682 lines
14 KiB
C
682 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Minimal file system backend for holding eBPF maps and programs,
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* used by bpf(2) object pinning.
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*
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* Authors:
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*
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* Daniel Borkmann <daniel@iogearbox.net>
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*/
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#include <linux/init.h>
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#include <linux/magic.h>
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#include <linux/major.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/fs.h>
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#include <linux/fs_context.h>
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#include <linux/fs_parser.h>
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#include <linux/kdev_t.h>
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#include <linux/filter.h>
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#include <linux/bpf.h>
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#include <linux/bpf_trace.h>
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enum bpf_type {
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BPF_TYPE_UNSPEC = 0,
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BPF_TYPE_PROG,
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BPF_TYPE_MAP,
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};
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static void *bpf_any_get(void *raw, enum bpf_type type)
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{
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switch (type) {
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case BPF_TYPE_PROG:
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bpf_prog_inc(raw);
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break;
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case BPF_TYPE_MAP:
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bpf_map_inc_with_uref(raw);
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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}
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return raw;
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}
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static void bpf_any_put(void *raw, enum bpf_type type)
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{
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switch (type) {
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case BPF_TYPE_PROG:
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bpf_prog_put(raw);
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break;
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case BPF_TYPE_MAP:
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bpf_map_put_with_uref(raw);
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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}
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}
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static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
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{
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void *raw;
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*type = BPF_TYPE_MAP;
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raw = bpf_map_get_with_uref(ufd);
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if (IS_ERR(raw)) {
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*type = BPF_TYPE_PROG;
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raw = bpf_prog_get(ufd);
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}
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return raw;
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}
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static const struct inode_operations bpf_dir_iops;
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static const struct inode_operations bpf_prog_iops = { };
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static const struct inode_operations bpf_map_iops = { };
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static struct inode *bpf_get_inode(struct super_block *sb,
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const struct inode *dir,
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umode_t mode)
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{
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struct inode *inode;
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switch (mode & S_IFMT) {
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case S_IFDIR:
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case S_IFREG:
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case S_IFLNK:
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break;
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default:
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return ERR_PTR(-EINVAL);
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}
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inode = new_inode(sb);
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if (!inode)
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return ERR_PTR(-ENOSPC);
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inode->i_ino = get_next_ino();
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inode->i_atime = current_time(inode);
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inode->i_mtime = inode->i_atime;
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inode->i_ctime = inode->i_atime;
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inode_init_owner(inode, dir, mode);
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return inode;
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}
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static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
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{
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*type = BPF_TYPE_UNSPEC;
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if (inode->i_op == &bpf_prog_iops)
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*type = BPF_TYPE_PROG;
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else if (inode->i_op == &bpf_map_iops)
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*type = BPF_TYPE_MAP;
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else
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return -EACCES;
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return 0;
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}
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static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,
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struct inode *dir)
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{
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d_instantiate(dentry, inode);
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dget(dentry);
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dir->i_mtime = current_time(dir);
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dir->i_ctime = dir->i_mtime;
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}
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static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
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{
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struct inode *inode;
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inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
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if (IS_ERR(inode))
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return PTR_ERR(inode);
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inode->i_op = &bpf_dir_iops;
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inode->i_fop = &simple_dir_operations;
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inc_nlink(inode);
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inc_nlink(dir);
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bpf_dentry_finalize(dentry, inode, dir);
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return 0;
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}
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struct map_iter {
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void *key;
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bool done;
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};
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static struct map_iter *map_iter(struct seq_file *m)
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{
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return m->private;
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}
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static struct bpf_map *seq_file_to_map(struct seq_file *m)
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{
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return file_inode(m->file)->i_private;
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}
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static void map_iter_free(struct map_iter *iter)
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{
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if (iter) {
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kfree(iter->key);
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kfree(iter);
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}
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}
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static struct map_iter *map_iter_alloc(struct bpf_map *map)
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{
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struct map_iter *iter;
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iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN);
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if (!iter)
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goto error;
