kernel/bpf/reuseport_array.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2018 Facebook
  */
 #include <linux/bpf.h>
 #include <linux/err.h>
 #include <linux/sock_diag.h>
 #include <net/sock_reuseport.h>

 struct reuseport_array {
 	struct bpf_map map;
 	struct sock __rcu *ptrs[];
 };

 static struct reuseport_array *reuseport_array(struct bpf_map *map)
 {
 	return (struct reuseport_array *)map;
 }

 /* The caller must hold the reuseport_lock */
 void bpf_sk_reuseport_detach(struct sock *sk)
 {
 	struct sock __rcu **socks;

 	write_lock_bh(&sk->sk_callback_lock);
 	socks = sk->sk_user_data;
 	if (socks) {
 		WRITE_ONCE(sk->sk_user_data, NULL);
 		/*
 		 * Do not move this NULL assignment outside of
 		 * sk->sk_callback_lock because there is
 		 * a race with reuseport_array_free()
 		 * which does not hold the reuseport_lock.
 		 */
 		RCU_INIT_POINTER(*socks, NULL);
 	}
 	write_unlock_bh(&sk->sk_callback_lock);
 }

 static int reuseport_array_alloc_check(union bpf_attr *attr)
 {
 	if (attr->value_size != sizeof(u32) &&
 	    attr->value_size != sizeof(u64))
 		return -EINVAL;

 	return array_map_alloc_check(attr);
 }

 static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct reuseport_array *array = reuseport_array(map);
 	u32 index = *(u32 *)key;

 	if (unlikely(index >= array->map.max_entries))
 		return NULL;

 	return rcu_dereference(array->ptrs[index]);
 }

 /* Called from syscall only */
 static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
 {
 	struct reuseport_array *array = reuseport_array(map);
 	u32 index = *(u32 *)key;
 	struct sock *sk;
 	int err;

 	if (index >= map->max_entries)
 		return -E2BIG;

 	if (!rcu_access_pointer(array->ptrs[index]))
 		return -ENOENT;

 	spin_lock_bh(&reuseport_lock);

 	sk = rcu_dereference_protected(array->ptrs[index],
 				       lockdep_is_held(&reuseport_lock));
 	if (sk) {
 		write_lock_bh(&sk->sk_callback_lock);
 		WRITE_ONCE(sk->sk_user_data, NULL);
 		RCU_INIT_POINTER(array->ptrs[index], NULL);
 		write_unlock_bh(&sk->sk_callback_lock);
 		err = 0;
 	} else {
 		err = -ENOENT;
 	}

 	spin_unlock_bh(&reuseport_lock);

 	return err;
 }

 static void reuseport_array_free(struct bpf_map *map)
 {
 	struct reuseport_array *array = reuseport_array(map);
 	struct sock *sk;
 	u32 i;

 	synchronize_rcu();

 	/*
 	 * ops->map_*_elem() will not be able to access this
 	 * array now. Hence, this function only races with
 	 * bpf_sk_reuseport_detach() which was triggerred by
 	 * close() or disconnect().
 	 *
 	 * This function and bpf_sk_reuseport_detach() are
 	 * both removing sk from "array".  Who removes it
 	 * first does not matter.
 	 *
 	 * The only concern here is bpf_sk_reuseport_detach()
 	 * may access "array" which is being freed here.
 	 * bpf_sk_reuseport_detach() access this "array"
 	 * through sk->sk_user_data _and_ with sk->sk_callback_lock
 	 * held which is enough because this "array" is not freed
 	 * until all sk->sk_user_data has stopped referencing this "array".
 	 *
 	 * Hence, due to the above, taking "reuseport_lock" is not
 	 * needed here.
 	 */

