// SPDX-License-Identifier: GPL-2.0-only /* * Minimal file system backend for holding eBPF maps and programs, * used by bpf(2) object pinning. * * Authors: * * Daniel Borkmann <daniel@iogearbox.net> */ #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/fs_context.h> #include <linux/fs_parser.h> #include <linux/kdev_t.h> #include <linux/filter.h> #include <linux/bpf.h> #include <linux/bpf_trace.h> #include "preload/bpf_preload.h" enum bpf_type { BPF_TYPE_UNSPEC = 0, BPF_TYPE_PROG, BPF_TYPE_MAP, BPF_TYPE_LINK, }; static void *bpf_any_get(void *raw, enum bpf_type type) { switch (type) { case BPF_TYPE_PROG: bpf_prog_inc(raw); break; case BPF_TYPE_MAP: bpf_map_inc_with_uref(raw); break; case BPF_TYPE_LINK: bpf_link_inc(raw); 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; case BPF_TYPE_LINK: bpf_link_put(raw); break; default: WARN_ON_ONCE(1); break; } } static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) { void *raw; raw = bpf_map_get_with_uref(ufd); if (!IS_ERR(raw)) { *type = BPF_TYPE_MAP; return raw; } raw = bpf_prog_get(ufd); if (!IS_ERR(raw)) { *type = BPF_TYPE_PROG; return raw; } raw = bpf_link_get_from_fd(ufd); if (!IS_ERR(raw)) { *type = BPF_TYPE_LINK; return raw; } return ERR_PTR(-EINVAL); } 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 const struct inode_operations bpf_link_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(&init_user_ns, 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 if (inode->i_op == &bpf_link_iops) *type = BPF_TYPE_LINK; 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 user_namespace *mnt_userns, 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; (*pos)++; if (map_iter(m)->done) return NULL; if (unlikely(v == SEQ_START_TOKEN)) prev_key = NULL; else prev_key = key; rcu_read_lock(); if (map->ops->map_get_next_key(map, prev_key, key)) { map_iter(m)->done = true; key = NULL; } rcu_read_unlock(); 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 int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg) { struct bpf_link *link = arg; return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops, bpf_link_is_iter(link) ? &bpf_iter_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. That allows popoulate_bpffs() create special files. */ if ((dir->i_mode & S_IALLUGO) && strchr(dentry->d_name.name, '.')) return ERR_PTR(-EPERM); return simple_lookup(dir, dentry, flags); } static int bpf_symlink(struct user_namespace *mnt_userns, 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, }; /* pin iterator link into bpffs */ static int bpf_iter_link_pin_kernel(struct dentry *parent, const char *name, struct bpf_link *link) { umode_t mode = S_IFREG | S_IRUSR; struct dentry *dentry; int ret; inode_lock(parent->d_inode); dentry = lookup_one_len(name, parent, strlen(name)); if (IS_ERR(dentry)) { inode_unlock(parent->d_inode); return PTR_ERR(dentry); } ret = bpf_mkobj_ops(dentry, mode, link, &bpf_link_iops, &bpf_iter_fops); dput(dentry); inode_unlock(parent->d_inode); return ret; } static int bpf_obj_do_pin(const char __user *pathname, void *raw, enum bpf_type type) { struct dentry *dentry; struct inode *dir; struct path path; umode_t mode; int ret; dentry = user_path_create(AT_FDCWD, pathname, &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; case BPF_TYPE_LINK: ret = vfs_mkobj(dentry, mode, bpf_mklink, raw); break; default: ret = -EPERM; } out: done_path_create(&path, dentry); return ret; } int bpf_obj_pin_user(u32 ufd, const char __user *pathname) { enum bpf_type type; void *raw; int ret; raw = bpf_fd_probe_obj(ufd, &type); if (IS_ERR(raw)) return PTR_ERR(raw); ret = bpf_obj_do_pin(pathname, raw, type); if (ret != 0) bpf_any_put(raw, type); return