// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2018 Facebook
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*/
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#include <linux/bpf.h>
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#include <linux/err.h>
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#include <linux/sock_diag.h>
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#include <net/sock_reuseport.h>
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struct reuseport_array {
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struct bpf_map map;
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struct sock __rcu *ptrs[];
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};
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static struct reuseport_array *reuseport_array(struct bpf_map *map)
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{
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return (struct reuseport_array *)map;
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}
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/* The caller must hold the reuseport_lock */
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void bpf_sk_reuseport_detach(struct sock *sk)
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{
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uintptr_t sk_user_data;
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write_lock_bh(&sk->sk_callback_lock);
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sk_user_data = (uintptr_t)sk->sk_user_data;
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if (sk_user_data & SK_USER_DATA_BPF) {
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struct sock __rcu **socks;
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socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
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WRITE_ONCE(sk->sk_user_data, NULL);
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/*
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* Do not move this NULL assignment outside of
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* sk->sk_callback_lock because there is
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* a race with reuseport_array_free()
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* which does not hold the reuseport_lock.
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*/
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RCU_INIT_POINTER(*socks, NULL);
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}
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write_unlock_bh(&sk->sk_callback_lock);
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}
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static int reuseport_array_alloc_check(union bpf_attr *attr)
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{
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if (attr->value_size != sizeof(u32) &&
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attr->value_size != sizeof(u64))
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return -EINVAL;
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return array_map_alloc_check(attr);
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}
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static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
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{
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struct reuseport_array *array = reuseport_array(map);
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u32 index = *(u32 *)key;
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if (unlikely(index >= array->map.max_entries))
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return NULL;
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return rcu_dereference(array->ptrs[index]);
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}
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/* Called from syscall only */
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static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
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{
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struct reuseport_array *array = reuseport_array(map);
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u32 index = *(u32 *)key;
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struct sock *sk;
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int err;
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if (index >= map->max_entries)
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return -E2BIG;
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if (!rcu_access_pointer(array->ptrs[index]))
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return -ENOENT;
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spin_lock_bh(&reuseport_lock);
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sk = rcu_dereference_protected(array->ptrs[index],
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lockdep_is_held(&reuseport_lock));
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if (sk) {
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write_lock_bh(&sk->sk_callback_lock);
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WRITE_ONCE(sk->sk_user_data, NULL);
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RCU_INIT_POINTER(array->ptrs[index], NULL);
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write_unlock_bh(&sk->sk_callback_lock);
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err = 0;
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} else {
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err = -ENOENT;
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}
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spin_unlock_bh(&reuseport_lock);
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return err;
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}
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static void reuseport_array_free(struct bpf_map *map)
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{
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struct reuseport_array *array = reuseport_array(map);
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struct sock *sk;
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u32 i;
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/*
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* ops->map_*_elem() will not be able to access this
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* array now. Hence, this function only races with
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* bpf_sk_reuseport_detach() which was triggerred by
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* close() or disconnect().
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*
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* This function and bpf_sk_reuseport_detach() are
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* both removing sk from "array". Who removes it
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* first does not matter.
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*
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* The only concern here is bpf_sk_reuseport_detach()
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* may access "array" which is being freed here.
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* bpf_sk_reuseport_detach() access this "array"
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* through sk->sk_user_data _and_ with sk->sk_callback_lock
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* held which is enough because this "array" is not freed
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* until all sk->sk_user_data has stopped referencing this "array".
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*
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* Hence, due to the above, taking "reuseport_lock" is not
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* needed here.
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*/
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/*
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* Since reuseport_lock is not taken, sk is accessed under
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* rcu_read_lock()
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*/
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rcu_read_lock();
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for (i = 0; i < map->max_entries; i++) {
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sk = rcu_dereference(array->ptrs[i]);
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if (sk) {
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write_lock_bh(&sk->sk_callback_lock);
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/*
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* No need for WRITE_ONCE(). At this point,
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* no one is reading it without taking the
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* sk->sk_callback_lock.
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*/
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sk->sk_user_data = NULL;
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write_unlock_bh(&sk->sk_callback_lock);
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RCU_INIT_POINTER(array->ptrs[i], NULL);
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}
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}
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rcu_read_unlock();
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/*
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* Once reaching here, all sk->sk_user_data is not
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* referenceing this "array". "array" can be freed now.