 	/*
 	 * Since reuseport_lock is not taken, sk is accessed under
 	 * rcu_read_lock()
 	 */
 	rcu_read_lock();
 	for (i = 0; i < map->max_entries; i++) {
 		sk = rcu_dereference(array->ptrs[i]);
 		if (sk) {
 			write_lock_bh(&sk->sk_callback_lock);
 			/*
 			 * No need for WRITE_ONCE(). At this point,
 			 * no one is reading it without taking the
 			 * sk->sk_callback_lock.
 			 */
 			sk->sk_user_data = NULL;
 			write_unlock_bh(&sk->sk_callback_lock);
 			RCU_INIT_POINTER(array->ptrs[i], NULL);
 		}
 	}
 	rcu_read_unlock();

 	/*
 	 * Once reaching here, all sk->sk_user_data is not
 	 * referenceing this "array".  "array" can be freed now.
 	 */
 	bpf_map_area_free(array);
 }

 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
 {
 	int err, numa_node = bpf_map_attr_numa_node(attr);
 	struct reuseport_array *array;
 	struct bpf_map_memory mem;
 	u64 array_size;

 	if (!bpf_capable())
 		return ERR_PTR(-EPERM);

 	array_size = sizeof(*array);
 	array_size += (u64)attr->max_entries * sizeof(struct sock *);

 	err = bpf_map_charge_init(&mem, array_size);
 	if (err)
 		return ERR_PTR(err);

 	/* allocate all map elements and zero-initialize them */
 	array = bpf_map_area_alloc(array_size, numa_node);
 	if (!array) {
 		bpf_map_charge_finish(&mem);
 		return ERR_PTR(-ENOMEM);
 	}

 	/* copy mandatory map attributes */
 	bpf_map_init_from_attr(&array->map, attr);
 	bpf_map_charge_move(&array->map.memory, &mem);

 	return &array->map;
 }

 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
 				       void *value)
 {
 	struct sock *sk;
 	int err;

 	if (map->value_size != sizeof(u64))
 		return -ENOSPC;

 	rcu_read_lock();
 	sk = reuseport_array_lookup_elem(map, key);
 	if (sk) {
 		*(u64 *)value = sock_gen_cookie(sk);
 		err = 0;
 	} else {
 		err = -ENOENT;
 	}
 	rcu_read_unlock();

 	return err;
 }

 static int
 reuseport_array_update_check(const struct reuseport_array *array,
 			     const struct sock *nsk,
 			     const struct sock *osk,
 			     const struct sock_reuseport *nsk_reuse,
 			     u32 map_flags)
 {
 	if (osk && map_flags == BPF_NOEXIST)
 		return -EEXIST;

 	if (!osk && map_flags == BPF_EXIST)
 		return -ENOENT;

 	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
 		return -ENOTSUPP;

 	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
 		return -ENOTSUPP;

 	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
 		return -ENOTSUPP;

 	/*
 	 * sk must be hashed (i.e. listening in the TCP case or binded
 	 * in the UDP case) and
 	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
 	 *
 	 * Also, sk will be used in bpf helper that is protected by
 	 * rcu_read_lock().
 	 */
 	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
 		return -EINVAL;

 	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
 	if (READ_ONCE(nsk->sk_user_data))
 		return -EBUSY;

 	return 0;
 }

 /*
  * Called from syscall only.
  * The "nsk" in the fd refcnt.
  * The "osk" and "reuse" are protected by reuseport_lock.
  */
 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
 				       void *value, u64 map_flags)
 {
 	struct reuseport_array *array = reuseport_array(map);
 	struct sock *free_osk = NULL, *osk, *nsk;
 	struct sock_reuseport *reuse;
 	u32 index = *(u32 *)key;
 	struct socket *socket;
 	int err, fd;

 	if (map_flags > BPF_EXIST)
 		return -EINVAL;

 	if (index >= map->max_entries)
 		return -E2BIG;

 	if (map->value_size == sizeof(u64)) {
 		u64 fd64 = *(u64 *)value;

 		if (fd64 > S32_MAX)
 			return -EINVAL;
 		fd = fd64;
 	} else {
 		fd = *(int *)value;
 	}

 	socket = sockfd_lookup(fd, &err);
 	if (!socket)
 		return err;

