/*

* Minimal file system backend for holding eBPF maps and programs,

* used by bpf(2) object pinning.

*

* Authors:

*

* Daniel Borkmann <daniel@iogearbox.net>

*

* This program is free software; you can redistribute it and/or

* modify it under the terms of the GNU General Public License

* version 2 as published by the Free Software Foundation.

*/

#include <linux/init.h>

#include <linux/magic.h>

#include <linux/major.h>

#include <linux/mount.h>

#include <linux/namei.h>

#include <linux/fs.h>

#include <linux/kdev_t.h>

#include <linux/parser.h>

#include <linux/filter.h>

#include <linux/bpf.h>

#include <linux/bpf_trace.h>

enum bpf_type {

BPF_TYPE_UNSPEC = 0,

BPF_TYPE_PROG,

BPF_TYPE_MAP,

};

static void *bpf_any_get(void *raw, enum bpf_type type)

{

switch (type) {

case BPF_TYPE_PROG:

raw = bpf_prog_inc(raw);

break;

case BPF_TYPE_MAP:

raw = bpf_map_inc(raw, true);

break;

default:

WARN_ON_ONCE(1);

break;

}

return raw;

}

static void bpf_any_put(void *raw, enum bpf_type type)

{

switch (type) {

case BPF_TYPE_PROG:

bpf_prog_put(raw);

break;

case BPF_TYPE_MAP:

bpf_map_put_with_uref(raw);

break;

default:

WARN_ON_ONCE(1);

break;

}

}

static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)

{

void *raw;

*type = BPF_TYPE_MAP;

raw = bpf_map_get_with_uref(ufd);

if (IS_ERR(raw)) {

*type = BPF_TYPE_PROG;

raw = bpf_prog_get(ufd);

}

return raw;

}

static const struct inode_operations bpf_dir_iops;

static const struct inode_operations bpf_prog_iops = { };

static const struct inode_operations bpf_map_iops = { };

static struct inode *bpf_get_inode(struct super_block *sb,

const struct inode *dir,

umode_t mode)

{

struct inode *inode;

switch (mode & S_IFMT) {

case S_IFDIR:

case S_IFREG:

case S_IFLNK:

break;

default:

return ERR_PTR(-EINVAL);

}

inode = new_inode(sb);

if (!inode)

return ERR_PTR(-ENOSPC);

inode->i_ino = get_next_ino();

inode->i_atime = current_time(inode);

inode->i_mtime = inode->i_atime;

inode->i_ctime = inode->i_atime;

inode_init_owner(inode, dir, mode);

return inode;

}

static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)

{

*type = BPF_TYPE_UNSPEC;

if (inode->i_op == &bpf_prog_iops)

*type = BPF_TYPE_PROG;

else if (inode->i_op == &bpf_map_iops)

*type = BPF_TYPE_MAP;

else

return -EACCES;

return 0;

}

static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,

struct inode *dir)

{

d_instantiate(dentry, inode);

dget(dentry);

dir->i_mtime = current_time(dir);

dir->i_ctime = dir->i_mtime;

}

static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

{

struct inode *inode;

inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);

if (IS_ERR(inode))

return PTR_ERR(inode);

inode->i_op = &bpf_dir_iops;

inode->i_fop = &simple_dir_operations;

inc_nlink(inode);

inc_nlink(dir);

bpf_dentry_finalize(dentry, inode, dir);

return 0;

}

struct map_iter {

void *key;

bool done;

};

static struct map_iter *map_iter(struct seq_file *m)

{

return m->private;

}

static struct bpf_map *seq_file_to_map(struct seq_file *m)

{

return file_inode(m->file)->i_private;

}

static void map_iter_free(struct map_iter *iter)

{

if (iter) {

kfree(iter->key);

kfree(iter);

}

}

static struct map_iter *map_iter_alloc(struct bpf_map *map)

{

struct map_iter *iter;

iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN);

if (!iter)

goto error;

iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN);

if (!iter->key)

goto error;

return iter;

error:

map_iter_free(iter);

return NULL;

}

static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)

{

struct bpf_map *map = seq_file_to_map(m);

void *key = map_iter(m)->key;

void *prev_key;

if (map_iter(m)->done)

return NULL;

if (unlikely(v == SEQ_START_TOKEN))

prev_key = NULL;

else

prev_key = key;

if (map->ops->map_get_next_key(map, prev_key, key)) {

map_iter(m)->done = true;

return NULL;

}

++(*pos);

return key;

}

static void *map_seq_start(struct seq_file *m, loff_t *pos)

{

if (map_iter(m)->done)

return NULL;

return *pos ? map_iter(m)->key : SEQ_START_TOKEN;

}

static void map_seq_stop(struct seq_file *m, void *v)

{

}

static int map_seq_show(struct seq_file *m, void *v)

{

struct bpf_map *map = seq_file_to_map(m);

void *key = map_iter(m)->key;

if (unlikely(v == SEQ_START_TOKEN)) {

seq_puts(m, "# WARNING!! The output is for debug purpose only\n");

seq_puts(m, "# WARNING!! The output format will change\n");