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iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN);
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if (!iter->key)
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goto error;
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return iter;
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error:
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map_iter_free(iter);
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return NULL;
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}
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static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
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{
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struct bpf_map *map = seq_file_to_map(m);
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void *key = map_iter(m)->key;
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void *prev_key;
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(*pos)++;
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if (map_iter(m)->done)
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return NULL;
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if (unlikely(v == SEQ_START_TOKEN))
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prev_key = NULL;
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else
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prev_key = key;
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if (map->ops->map_get_next_key(map, prev_key, key)) {
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map_iter(m)->done = true;
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return NULL;
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}
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return key;
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}
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static void *map_seq_start(struct seq_file *m, loff_t *pos)
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{
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if (map_iter(m)->done)
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return NULL;
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return *pos ? map_iter(m)->key : SEQ_START_TOKEN;
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}
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static void map_seq_stop(struct seq_file *m, void *v)
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{
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}
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static int map_seq_show(struct seq_file *m, void *v)
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{
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struct bpf_map *map = seq_file_to_map(m);
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void *key = map_iter(m)->key;
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if (unlikely(v == SEQ_START_TOKEN)) {
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seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
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seq_puts(m, "# WARNING!! The output format will change\n");
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} else {
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map->ops->map_seq_show_elem(map, key, m);
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}
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return 0;
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}
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static const struct seq_operations bpffs_map_seq_ops = {
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.start = map_seq_start,
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.next = map_seq_next,
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.show = map_seq_show,
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.stop = map_seq_stop,
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};
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static int bpffs_map_open(struct inode *inode, struct file *file)
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{
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struct bpf_map *map = inode->i_private;
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struct map_iter *iter;
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struct seq_file *m;
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int err;
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iter = map_iter_alloc(map);
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if (!iter)
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return -ENOMEM;
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err = seq_open(file, &bpffs_map_seq_ops);
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if (err) {
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map_iter_free(iter);
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return err;
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}
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m = file->private_data;
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m->private = iter;
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return 0;
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}
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static int bpffs_map_release(struct inode *inode, struct file *file)
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{
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struct seq_file *m = file->private_data;
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map_iter_free(map_iter(m));
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return seq_release(inode, file);
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}
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/* bpffs_map_fops should only implement the basic
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* read operation for a BPF map. The purpose is to
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* provide a simple user intuitive way to do
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* "cat bpffs/pathto/a-pinned-map".
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*
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* Other operations (e.g. write, lookup...) should be realized by
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* the userspace tools (e.g. bpftool) through the
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* BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update
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* interface.
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*/
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static const struct file_operations bpffs_map_fops = {
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.open = bpffs_map_open,
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.read = seq_read,
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.release = bpffs_map_release,
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};
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static int bpffs_obj_open(struct inode *inode, struct file *file)
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{
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return -EIO;
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}
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static const struct file_operations bpffs_obj_fops = {
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.open = bpffs_obj_open,
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};
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static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
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const struct inode_operations *iops,
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const struct file_operations *fops)
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{
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struct inode *dir = dentry->d_parent->d_inode;
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struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode);
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if (IS_ERR(inode))
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return PTR_ERR(inode);
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inode->i_op = iops;
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inode->i_fop = fops;
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inode->i_private = raw;
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bpf_dentry_finalize(dentry, inode, dir);
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return 0;
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}
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static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
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{
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
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&bpffs_obj_fops);
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}
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static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
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{
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struct bpf_map *map = arg;
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
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bpf_map_support_seq_show(map) ?
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&bpffs_map_fops : &bpffs_obj_fops);
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}
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static struct dentry *
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bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
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{
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/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
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* extensions.
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*/
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if (strchr(dentry->d_name.name, '.'))
