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 dentry *ovl_i_dentry_upper(struct inode *inode)
 161 {
 162         return ovl_upperdentry_dereference(OVL_I(inode));
 163 }
 164
 165 struct inode *ovl_inode_upper(struct inode *inode)
 166 {
 167         struct dentry *upperdentry = ovl_i_dentry_upper(inode);
 168
 169         return upperdentry ? d_inode(upperdentry) : NULL;
 170 }
 171
 172 struct inode *ovl_inode_lower(struct inode *inode)
 173 {
 174         return OVL_I(inode)->lower;
 175 }
 176
 177 struct inode *ovl_inode_real(struct inode *inode)
 178 {
 179         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
 180 }
 181
 182
 183 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 184 {
 185         return OVL_I(d_inode(dentry))->cache;
 186 }
 187
 188 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 189 {
 190         OVL_I(d_inode(dentry))->cache = cache;
 191 }
 192
 193 bool ovl_dentry_is_opaque(struct dentry *dentry)
 194 {
 195         struct ovl_entry *oe = dentry->d_fsdata;
 196         return oe->opaque;
 197 }
 198
 199 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 200 {
 201         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 202 }
 203
 204 void ovl_dentry_set_opaque(struct dentry *dentry)
 205 {
 206         struct ovl_entry *oe = dentry->d_fsdata;
 207
 208         oe->opaque = true;
 209 }
 210
 211 /*
 212  * For hard links it's possible for ovl_dentry_upper() to return positive, while
 213  * there's no actual upper alias for the inode.  Copy up code needs to know
 214  * about the existence of the upper alias, so it can't use ovl_dentry_upper().
 215  */
 216 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
 217 {
 218         struct ovl_entry *oe = dentry->d_fsdata;
 219
 220         return oe->has_upper;
 221 }
 222
 223 void ovl_dentry_set_upper_alias(struct dentry *dentry)
 224 {
 225         struct ovl_entry *oe = dentry->d_fsdata;
 226
 227         oe->has_upper = true;
 228 }
 229
 230 bool ovl_redirect_dir(struct super_block *sb)
 231 {
 232         struct ovl_fs *ofs = sb->s_fs_info;
 233
 234         return ofs->config.redirect_dir && !ofs->noxattr;
 235 }
 236
 237 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 238 {
 239         return OVL_I(d_inode(dentry))->redirect;
 240 }
 241
 242 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 243 {
 244         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 245
 246         kfree(oi->redirect);
 247         oi->redirect = redirect;
 248 }
 249
 250 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 251                     struct dentry *lowerdentry)
 252 {
 253         if (upperdentry)
 254                 OVL_I(inode)->__upperdentry = upperdentry;
 255         if (lowerdentry)
 256                 OVL_I(inode)->lower = d_inode(lowerdentry);
 257
 258         ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
 259 }
 260
 261 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 262 {
 263         struct inode *upperinode = d_inode(upperdentry);
 264
 265         WARN_ON(OVL_I(inode)->__upperdentry);
 266
 267         /*
 268          * Make sure upperdentry is consistent before making it visible
 269          */
 270         smp_wmb();
 271         OVL_I(inode)->__upperdentry = upperdentry;
 272         if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
 273                 inode->i_private = upperinode;
 274                 __insert_inode_hash(inode, (unsigned long) upperinode);
 275         }
 276 }
 277
 278 void ovl_dentry_version_inc(struct dentry *dentry)
 279 {
 280         struct inode *inode = d_inode(dentry);
 281
 282         WARN_ON(!inode_is_locked(inode));
 283         OVL_I(inode)->version++;
 284 }
 285
 286 u64 ovl_dentry_version_get(struct dentry *dentry)
 287 {
 288         struct inode *inode = d_inode(dentry);
 289
 290         WARN_ON(!inode_is_locked(inode));
 291         return OVL_I(inode)->version;
 292 }
 293
 294 bool ovl_is_whiteout(struct dentry *dentry)
 295 {
 296         struct inode *inode = dentry->d_inode;
 297
 298         return inode && IS_WHITEOUT(inode);
 299 }
 300
 301 struct file *ovl_path_open(struct path *path, int flags)
 302 {
 303         return dentry_open(path, flags | O_NOATIME, current_cred());
 304 }
 305
 306 int ovl_copy_up_start(struct dentry *dentry)
 307 {
 308         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 309         int err;
 310
