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 atomic_inc(&((struct bpf_map *)raw)->refcnt); 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(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(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 const struct inode_operations bpf_dir_iops = { 191 .lookup = simple_lookup, 192 .mknod = bpf_mkobj, 193 .mkdir = bpf_mkdir, 194 .rmdir = simple_rmdir, 195 .unlink = simple_unlink, 196 }; 197 198 static int bpf_obj_do_pin(const struct filename *pathname, void *raw, 199 enum bpf_type type) 200 { 201 struct dentry *dentry; 202 struct inode *dir; 203 struct path path; 204 umode_t mode; 205 dev_t devt; 206 int ret; 207 208 dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0); 209 if (IS_ERR(dentry)) 210 return PTR_ERR(dentry); 211 212 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 213 devt = MKDEV(UNNAMED_MAJOR, type); 214 215 ret = security_path_mknod(&path, dentry, mode, devt); 216 if (ret) 217 goto out; 218 219 dir = d_inode(path.dentry); 220 if (dir->i_op != &bpf_dir_iops) { 221 ret = -EPERM; 222 goto out; 223 } 224 225 dentry->d_fsdata = raw; 226 ret = vfs_mknod(dir, dentry, mode, devt); 227 dentry->d_fsdata = NULL; 228 out: 229 done_path_create(&path, dentry); 230 return ret; 231 } 232 233 int bpf_obj_pin_user(u32 ufd, const char __user *pathname) 234 { 235 struct filename *pname; 236 enum bpf_type type; 237 void *raw; 238 int ret; 239 240 pname = getname(pathname); 241 if (IS_ERR(pname)) 242 return PTR_ERR(pname); 243 244 raw = bpf_fd_probe_obj(ufd, &type); 245 if (IS_ERR(raw)) { 246 ret = PTR_ERR(raw); 247 goto out; 248 } 249 250 ret = bpf_obj_do_pin(pname, raw, type); 251 if (ret != 0) 252 bpf_any_put(raw, type); 253 out: 254 putname(pname); 255 return ret; 256 } 257 258 static void *bpf_obj_do_get(const struct filename *pathname, 259 enum bpf_type *type) 260 { 261 struct inode *inode; 262 struct path path; 263 void *raw; 264 int ret; 265 266 ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path); 267 if (ret) 268 return ERR_PTR(ret); 269 270 inode = d_backing_inode(path.dentry); 271 ret = inode_permission(inode, MAY_WRITE); 272 if (ret) 273 goto out; 274 275 ret = bpf_inode_type(inode, type); 276 if (ret) 277 goto out; 278 279 raw = bpf_any_get(inode->i_private, *type); 280 touch_atime(&path); 281 282 path_put(&path); 283 return raw; 284 out: 285 path_put(&path); 286 return ERR_PTR(ret); 287 } 288 289 int bpf_obj_get_user(const char __user *pathname) 290 { 291 enum bpf_type type = BPF_TYPE_UNSPEC; 292 struct filename *pname; 293 int ret = -ENOENT; 294 void *raw; 295 296 pname = getname(pathname); 297 if (IS_ERR(pname)) 298 return PTR_ERR(pname); 299 300 raw = bpf_obj_do_get(pname, &type); 301 if (IS_ERR(raw)) { 302 ret = PTR_ERR(raw); 303 goto out; 304 } 305 306 if (type == BPF_TYPE_PROG) 307 ret = bpf_prog_new_fd(raw); 308 else if (type == BPF_TYPE_MAP) 309 ret = bpf_map_new_fd(raw); 310 else 311 goto out; 312 313 if (ret < 0) 314 bpf_any_put(raw, type); 315 out: 316 putname(pname); 317 return ret; 318 } 319 320 static void bpf_evict_inode(struct inode *inode) 321 { 322 enum bpf_type type; 323 324 truncate_inode_pages_final(&inode->i_data); 325 clear_inode(inode); 326 327 if (!bpf_inode_type(inode, &type)) 328 bpf_any_put(inode->i_private, type); 329 } 330 331 static const struct super_operations bpf_super_ops = { 332 .statfs = simple_statfs, 333 .drop_inode = generic_delete_inode, 334 .evict_inode = bpf_evict_inode, 335 }; 336 337 static int bpf_fill_super(struct super_block *sb, void *data, int silent) 338 { 339 static struct tree_descr bpf_rfiles[] = { { "" } }; 340 struct inode *inode; 341 int ret; 342 343 ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); 344 if (ret) 345 return ret; 346 347 sb->s_op = &bpf_super_ops; 348 349 inode = sb->s_root->d_inode; 350 inode->i_op = &bpf_dir_iops; 351 inode->i_mode &= ~S_IALLUGO; 352 inode->i_mode |= S_ISVTX | S_IRWXUGO; 353 354 return 0; 355 } 356 357 static struct dentry *bpf_mount(struct file_system_type *type, int flags, 358 const char *dev_name, void *data) 359 { 360 return mount_ns(type, flags, current->nsproxy->mnt_ns, bpf_fill_super); 361 } 362 363 static struct file_system_type bpf_fs_type = { 364 .owner = THIS_MODULE, 365 .name = "bpf", 366 .mount = bpf_mount, 367 .kill_sb = kill_litter_super, 368 .fs_flags = FS_USERNS_MOUNT, 369 }; 370 371 MODULE_ALIAS_FS("bpf"); 372 373 static int __init bpf_init(void) 374 { 375 int ret; 376 377 ret = sysfs_create_mount_point(fs_kobj, "bpf"); 378 if (ret) 379 return ret; 380 381 ret = register_filesystem(&bpf_fs_type); 382 if (ret) 383 sysfs_remove_mount_point(fs_kobj, "bpf"); 384 385 return ret; 386 } 387 fs_initcall(bpf_init); 388