prog nor the bpf-map's syscall
* could be modifying the sk_storage->list now.
* Thus, no elem can be added-to or deleted-from the
* sk_storage->list by the bpf_prog or by the bpf-map's syscall.
*
* It is racing with bpf_sk_storage_map_free() alone
* when unlinking elem from the sk_storage->list and
* the map's bucket->list.
*/
raw_spin_lock_bh(&sk_storage->lock);
hlist_for_each_entry_safe(selem, n, &sk_storage->list, snode) {
/* Always unlink from map before unlinking from
* sk_storage.
*/
selem_unlink_map(selem);
free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
}
raw_spin_unlock_bh(&sk_storage->lock);
rcu_read_unlock();
if (free_sk_storage)
kfree_rcu(sk_storage, rcu);
}
static void bpf_sk_storage_map_free(struct bpf_map *map)
{
struct bpf_sk_storage_elem *selem;
struct bpf_sk_storage_map *smap;
struct bucket *b;
unsigned int i;
smap = (struct bpf_sk_storage_map *)map;
/* 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 sk->sk_bpf_storage or to the map bucket's list.
*
* The elem of this map can be cleaned up here
* or
* 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_sk_storage_elem,
map_node))) {
selem_unlink(selem);
cond_resched_rcu();
}
rcu_read_unlock();
}
/* bpf_sk_storage_free() may still need to access the map.
* e.g. bpf_sk_storage_free() has unlinked selem from the map
* which then made the above while((selem = ...)) loop
* exited immediately.
*
* However, the bpf_sk_storage_free() still needs to access
* the smap->elem_size to do the uncharging in
* __selem_unlink_sk().
*
* Hence, wait another rcu grace period for the
* bpf_sk_storage_free() to finish.
*/
synchronize_rcu();
kvfree(smap->buckets);
kfree(map);
}
static int bpf_sk_storage_map_alloc_check(union bpf_attr *attr)
{
if (attr->map_flags & ~SK_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 (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (attr->value_size >= KMALLOC_MAX_SIZE -
MAX_BPF_STACK - sizeof(struct bpf_sk_storage_elem) ||
/* U16_MAX is much more than enough for sk local storage
* considering a tcp_sock is ~2k.
*/
attr->value_size > U16_MAX - sizeof(struct bpf_sk_storage_elem))
return -E2BIG;
return 0;
}
static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr)
{
struct bpf_sk_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);
/* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
smap->bucket_log = max_t(u32, 1, ilog2(roundup_pow_of_two(num_possible_cpus())));
nbuckets = 1U << smap->bucket_log;
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_sk_storage_elem) + attr->value_size;
smap->cache_idx = (unsigned int)atomic_inc_return(&cache_idx) %
BPF_SK_STORAGE_CACHE_SIZE;
return &smap->map;
}
static int notsupp_get_next_key(struct bpf_map *map, void *key,
void *next_key)
{
return -ENOTSUPP;
}
static int bpf_sk_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;
}
static void *bpf_fd_sk_storage_lookup_elem(struct bpf_map *map, void *key)
{
struct bpf_sk_storage_data *sdata;
struct socket *sock;
int fd, err;
fd = *(int *)key;
sock = sockfd_lookup(fd, &err);
if (sock) {
sdata = sk_storage_lookup(sock->sk, map, true);
sockfd_put(sock);
return sdata ? sdata->data : NULL;
}
return ERR_PTR(err);
}
static int bpf_fd_sk_storage_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags)
{
struct bpf_sk_storage_data *sdata;
struct socket *sock;
int fd, err;
fd = *(int *)key;
sock = sockfd_lookup(fd, &err);
if (sock) {
sdata = sk_storage_update(sock->sk, map, value, map_flags);
sockfd_put(sock);
return PTR_ERR_OR_ZERO(sdata);
}
return err;
}
static int bpf_fd_sk_storage_delete_elem(struct bpf_map *map, void *key)
{
struct socket *sock;
int fd, err;
fd = *(int *)key;
sock = sockfd_lookup(fd, &err);
if (sock) {
err = sk_storage_delete(sock->sk, map);
sockfd_put(sock);
return err;
}
return err;
}
static struct bpf_sk_storage_elem *
bpf_sk_storage_clone_elem(struct sock *newsk,
struct bpf_sk_storage_map *smap,
struct bpf_sk_storage_elem *selem)
{
struct bpf_sk_storage_elem *copy_selem;
copy_selem = selem_alloc(smap, newsk, NULL, true);
if (!copy_selem)
return NULL;
if (map_value_has_spin_lock(&smap->map))
copy_map_value_locked(&smap->map, SDATA(copy_selem)->data,
SDATA(selem)->data, true);
else
copy_map_value(&smap->map, SDATA(copy_selem)->data,
SDATA(selem)->data);
return copy_selem;
}
int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
{
struct bpf_sk_storage *new_sk_storage = NULL;
struct bpf_sk_storage *sk_storage;
struct bpf_sk_storage_elem *selem;
int ret = 0;
RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
rcu_read_lock();
sk_storage = rcu_dereference(sk->sk_bpf_storage);
if (!sk_storage || hlist_empty(&sk_storage->list))
goto out;
hlist_for_each_entry_rcu(selem, &sk_storage->list, snode) {
struct bpf_sk_storage_elem *copy_selem;
struct bpf_sk_storage_map *smap;
struct bpf_map *map;
smap = rcu_dereference(SDATA(selem)->smap);
if (!(smap->map.map_flags & BPF_F_CLONE))
continue;
/* Note that for lockless listeners adding new element
* here can race with cleanup in bpf_sk_storage_map_free.