} else {

map->ops->map_seq_show_elem(map, key, m);

}

return 0;

}

static const struct seq_operations bpffs_map_seq_ops = {

.start = map_seq_start,

.next = map_seq_next,

.show = map_seq_show,

.stop = map_seq_stop,

};

static int bpffs_map_open(struct inode *inode, struct file *file)

{

struct bpf_map *map = inode->i_private;

struct map_iter *iter;

struct seq_file *m;

int err;

iter = map_iter_alloc(map);

if (!iter)

return -ENOMEM;

err = seq_open(file, &bpffs_map_seq_ops);

if (err) {

map_iter_free(iter);

return err;

}

m = file->private_data;

m->private = iter;

return 0;

}

static int bpffs_map_release(struct inode *inode, struct file *file)

{

struct seq_file *m = file->private_data;

map_iter_free(map_iter(m));

return seq_release(inode, file);

}

/* bpffs_map_fops should only implement the basic

* read operation for a BPF map. The purpose is to

* provide a simple user intuitive way to do

* "cat bpffs/pathto/a-pinned-map".

*

* Other operations (e.g. write, lookup...) should be realized by

* the userspace tools (e.g. bpftool) through the

* BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update

* interface.

*/

static const struct file_operations bpffs_map_fops = {

.open = bpffs_map_open,

.read = seq_read,

.release = bpffs_map_release,

};

static int bpffs_obj_open(struct inode *inode, struct file *file)

{

return -EIO;

}

static const struct file_operations bpffs_obj_fops = {

.open = bpffs_obj_open,

};

static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,

const struct inode_operations *iops,

const struct file_operations *fops)

{

struct inode *dir = dentry->d_parent->d_inode;

struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode);

if (IS_ERR(inode))

return PTR_ERR(inode);

inode->i_op = iops;

inode->i_fop = fops;

inode->i_private = raw;

bpf_dentry_finalize(dentry, inode, dir);

return 0;

}

static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)

{

return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,

&bpffs_obj_fops);

}

static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)

{

struct bpf_map *map = arg;

return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,

bpf_map_support_seq_show(map) ?

&bpffs_map_fops : &bpffs_obj_fops);

}

static struct dentry *

bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)

{

/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future

* extensions.

*/

if (strchr(dentry->d_name.name, '.'))

return ERR_PTR(-EPERM);

return simple_lookup(dir, dentry, flags);

}

static int bpf_symlink(struct inode *dir, struct dentry *dentry,

const char *target)

{

char *link = kstrdup(target, GFP_USER | __GFP_NOWARN);

struct inode *inode;

if (!link)

return -ENOMEM;

inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK);

if (IS_ERR(inode)) {

kfree(link);

return PTR_ERR(inode);

}

inode->i_op = &simple_symlink_inode_operations;

inode->i_link = link;

bpf_dentry_finalize(dentry, inode, dir);

return 0;

}

static const struct inode_operations bpf_dir_iops = {

.lookup = bpf_lookup,

.mkdir = bpf_mkdir,

.symlink = bpf_symlink,

.rmdir = simple_rmdir,

.rename = simple_rename,

.link = simple_link,

.unlink = simple_unlink,

};

static int bpf_obj_do_pin(const struct filename *pathname, void *raw,

enum bpf_type type)

{

struct dentry *dentry;

struct inode *dir;

struct path path;

umode_t mode;

int ret;

dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);

if (IS_ERR(dentry))

return PTR_ERR(dentry);

mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());

ret = security_path_mknod(&path, dentry, mode, 0);

if (ret)

goto out;

dir = d_inode(path.dentry);

if (dir->i_op != &bpf_dir_iops) {

ret = -EPERM;

goto out;

}

switch (type) {

case BPF_TYPE_PROG:

ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);

break;

case BPF_TYPE_MAP:

ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);

break;

default:

ret = -EPERM;

}

out:

done_path_create(&path, dentry);

return ret;

}

int bpf_obj_pin_user(u32 ufd, const char __user *pathname)

{

struct filename *pname;

enum bpf_type type;

void *raw;

int ret;

pname = getname(pathname);

if (IS_ERR(pname))

return PTR_ERR(pname);

raw = bpf_fd_probe_obj(ufd, &type);

if (IS_ERR(raw)) {

ret = PTR_ERR(raw);

goto out;

}

ret = bpf_obj_do_pin(pname, raw, type);

if (ret != 0)

bpf_any_put(raw, type);

out:

putname(pname);

return ret;

}

static void *bpf_obj_do_get(const struct filename *pathname,

enum bpf_type *type, int flags)

{

struct inode *inode;

struct path path;

void *raw;

int ret;

ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);

if (ret)

return ERR_PTR(ret);

inode = d_backing_inode(path.dentry);

ret = inode_permission(inode, ACC_MODE(flags));

if (ret)

goto out;

ret = bpf_inode_type(inode, type);

if (ret)

goto out;

raw = bpf_any_get(inode->i_private, *type);

if (!IS_ERR(raw))

touch_atime(&path);

path_put(&path);

return raw;

out:

path_put(&path);

return ERR_PTR(ret);

}

int bpf_obj_get_user(const char __user *pathname, int flags)

