fs/overlayfs/util.c

   1 /*
   2  * Copyright (C) 2011 Novell Inc.
   3  * Copyright (C) 2016 Red Hat, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  */
   9
  10 #include <linux/fs.h>
  11 #include <linux/mount.h>
  12 #include <linux/slab.h>
  13 #include <linux/cred.h>
  14 #include <linux/xattr.h>
  15 #include <linux/exportfs.h>
  16 #include <linux/uuid.h>
  17 #include <linux/namei.h>
  18 #include <linux/ratelimit.h>
  19 #include "overlayfs.h"
  20 #include "ovl_entry.h"
  21
  22 int ovl_want_write(struct dentry *dentry)
  23 {
  24         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  25         return mnt_want_write(ofs->upper_mnt);
  26 }
  27
  28 void ovl_drop_write(struct dentry *dentry)
  29 {
  30         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  31         mnt_drop_write(ofs->upper_mnt);
  32 }
  33
  34 struct dentry *ovl_workdir(struct dentry *dentry)
  35 {
  36         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  37         return ofs->workdir;
  38 }
  39
  40 const struct cred *ovl_override_creds(struct super_block *sb)
  41 {
  42         struct ovl_fs *ofs = sb->s_fs_info;
  43
  44         return override_creds(ofs->creator_cred);
  45 }
  46
  47 struct super_block *ovl_same_sb(struct super_block *sb)
  48 {
  49         struct ovl_fs *ofs = sb->s_fs_info;
  50
  51         return ofs->same_sb;
  52 }
  53
  54 bool ovl_can_decode_fh(struct super_block *sb)
  55 {
  56         return (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
  57                 !uuid_is_null(&sb->s_uuid));
  58 }
  59
  60 struct dentry *ovl_indexdir(struct super_block *sb)
  61 {
  62         struct ovl_fs *ofs = sb->s_fs_info;
  63
  64         return ofs->indexdir;
  65 }
  66
  67 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  68 {
  69         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  70         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  71
  72         if (oe)
  73                 oe->numlower = numlower;
  74
  75         return oe;
  76 }
  77
  78 bool ovl_dentry_remote(struct dentry *dentry)
  79 {
  80         return dentry->d_flags &
  81                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
  82                  DCACHE_OP_REAL);
  83 }
  84
  85 bool ovl_dentry_weird(struct dentry *dentry)
  86 {
  87         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
  88                                   DCACHE_MANAGE_TRANSIT |
  89                                   DCACHE_OP_HASH |
  90                                   DCACHE_OP_COMPARE);
  91 }
  92
  93 enum ovl_path_type ovl_path_type(struct dentry *dentry)
  94 {
  95         struct ovl_entry *oe = dentry->d_fsdata;
  96         enum ovl_path_type type = 0;
  97
  98         if (ovl_dentry_upper(dentry)) {
  99                 type = __OVL_PATH_UPPER;
 100
 101                 /*
 102                  * Non-dir dentry can hold lower dentry of its copy up origin.
