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

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2020 Facebook
  * Copyright 2020 Google LLC.
  */

 #include <linux/pid.h>
 #include <linux/sched.h>
 #include <linux/rculist.h>
 #include <linux/list.h>
 #include <linux/hash.h>
 #include <linux/types.h>
 #include <linux/spinlock.h>
 #include <linux/bpf.h>
 #include <linux/bpf_local_storage.h>
 #include <linux/filter.h>
 #include <uapi/linux/btf.h>
 #include <linux/btf_ids.h>
 #include <linux/fdtable.h>

 DEFINE_BPF_STORAGE_CACHE(task_cache);

 static DEFINE_PER_CPU(int, bpf_task_storage_busy);

 static void bpf_task_storage_lock(void)
 {
 	migrate_disable();
 	__this_cpu_inc(bpf_task_storage_busy);
 }

 static void bpf_task_storage_unlock(void)
 {
 	__this_cpu_dec(bpf_task_storage_busy);
 	migrate_enable();
 }

 static bool bpf_task_storage_trylock(void)
 {
 	migrate_disable();
 	if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
 		__this_cpu_dec(bpf_task_storage_busy);
 		migrate_enable();
 		return false;
 	}
 	return true;
 }

 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
 {
 	struct task_struct *task = owner;

 	return &task->bpf_storage;
 }

 static struct bpf_local_storage_data *
 task_storage_lookup(struct task_struct *task, struct bpf_map *map,
 		    bool cacheit_lockit)
 {
 	struct bpf_local_storage *task_storage;
 	struct bpf_local_storage_map *smap;

 	task_storage = rcu_dereference(task->bpf_storage);
 	if (!task_storage)
 		return NULL;

 	smap = (struct bpf_local_storage_map *)map;
 	return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
 }

 void bpf_task_storage_free(struct task_struct *task)
 {
 	struct bpf_local_storage_elem *selem;
 	struct bpf_local_storage *local_storage;
 	bool free_task_storage = false;
 	struct hlist_node *n;
 	unsigned long flags;

 	rcu_read_lock();

 	local_storage = rcu_dereference(task->bpf_storage);
 	if (!local_storage) {
 		rcu_read_unlock();
 		return;
 	}

 	/* Neither the bpf_prog nor the bpf-map's syscall
 	 * could be modifying the local_storage->list now.
 	 * Thus, no elem can be added-to or deleted-from the
 	 * local_storage->list by the bpf_prog or by the bpf-map's syscall.
 	 *
 	 * It is racing with bpf_local_storage_map_free() alone
 	 * when unlinking elem from the local_storage->list and
 	 * the map's bucket->list.
 	 */
 	bpf_task_storage_lock();
 	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
 		/* Always unlink from map before unlinking from
 		 * local_storage.
 		 */
 		bpf_selem_unlink_map(selem);
 		free_task_storage = bpf_selem_unlink_storage_nolock(
 			local_storage, selem, false);
 	}
 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	bpf_task_storage_unlock();
 	rcu_read_unlock();

 	/* free_task_storage should always be true as long as
 	 * local_storage->list was non-empty.
 	 */
 	if (free_task_storage)
 		kfree_rcu(local_storage, rcu);
 }

 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_local_storage_data *sdata;
 	struct task_struct *task;
 	unsigned int f_flags;
 	struct pid *pid;
 	int fd, err;

 	fd = *(int *)key;
 	pid = pidfd_get_pid(fd, &f_flags);
 	if (IS_ERR(pid))
 		return ERR_CAST(pid);

 	/* We should be in an RCU read side critical section, it should be safe
 	 * to call pid_task.
 	 */
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	task = pid_task(pid, PIDTYPE_PID);
 	if (!task) {
 		err = -ENOENT;
 		goto out;
 	}

 	bpf_task_storage_lock();
 	sdata = task_storage_lookup(task, map, true);
 	bpf_task_storage_unlock();
 	put_pid(pid);
 	return sdata ? sdata->data : NULL;
 out:
 	put_pid(pid);
 	return ERR_PTR(err);
 }

 static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 					    void *value, u64 map_flags)
 {
 	struct bpf_local_storage_data *sdata;
 	struct task_struct *task;
 	unsigned int f_flags;
 	struct pid *pid;
 	int fd, err;

 	fd = *(int *)key;
 	pid = pidfd_get_pid(fd, &f_flags);
 	if (IS_ERR(pid))
 		return PTR_ERR(pid);