 311         err = mutex_lock_interruptible(&oi->lock);
 312         if (!err && ovl_dentry_has_upper_alias(dentry)) {
 313                 err = 1; /* Already copied up */
 314                 mutex_unlock(&oi->lock);
 315         }
 316
 317         return err;
 318 }
 319
 320 void ovl_copy_up_end(struct dentry *dentry)
 321 {
 322         mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 323 }
 324
 325 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
 326 {
 327         int res;
 328         char val;
 329
 330         if (!d_is_dir(dentry))
 331                 return false;
 332
 333         res = vfs_getxattr(dentry, name, &val, 1);
 334         if (res == 1 && val == 'y')
 335                 return true;
 336
 337         return false;
 338 }
 339
 340 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
 341                        const char *name, const void *value, size_t size,
 342                        int xerr)
 343 {
 344         int err;
 345         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 346
 347         if (ofs->noxattr)
 348                 return xerr;
 349
 350         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
 351
 352         if (err == -EOPNOTSUPP) {
 353                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
 354                 ofs->noxattr = true;
 355                 return xerr;
 356         }
 357
 358         return err;
 359 }
 360
 361 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
 362 {
 363         int err;
 364
 365         if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
 366                 return 0;
 367
 368         /*
 369          * Do not fail when upper doesn't support xattrs.
 370          * Upper inodes won't have origin nor redirect xattr anyway.
 371          */
 372         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
 373                                  "y", 1, 0);
 374         if (!err)
 375                 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
 376
 377         return err;
 378 }
 379
 380 void ovl_set_flag(unsigned long flag, struct inode *inode)
 381 {
 382         set_bit(flag, &OVL_I(inode)->flags);
 383 }
 384
 385 bool ovl_test_flag(unsigned long flag, struct inode *inode)
 386 {
 387         return test_bit(flag, &OVL_I(inode)->flags);
 388 }
 389
 390 /**
 391  * Caller must hold a reference to inode to prevent it from being freed while
 392  * it is marked inuse.
 393  */
 394 bool ovl_inuse_trylock(struct dentry *dentry)
 395 {
 396         struct inode *inode = d_inode(dentry);
 397         bool locked = false;
 398
 399         spin_lock(&inode->i_lock);
 400         if (!(inode->i_state & I_OVL_INUSE)) {
 401                 inode->i_state |= I_OVL_INUSE;
 402                 locked = true;
 403         }
 404         spin_unlock(&inode->i_lock);
 405
 406         return locked;
 407 }
 408
 409 void ovl_inuse_unlock(struct dentry *dentry)
 410 {
 411         if (dentry) {
 412                 struct inode *inode = d_inode(dentry);
 413
 414                 spin_lock(&inode->i_lock);
 415                 WARN_ON(!(inode->i_state & I_OVL_INUSE));
 416                 inode->i_state &= ~I_OVL_INUSE;
 417                 spin_unlock(&inode->i_lock);
 418         }
 419 }
 420
 421 /* Called must hold OVL_I(inode)->oi_lock */
 422 static void ovl_cleanup_index(struct dentry *dentry)
 423 {
 424         struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
 425         struct dentry *lowerdentry = ovl_dentry_lower(dentry);
 426         struct dentry *upperdentry = ovl_dentry_upper(dentry);
 427         struct dentry *index = NULL;
 428         struct inode *inode;
 429         struct qstr name;
 430         int err;
 431
 432         err = ovl_get_index_name(lowerdentry, &name);
 433         if (err)
 434                 goto fail;
 435
 436         inode = d_inode(upperdentry);
 437         if (inode->i_nlink != 1) {
 438                 pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
 439                                     upperdentry, inode->i_ino, inode->i_nlink);
 440                 /*
 441                  * We either have a bug with persistent union nlink or a lower
 442                  * hardlink was added while overlay is mounted. Adding a lower
 443                  * hardlink and then unlinking all overlay hardlinks would drop
 444                  * overlay nlink to zero before all upper inodes are unlinked.