 103                  */
 104                 if (oe->numlower) {
 105                         type |= __OVL_PATH_ORIGIN;
 106                         if (d_is_dir(dentry))
 107                                 type |= __OVL_PATH_MERGE;
 108                 }
 109         } else {
 110                 if (oe->numlower > 1)
 111                         type |= __OVL_PATH_MERGE;
 112         }
 113         return type;
 114 }
 115
 116 void ovl_path_upper(struct dentry *dentry, struct path *path)
 117 {
 118         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 119
 120         path->mnt = ofs->upper_mnt;
 121         path->dentry = ovl_dentry_upper(dentry);
 122 }
 123
 124 void ovl_path_lower(struct dentry *dentry, struct path *path)
 125 {
 126         struct ovl_entry *oe = dentry->d_fsdata;
 127
 128         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { };
 129 }
 130
 131 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 132 {
 133         enum ovl_path_type type = ovl_path_type(dentry);
 134
 135         if (!OVL_TYPE_UPPER(type))
 136                 ovl_path_lower(dentry, path);
 137         else
 138                 ovl_path_upper(dentry, path);
 139
 140         return type;
 141 }
 142
 143 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 144 {
 145         return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
 146 }
 147
 148 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 149 {
 150         struct ovl_entry *oe = dentry->d_fsdata;
 151
 152         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 153 }
 154
 155 struct dentry *ovl_dentry_real(struct dentry *dentry)
 156 {
 157         return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
 158 }
 159
 160 struct inode *ovl_inode_upper(struct inode *inode)
 161 {
 162         struct dentry *upperdentry = ovl_upperdentry_dereference(OVL_I(inode));
 163
 164         return upperdentry ? d_inode(upperdentry) : NULL;
 165 }
 166
 167 struct inode *ovl_inode_lower(struct inode *inode)
 168 {
 169         return OVL_I(inode)->lower;
 170 }
 171
 172 struct inode *ovl_inode_real(struct inode *inode)
 173 {
 174         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
 175 }
 176
 177
 178 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 179 {
 180         return OVL_I(d_inode(dentry))->cache;
 181 }
 182
 183 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 184 {
 185         OVL_I(d_inode(dentry))->cache = cache;
 186 }
 187
 188 bool ovl_dentry_is_opaque(struct dentry *dentry)
 189 {
 190         struct ovl_entry *oe = dentry->d_fsdata;
 191         return oe->opaque;
 192 }
 193
 194 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 195 {
 196         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 197 }
 198
 199 void ovl_dentry_set_opaque(struct dentry *dentry)
 200 {
 201         struct ovl_entry *oe = dentry->d_fsdata;
 202
 203         oe->opaque = true;
 204 }
 205
 206 /*
 207  * For hard links it's possible for ovl_dentry_upper() to return positive, while
 208  * there's no actual upper alias for the inode.  Copy up code needs to know
 209  * about the existence of the upper alias, so it can't use ovl_dentry_upper().
 210  */
 211 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
 212 {
 213         struct ovl_entry *oe = dentry->d_fsdata;
 214
 215         return oe->has_upper;
 216 }
 217
 218 void ovl_dentry_set_upper_alias(struct dentry *dentry)
 219 {
 220         struct ovl_entry *oe = dentry->d_fsdata;
 221
 222         oe->has_upper = true;
 223 }
 224
 225 bool ovl_redirect_dir(struct super_block *sb)
 226 {
 227         struct ovl_fs *ofs = sb->s_fs_info;
 228
 229         return ofs->config.redirect_dir && !ofs->noxattr;
 230 }
 231
 232 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 233 {
 234         return OVL_I(d_inode(dentry))->redirect;
 235 }
 236
 237 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 238 {
 239         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 240
 241         kfree(oi->redirect);
 242         oi->redirect = redirect;
 243 }
 244
 245 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 246                     struct dentry *lowerdentry)
 247 {
 248         if (upperdentry)
 249                 OVL_I(inode)->__upperdentry = upperdentry;
 250         if (lowerdentry)
 251                 OVL_I(inode)->lower = d_inode(lowerdentry);
 252
 253         ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
 254 }
 255
 256 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 257 {
 258         struct inode *upperinode = d_inode(upperdentry);
 259
 260         WARN_ON(OVL_I(inode)->__upperdentry);
 261
 262         /*
 263          * Make sure upperdentry is consistent before making it visible
 264          */
 265         smp_wmb();
 266         OVL_I(inode)->__upperdentry = upperdentry;
 267         if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
 268                 inode->i_private = upperinode;
 269                 __insert_inode_hash(inode, (unsigned long) upperinode);
 270         }
 271 }
 272
 273 void ovl_dentry_version_inc(struct dentry *dentry)
 274 {
 275         struct inode *inode = d_inode(dentry);
 276
 277         WARN_ON(!inode_is_locked(inode));