* Try to grab map refcnt to make sure that it's still
* alive and prevent concurrent removal.
*/
map = bpf_map_inc_not_zero(&smap->map);
if (IS_ERR(map))
continue;
copy_selem = bpf_sk_storage_clone_elem(newsk, smap, selem);
if (!copy_selem) {
ret = -ENOMEM;
bpf_map_put(map);
goto out;
}
if (new_sk_storage) {
selem_link_map(smap, copy_selem);
__selem_link_sk(new_sk_storage, copy_selem);
} else {
ret = sk_storage_alloc(newsk, smap, copy_selem);
if (ret) {
kfree(copy_selem);
atomic_sub(smap->elem_size,
&newsk->sk_omem_alloc);
bpf_map_put(map);
goto out;
}
new_sk_storage = rcu_dereference(copy_selem->sk_storage);
}
bpf_map_put(map);
}
out:
rcu_read_unlock();
/* In case of an error, don't free anything explicitly here, the
* caller is responsible to call bpf_sk_storage_free.
*/
return ret;
}
BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags)
{
struct bpf_sk_storage_data *sdata;
if (flags > BPF_SK_STORAGE_GET_F_CREATE)
return (unsigned long)NULL;
sdata = sk_storage_lookup(sk, map, true);
if (sdata)
return (unsigned long)sdata->data;
if (flags == BPF_SK_STORAGE_GET_F_CREATE &&
/* Cannot add new elem to a going away sk.
* Otherwise, the new elem may become a leak
* (and also other memory issues during map
* destruction).
*/
refcount_inc_not_zero(&sk->sk_refcnt)) {
sdata = sk_storage_update(sk, map, value, BPF_NOEXIST);
/* sk must be a fullsock (guaranteed by verifier),
* so sock_gen_put() is unnecessary.
*/
sock_put(sk);
return IS_ERR(sdata) ?
(unsigned long)NULL : (unsigned long)sdata->data;
}
return (unsigned long)NULL;
}
BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
{
if (refcount_inc_not_zero(&sk->sk_refcnt)) {
int err;
err = sk_storage_delete(sk, map);
sock_put(sk);
return err;
}
return -ENOENT;
}
const struct bpf_map_ops sk_storage_map_ops = {
.map_alloc_check = bpf_sk_storage_map_alloc_check,
.map_alloc = bpf_sk_storage_map_alloc,
.map_free = bpf_sk_storage_map_free,
.map_get_next_key = notsupp_get_next_key,
.map_lookup_elem = bpf_fd_sk_storage_lookup_elem,
.map_update_elem = bpf_fd_sk_storage_update_elem,
.map_delete_elem = bpf_fd_sk_storage_delete_elem,
.map_check_btf = bpf_sk_storage_map_check_btf,
};
const struct bpf_func_proto bpf_sk_storage_get_proto = {
.func = bpf_sk_storage_get,
.gpl_only = false,
.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_SOCKET,
.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
.arg4_type = ARG_ANYTHING,
};
const struct bpf_func_proto bpf_sk_storage_delete_proto = {
.func = bpf_sk_storage_delete,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_SOCKET,
};