Release 4.15 kernel/bpf/syscall.c

/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/vmalloc.h>
#include <linux/mmzone.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/license.h>
#include <linux/filter.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/cred.h>
#include <linux/timekeeping.h>
#include <linux/ctype.h>


#define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PROG_ARRAY || \
                           (map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
                           (map)->map_type == BPF_MAP_TYPE_CGROUP_ARRAY || \
                           (map)->map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS)

#define IS_FD_HASH(map) ((map)->map_type == BPF_MAP_TYPE_HASH_OF_MAPS)

#define IS_FD_MAP(map) (IS_FD_ARRAY(map) || IS_FD_HASH(map))


#define BPF_OBJ_FLAG_MASK   (BPF_F_RDONLY | BPF_F_WRONLY)

DEFINE_PER_CPU(int, bpf_prog_active);
static DEFINE_IDR(prog_idr);
static DEFINE_SPINLOCK(prog_idr_lock);
static DEFINE_IDR(map_idr);
static DEFINE_SPINLOCK(map_idr_lock);


int sysctl_unprivileged_bpf_disabled __read_mostly;


static const struct bpf_map_ops * const bpf_map_types[] = {

#define BPF_PROG_TYPE(_id, _ops)

#define BPF_MAP_TYPE(_id, _ops) \
	[_id] = &_ops,
#include <linux/bpf_types.h>

#undef BPF_PROG_TYPE

#undef BPF_MAP_TYPE
};

/*
 * If we're handed a bigger struct than we know of, ensure all the unknown bits
 * are 0 - i.e. new user-space does not rely on any kernel feature extensions
 * we don't know about yet.
 *
 * There is a ToCToU between this function call and the following
 * copy_from_user() call. However, this is not a concern since this function is
 * meant to be a future-proofing of bits.
 */


static int check_uarg_tail_zero(void __user *uaddr,
				size_t expected_size,
				size_t actual_size)
{
	unsigned char __user *addr;
	unsigned char __user *end;
	unsigned char val;
	int err;

	if (unlikely(actual_size > PAGE_SIZE))	/* silly large */
		return -E2BIG;

	if (unlikely(!access_ok(VERIFY_READ, uaddr, actual_size)))
		return -EFAULT;

	if (actual_size <= expected_size)
		return 0;

	addr = uaddr + expected_size;
	end  = uaddr + actual_size;

	for (; addr < end; addr++) {
		err = get_user(val, addr);
		if (err)
			return err;
		if (val)
			return -E2BIG;
	}

	return 0;
}

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static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
{
	struct bpf_map *map;

	if (attr->map_type >= ARRAY_SIZE(bpf_map_types) ||
	    !bpf_map_types[attr->map_type])
		return ERR_PTR(-EINVAL);

	map = bpf_map_types[attr->map_type]->map_alloc(attr);
	if (IS_ERR(map))
		return map;
	map->ops = bpf_map_types[attr->map_type];
	map->map_type = attr->map_type;
	return map;
}

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void *bpf_map_area_alloc(size_t size, int numa_node)
{
	/* We definitely need __GFP_NORETRY, so OOM killer doesn't
         * trigger under memory pressure as we really just want to
         * fail instead.
         */
	const gfp_t flags = __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO;
	void *area;

	if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
		area = kmalloc_node(size, GFP_USER | flags, numa_node);
		if (area != NULL)
			return area;
	}

	return __vmalloc_node_flags_caller(size, numa_node, GFP_KERNEL | flags,
					   __builtin_return_address(0));
}

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void bpf_map_area_free(void *area)
{
	kvfree(area);
}

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int bpf_map_precharge_memlock(u32 pages)
{
	struct user_struct *user = get_current_user();
	unsigned long memlock_limit, cur;

	memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
	cur = atomic_long_read(&user->locked_vm);
	free_uid(user);
	if (cur + pages > memlock_limit)
		return -EPERM;
	return 0;
}

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static int bpf_map_charge_memlock(struct bpf_map *map)
{
	struct user_struct *user = get_current_user();
	unsigned long memlock_limit;

	memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

	atomic_long_add(map->pages, &user->locked_vm);

	if (atomic_long_read(&user->locked_vm) > memlock_limit) {
		atomic_long_sub(map->pages, &user->locked_vm);
		free_uid(user);
		return -EPERM;
	}
	map->user = user;
	return 0;
}