 	nsk = socket->sk;
 	if (!nsk) {
 		err = -EINVAL;
 		goto put_file;
 	}

 	/* Quick checks before taking reuseport_lock */
 	err = reuseport_array_update_check(array, nsk,
 					   rcu_access_pointer(array->ptrs[index]),
 					   rcu_access_pointer(nsk->sk_reuseport_cb),
 					   map_flags);
 	if (err)
 		goto put_file;

 	spin_lock_bh(&reuseport_lock);
 	/*
 	 * Some of the checks only need reuseport_lock
 	 * but it is done under sk_callback_lock also
 	 * for simplicity reason.
 	 */
 	write_lock_bh(&nsk->sk_callback_lock);

 	osk = rcu_dereference_protected(array->ptrs[index],
 					lockdep_is_held(&reuseport_lock));
 	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
 					  lockdep_is_held(&reuseport_lock));
 	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
 	if (err)
 		goto put_file_unlock;

 	WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
 	rcu_assign_pointer(array->ptrs[index], nsk);
 	free_osk = osk;
 	err = 0;

 put_file_unlock:
 	write_unlock_bh(&nsk->sk_callback_lock);

 	if (free_osk) {
 		write_lock_bh(&free_osk->sk_callback_lock);
 		WRITE_ONCE(free_osk->sk_user_data, NULL);
 		write_unlock_bh(&free_osk->sk_callback_lock);
 	}

 	spin_unlock_bh(&reuseport_lock);
 put_file:
 	fput(socket->file);
 	return err;
 }

 /* Called from syscall */
 static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
 					void *next_key)
 {
 	struct reuseport_array *array = reuseport_array(map);
 	u32 index = key ? *(u32 *)key : U32_MAX;
 	u32 *next = (u32 *)next_key;

 	if (index >= array->map.max_entries) {
 		*next = 0;
 		return 0;
 	}

 	if (index == array->map.max_entries - 1)
 		return -ENOENT;

 	*next = index + 1;
 	return 0;
 }

 const struct bpf_map_ops reuseport_array_ops = {
 	.map_alloc_check = reuseport_array_alloc_check,
 	.map_alloc = reuseport_array_alloc,
 	.map_free = reuseport_array_free,
 	.map_lookup_elem = reuseport_array_lookup_elem,
 	.map_get_next_key = reuseport_array_get_next_key,
 	.map_delete_elem = reuseport_array_delete_elem,
 };
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (c) 2018 Facebook
	*/
	#include <linux/bpf.h>
	#include <linux/err.h>
	#include <linux/sock_diag.h>
	#include <net/sock_reuseport.h>

	struct reuseport_array {
	struct bpf_map map;
	struct sock __rcu *ptrs[];
	};

	static struct reuseport_array reuseport_array(struct bpf_map map)
	{
	return (struct reuseport_array *)map;
	}

	/* The caller must hold the reuseport_lock */
	void bpf_sk_reuseport_detach(struct sock *sk)
	{
	struct sock __rcu **socks;

	write_lock_bh(&sk->sk_callback_lock);
	socks = sk->sk_user_data;
	if (socks) {
	WRITE_ONCE(sk->sk_user_data, NULL);
	/*
	* Do not move this NULL assignment outside of
	* sk->sk_callback_lock because there is
	* a race with reuseport_array_free()
	* which does not hold the reuseport_lock.
	*/
	RCU_INIT_POINTER(*socks, NULL);
	}
	write_unlock_bh(&sk->sk_callback_lock);
	}

	static int reuseport_array_alloc_check(union bpf_attr *attr)
	{
	if (attr->value_size != sizeof(u32) &&
	attr->value_size != sizeof(u64))
	return -EINVAL;

	return array_map_alloc_check(attr);
	}

	static void reuseport_array_lookup_elem(struct bpf_map map, void *key)
	{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = (u32 )key;

	if (unlikely(index >= array->map.max_entries))
	return NULL;

	return rcu_dereference(array->ptrs[index]);
	}

	/* Called from syscall only */
	static int reuseport_array_delete_elem(struct bpf_map map, void key)
	{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = (u32 )key;
	struct sock *sk;
	int err;

	if (index >= map->max_entries)
	return -E2BIG;