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return ERR_PTR(-EPERM);
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return simple_lookup(dir, dentry, flags);
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}
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static int bpf_symlink(struct inode *dir, struct dentry *dentry,
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const char *target)
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{
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char *link = kstrdup(target, GFP_USER | __GFP_NOWARN);
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struct inode *inode;
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if (!link)
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return -ENOMEM;
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inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK);
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if (IS_ERR(inode)) {
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kfree(link);
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return PTR_ERR(inode);
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}
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inode->i_op = &simple_symlink_inode_operations;
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inode->i_link = link;
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bpf_dentry_finalize(dentry, inode, dir);
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return 0;
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}
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static const struct inode_operations bpf_dir_iops = {
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.lookup = bpf_lookup,
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.mkdir = bpf_mkdir,
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.symlink = bpf_symlink,
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.rmdir = simple_rmdir,
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.rename = simple_rename,
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.link = simple_link,
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.unlink = simple_unlink,
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};
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static int bpf_obj_do_pin(const char __user *pathname, void *raw,
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enum bpf_type type)
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{
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struct dentry *dentry;
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struct inode *dir;
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struct path path;
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umode_t mode;
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int ret;
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dentry = user_path_create(AT_FDCWD, pathname, &path, 0);
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if (IS_ERR(dentry))
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return PTR_ERR(dentry);
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mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
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ret = security_path_mknod(&path, dentry, mode, 0);
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if (ret)
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goto out;
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dir = d_inode(path.dentry);
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if (dir->i_op != &bpf_dir_iops) {
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ret = -EPERM;
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goto out;
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}
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switch (type) {
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case BPF_TYPE_PROG:
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ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);
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break;
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case BPF_TYPE_MAP:
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ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
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break;
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default:
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ret = -EPERM;
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}
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out:
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done_path_create(&path, dentry);
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return ret;
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}
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int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
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{
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enum bpf_type type;
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void *raw;
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int ret;
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raw = bpf_fd_probe_obj(ufd, &type);
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if (IS_ERR(raw))
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return PTR_ERR(raw);
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ret = bpf_obj_do_pin(pathname, raw, type);
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if (ret != 0)
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bpf_any_put(raw, type);
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return ret;
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}
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static void *bpf_obj_do_get(const char __user *pathname,
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enum bpf_type *type, int flags)
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{
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struct inode *inode;
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struct path path;
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void *raw;
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int ret;
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ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path);
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if (ret)
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return ERR_PTR(ret);
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inode = d_backing_inode(path.dentry);
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ret = inode_permission(inode, ACC_MODE(flags));
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if (ret)
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goto out;
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ret = bpf_inode_type(inode, type);
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if (ret)
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goto out;
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raw = bpf_any_get(inode->i_private, *type);
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if (!IS_ERR(raw))
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touch_atime(&path);
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path_put(&path);
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return raw;
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out:
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path_put(&path);
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return ERR_PTR(ret);
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}
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int bpf_obj_get_user(const char __user *pathname, int flags)
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{
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enum bpf_type type = BPF_TYPE_UNSPEC;
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int f_flags;
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void *raw;
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int ret;
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f_flags = bpf_get_file_flag(flags);
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if (f_flags < 0)
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return f_flags;
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raw = bpf_obj_do_get(pathname, &type, f_flags);
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if (IS_ERR(raw))
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return PTR_ERR(raw);
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if (type == BPF_TYPE_PROG)
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ret = bpf_prog_new_fd(raw);
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else if (type == BPF_TYPE_MAP)
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ret = bpf_map_new_fd(raw, f_flags);
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else
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return -ENOENT;
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if (ret < 0)
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bpf_any_put(raw, type);
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return ret;
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}
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static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
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{
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struct bpf_prog *prog;
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int ret = inode_permission(inode, MAY_READ);
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if (ret)
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return ERR_PTR(ret);
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if (inode->i_op == &bpf_map_iops)
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return ERR_PTR(-EINVAL);
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if (inode->i_op != &bpf_prog_iops)
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return ERR_PTR(-EACCES);
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prog = inode->i_private;
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ret = security_bpf_prog(prog);
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if (ret < 0)
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return ERR_PTR(ret);
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if (!bpf_prog_get_ok(prog, &type, false))
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return ERR_PTR(-EINVAL);
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bpf_prog_inc(prog);
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return prog;
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}
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struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
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{
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struct bpf_prog *prog;
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struct path path;
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int ret = kern_path(name, LOOKUP_FOLLOW, &path);
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if (ret)
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return ERR_PTR(ret);
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prog = __get_prog_inode(d_backing_inode(path.dentry), type);
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if (!IS_ERR(prog))
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touch_atime(&path);
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path_put(&path);
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return prog;
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}
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EXPORT_SYMBOL(bpf_prog_get_type_path);
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/*
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* Display the mount options in /proc/mounts.
