fs/fat/file.c

   1 /*
   2  *  linux/fs/fat/file.c
   3  *
   4  *  Written 1992,1993 by Werner Almesberger
   5  *
   6  *  regular file handling primitives for fat-based filesystems
   7  */
   8
   9 #include <linux/capability.h>
  10 #include <linux/module.h>
  11 #include <linux/compat.h>
  12 #include <linux/mount.h>
  13 #include <linux/blkdev.h>
  14 #include <linux/backing-dev.h>
  15 #include <linux/fsnotify.h>
  16 #include <linux/security.h>
  17 #include <linux/falloc.h>
  18 #include "fat.h"
  19
  20 static long fat_fallocate(struct file *file, int mode,
  21                           loff_t offset, loff_t len);
  22
  23 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
  24 {
  25         u32 attr;
  26
  27         inode_lock(inode);
  28         attr = fat_make_attrs(inode);
  29         inode_unlock(inode);
  30
  31         return put_user(attr, user_attr);
  32 }
  33
  34 static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
  35 {
  36         struct inode *inode = file_inode(file);
  37         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  38         int is_dir = S_ISDIR(inode->i_mode);
  39         u32 attr, oldattr;
  40         struct iattr ia;
  41         int err;
  42
  43         err = get_user(attr, user_attr);
  44         if (err)
  45                 goto out;
  46
  47         err = mnt_want_write_file(file);
  48         if (err)
  49                 goto out;
  50         inode_lock(inode);
  51
  52         /*
  53          * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
  54          * prevents the user from turning us into a VFAT
  55          * longname entry.  Also, we obviously can't set
  56          * any of the NTFS attributes in the high 24 bits.
  57          */
  58         attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
  59         /* Merge in ATTR_VOLUME and ATTR_DIR */
  60         attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
  61                 (is_dir ? ATTR_DIR : 0);
  62         oldattr = fat_make_attrs(inode);
  63
  64         /* Equivalent to a chmod() */
  65         ia.ia_valid = ATTR_MODE | ATTR_CTIME;
  66         ia.ia_ctime = current_time(inode);
  67         if (is_dir)
  68                 ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
  69         else {
  70                 ia.ia_mode = fat_make_mode(sbi, attr,
  71                         S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
  72         }
  73
  74         /* The root directory has no attributes */
  75         if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
  76                 err = -EINVAL;
  77                 goto out_unlock_inode;
  78         }
  79
  80         if (sbi->options.sys_immutable &&
  81             ((attr | oldattr) & ATTR_SYS) &&
  82             !capable(CAP_LINUX_IMMUTABLE)) {
  83                 err = -EPERM;
  84                 goto out_unlock_inode;
  85         }
  86
  87         /*
  88          * The security check is questionable...  We single
  89          * out the RO attribute for checking by the security
  90          * module, just because it maps to a file mode.
  91          */
  92         err = security_inode_setattr(file->f_path.dentry, &ia);
  93         if (err)
  94                 goto out_unlock_inode;
  95
  96         /* This MUST be done before doing anything irreversible... */
  97         err = fat_setattr(file->f_path.dentry, &ia);
  98         if (err)
  99                 goto out_unlock_inode;
 100
 101         fsnotify_change(file->f_path.dentry, ia.ia_valid);
 102         if (sbi->options.sys_immutable) {
 103                 if (attr & ATTR_SYS)
 104                         inode->i_flags |= S_IMMUTABLE;
 105                 else
 106                         inode->i_flags &= ~S_IMMUTABLE;
 107         }
 108
 109         fat_save_attrs(inode, attr);
 110         mark_inode_dirty(inode);
 111 out_unlock_inode:
 112         inode_unlock(inode);
 113         mnt_drop_write_file(file);
 114 out:
 115         return err;
 116 }
 117
 118 static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
 119 {
 120         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 121         return put_user(sbi->vol_id, user_attr);
