1 /* 2 * Minimal file system backend for holding eBPF maps and programs, 3 * used by bpf(2) object pinning. 4 * 5 * Authors: 6 * 7 * Daniel Borkmann <daniel@iogearbox.net> 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License 11 * version 2 as published by the Free Software Foundation. 12 */ 13 14 #include <linux/module.h> 15 #include <linux/magic.h> 16 #include <linux/major.h> 17 #include <linux/mount.h> 18 #include <linux/namei.h> 19 #include <linux/fs.h> 20 #include <linux/kdev_t.h> 21 #include <linux/filter.h> 22 #include <linux/bpf.h> 23 24 enum bpf_type { 25 BPF_TYPE_UNSPEC = 0, 26 BPF_TYPE_PROG, 27 BPF_TYPE_MAP, 28 }; 29 30 static void *bpf_any_get(void *raw, enum bpf_type type) 31 { 32 switch (type) { 33 case BPF_TYPE_PROG: 34 atomic_inc(&((struct bpf_prog *)raw)->aux->refcnt); 35 break; 36 case BPF_TYPE_MAP: 37 bpf_map_inc(raw, true); 38 break; 39 default: 40 WARN_ON_ONCE(1); 41 break; 42 } 43 44 return raw; 45 } 46 47 static void bpf_any_put(void *raw, enum bpf_type type) 48 { 49 switch (type) { 50 case BPF_TYPE_PROG: 51 bpf_prog_put(raw); 52 break; 53 case BPF_TYPE_MAP: 54 bpf_map_put_with_uref(raw); 55 break; 56 default: 57 WARN_ON_ONCE(1); 58 break; 59 } 60 } 61 62 static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) 63 { 64 void *raw; 65 66 *type = BPF_TYPE_MAP; 67 raw = bpf_map_get_with_uref(ufd); 68 if (IS_ERR(raw)) { 69 *type = BPF_TYPE_PROG; 70 raw = bpf_prog_get(ufd); 71 } 72 73 return raw; 74 } 75 76 static const struct inode_operations bpf_dir_iops; 77 78 static const struct inode_operations bpf_prog_iops = { }; 79 static const struct inode_operations bpf_map_iops = { }; 80 81 static struct inode *bpf_get_inode(struct super_block *sb, 82 const struct inode *dir, 83 umode_t mode) 84 { 85 struct inode *inode; 86 87 switch (mode & S_IFMT) { 88 case S_IFDIR: 89 case S_IFREG: 90 break; 91 default: 92 return ERR_PTR(-EINVAL); 93 } 94 95 inode = new_inode(sb); 96 if (!inode) 97 return ERR_PTR(-ENOSPC); 98 99 inode->i_ino = get_next_ino(); 100 inode->i_atime = CURRENT_TIME; 101 inode->i_mtime = inode->i_atime; 102 inode->i_ctime = inode->i_atime; 103 104 inode_init_owner(inode, dir, mode); 105 106 return inode; 107 } 108 109 static int bpf_inode_type(const struct inode *inode, enum bpf_type *type) 110 { 111 *type = BPF_TYPE_UNSPEC; 112 if (inode->i_op == &bpf_prog_iops) 113 *type = BPF_TYPE_PROG; 114 else if (inode->i_op == &bpf_map_iops) 115 *type = BPF_TYPE_MAP; 116 else 117 return -EACCES; 118 119 return 0; 120 } 121 122 static bool bpf_dname_reserved(const struct dentry *dentry) 123 { 124 return strchr(dentry->d_name.name, '.'); 125 } 126 127 static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 128 { 129 struct inode *inode; 130 131 if (bpf_dname_reserved(dentry)) 132 return -EPERM; 133 134 inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR); 135 if (IS_ERR(inode)) 136 return PTR_ERR(inode); 137 138 inode->i_op = &bpf_dir_iops; 139 inode->i_fop = &simple_dir_operations; 140 141 inc_nlink(inode); 142 inc_nlink(dir); 143 144 d_instantiate(dentry, inode); 145 dget(dentry); 146 147 return 0; 148 } 149 150 static int bpf_mkobj_ops(struct inode *dir, struct dentry *dentry, 151 umode_t mode, const struct inode_operations *iops) 152 { 153 struct inode *inode; 154 155 if (bpf_dname_reserved(dentry)) 156 return -EPERM; 157 158 inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFREG); 159 if (IS_ERR(inode)) 160 return PTR_ERR(inode); 161 162 inode->i_op = iops; 163 inode->i_private = dentry->d_fsdata; 164 165 d_instantiate(dentry, inode); 166 dget(dentry); 167 168 return 0; 169 } 170 171 static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode, 172 dev_t devt) 173 { 174 enum bpf_type type = MINOR(devt); 175 176 if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) || 177 dentry->d_fsdata == NULL) 178 return -EPERM; 179 180 switch (type) { 181 case BPF_TYPE_PROG: 182 return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops); 183 case BPF_TYPE_MAP: 184 return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops); 185 default: 186 return -EPERM; 187 } 188 } 189 190 static int bpf_link(struct dentry *old_dentry, struct inode *dir, 191 struct dentry *new_dentry) 192 { 193 if (bpf_dname_reserved(new_dentry)) 194 return -EPERM; 195 196 return simple_link(old_dentry, dir, new_dentry); 197 } 198 199 static int bpf_rename(struct inode *old_dir, struct dentry *old_dentry, 200 struct inode *new_dir, struct dentry *new_dentry) 201 { 202 if (bpf_dname_reserved(new_dentry)) 203 return -EPERM; 204 205 return