 	/* We should be in an RCU read side critical section, it should be safe
 	 * to call pid_task.
 	 */
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	task = pid_task(pid, PIDTYPE_PID);
 	if (!task) {
 		err = -ENOENT;
 		goto out;
 	}

 	bpf_task_storage_lock();
 	sdata = bpf_local_storage_update(
 		task, (struct bpf_local_storage_map *)map, value, map_flags);
 	bpf_task_storage_unlock();

 	err = PTR_ERR_OR_ZERO(sdata);
 out:
 	put_pid(pid);
 	return err;
 }

 static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
 {
 	struct bpf_local_storage_data *sdata;

 	sdata = task_storage_lookup(task, map, false);
 	if (!sdata)
 		return -ENOENT;

 	bpf_selem_unlink(SELEM(sdata));

 	return 0;
 }

 static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
 {
 	struct task_struct *task;
 	unsigned int f_flags;
 	struct pid *pid;
 	int fd, err;

 	fd = *(int *)key;
 	pid = pidfd_get_pid(fd, &f_flags);
 	if (IS_ERR(pid))
 		return PTR_ERR(pid);

 	/* We should be in an RCU read side critical section, it should be safe
 	 * to call pid_task.
 	 */
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	task = pid_task(pid, PIDTYPE_PID);
 	if (!task) {
 		err = -ENOENT;
 		goto out;
 	}

 	bpf_task_storage_lock();
 	err = task_storage_delete(task, map);
 	bpf_task_storage_unlock();
 out:
 	put_pid(pid);
 	return err;
 }

 BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
 	   task, void *, value, u64, flags)
 {
 	struct bpf_local_storage_data *sdata;

 	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
 		return (unsigned long)NULL;

 	if (!task)
 		return (unsigned long)NULL;

 	if (!bpf_task_storage_trylock())
 		return (unsigned long)NULL;

 	sdata = task_storage_lookup(task, map, true);
 	if (sdata)
 		goto unlock;

 	/* only allocate new storage, when the task is refcounted */
 	if (refcount_read(&task->usage) &&
 	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
 		sdata = bpf_local_storage_update(
 			task, (struct bpf_local_storage_map *)map, value,
 			BPF_NOEXIST);

 unlock:
 	bpf_task_storage_unlock();
 	return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL :
 		(unsigned long)sdata->data;
 }

 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
 	   task)
 {
 	int ret;

 	if (!task)
 		return -EINVAL;

 	if (!bpf_task_storage_trylock())
 		return -EBUSY;

 	/* This helper must only be called from places where the lifetime of the task
 	 * is guaranteed. Either by being refcounted or by being protected
 	 * by an RCU read-side critical section.
 	 */
 	ret = task_storage_delete(task, map);
 	bpf_task_storage_unlock();
 	return ret;
 }

 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
 {
 	return -ENOTSUPP;
 }

 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
 {
 	struct bpf_local_storage_map *smap;

 	smap = bpf_local_storage_map_alloc(attr);
 	if (IS_ERR(smap))
 		return ERR_CAST(smap);

 	smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
 	return &smap->map;
 }

 static void task_storage_map_free(struct bpf_map *map)
 {
 	struct bpf_local_storage_map *smap;

 	smap = (struct bpf_local_storage_map *)map;
 	bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
 	bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
 }

 static int task_storage_map_btf_id;
 const struct bpf_map_ops task_storage_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = bpf_local_storage_map_alloc_check,
 	.map_alloc = task_storage_map_alloc,
 	.map_free = task_storage_map_free,
 	.map_get_next_key = notsupp_get_next_key,
 	.map_lookup_elem = bpf_pid_task_storage_lookup_elem,
 	.map_update_elem = bpf_pid_task_storage_update_elem,
 	.map_delete_elem = bpf_pid_task_storage_delete_elem,
 	.map_check_btf = bpf_local_storage_map_check_btf,
 	.map_btf_name = "bpf_local_storage_map",
 	.map_btf_id = &task_storage_map_btf_id,
 	.map_owner_storage_ptr = task_storage_ptr,
 };

 const struct bpf_func_proto bpf_task_storage_get_proto = {
 	.func = bpf_task_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_BTF_ID,
 	.arg2_btf_id = &btf_task_struct_ids[0],
 	.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
 	.arg4_type = ARG_ANYTHING,
 };

 const struct bpf_func_proto bpf_task_storage_delete_proto = {
 	.func = bpf_task_storage_delete,
 	.gpl_only = false,
 	.ret_type = RET_INTEGER,
 	.arg1_type = ARG_CONST_MAP_PTR,
 	.arg2_type = ARG_PTR_TO_BTF_ID,
 	.arg2_btf_id = &btf_task_struct_ids[0],
 };
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (c) 2020 Facebook
	* Copyright 2020 Google LLC.
	*/

