kernel/bpf/inode.c

   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/init.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                 raw = bpf_prog_inc(raw);
  35                 break;
  36         case BPF_TYPE_MAP:
  37                 raw = 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(inode);
 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 int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 123 {
 124         struct inode *inode;
 125
 126         inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
 127         if (IS_ERR(inode))
 128                 return PTR_ERR(inode);
 129
 130         inode->i_op = &bpf_dir_iops;
 131         inode->i_fop = &simple_dir_operations;
 132
 133         inc_nlink(inode);
 134         inc_nlink(dir);
 135
 136         d_instantiate(dentry, inode);
 137         dget(dentry);
 138
 139         return 0;
 140 }
 141
 142 static int bpf_mkobj_ops(struct inode *dir, struct dentry *dentry,
 143                          umode_t mode, const struct inode_operations *iops)
 144 {
 145         struct inode *inode;
 146
 147         inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFREG);
 148         if (IS_ERR(inode))
 149                 return PTR_ERR(inode);
 150
 151         inode->i_op = iops;
 152         inode->i_private = dentry->d_fsdata;
 153
 154         d_instantiate(dentry, inode);
 155         dget(dentry);
 156
 157         return 0;
 158 }
 159
 160 static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode,
 161                      dev_t devt)
 162 {
 163         enum bpf_type type = MINOR(devt);
 164
 165         if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) ||
 166             dentry->d_fsdata == NULL)
 167                 return -EPERM;
 168
 169         switch (type) {
 170         case BPF_TYPE_PROG:
 171                 return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops);
 172         case BPF_TYPE_MAP:
 173                 return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops);
 174         default:
 175                 return -EPERM;
 176         }
 177 }
 178
 179 static struct dentry *
 180 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
 181 {
 182         if (strchr(dentry->d_name.name, '.'))
 183                 return ERR_PTR(-EPERM);
 184         return simple_lookup(dir, dentry, flags);
 185 }
 186
 187 static const struct inode_operations bpf_dir_iops = {
 188         .lookup         = bpf_lookup,
 189         .mknod          = bpf_mkobj,
 190         .mkdir          = bpf_mkdir,
 191         .rmdir          = simple_rmdir,
 192         .rename         = simple_rename,
 193         .link           = simple_link,
 194         .unlink         = simple_unlink,
 195 };
 196
 197 static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
 198                           enum bpf_type type)
 199 {
 200         struct dentry *dentry;
 201         struct inode *dir;
 202         struct path path;
 203         umode_t mode;
 204         dev_t devt;
 205         int ret;
 206
 207         dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
 208         if (IS_ERR(dentry))
 209                 return PTR_ERR(dentry);
 210
 211         mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
 212         devt = MKDEV(UNNAMED_MAJOR, type);
 213
 214         ret = security_path_mknod(&path, dentry, mode, devt);
 215         if (ret)
 216                 goto out;
 217
 218         dir = d_inode(path.dentry);
 219         if (dir->i_op != &bpf_dir_iops) {
 220                 ret = -EPERM;
 221                 goto out;
 222         }
 223
 224         dentry->d_fsdata = raw;
 225         ret = vfs_mknod(dir, dentry, mode, devt);
 226         dentry->d_fsdata = NULL;
 227 out:
 228         done_path_create(&path, dentry);
 229         return ret;
 230 }
 231
 232 int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
 233 {
 234         struct filename *pname;
 235         enum bpf_type type;
 236         void *raw;
 237         int ret;
 238
 239         pname = getname(pathname);
 240         if (IS_ERR(pname))
 241                 return PTR_ERR(pname);
 242
 243         raw = bpf_fd_probe_obj(ufd, &type);
 244         if (IS_ERR(raw)) {
 245                 ret = PTR_ERR(raw);
 246                 goto out;
 247         }
 248
 249         ret = bpf_obj_do_pin(pname, raw, type);
 250         if (ret != 0)
 251                 bpf_any_put(raw, type);
 252 out:
 253         putname(pname);
 254         return ret;
 255 }
 256
 257 static void *bpf_obj_do_get(const struct filename *pathname,
 258                             enum bpf_type *type)
 259 {
 260         struct inode *inode;
 261         struct path path;
 262         void *raw;
 263         int ret;
 264
 265         ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
 266         if (ret)
 267                 return ERR_PTR(ret);
 268
 269         inode = d_backing_inode(path.dentry);
 270         ret = inode_permission(inode, MAY_WRITE);
 271         if (ret)
 272                 goto out;
 273
 274         ret = bpf_inode_type(inode, type);
 275         if (ret)
 276                 goto out;
 277
 278         raw = bpf_any_get(inode->i_private, *type);
 279         if (!IS_ERR(raw))
 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_nodev(type, flags, data, 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 };
 369
 370 static int __init bpf_init(void)
 371 {
 372         int ret;
 373
 374         ret = sysfs_create_mount_point(fs_kobj, "bpf");
 375         if (ret)
 376                 return ret;
 377
 378         ret = register_filesystem(&bpf_fs_type);
 379         if (ret)
 380                 sysfs_remove_mount_point(fs_kobj, "bpf");
 381
 382         return ret;
 383 }
 384 fs_initcall(bpf_init);