{

enum bpf_type type = BPF_TYPE_UNSPEC;

struct filename *pname;

int ret = -ENOENT;

int f_flags;

void *raw;

f_flags = bpf_get_file_flag(flags);

if (f_flags < 0)

return f_flags;

pname = getname(pathname);

if (IS_ERR(pname))

return PTR_ERR(pname);

raw = bpf_obj_do_get(pname, &type, f_flags);

if (IS_ERR(raw)) {

ret = PTR_ERR(raw);

goto out;

}

if (type == BPF_TYPE_PROG)

ret = bpf_prog_new_fd(raw);

else if (type == BPF_TYPE_MAP)

ret = bpf_map_new_fd(raw, f_flags);

else

goto out;

if (ret < 0)

bpf_any_put(raw, type);

out:

putname(pname);

return ret;

}

static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)

{

struct bpf_prog *prog;

int ret = inode_permission(inode, MAY_READ | MAY_WRITE);

if (ret)

return ERR_PTR(ret);

if (inode->i_op == &bpf_map_iops)

return ERR_PTR(-EINVAL);

if (inode->i_op != &bpf_prog_iops)

return ERR_PTR(-EACCES);

prog = inode->i_private;

ret = security_bpf_prog(prog);

if (ret < 0)

return ERR_PTR(ret);

if (!bpf_prog_get_ok(prog, &type, false))

return ERR_PTR(-EINVAL);

return bpf_prog_inc(prog);

}

struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)

{

struct bpf_prog *prog;

struct path path;

int ret = kern_path(name, LOOKUP_FOLLOW, &path);

if (ret)

return ERR_PTR(ret);

prog = __get_prog_inode(d_backing_inode(path.dentry), type);

if (!IS_ERR(prog))

touch_atime(&path);

path_put(&path);

return prog;

}

EXPORT_SYMBOL(bpf_prog_get_type_path);

/*

* Display the mount options in /proc/mounts.

*/

static int bpf_show_options(struct seq_file *m, struct dentry *root)

{

umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;

if (mode != S_IRWXUGO)

seq_printf(m, ",mode=%o", mode);

return 0;

}

static void bpf_destroy_inode_deferred(struct rcu_head *head)

{

struct inode *inode = container_of(head, struct inode, i_rcu);

enum bpf_type type;

if (S_ISLNK(inode->i_mode))

kfree(inode->i_link);

if (!bpf_inode_type(inode, &type))

bpf_any_put(inode->i_private, type);

free_inode_nonrcu(inode);

}

static void bpf_destroy_inode(struct inode *inode)

{

call_rcu(&inode->i_rcu, bpf_destroy_inode_deferred);

}

static const struct super_operations bpf_super_ops = {

.statfs = simple_statfs,

.drop_inode = generic_delete_inode,

.show_options = bpf_show_options,

.destroy_inode = bpf_destroy_inode,

};

enum {

OPT_MODE,

OPT_ERR,

};

static const match_table_t bpf_mount_tokens = {

{ OPT_MODE, "mode=%o" },

{ OPT_ERR, NULL },

};

struct bpf_mount_opts {

umode_t mode;

};

static int bpf_parse_options(char *data, struct bpf_mount_opts *opts)

{

substring_t args[MAX_OPT_ARGS];

int option, token;

char *ptr;

opts->mode = S_IRWXUGO;

while ((ptr = strsep(&data, ",")) != NULL) {

if (!*ptr)

continue;

token = match_token(ptr, bpf_mount_tokens, args);

switch (token) {

case OPT_MODE:

if (match_octal(&args[0], &option))

return -EINVAL;

opts->mode = option & S_IALLUGO;

break;

/* We might like to report bad mount options here, but

* traditionally we've ignored all mount options, so we'd

* better continue to ignore non-existing options for bpf.

*/

}

}

return 0;

}

static int bpf_fill_super(struct super_block *sb, void *data, int silent)

{

static const struct tree_descr bpf_rfiles[] = { { "" } };

struct bpf_mount_opts opts;

struct inode *inode;

int ret;

ret = bpf_parse_options(data, &opts);

if (ret)

return ret;

ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);

if (ret)

return ret;

sb->s_op = &bpf_super_ops;

inode = sb->s_root->d_inode;

inode->i_op = &bpf_dir_iops;

inode->i_mode &= ~S_IALLUGO;

inode->i_mode |= S_ISVTX | opts.mode;

return 0;

}

static struct dentry *bpf_mount(struct file_system_type *type, int flags,

const char *dev_name, void *data)

{

return mount_nodev(type, flags, data, bpf_fill_super);

}

static struct file_system_type bpf_fs_type = {

.owner = THIS_MODULE,

.name = "bpf",

.mount = bpf_mount,

.kill_sb = kill_litter_super,

};

static int __init bpf_init(void)

{

int ret;

ret = sysfs_create_mount_point(fs_kobj, "bpf");

if (ret)

return ret;

ret = register_filesystem(&bpf_fs_type);

if (ret)

sysfs_remove_mount_point(fs_kobj, "bpf");

return ret;

}

fs_initcall(bpf_init);