	#include <linux/pid.h>
	#include <linux/sched.h>
	#include <linux/rculist.h>
	#include <linux/list.h>
	#include <linux/hash.h>
	#include <linux/types.h>
	#include <linux/spinlock.h>
	#include <linux/bpf.h>
	#include <linux/bpf_local_storage.h>
	#include <linux/filter.h>
	#include <uapi/linux/btf.h>
	#include <linux/btf_ids.h>
	#include <linux/fdtable.h>

	DEFINE_BPF_STORAGE_CACHE(task_cache);

	static DEFINE_PER_CPU(int, bpf_task_storage_busy);

	static void bpf_task_storage_lock(void)
	{
	migrate_disable();
	__this_cpu_inc(bpf_task_storage_busy);
	}

	static void bpf_task_storage_unlock(void)
	{
	__this_cpu_dec(bpf_task_storage_busy);
	migrate_enable();
	}

	static bool bpf_task_storage_trylock(void)
	{
	migrate_disable();
	if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
	__this_cpu_dec(bpf_task_storage_busy);
	migrate_enable();
	return false;
	}
	return true;
	}

	static struct bpf_local_storage __rcu *task_storage_ptr(void owner)
	{
	struct task_struct *task = owner;

	return &task->bpf_storage;
	}

	static struct bpf_local_storage_data *
	task_storage_lookup(struct task_struct task, struct bpf_map map,
	bool cacheit_lockit)
	{
	struct bpf_local_storage *task_storage;
	struct bpf_local_storage_map *smap;

	task_storage = rcu_dereference(task->bpf_storage);
	if (!task_storage)
	return NULL;

	smap = (struct bpf_local_storage_map *)map;
	return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
	}

	void bpf_task_storage_free(struct task_struct *task)
	{
	struct bpf_local_storage_elem *selem;
	struct bpf_local_storage *local_storage;
	bool free_task_storage = false;
	struct hlist_node *n;
	unsigned long flags;

	rcu_read_lock();

	local_storage = rcu_dereference(task->bpf_storage);
	if (!local_storage) {
	rcu_read_unlock();
	return;
	}

	/* Neither the bpf_prog nor the bpf-map's syscall
	* could be modifying the local_storage->list now.
	* Thus, no elem can be added-to or deleted-from the
	* local_storage->list by the bpf_prog or by the bpf-map's syscall.
	*
	* It is racing with bpf_local_storage_map_free() alone
	* when unlinking elem from the local_storage->list and
	* the map's bucket->list.
	*/
	bpf_task_storage_lock();
	raw_spin_lock_irqsave(&local_storage->lock, flags);
	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
	/* Always unlink from map before unlinking from
	* local_storage.
	*/
	bpf_selem_unlink_map(selem);
	free_task_storage = bpf_selem_unlink_storage_nolock(
	local_storage, selem, false);
	}
	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
	bpf_task_storage_unlock();
	rcu_read_unlock();

	/* free_task_storage should always be true as long as
	* local_storage->list was non-empty.
	*/
	if (free_task_storage)
	kfree_rcu(local_storage, rcu);
	}

	static void bpf_pid_task_storage_lookup_elem(struct bpf_map map, void *key)
	{
	struct bpf_local_storage_data *sdata;
	struct task_struct *task;
	unsigned int f_flags;
	struct pid *pid;
	int fd, err;

	fd = (int )key;
	pid = pidfd_get_pid(fd, &f_flags);
	if (IS_ERR(pid))
	return ERR_CAST(pid);

	/* We should be in an RCU read side critical section, it should be safe
	* to call pid_task.
	*/
	WARN_ON_ONCE(!rcu_read_lock_held());
	task = pid_task(pid, PIDTYPE_PID);
	if (!task) {
	err = -ENOENT;
	goto out;
	}

	bpf_task_storage_lock();
	sdata = task_storage_lookup(task, map, true);
	bpf_task_storage_unlock();
	put_pid(pid);
	return sdata ? sdata->data : NULL;
	out:
	put_pid(pid);
	return ERR_PTR(err);
	}

	static int bpf_pid_task_storage_update_elem(struct bpf_map map, void key,
	void *value, u64 map_flags)
	{
	struct bpf_local_storage_data *sdata;
	struct task_struct *task;
	unsigned int f_flags;
	struct pid *pid;
	int fd, err;

	fd = (int )key;
	pid = pidfd_get_pid(fd, &f_flags);
	if (IS_ERR(pid))
	return PTR_ERR(pid);