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static void bpf_map_uncharge_memlock(struct bpf_map *map)
{
	struct user_struct *user = map->user;

	atomic_long_sub(map->pages, &user->locked_vm);
	free_uid(user);
}

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static int bpf_map_alloc_id(struct bpf_map *map)
{
	int id;

	spin_lock_bh(&map_idr_lock);
	id = idr_alloc_cyclic(&map_idr, map, 1, INT_MAX, GFP_ATOMIC);
	if (id > 0)
		map->id = id;
	spin_unlock_bh(&map_idr_lock);

	if (WARN_ON_ONCE(!id))
		return -ENOSPC;

	return id > 0 ? 0 : id;
}

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static void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock)
{
	unsigned long flags;

	if (do_idr_lock)
		spin_lock_irqsave(&map_idr_lock, flags);
	else
		__acquire(&map_idr_lock);

	idr_remove(&map_idr, map->id);

	if (do_idr_lock)
		spin_unlock_irqrestore(&map_idr_lock, flags);
	else
		__release(&map_idr_lock);
}

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/* called from workqueue */


static void bpf_map_free_deferred(struct work_struct *work)
{
	struct bpf_map *map = container_of(work, struct bpf_map, work);

	bpf_map_uncharge_memlock(map);
	security_bpf_map_free(map);
	/* implementation dependent freeing */
	map->ops->map_free(map);
}

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static void bpf_map_put_uref(struct bpf_map *map)
{
	if (atomic_dec_and_test(&map->usercnt)) {
		if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
			bpf_fd_array_map_clear(map);
	}
}

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/* decrement map refcnt and schedule it for freeing via workqueue
 * (unrelying map implementation ops->map_free() might sleep)
 */


static void __bpf_map_put(struct bpf_map *map, bool do_idr_lock)
{
	if (atomic_dec_and_test(&map->refcnt)) {
		/* bpf_map_free_id() must be called first */
		bpf_map_free_id(map, do_idr_lock);
		INIT_WORK(&map->work, bpf_map_free_deferred);
		schedule_work(&map->work);
	}
}

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void bpf_map_put(struct bpf_map *map)
{
	__bpf_map_put(map, true);
}

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void bpf_map_put_with_uref(struct bpf_map *map)
{
	bpf_map_put_uref(map);
	bpf_map_put(map);
}

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static int bpf_map_release(struct inode *inode, struct file *filp)
{
	struct bpf_map *map = filp->private_data;

	if (map->ops->map_release)
		map->ops->map_release(map, filp);

	bpf_map_put_with_uref(map);
	return 0;
}

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#ifdef CONFIG_PROC_FS


static void bpf_map_show_fdinfo(struct seq_file *m, struct file *filp)
{
	const struct bpf_map *map = filp->private_data;
	const struct bpf_array *array;
	u32 owner_prog_type = 0;
	u32 owner_jited = 0;

	if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY) {
		array = container_of(map, struct bpf_array, map);
		owner_prog_type = array->owner_prog_type;
		owner_jited = array->owner_jited;
	}

	seq_printf(m,
		   "map_type:\t%u\n"
		   "key_size:\t%u\n"
		   "value_size:\t%u\n"
		   "max_entries:\t%u\n"
		   "map_flags:\t%#x\n"
		   "memlock:\t%llu\n",
		   map->map_type,
		   map->key_size,
		   map->value_size,
		   map->max_entries,
		   map->map_flags,
		   map->pages * 1ULL << PAGE_SHIFT);

	if (owner_prog_type) {
		seq_printf(m, "owner_prog_type:\t%u\n",
			   owner_prog_type);
		seq_printf(m, "owner_jited:\t%u\n",
			   owner_jited);
	}
}
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#endif



static ssize_t bpf_dummy_read(struct file *filp, char __user *buf, size_t siz,
			      loff_t *ppos)
{
	/* We need this handler such that alloc_file() enables
         * f_mode with FMODE_CAN_READ.
         */
	return -EINVAL;
}

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static ssize_t bpf_dummy_write(struct file *filp, const char __user *buf,
			       size_t siz, loff_t *ppos)
{
	/* We need this handler such that alloc_file() enables
         * f_mode with FMODE_CAN_WRITE.
         */
	return -EINVAL;
}

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const struct file_operations bpf_map_fops = {
#ifdef CONFIG_PROC_FS
	.show_fdinfo	= bpf_map_show_fdinfo,
#endif
	.release	= bpf_map_release,
	.read		= bpf_dummy_read,
	.write		= bpf_dummy_write,
};



int bpf_map_new_fd(struct bpf_map *map, int flags)
{
	int ret;

	ret = security_bpf_map(map, OPEN_FMODE(flags));
	if (ret < 0)
		return ret;

	return anon_inode_getfd("bpf-map", &bpf_map_fops, map,
				flags | O_CLOEXEC);
}

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int bpf_get_file_flag(int flags)
{
	if ((flags & BPF_F_RDONLY) && (flags & BPF_F_WRONLY))
		return -EINVAL;
	if (flags & BPF_F_RDONLY)
		return O_RDONLY;
	if (flags & BPF_F_WRONLY)
		return O_WRONLY;
	return O_RDWR;
}