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*/
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bpf_map_area_free(array);
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}
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static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
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{
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int err, numa_node = bpf_map_attr_numa_node(attr);
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struct reuseport_array *array;
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struct bpf_map_memory mem;
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u64 array_size;
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if (!bpf_capable())
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return ERR_PTR(-EPERM);
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array_size = sizeof(*array);
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array_size += (u64)attr->max_entries * sizeof(struct sock *);
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err = bpf_map_charge_init(&mem, array_size);
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if (err)
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return ERR_PTR(err);
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/* allocate all map elements and zero-initialize them */
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array = bpf_map_area_alloc(array_size, numa_node);
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if (!array) {
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bpf_map_charge_finish(&mem);
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return ERR_PTR(-ENOMEM);
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}
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/* copy mandatory map attributes */
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bpf_map_init_from_attr(&array->map, attr);
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bpf_map_charge_move(&array->map.memory, &mem);
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return &array->map;
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}
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int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
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void *value)
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{
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struct sock *sk;
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int err;
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if (map->value_size != sizeof(u64))
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return -ENOSPC;
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rcu_read_lock();
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sk = reuseport_array_lookup_elem(map, key);
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if (sk) {
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*(u64 *)value = __sock_gen_cookie(sk);
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err = 0;
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} else {
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err = -ENOENT;
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}
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rcu_read_unlock();
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return err;
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}
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static int
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reuseport_array_update_check(const struct reuseport_array *array,
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const struct sock *nsk,
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const struct sock *osk,
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const struct sock_reuseport *nsk_reuse,
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u32 map_flags)
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{
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if (osk && map_flags == BPF_NOEXIST)
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return -EEXIST;
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if (!osk && map_flags == BPF_EXIST)
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return -ENOENT;
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if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
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return -ENOTSUPP;
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if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
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return -ENOTSUPP;
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if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
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return -ENOTSUPP;
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/*
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* sk must be hashed (i.e. listening in the TCP case or binded
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* in the UDP case) and
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* it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
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*
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* Also, sk will be used in bpf helper that is protected by
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* rcu_read_lock().
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*/
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if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
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return -EINVAL;
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/* READ_ONCE because the sk->sk_callback_lock may not be held here */
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if (READ_ONCE(nsk->sk_user_data))
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return -EBUSY;
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return 0;
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}
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/*
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* Called from syscall only.
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* The "nsk" in the fd refcnt.
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* The "osk" and "reuse" are protected by reuseport_lock.
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*/
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int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
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void *value, u64 map_flags)
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{
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struct reuseport_array *array = reuseport_array(map);
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struct sock *free_osk = NULL, *osk, *nsk;
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struct sock_reuseport *reuse;
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u32 index = *(u32 *)key;
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uintptr_t sk_user_data;
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struct socket *socket;
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int err, fd;
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if (map_flags > BPF_EXIST)
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return -EINVAL;
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if (index >= map->max_entries)
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return -E2BIG;
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if (map->value_size == sizeof(u64)) {
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u64 fd64 = *(u64 *)value;
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if (fd64 > S32_MAX)
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return -EINVAL;
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fd = fd64;
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} else {
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fd = *(int *)value;
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}
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socket = sockfd_lookup(fd, &err);
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if (!socket)
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return err;
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nsk = socket->sk;
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if (!nsk) {
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err = -EINVAL;
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goto put_file;
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}
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/* Quick checks before taking reuseport_lock */
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err = reuseport_array_update_check(array, nsk,
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rcu_access_pointer(array->ptrs[index]),
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rcu_access_pointer(nsk->sk_reuseport_cb),
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map_flags);
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if (err)
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goto put_file;
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spin_lock_bh(&reuseport_lock);
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/*
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* Some of the checks only need reuseport_lock
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* but it is done under sk_callback_lock also
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* for simplicity reason.
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*/
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write_lock_bh(&nsk->sk_callback_lock);
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osk = rcu_dereference_protected(array->ptrs[index],
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lockdep_is_held(&reuseport_lock));
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reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
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if (err)
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goto put_file_unlock;
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sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
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SK_USER_DATA_BPF;
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WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
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rcu_assign_pointer(array->ptrs[index], nsk);
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free_osk = osk;
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err = 0;
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put_file_unlock:
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write_unlock_bh(&nsk->sk_callback_lock);
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if (free_osk) {
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write_lock_bh(&free_osk->sk_callback_lock);
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WRITE_ONCE(free_osk->sk_user_data, NULL);
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write_unlock_bh(&free_osk->sk_callback_lock);
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}
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spin_unlock_bh(&reuseport_lock);
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put_file:
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fput(socket->file);
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return err;
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}
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/* Called from syscall */
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static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
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void *next_key)
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{
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struct reuseport_array *array = reuseport_array(map);
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u32 index = key ? *(u32 *)key : U32_MAX;
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u32 *next = (u32 *)next_key;
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if (index >= array->map.max_entries) {
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*next = 0;
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return 0;
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}
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if (index == array->map.max_entries - 1)
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return -ENOENT;
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*next = index + 1;
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return 0;
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}
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static int reuseport_array_map_btf_id;
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const struct bpf_map_ops reuseport_array_ops = {
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.map_meta_equal = bpf_map_meta_equal,
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.map_alloc_check = reuseport_array_alloc_check,
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.map_alloc = reuseport_array_alloc,
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.map_free = reuseport_array_free,
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.map_lookup_elem = reuseport_array_lookup_elem,
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.map_get_next_key = reuseport_array_get_next_key,
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.map_delete_elem = reuseport_array_delete_elem,
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.map_btf_name = "reuseport_array",
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.map_btf_id = &reuseport_array_map_btf_id,
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};
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