 278         OVL_I(inode)->version++;
 279 }
 280
 281 u64 ovl_dentry_version_get(struct dentry *dentry)
 282 {
 283         struct inode *inode = d_inode(dentry);
 284
 285         WARN_ON(!inode_is_locked(inode));
 286         return OVL_I(inode)->version;
 287 }
 288
 289 bool ovl_is_whiteout(struct dentry *dentry)
 290 {
 291         struct inode *inode = dentry->d_inode;
 292
 293         return inode && IS_WHITEOUT(inode);
 294 }
 295
 296 struct file *ovl_path_open(struct path *path, int flags)
 297 {
 298         return dentry_open(path, flags | O_NOATIME, current_cred());
 299 }
 300
 301 int ovl_copy_up_start(struct dentry *dentry)
 302 {
 303         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 304         int err;
 305
 306         err = mutex_lock_interruptible(&oi->lock);
 307         if (!err && ovl_dentry_has_upper_alias(dentry)) {
 308                 err = 1; /* Already copied up */
 309                 mutex_unlock(&oi->lock);
 310         }
 311
 312         return err;
 313 }
 314
 315 void ovl_copy_up_end(struct dentry *dentry)
 316 {
 317         mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 318 }
 319
 320 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
 321 {
 322         int res;
 323         char val;
 324
 325         if (!d_is_dir(dentry))
 326                 return false;
 327
 328         res = vfs_getxattr(dentry, name, &val, 1);
 329         if (res == 1 && val == 'y')
 330                 return true;
 331
 332         return false;
 333 }
 334
 335 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
 336                        const char *name, const void *value, size_t size,
 337                        int xerr)
 338 {
 339         int err;
 340         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 341
 342         if (ofs->noxattr)
 343                 return xerr;
 344
 345         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
 346
 347         if (err == -EOPNOTSUPP) {
 348                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
 349                 ofs->noxattr = true;
 350                 return xerr;
 351         }
 352
 353         return err;
 354 }
 355
 356 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
 357 {
 358         int err;
 359
 360         if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
 361                 return 0;
 362
 363         /*
 364          * Do not fail when upper doesn't support xattrs.
 365          * Upper inodes won't have origin nor redirect xattr anyway.
 366          */
 367         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
 368                                  "y", 1, 0);
 369         if (!err)
 370                 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
 371
 372         return err;
 373 }
 374
 375 void ovl_set_flag(unsigned long flag, struct inode *inode)
 376 {
 377         set_bit(flag, &OVL_I(inode)->flags);
 378 }
 379
 380 bool ovl_test_flag(unsigned long flag, struct inode *inode)
 381 {
 382         return test_bit(flag, &OVL_I(inode)->flags);
 383 }
 384
 385 /**
 386  * Caller must hold a reference to inode to prevent it from being freed while
 387  * it is marked inuse.
 388  */
 389 bool ovl_inuse_trylock(struct dentry *dentry)
 390 {
 391         struct inode *inode = d_inode(dentry);
 392         bool locked = false;
 393
 394         spin_lock(&inode->i_lock);
 395         if (!(inode->i_state & I_OVL_INUSE)) {
 396                 inode->i_state |= I_OVL_INUSE;
 397                 locked = true;
 398         }
 399         spin_unlock(&inode->i_lock);
 400
 401         return locked;
 402 }
 403
 404 void ovl_inuse_unlock(struct dentry *dentry)
 405 {
 406         if (dentry) {
 407                 struct inode *inode = d_inode(dentry);
 408
 409                 spin_lock(&inode->i_lock);
 410                 WARN_ON(!(inode->i_state & I_OVL_INUSE));
 411                 inode->i_state &= ~I_OVL_INUSE;
 412                 spin_unlock(&inode->i_lock);
 413         }
 414 }
 415
 416 /* Called must hold OVL_I(inode)->oi_lock */
 417 static void ovl_cleanup_index(struct dentry *dentry)
 418 {
 419         struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
 420         struct dentry *lowerdentry = ovl_dentry_lower(dentry);
 421         struct dentry *upperdentry = ovl_dentry_upper(dentry);
 422         struct dentry *index = NULL;
 423         struct inode *inode;
 424         struct qstr name;
 425         int err;
 426
 427         err = ovl_get_index_name(lowerdentry, &name);
 428         if (err)
 429                 goto fail;
 430
 431         inode = d_inode(upperdentry);
 432         if (inode->i_nlink != 1) {
 433                 pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
 434                                     upperdentry, inode->i_ino, inode->i_nlink);
 435                 /*
 436                  * We either have a bug with persistent union nlink or a lower
 437                  * hardlink was added while overlay is mounted. Adding a lower
 438                  * hardlink and then unlinking all overlay hardlinks would drop
 439                  * overlay nlink to zero before all upper inodes are unlinked.