ret; } static void *bpf_obj_do_get(const char __user *pathname, enum bpf_type *type, int flags) { struct inode *inode; struct path path; void *raw; int ret; ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path); if (ret) return ERR_PTR(ret); inode = d_backing_inode(path.dentry); ret = path_permission(&path, 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; int f_flags; void *raw; int ret; f_flags = bpf_get_file_flag(flags); if (f_flags < 0) return f_flags; raw = bpf_obj_do_get(pathname, &type, f_flags); if (IS_ERR(raw)) return PTR_ERR(raw); 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 if (type == BPF_TYPE_LINK) ret = (f_flags != O_RDWR) ? -EINVAL : bpf_link_new_fd(raw); else return -ENOENT; if (ret < 0) bpf_any_put(raw, type); 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(&init_user_ns, inode, MAY_READ); if (ret) return ERR_PTR(ret); if (inode->i_op == &bpf_map_iops) return ERR_PTR(-EINVAL); if (inode->i_op == &bpf_link_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); bpf_prog_inc(prog); return 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_free_inode(struct inode *inode) { 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 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. */ if (opt == -ENOPARAM) { opt = vfs_parse_fs_param_source(fc, param); if (opt != -ENOPARAM) return opt; return 0; } if (opt < 0) return opt; } switch (opt) { case OPT_MODE: opts->mode = result.uint_32 & S_IALLUGO; break; } return 0; } struct bpf_preload_ops *bpf_preload_ops; EXPORT_SYMBOL_GPL(bpf_preload_ops); static bool bpf_preload_mod_get(void) { /* If bpf_preload.ko wasn't loaded earlier then load it now. * When bpf_preload is built into vmlinux the module's __init * function will populate it. */ if (!bpf_preload_ops) { request_module("bpf_preload"); if (!bpf_preload_ops) return false; } /* And grab the reference, so the module doesn't disappear while the * kernel is interacting with the kernel module and its UMD. */ if (!try_module_get(bpf_preload_ops->owner)) { pr_err("bpf_preload module get failed.\n"); return false; } return true; } static void bpf_preload_mod_put(void) { if (bpf_preload_ops) /* now user can "rmmod bpf_preload" if necessary */ module_put(bpf_preload_ops->owner); } static DEFINE_MUTEX(bpf_preload_lock); static int populate_bpffs(struct dentry *parent) { struct bpf_preload_info objs[BPF_PRELOAD_LINKS] = {}; struct bpf_link *links[BPF_PRELOAD_LINKS] = {}; int err = 0, i; /* grab the mutex to make sure the kernel interactions with bpf_preload * UMD are serialized */ mutex_lock(&bpf_preload_lock); /* if bpf_preload.ko wasn't built into vmlinux then load it */ if (!bpf_preload_mod_get()) goto out; if (!bpf_preload_ops->info.tgid) { /* preload() will start UMD that will load BPF iterator programs */ err = bpf_preload_ops->preload(objs); if (err) goto out_put; for (i = 0; i < BPF_PRELOAD_LINKS; i++) { links[i] = bpf_link_by_id(objs[i].link_id); if (IS_ERR(links[i])) { err = PTR_ERR(links[i]); goto out_put; } } for (i = 0; i < BPF_PRELOAD_LINKS; i++) { err = bpf_iter_link_pin_kernel(parent, objs[i].link_name, links[i]); if (err) goto out_put; /* do not unlink successfully pinned links even * if later link fails to pin */ links[i] = NULL; } /* finish() will tell UMD process to exit */ err = bpf_preload_ops->finish(); if (err) goto out_put; } out_put: bpf_preload_mod_put(); out: mutex_unlock(&bpf_preload_lock); for (i = 0; i < BPF_PRELOAD_LINKS && err; i++) if (!IS_ERR_OR_NULL(links[i])) bpf_link_put(links[i]); return err; } 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; populate_bpffs(sb->s_root); 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);