 445                  * As a safety measure, when that situation is detected, set
 446                  * the overlay nlink to the index inode nlink minus one for the
 447                  * index entry itself.
 448                  */
 449                 set_nlink(d_inode(dentry), inode->i_nlink - 1);
 450                 ovl_set_nlink_upper(dentry);
 451                 goto out;
 452         }
 453
 454         inode_lock_nested(dir, I_MUTEX_PARENT);
 455         /* TODO: whiteout instead of cleanup to block future open by handle */
 456         index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
 457         err = PTR_ERR(index);
 458         if (!IS_ERR(index))
 459                 err = ovl_cleanup(dir, index);
 460         inode_unlock(dir);
 461         if (err)
 462                 goto fail;
 463
 464 out:
 465         dput(index);
 466         return;
 467
 468 fail:
 469         pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
 470         goto out;
 471 }
 472
 473 /*
 474  * Operations that change overlay inode and upper inode nlink need to be
 475  * synchronized with copy up for persistent nlink accounting.
 476  */
 477 int ovl_nlink_start(struct dentry *dentry, bool *locked)
 478 {
 479         struct ovl_inode *oi = OVL_I(d_inode(dentry));
 480         const struct cred *old_cred;
 481         int err;
 482
 483         if (!d_inode(dentry) || d_is_dir(dentry))
 484                 return 0;
 485
 486         /*
 487          * With inodes index is enabled, we store the union overlay nlink
 488          * in an xattr on the index inode. When whiting out lower hardlinks
 489          * we need to decrement the overlay persistent nlink, but before the
 490          * first copy up, we have no upper index inode to store the xattr.
 491          *
 492          * As a workaround, before whiteout/rename over of a lower hardlink,
 493          * copy up to create the upper index. Creating the upper index will
 494          * initialize the overlay nlink, so it could be dropped if unlink
 495          * or rename succeeds.
 496          *
 497          * TODO: implement metadata only index copy up when called with
 498          *       ovl_copy_up_flags(dentry, O_PATH).
 499          */
 500         if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
 501             d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
 502                 err = ovl_copy_up(dentry);
 503                 if (err)
 504                         return err;
 505         }
 506
 507         err = mutex_lock_interruptible(&oi->lock);
 508         if (err)
 509                 return err;
 510
 511         if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
 512                 goto out;
 513
 514         old_cred = ovl_override_creds(dentry->d_sb);
 515         /*
 516          * The overlay inode nlink should be incremented/decremented IFF the
 517          * upper operation succeeds, along with nlink change of upper inode.
 518          * Therefore, before link/unlink/rename, we store the union nlink
 519          * value relative to the upper inode nlink in an upper inode xattr.
 520          */
 521         err = ovl_set_nlink_upper(dentry);
 522         revert_creds(old_cred);
 523
 524 out:
 525         if (err)
 526                 mutex_unlock(&oi->lock);
 527         else
 528                 *locked = true;
 529
 530         return err;
 531 }
 532
 533 void ovl_nlink_end(struct dentry *dentry, bool locked)
 534 {
 535         if (locked) {
 536                 if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
 537                     d_inode(dentry)->i_nlink == 0) {
 538                         const struct cred *old_cred;
 539
 540                         old_cred = ovl_override_creds(dentry->d_sb);
 541                         ovl_cleanup_index(dentry);
 542                         revert_creds(old_cred);
 543                 }
 544
 545                 mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 546         }
 547 }