	if (!rcu_access_pointer(array->ptrs[index]))
	return -ENOENT;

	spin_lock_bh(&reuseport_lock);

	sk = rcu_dereference_protected(array->ptrs[index],
	lockdep_is_held(&reuseport_lock));
	if (sk) {
	write_lock_bh(&sk->sk_callback_lock);
	WRITE_ONCE(sk->sk_user_data, NULL);
	RCU_INIT_POINTER(array->ptrs[index], NULL);
	write_unlock_bh(&sk->sk_callback_lock);
	err = 0;
	} else {
	err = -ENOENT;
	}

	spin_unlock_bh(&reuseport_lock);

	return err;
	}

	static void reuseport_array_free(struct bpf_map *map)
	{
	struct reuseport_array *array = reuseport_array(map);
	struct sock *sk;
	u32 i;

	synchronize_rcu();

	/*
	* ops->map_*_elem() will not be able to access this
	* array now. Hence, this function only races with
	* bpf_sk_reuseport_detach() which was triggerred by
	* close() or disconnect().
	*
	* This function and bpf_sk_reuseport_detach() are
	* both removing sk from "array". Who removes it
	* first does not matter.
	*
	* The only concern here is bpf_sk_reuseport_detach()
	* may access "array" which is being freed here.
	* bpf_sk_reuseport_detach() access this "array"
	* through sk->sk_user_data _and_ with sk->sk_callback_lock
	* held which is enough because this "array" is not freed
	* until all sk->sk_user_data has stopped referencing this "array".
	*
	* Hence, due to the above, taking "reuseport_lock" is not
	* needed here.
	*/

	/*
	* Since reuseport_lock is not taken, sk is accessed under
	* rcu_read_lock()
	*/
	rcu_read_lock();
	for (i = 0; i < map->max_entries; i++) {
	sk = rcu_dereference(array->ptrs[i]);
	if (sk) {
	write_lock_bh(&sk->sk_callback_lock);
	/*
	* No need for WRITE_ONCE(). At this point,
	* no one is reading it without taking the
	* sk->sk_callback_lock.
	*/
	sk->sk_user_data = NULL;
	write_unlock_bh(&sk->sk_callback_lock);
	RCU_INIT_POINTER(array->ptrs[i], NULL);
	}
	}
	rcu_read_unlock();

	/*
	* Once reaching here, all sk->sk_user_data is not
	* referenceing this "array". "array" can be freed now.
	*/
	bpf_map_area_free(array);
	}

	static struct bpf_map reuseport_array_alloc(union bpf_attr attr)
	{
	int err, numa_node = bpf_map_attr_numa_node(attr);
	struct reuseport_array *array;
	struct bpf_map_memory mem;
	u64 array_size;

	if (!bpf_capable())
	return ERR_PTR(-EPERM);

	array_size = sizeof(*array);
	array_size += (u64)attr->max_entries * sizeof(struct sock *);

	err = bpf_map_charge_init(&mem, array_size);
	if (err)
	return ERR_PTR(err);

	/* allocate all map elements and zero-initialize them */
	array = bpf_map_area_alloc(array_size, numa_node);
	if (!array) {
	bpf_map_charge_finish(&mem);
	return ERR_PTR(-ENOMEM);
	}

	/* copy mandatory map attributes */
	bpf_map_init_from_attr(&array->map, attr);
	bpf_map_charge_move(&array->map.memory, &mem);

	return &array->map;
	}

	int bpf_fd_reuseport_array_lookup_elem(struct bpf_map map, void key,
	void *value)
	{
	struct sock *sk;
	int err;

	if (map->value_size != sizeof(u64))
	return -ENOSPC;

	rcu_read_lock();
	sk = reuseport_array_lookup_elem(map, key);
	if (sk) {
	(u64 )value = sock_gen_cookie(sk);
	err = 0;
	} else {
	err = -ENOENT;
	}
	rcu_read_unlock();

	return err;
	}

	static int
	reuseport_array_update_check(const struct reuseport_array *array,
	const struct sock *nsk,
	const struct sock *osk,
	const struct sock_reuseport *nsk_reuse,
	u32 map_flags)
	{
	if (osk && map_flags == BPF_NOEXIST)
	return -EEXIST;

	if (!osk && map_flags == BPF_EXIST)
	return -ENOENT;