	/* We should be in an RCU read side critical section, it should be safe
	* to call pid_task.
	*/
	WARN_ON_ONCE(!rcu_read_lock_held());
	task = pid_task(pid, PIDTYPE_PID);
	if (!task) {
	err = -ENOENT;
	goto out;
	}

	bpf_task_storage_lock();
	sdata = bpf_local_storage_update(
	task, (struct bpf_local_storage_map *)map, value, map_flags);
	bpf_task_storage_unlock();

	err = PTR_ERR_OR_ZERO(sdata);
	out:
	put_pid(pid);
	return err;
	}

	static int task_storage_delete(struct task_struct task, struct bpf_map map)
	{
	struct bpf_local_storage_data *sdata;

	sdata = task_storage_lookup(task, map, false);
	if (!sdata)
	return -ENOENT;

	bpf_selem_unlink(SELEM(sdata));

	return 0;
	}

	static int bpf_pid_task_storage_delete_elem(struct bpf_map map, void key)
	{
	struct task_struct *task;
	unsigned int f_flags;
	struct pid *pid;
	int fd, err;

	fd = (int )key;
	pid = pidfd_get_pid(fd, &f_flags);
	if (IS_ERR(pid))
	return PTR_ERR(pid);

	/* We should be in an RCU read side critical section, it should be safe
	* to call pid_task.
	*/
	WARN_ON_ONCE(!rcu_read_lock_held());
	task = pid_task(pid, PIDTYPE_PID);
	if (!task) {
	err = -ENOENT;
	goto out;
	}

	bpf_task_storage_lock();
	err = task_storage_delete(task, map);
	bpf_task_storage_unlock();
	out:
	put_pid(pid);
	return err;
	}

	BPF_CALL_4(bpf_task_storage_get, struct bpf_map , map, struct task_struct ,
	task, void *, value, u64, flags)
	{
	struct bpf_local_storage_data *sdata;

	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
	return (unsigned long)NULL;

	if (!task)
	return (unsigned long)NULL;

	if (!bpf_task_storage_trylock())
	return (unsigned long)NULL;

	sdata = task_storage_lookup(task, map, true);
	if (sdata)
	goto unlock;

	/* only allocate new storage, when the task is refcounted */
	if (refcount_read(&task->usage) &&
	(flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
	sdata = bpf_local_storage_update(
	task, (struct bpf_local_storage_map *)map, value,
	BPF_NOEXIST);

	unlock:
	bpf_task_storage_unlock();
	return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL :
	(unsigned long)sdata->data;
	}

	BPF_CALL_2(bpf_task_storage_delete, struct bpf_map , map, struct task_struct ,
	task)
	{
	int ret;

	if (!task)
	return -EINVAL;

	if (!bpf_task_storage_trylock())
	return -EBUSY;

	/* This helper must only be called from places where the lifetime of the task
	* is guaranteed. Either by being refcounted or by being protected
	* by an RCU read-side critical section.
	*/
	ret = task_storage_delete(task, map);
	bpf_task_storage_unlock();
	return ret;
	}

	static int notsupp_get_next_key(struct bpf_map map, void key, void *next_key)
	{
	return -ENOTSUPP;
	}

	static struct bpf_map task_storage_map_alloc(union bpf_attr attr)
	{
	struct bpf_local_storage_map *smap;

	smap = bpf_local_storage_map_alloc(attr);
	if (IS_ERR(smap))
	return ERR_CAST(smap);

	smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
	return &smap->map;
	}

	static void task_storage_map_free(struct bpf_map *map)
	{
	struct bpf_local_storage_map *smap;

	smap = (struct bpf_local_storage_map *)map;
	bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
	bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
	}

	static int task_storage_map_btf_id;
	const struct bpf_map_ops task_storage_map_ops = {
	.map_meta_equal = bpf_map_meta_equal,
	.map_alloc_check = bpf_local_storage_map_alloc_check,
	.map_alloc = task_storage_map_alloc,
	.map_free = task_storage_map_free,
	.map_get_next_key = notsupp_get_next_key,
	.map_lookup_elem = bpf_pid_task_storage_lookup_elem,
	.map_update_elem = bpf_pid_task_storage_update_elem,
	.map_delete_elem = bpf_pid_task_storage_delete_elem,
	.map_check_btf = bpf_local_storage_map_check_btf,
	.map_btf_name = "bpf_local_storage_map",
	.map_btf_id = &task_storage_map_btf_id,
	.map_owner_storage_ptr = task_storage_ptr,
	};

	const struct bpf_func_proto bpf_task_storage_get_proto = {
	.func = bpf_task_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_BTF_ID,
	.arg2_btf_id = &btf_task_struct_ids[0],
	.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
	.arg4_type = ARG_ANYTHING,
	};

	const struct bpf_func_proto bpf_task_storage_delete_proto = {
	.func = bpf_task_storage_delete,
	.gpl_only = false,
	.ret_type = RET_INTEGER,
	.arg1_type = ARG_CONST_MAP_PTR,
	.arg2_type = ARG_PTR_TO_BTF_ID,
	.arg2_btf_id = &btf_task_struct_ids[0],
	};