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*/
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static int bpf_show_options(struct seq_file *m, struct dentry *root)
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{
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umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;
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if (mode != S_IRWXUGO)
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seq_printf(m, ",mode=%o", mode);
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return 0;
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}
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static void bpf_free_inode(struct inode *inode)
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{
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enum bpf_type type;
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if (S_ISLNK(inode->i_mode))
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kfree(inode->i_link);
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if (!bpf_inode_type(inode, &type))
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bpf_any_put(inode->i_private, type);
|
|
free_inode_nonrcu(inode);
|
|
}
|
|
|
|
static const struct super_operations bpf_super_ops = {
|
|
.statfs = simple_statfs,
|
|
.drop_inode = generic_delete_inode,
|
|
.show_options = bpf_show_options,
|
|
.free_inode = bpf_free_inode,
|
|
};
|
|
|
|
enum {
|
|
OPT_MODE,
|
|
};
|
|
|
|
static const struct fs_parameter_spec bpf_fs_parameters[] = {
|
|
fsparam_u32oct ("mode", OPT_MODE),
|
|
{}
|
|
};
|
|
|
|
struct bpf_mount_opts {
|
|
umode_t mode;
|
|
};
|
|
|
|
static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param)
|
|
{
|
|
struct bpf_mount_opts *opts = fc->fs_private;
|
|
struct fs_parse_result result;
|
|
int opt;
|
|
|
|
opt = fs_parse(fc, bpf_fs_parameters, param, &result);
|
|
if (opt < 0)
|
|
/* 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 opt == -ENOPARAM ? 0 : opt;
|
|
|
|
switch (opt) {
|
|
case OPT_MODE:
|
|
opts->mode = result.uint_32 & S_IALLUGO;
|
|
break;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int bpf_fill_super(struct super_block *sb, struct fs_context *fc)
|
|
{
|
|
static const struct tree_descr bpf_rfiles[] = { { "" } };
|
|
struct bpf_mount_opts *opts = fc->fs_private;
|
|
struct inode *inode;
|
|
int 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 int bpf_get_tree(struct fs_context *fc)
|
|
{
|
|
return get_tree_nodev(fc, bpf_fill_super);
|
|
}
|
|
|
|
static void bpf_free_fc(struct fs_context *fc)
|
|
{
|
|
kfree(fc->fs_private);
|
|
}
|
|
|
|
static const struct fs_context_operations bpf_context_ops = {
|
|
.free = bpf_free_fc,
|
|
.parse_param = bpf_parse_param,
|
|
.get_tree = bpf_get_tree,
|
|
};
|
|
|
|
/*
|
|
* Set up the filesystem mount context.
|
|
*/
|
|
static int bpf_init_fs_context(struct fs_context *fc)
|
|
{
|
|
struct bpf_mount_opts *opts;
|
|
|
|
opts = kzalloc(sizeof(struct bpf_mount_opts), GFP_KERNEL);
|
|
if (!opts)
|
|
return -ENOMEM;
|
|
|
|
opts->mode = S_IRWXUGO;
|
|
|
|
fc->fs_private = opts;
|
|
fc->ops = &bpf_context_ops;
|
|
return 0;
|
|
}
|
|
|
|
static struct file_system_type bpf_fs_type = {
|
|
.owner = THIS_MODULE,
|
|
.name = "bpf",
|
|
.init_fs_context = bpf_init_fs_context,
|
|
.parameters = bpf_fs_parameters,
|
|
.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);
|