 122 }
 123
 124 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 125 {
 126         struct inode *inode = file_inode(filp);
 127         u32 __user *user_attr = (u32 __user *)arg;
 128
 129         switch (cmd) {
 130         case FAT_IOCTL_GET_ATTRIBUTES:
 131                 return fat_ioctl_get_attributes(inode, user_attr);
 132         case FAT_IOCTL_SET_ATTRIBUTES:
 133                 return fat_ioctl_set_attributes(filp, user_attr);
 134         case FAT_IOCTL_GET_VOLUME_ID:
 135                 return fat_ioctl_get_volume_id(inode, user_attr);
 136         default:
 137                 return -ENOTTY; /* Inappropriate ioctl for device */
 138         }
 139 }
 140
 141 #ifdef CONFIG_COMPAT
 142 static long fat_generic_compat_ioctl(struct file *filp, unsigned int cmd,
 143                                       unsigned long arg)
 144
 145 {
 146         return fat_generic_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 147 }
 148 #endif
 149
 150 static int fat_file_release(struct inode *inode, struct file *filp)
 151 {
 152         if ((filp->f_mode & FMODE_WRITE) &&
 153              MSDOS_SB(inode->i_sb)->options.flush) {
 154                 fat_flush_inodes(inode->i_sb, inode, NULL);
 155                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 156         }
 157         return 0;
 158 }
 159
 160 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 161 {
 162         struct inode *inode = filp->f_mapping->host;
 163         int err;
 164
 165         err = __generic_file_fsync(filp, start, end, datasync);
 166         if (err)
 167                 return err;
 168
 169         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
 170         if (err)
 171                 return err;
 172
 173         return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 174 }
 175
 176
 177 const struct file_operations fat_file_operations = {
 178         .llseek         = generic_file_llseek,
 179         .read_iter      = generic_file_read_iter,
 180         .write_iter     = generic_file_write_iter,
 181         .mmap           = generic_file_mmap,
 182         .release        = fat_file_release,
 183         .unlocked_ioctl = fat_generic_ioctl,
 184 #ifdef CONFIG_COMPAT
 185         .compat_ioctl   = fat_generic_compat_ioctl,
 186 #endif
 187         .fsync          = fat_file_fsync,
 188         .splice_read    = generic_file_splice_read,
 189         .fallocate      = fat_fallocate,
 190 };
 191
 192 static int fat_cont_expand(struct inode *inode, loff_t size)
 193 {
 194         struct address_space *mapping = inode->i_mapping;
 195         loff_t start = inode->i_size, count = size - inode->i_size;
 196         int err;
 197
 198         err = generic_cont_expand_simple(inode, size);
 199         if (err)
 200                 goto out;
 201
 202         inode->i_ctime = inode->i_mtime = current_time(inode);
 203         mark_inode_dirty(inode);
 204         if (IS_SYNC(inode)) {
 205                 int err2;
 206
 207                 /*
 208                  * Opencode syncing since we don't have a file open to use
 209                  * standard fsync path.
 210                  */
 211                 err = filemap_fdatawrite_range(mapping, start,
 212                                                start + count - 1);
 213                 err2 = sync_mapping_buffers(mapping);
 214                 if (!err)
 215                         err = err2;
 216                 err2 = write_inode_now(inode, 1);
 217                 if (!err)
 218                         err = err2;
 219                 if (!err) {
 220                         err =  filemap_fdatawait_range(mapping, start,
 221                                                        start + count - 1);
 222                 }
 223         }
 224 out:
 225         return err;
 226 }
 227
 228 /*
 229  * Preallocate space for a file. This implements fat's fallocate file
 230  * operation, which gets called from sys_fallocate system call. User
 231  * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
 232  * we just allocate clusters without zeroing them out. Otherwise we
 233  * allocate and zero out clusters via an expanding truncate.