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/* helper macro to check that unused fields 'union bpf_attr' are zero */

#define CHECK_ATTR(CMD) \
	memchr_inv((void *) &attr->CMD##_LAST_FIELD + \
                   sizeof(attr->CMD##_LAST_FIELD), 0, \
                   sizeof(*attr) - \
                   offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
                   sizeof(attr->CMD##_LAST_FIELD)) != NULL

/* dst and src must have at least BPF_OBJ_NAME_LEN number of bytes.
 * Return 0 on success and < 0 on error.
 */


static int bpf_obj_name_cpy(char *dst, const char *src)
{
	const char *end = src + BPF_OBJ_NAME_LEN;

	memset(dst, 0, BPF_OBJ_NAME_LEN);

	/* Copy all isalnum() and '_' char */
	while (src < end && *src) {
		if (!isalnum(*src) && *src != '_')
			return -EINVAL;
		*dst++ = *src++;
	}

	/* No '\0' found in BPF_OBJ_NAME_LEN number of bytes */
	if (src == end)
		return -EINVAL;

	return 0;
}

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#define BPF_MAP_CREATE_LAST_FIELD map_name
/* called via syscall */


static int map_create(union bpf_attr *attr)
{
	int numa_node = bpf_map_attr_numa_node(attr);
	struct bpf_map *map;
	int f_flags;
	int err;

	err = CHECK_ATTR(BPF_MAP_CREATE);
	if (err)
		return -EINVAL;

	f_flags = bpf_get_file_flag(attr->map_flags);
	if (f_flags < 0)
		return f_flags;

	if (numa_node != NUMA_NO_NODE &&
	    ((unsigned int)numa_node >= nr_node_ids ||
	     !node_online(numa_node)))
		return -EINVAL;

	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
	map = find_and_alloc_map(attr);
	if (IS_ERR(map))
		return PTR_ERR(map);

	err = bpf_obj_name_cpy(map->name, attr->map_name);
	if (err)
		goto free_map_nouncharge;

	atomic_set(&map->refcnt, 1);
	atomic_set(&map->usercnt, 1);

	err = security_bpf_map_alloc(map);
	if (err)
		goto free_map_nouncharge;

	err = bpf_map_charge_memlock(map);
	if (err)
		goto free_map_sec;

	err = bpf_map_alloc_id(map);
	if (err)
		goto free_map;

	err = bpf_map_new_fd(map, f_flags);
	if (err < 0) {
		/* failed to allocate fd.
                 * bpf_map_put() is needed because the above
                 * bpf_map_alloc_id() has published the map
                 * to the userspace and the userspace may
                 * have refcnt-ed it through BPF_MAP_GET_FD_BY_ID.
                 */
		bpf_map_put(map);
		return err;
	}

	trace_bpf_map_create(map, err);
	return err;

free_map:
	bpf_map_uncharge_memlock(map);
free_map_sec:
	security_bpf_map_free(map);
free_map_nouncharge:
	map->ops->map_free(map);
	return err;
}

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/* if error is returned, fd is released.
 * On success caller should complete fd access with matching fdput()
 */


struct bpf_map *__bpf_map_get(struct fd f)
{
	if (!f.file)
		return ERR_PTR(-EBADF);
	if (f.file->f_op != &bpf_map_fops) {
		fdput(f);
		return ERR_PTR(-EINVAL);
	}

	return f.file->private_data;
}

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/* prog's and map's refcnt limit */

#define BPF_MAX_REFCNT 32768



struct bpf_map *bpf_map_inc(struct bpf_map *map, bool uref)
{
	if (atomic_inc_return(&map->refcnt) > BPF_MAX_REFCNT) {
		atomic_dec(&map->refcnt);
		return ERR_PTR(-EBUSY);
	}
	if (uref)
		atomic_inc(&map->usercnt);
	return map;
}

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struct bpf_map *bpf_map_get_with_uref(u32 ufd)
{
	struct fd f = fdget(ufd);
	struct bpf_map *map;

	map = __bpf_map_get(f);
	if (IS_ERR(map))
		return map;

	map = bpf_map_inc(map, true);
	fdput(f);

	return map;
}

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/* map_idr_lock should have been held */


static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
					    bool uref)
{
	int refold;

	refold = __atomic_add_unless(&map->refcnt, 1, 0);

	if (refold >= BPF_MAX_REFCNT) {
		__bpf_map_put(map, false);
		return ERR_PTR(-EBUSY);
	}

	if (!refold)
		return ERR_PTR(-ENOENT);

	if (uref)
		atomic_inc(&map->usercnt);

	return map;
}

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int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
{
	return -ENOTSUPP;
}