simple_rename(old_dir, old_dentry, new_dir, new_dentry); 206 } 207 208 static const struct inode_operations bpf_dir_iops = { 209 .lookup = simple_lookup, 210 .mknod = bpf_mkobj, 211 .mkdir = bpf_mkdir, 212 .rmdir = simple_rmdir, 213 .rename = bpf_rename, 214 .link = bpf_link, 215 .unlink = simple_unlink, 216 }; 217 218 static int bpf_obj_do_pin(const struct filename *pathname, void *raw, 219 enum bpf_type type) 220 { 221 struct dentry *dentry; 222 struct inode *dir; 223 struct path path; 224 umode_t mode; 225 dev_t devt; 226 int ret; 227 228 dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0); 229 if (IS_ERR(dentry)) 230 return PTR_ERR(dentry); 231 232 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 233 devt = MKDEV(UNNAMED_MAJOR, type); 234 235 ret = security_path_mknod(&path, dentry, mode, devt); 236 if (ret) 237 goto out; 238 239 dir = d_inode(path.dentry); 240 if (dir->i_op != &bpf_dir_iops) { 241 ret = -EPERM; 242 goto out; 243 } 244 245 dentry->d_fsdata = raw; 246 ret = vfs_mknod(dir, dentry, mode, devt); 247 dentry->d_fsdata = NULL; 248 out: 249 done_path_create(&path, dentry); 250 return ret; 251 } 252 253 int bpf_obj_pin_user(u32 ufd, const char __user *pathname) 254 { 255 struct filename *pname; 256 enum bpf_type type; 257 void *raw; 258 int ret; 259 260 pname = getname(pathname); 261 if (IS_ERR(pname)) 262 return PTR_ERR(pname); 263 264 raw = bpf_fd_probe_obj(ufd, &type); 265 if (IS_ERR(raw)) { 266 ret = PTR_ERR(raw); 267 goto out; 268 } 269 270 ret = bpf_obj_do_pin(pname, raw, type); 271 if (ret != 0) 272 bpf_any_put(raw, type); 273 out: 274 putname(pname); 275 return ret; 276 } 277 278 static void *bpf_obj_do_get(const struct filename *pathname, 279 enum bpf_type *type) 280 { 281 struct inode *inode; 282 struct path path; 283 void *raw; 284 int ret; 285 286 ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path); 287 if (ret) 288 return ERR_PTR(ret); 289 290 inode = d_backing_inode(path.dentry); 291 ret = inode_permission(inode, MAY_WRITE); 292 if (ret) 293 goto out; 294 295 ret = bpf_inode_type(inode, type); 296 if (ret) 297 goto out; 298 299 raw = bpf_any_get(inode->i_private, *type); 300 touch_atime(&path); 301 302 path_put(&path); 303 return raw; 304 out: 305 path_put(&path); 306 return ERR_PTR(ret); 307 } 308 309 int bpf_obj_get_user(const char __user *pathname) 310 { 311 enum bpf_type type = BPF_TYPE_UNSPEC; 312 struct filename *pname; 313 int ret = -ENOENT; 314 void *raw; 315 316 pname = getname(pathname); 317 if (IS_ERR(pname)) 318 return PTR_ERR(pname); 319 320 raw = bpf_obj_do_get(pname, &type); 321 if (IS_ERR(raw)) { 322 ret = PTR_ERR(raw); 323 goto out; 324 } 325 326 if (type == BPF_TYPE_PROG) 327 ret = bpf_prog_new_fd(raw); 328 else if (type == BPF_TYPE_MAP) 329 ret = bpf_map_new_fd(raw); 330 else 331 goto out; 332 333 if (ret < 0) 334 bpf_any_put(raw, type); 335 out: 336 putname(pname); 337 return ret; 338 } 339 340 static void bpf_evict_inode(struct inode *inode) 341 { 342 enum bpf_type type; 343 344 truncate_inode_pages_final(&inode->i_data); 345 clear_inode(inode); 346 347 if (!bpf_inode_type(inode, &type)) 348 bpf_any_put(inode->i_private, type); 349 } 350 351 static const struct super_operations bpf_super_ops = { 352 .statfs = simple_statfs, 353 .drop_inode = generic_delete_inode, 354 .evict_inode = bpf_evict_inode, 355 }; 356 357 static int bpf_fill_super(struct super_block *sb, void *data, int silent) 358 { 359 static struct tree_descr bpf_rfiles[] = { { "" } }; 360 struct inode *inode; 361 int ret; 362 363 ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); 364 if (ret) 365 return ret; 366 367 sb->s_op = &bpf_super_ops; 368 369 inode = sb->s_root->d_inode; 370 inode->i_op = &bpf_dir_iops; 371 inode->i_mode &= ~S_IALLUGO; 372 inode->i_mode |= S_ISVTX | S_IRWXUGO; 373 374 return 0; 375 } 376 377 static struct dentry *bpf_mount(struct file_system_type *type, int flags, 378 const char *dev_name, void *data) 379 { 380 return mount_ns(type, flags, current->nsproxy->mnt_ns, bpf_fill_super); 381 } 382 383 static struct file_system_type bpf_fs_type = { 384 .owner = THIS_MODULE, 385 .name = "bpf", 386 .mount = bpf_mount, 387 .kill_sb = kill_litter_super, 388 .fs_flags = FS_USERNS_MOUNT, 389 }; 390 391 MODULE_ALIAS_FS("bpf"); 392 393 static int __init bpf_init(void) 394 { 395 int ret; 396 397 ret = sysfs_create_mount_point(fs_kobj, "bpf"); 398 if (ret) 399 return ret; 400 401 ret = register_filesystem(&bpf_fs_type); 402 if (ret) 403 sysfs_remove_mount_point(fs_kobj, "bpf"); 404 405 return ret; 406 } 407 fs_initcall(bpf_init); 408