	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
	return -ENOTSUPP;

	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
	return -ENOTSUPP;

	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
	return -ENOTSUPP;

	/*
	* sk must be hashed (i.e. listening in the TCP case or binded
	* in the UDP case) and
	* it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
	*
	* Also, sk will be used in bpf helper that is protected by
	* rcu_read_lock().
	*/
	if (!sock_flag(nsk, SOCK_RCU_FREE) \|\| !sk_hashed(nsk) \|\| !nsk_reuse)
	return -EINVAL;

	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
	if (READ_ONCE(nsk->sk_user_data))
	return -EBUSY;

	return 0;
	}

	/*
	* Called from syscall only.
	* The "nsk" in the fd refcnt.
	* The "osk" and "reuse" are protected by reuseport_lock.
	*/
	int bpf_fd_reuseport_array_update_elem(struct bpf_map map, void key,
	void *value, u64 map_flags)
	{
	struct reuseport_array *array = reuseport_array(map);
	struct sock free_osk = NULL, osk, *nsk;
	struct sock_reuseport *reuse;
	u32 index = (u32 )key;
	struct socket *socket;
	int err, fd;

	if (map_flags > BPF_EXIST)
	return -EINVAL;

	if (index >= map->max_entries)
	return -E2BIG;

	if (map->value_size == sizeof(u64)) {
	u64 fd64 = (u64 )value;

	if (fd64 > S32_MAX)
	return -EINVAL;
	fd = fd64;
	} else {
	fd = (int )value;
	}

	socket = sockfd_lookup(fd, &err);
	if (!socket)
	return err;

	nsk = socket->sk;
	if (!nsk) {
	err = -EINVAL;
	goto put_file;
	}

	/* Quick checks before taking reuseport_lock */
	err = reuseport_array_update_check(array, nsk,
	rcu_access_pointer(array->ptrs[index]),
	rcu_access_pointer(nsk->sk_reuseport_cb),
	map_flags);
	if (err)
	goto put_file;

	spin_lock_bh(&reuseport_lock);
	/*
	* Some of the checks only need reuseport_lock
	* but it is done under sk_callback_lock also
	* for simplicity reason.
	*/
	write_lock_bh(&nsk->sk_callback_lock);

	osk = rcu_dereference_protected(array->ptrs[index],
	lockdep_is_held(&reuseport_lock));
	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
	lockdep_is_held(&reuseport_lock));
	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
	if (err)
	goto put_file_unlock;

	WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
	rcu_assign_pointer(array->ptrs[index], nsk);
	free_osk = osk;
	err = 0;

	put_file_unlock:
	write_unlock_bh(&nsk->sk_callback_lock);

	if (free_osk) {
	write_lock_bh(&free_osk->sk_callback_lock);
	WRITE_ONCE(free_osk->sk_user_data, NULL);
	write_unlock_bh(&free_osk->sk_callback_lock);
	}

	spin_unlock_bh(&reuseport_lock);
	put_file:
	fput(socket->file);
	return err;
	}

	/* Called from syscall */
	static int reuseport_array_get_next_key(struct bpf_map map, void key,
	void *next_key)
	{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = key ? (u32 )key : U32_MAX;
	u32 next = (u32 )next_key;

	if (index >= array->map.max_entries) {
	*next = 0;
	return 0;
	}

	if (index == array->map.max_entries - 1)
	return -ENOENT;

	*next = index + 1;
	return 0;
	}

	const struct bpf_map_ops reuseport_array_ops = {
	.map_alloc_check = reuseport_array_alloc_check,
	.map_alloc = reuseport_array_alloc,
	.map_free = reuseport_array_free,
	.map_lookup_elem = reuseport_array_lookup_elem,
	.map_get_next_key = reuseport_array_get_next_key,
	.map_delete_elem = reuseport_array_delete_elem,
	};