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/* last field in 'union bpf_attr' used by this command */

#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value



static int map_lookup_elem(union bpf_attr *attr)
{
	void __user *ukey = u64_to_user_ptr(attr->key);
	void __user *uvalue = u64_to_user_ptr(attr->value);
	int ufd = attr->map_fd;
	struct bpf_map *map;
	void *key, *value, *ptr;
	u32 value_size;
	struct fd f;
	int err;

	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
		return -EINVAL;

	f = fdget(ufd);
	map = __bpf_map_get(f);
	if (IS_ERR(map))
		return PTR_ERR(map);

	if (!(f.file->f_mode & FMODE_CAN_READ)) {
		err = -EPERM;
		goto err_put;
	}

	key = memdup_user(ukey, map->key_size);
	if (IS_ERR(key)) {
		err = PTR_ERR(key);
		goto err_put;
	}

	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
		value_size = round_up(map->value_size, 8) * num_possible_cpus();
	else if (IS_FD_MAP(map))
		value_size = sizeof(u32);
	else
		value_size = map->value_size;

	err = -ENOMEM;
	value = kmalloc(value_size, GFP_USER | __GFP_NOWARN);
	if (!value)
		goto free_key;

	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
		err = bpf_percpu_hash_copy(map, key, value);
	} else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
		err = bpf_percpu_array_copy(map, key, value);
	} else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) {
		err = bpf_stackmap_copy(map, key, value);
	} else if (IS_FD_ARRAY(map)) {
		err = bpf_fd_array_map_lookup_elem(map, key, value);
	} else if (IS_FD_HASH(map)) {
		err = bpf_fd_htab_map_lookup_elem(map, key, value);
	} else {
		rcu_read_lock();
		ptr = map->ops->map_lookup_elem(map, key);
		if (ptr)
			memcpy(value, ptr, value_size);
		rcu_read_unlock();
		err = ptr ? 0 : -ENOENT;
	}

	if (err)
		goto free_value;

	err = -EFAULT;
	if (copy_to_user(uvalue, value, value_size) != 0)
		goto free_value;

	trace_bpf_map_lookup_elem(map, ufd, key, value);
	err = 0;

free_value:
	kfree(value);
free_key:
	kfree(key);
err_put:
	fdput(f);
	return err;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Alexei Starovoitov
334
72.29%
6
37.50%
Martin KaFai Lau
69
14.94%
4
25.00%
Chenbo Feng
23
4.98%
1
6.25%
Daniel Borkmann
23
4.98%
3
18.75%
Al Viro
11
2.38%
1
6.25%
Mickaël Salaün
2
0.43%
1
6.25%
Total
462
100.00%
16
100.00%


#define BPF_MAP_UPDATE_ELEM_LAST_FIELD flags



static int map_update_elem(union bpf_attr *attr)
{
	void __user *ukey = u64_to_user_ptr(attr->key);
	void __user *uvalue = u64_to_user_ptr(attr->value);
	int ufd = attr->map_fd;
	struct bpf_map *map;
	void *key, *value;
	u32 value_size;
	struct fd f;
	int err;

	if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
		return -EINVAL;

	f = fdget(ufd);
	map = __bpf_map_get(f);
	if (IS_ERR(map))
		return PTR_ERR(map);

	if (!(f.file->f_mode & FMODE_CAN_WRITE)) {
		err = -EPERM;
		goto err_put;
	}

	key = memdup_user(ukey, map->key_size);
	if (IS_ERR(key)) {
		err = PTR_ERR(key);
		goto err_put;
	}

	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
		value_size = round_up(map->value_size, 8) * num_possible_cpus();
	else
		value_size = map->value_size;

	err = -ENOMEM;
	value = kmalloc(value_size, GFP_USER | __GFP_NOWARN);
	if (!value)
		goto free_key;

	err = -EFAULT;
	if (copy_from_user(value, uvalue, value_size) != 0)
		goto free_value;

	/* Need to create a kthread, thus must support schedule */
	if (map->map_type == BPF_MAP_TYPE_CPUMAP) {
		err = map->ops->map_update_elem(map, key, value, attr->flags);
		goto out;
	}

	/* must increment bpf_prog_active to avoid kprobe+bpf triggering from
         * inside bpf map update or delete otherwise deadlocks are possible
         */
	preempt_disable();
	__this_cpu_inc(bpf_prog_active);
	if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
	    map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
		err = bpf_percpu_hash_update(map, key, value, attr->flags);