388 строки
7.4 KiB
C
388 строки
7.4 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* version 2 as published by the Free Software Foundation.
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*/
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#include <linux/module.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/kdev_t.h>
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#include <linux/filter.h>
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#include <linux/bpf.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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raw = bpf_prog_inc(raw);
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break;
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case BPF_TYPE_MAP:
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raw = bpf_map_inc(raw, true);
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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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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;
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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 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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d_instantiate(dentry, inode);
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dget(dentry);
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return 0;
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}
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static int bpf_mkobj_ops(struct inode *dir, struct dentry *dentry,
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umode_t mode, const struct inode_operations *iops)
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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_IFREG);
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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_private = dentry->d_fsdata;
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d_instantiate(dentry, inode);
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dget(dentry);
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return 0;
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}
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static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode,
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dev_t devt)
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{
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enum bpf_type type = MINOR(devt);
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if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) ||
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dentry->d_fsdata == NULL)
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return -EPERM;
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switch (type) {
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case BPF_TYPE_PROG:
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return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops);
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case BPF_TYPE_MAP:
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return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops);
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default:
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return -EPERM;
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}
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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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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 const struct inode_operations bpf_dir_iops = {
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.lookup = bpf_lookup,
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.mknod = bpf_mkobj,
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.mkdir = bpf_mkdir,
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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 struct filename *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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dev_t devt;
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int ret;
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dentry = kern_path_create(AT_FDCWD, pathname->name, &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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devt = MKDEV(UNNAMED_MAJOR, type);
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ret = security_path_mknod(&path, dentry, mode, devt);
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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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dentry->d_fsdata = raw;
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ret = vfs_mknod(dir, dentry, mode, devt);
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dentry->d_fsdata = NULL;
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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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struct filename *pname;
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enum bpf_type type;
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void *raw;
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int ret;
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pname = getname(pathname);
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if (IS_ERR(pname))
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return PTR_ERR(pname);
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raw = bpf_fd_probe_obj(ufd, &type);
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if (IS_ERR(raw)) {
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ret = PTR_ERR(raw);
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goto out;
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}
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ret = bpf_obj_do_pin(pname, raw, type);
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if (ret != 0)
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bpf_any_put(raw, type);
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out:
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putname(pname);
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return ret;
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}
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static void *bpf_obj_do_get(const struct filename *pathname,
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enum bpf_type *type)
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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 = kern_path(pathname->name, 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, MAY_WRITE);
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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)
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{
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enum bpf_type type = BPF_TYPE_UNSPEC;
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struct filename *pname;
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int ret = -ENOENT;
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void *raw;
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pname = getname(pathname);
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if (IS_ERR(pname))
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return PTR_ERR(pname);
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raw = bpf_obj_do_get(pname, &type);
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if (IS_ERR(raw)) {
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ret = PTR_ERR(raw);
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goto out;
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}
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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);
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else
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goto out;
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if (ret < 0)
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bpf_any_put(raw, type);
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out:
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putname(pname);
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return ret;
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}
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static void bpf_evict_inode(struct inode *inode)
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{
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enum bpf_type type;
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truncate_inode_pages_final(&inode->i_data);
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clear_inode(inode);
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if (!bpf_inode_type(inode, &type))
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bpf_any_put(inode->i_private, type);
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}
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static const struct super_operations bpf_super_ops = {
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.statfs = simple_statfs,
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.drop_inode = generic_delete_inode,
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.evict_inode = bpf_evict_inode,
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};
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static int bpf_fill_super(struct super_block *sb, void *data, int silent)
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{
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static struct tree_descr bpf_rfiles[] = { { "" } };
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struct inode *inode;
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int ret;
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ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
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if (ret)
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return ret;
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sb->s_op = &bpf_super_ops;
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inode = sb->s_root->d_inode;
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inode->i_op = &bpf_dir_iops;
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inode->i_mode &= ~S_IALLUGO;
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inode->i_mode |= S_ISVTX | S_IRWXUGO;
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return 0;
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}
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static struct dentry *bpf_mount(struct file_system_type *type, int flags,
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const char *dev_name, void *data)
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{
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return mount_nodev(type, flags, data, bpf_fill_super);
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}
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static struct file_system_type bpf_fs_type = {
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.owner = THIS_MODULE,
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.name = "bpf",
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.mount = bpf_mount,
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.kill_sb = kill_litter_super,
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.fs_flags = FS_USERNS_MOUNT,
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};
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MODULE_ALIAS_FS("bpf");
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static int __init bpf_init(void)
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{
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int ret;
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ret = sysfs_create_mount_point(fs_kobj, "bpf");
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if (ret)
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return ret;
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ret = register_filesystem(&bpf_fs_type);
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if (ret)
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sysfs_remove_mount_point(fs_kobj, "bpf");
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return ret;
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}
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fs_initcall(bpf_init);
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