 440                  * As a safety measure, when that situation is detected, set
 441                  * the overlay nlink to the index inode nlink minus one for the
 442                  * index entry itself.
 443                  */
 444                 set_nlink(d_inode(dentry), inode->i_nlink - 1);
 445                 ovl_set_nlink_upper(dentry);
 446                 goto out;
 447         }
 448
 449         inode_lock_nested(dir, I_MUTEX_PARENT);
 450         /* TODO: whiteout instead of cleanup to block future open by handle */
 451         index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
 452         err = PTR_ERR(index);
 453         if (!IS_ERR(index))
 454                 err = ovl_cleanup(dir, index);
 455         inode_unlock(dir);
 456         if (err)
 457                 goto fail;
 458
 459 out:
 460         dput(index);
 461         return;
 462
 463 fail:
 464         pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
 465         goto out;
 466 }
 467
 468 /*
 469  * Operations that change overlay inode and upper inode nlink need to be
 470  * synchronized with copy up for persistent nlink accounting.
 471  */
 472 int ovl_nlink_start(struct dentry *dentry, bool *locked)
 473 {
 474         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 475         const struct cred *old_cred;
 476         int err;
 477
 478         if (!d_inode(dentry) || d_is_dir(dentry))
 479                 return 0;
 480
 481         /*
 482          * With inodes index is enabled, we store the union overlay nlink
 483          * in an xattr on the index inode. When whiting out lower hardlinks
 484          * we need to decrement the overlay persistent nlink, but before the
 485          * first copy up, we have no upper index inode to store the xattr.
 486          *
 487          * As a workaround, before whiteout/rename over of a lower hardlink,
 488          * copy up to create the upper index. Creating the upper index will
 489          * initialize the overlay nlink, so it could be dropped if unlink
 490          * or rename succeeds.
 491          *
 492          * TODO: implement metadata only index copy up when called with
 493          *       ovl_copy_up_flags(dentry, O_PATH).
 494          */
 495         if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
 496             d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
 497                 err = ovl_copy_up(dentry);
 498                 if (err)
 499                         return err;
 500         }
 501
 502         err = mutex_lock_interruptible(&oi->lock);
 503         if (err)
 504                 return err;
 505
 506         if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
 507                 goto out;
 508
 509         old_cred = ovl_override_creds(dentry->d_sb);
 510         /*
 511          * The overlay inode nlink should be incremented/decremented IFF the
 512          * upper operation succeeds, along with nlink change of upper inode.
 513          * Therefore, before link/unlink/rename, we store the union nlink
 514          * value relative to the upper inode nlink in an upper inode xattr.
 515          */
 516         err = ovl_set_nlink_upper(dentry);
 517         revert_creds(old_cred);
 518
 519 out:
 520         if (err)
 521                 mutex_unlock(&oi->lock);
 522         else
 523                 *locked = true;
 524
 525         return err;
 526 }
 527
 528 void ovl_nlink_end(struct dentry *dentry, bool locked)
 529 {
 530         if (locked) {
 531                 if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
 532                     d_inode(dentry)->i_nlink == 0) {
 533                         const struct cred *old_cred;
 534
 535                         old_cred = ovl_override_creds(dentry->d_sb);
 536                         ovl_cleanup_index(dentry);
 537                         revert_creds(old_cred);
 538                 }
 539
 540                 mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 541         }
 542 }