 234  */
 235 static long fat_fallocate(struct file *file, int mode,
 236                           loff_t offset, loff_t len)
 237 {
 238         int nr_cluster; /* Number of clusters to be allocated */
 239         loff_t mm_bytes; /* Number of bytes to be allocated for file */
 240         loff_t ondisksize; /* block aligned on-disk size in bytes*/
 241         struct inode *inode = file->f_mapping->host;
 242         struct super_block *sb = inode->i_sb;
 243         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 244         int err = 0;
 245
 246         /* No support for hole punch or other fallocate flags. */
 247         if (mode & ~FALLOC_FL_KEEP_SIZE)
 248                 return -EOPNOTSUPP;
 249
 250         /* No support for dir */
 251         if (!S_ISREG(inode->i_mode))
 252                 return -EOPNOTSUPP;
 253
 254         inode_lock(inode);
 255         if (mode & FALLOC_FL_KEEP_SIZE) {
 256                 ondisksize = inode->i_blocks << 9;
 257                 if ((offset + len) <= ondisksize)
 258                         goto error;
 259
 260                 /* First compute the number of clusters to be allocated */
 261                 mm_bytes = offset + len - ondisksize;
 262                 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
 263                         sbi->cluster_bits;
 264
 265                 /* Start the allocation.We are not zeroing out the clusters */
 266                 while (nr_cluster-- > 0) {
 267                         err = fat_add_cluster(inode);
 268                         if (err)
 269                                 goto error;
 270                 }
 271         } else {
 272                 if ((offset + len) <= i_size_read(inode))
 273                         goto error;
 274
 275                 /* This is just an expanding truncate */
 276                 err = fat_cont_expand(inode, (offset + len));
 277         }
 278
 279 error:
 280         inode_unlock(inode);
 281         return err;
 282 }
 283
 284 /* Free all clusters after the skip'th cluster. */
 285 static int fat_free(struct inode *inode, int skip)
 286 {
 287         struct super_block *sb = inode->i_sb;
 288         int err, wait, free_start, i_start, i_logstart;
 289
 290         if (MSDOS_I(inode)->i_start == 0)
 291                 return 0;
 292
 293         fat_cache_inval_inode(inode);
 294
 295         wait = IS_DIRSYNC(inode);
 296         i_start = free_start = MSDOS_I(inode)->i_start;
 297         i_logstart = MSDOS_I(inode)->i_logstart;
 298
 299         /* First, we write the new file size. */
 300         if (!skip) {
 301                 MSDOS_I(inode)->i_start = 0;
 302                 MSDOS_I(inode)->i_logstart = 0;
 303         }
 304         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 305         inode->i_ctime = inode->i_mtime = current_time(inode);
 306         if (wait) {
 307                 err = fat_sync_inode(inode);
 308                 if (err) {
 309                         MSDOS_I(inode)->i_start = i_start;
 310                         MSDOS_I(inode)->i_logstart = i_logstart;
 311                         return err;
 312                 }
 313         } else
 314                 mark_inode_dirty(inode);
 315
 316         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 317         if (skip) {
 318                 struct fat_entry fatent;
 319                 int ret, fclus, dclus;
 320
 321                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 322                 if (ret < 0)
 323                         return ret;
 324                 else if (ret == FAT_ENT_EOF)
 325                         return 0;
 326
 327                 fatent_init(&fatent);
 328                 ret = fat_ent_read(inode, &fatent, dclus);
 329                 if (ret == FAT_ENT_EOF) {
 330                         fatent_brelse(&fatent);
 331                         return 0;
 332                 } else if (ret == FAT_ENT_FREE) {
 333                         fat_fs_error(sb,
 334                                      "%s: invalid cluster chain (i_pos %lld)",
 335                                      __func__, MSDOS_I(inode)->i_pos);
 336                         ret = -EIO;
 337                 } else if (ret > 0) {
 338                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 339                         if (err)
 340                                 ret = err;
 341                 }
 342                 fatent_brelse(&fatent);
 343                 if (ret < 0)
 344                         return ret;
 345
 346                 free_start = ret;
 347         }
 348         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 349
 350         /* Freeing the remained cluster chain */
 351         return fat_free_clusters(inode, free_start);
 352 }
 353
 354 void fat_truncate_blocks(struct inode *inode, loff_t offset)
 355 {
 356         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 357         const unsigned int cluster_size = sbi->cluster_size;
 358         int nr_clusters;
 359
 360         /*
 361          * This protects against truncating a file bigger than it was then
 362          * trying to write into the hole.
 363          */
 364         if (MSDOS_I(inode)->mmu_private > offset)
 365                 MSDOS_I(inode)->mmu_private = offset;
 366
 367         nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
 368
 369         fat_free(inode, nr_clusters);
 370         fat_flush_inodes(inode->i_sb, inode, NULL);
 371 }
 372
 373 int fat_getattr(const struct path *path, struct kstat *stat,
 374                 u32 request_mask, unsigned int flags)
 375 {
 376         struct inode *inode = d_inode(path->dentry);
 377         generic_fillattr(inode, stat);
 378         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 379
 380         if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
 381                 /* Use i_pos for ino. This is used as fileid of nfs. */
 382                 stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
 383         }
 384         return 0;
 385 }
 386 EXPORT_SYMBOL_GPL(fat_getattr);
 387
 388 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 389                              struct inode *inode, umode_t *mode_ptr)
 390 {
 391         umode_t mask, perm;
 392
 393         /*
 394          * Note, the basic check is already done by a caller of
 395          * (attr->ia_mode & ~FAT_VALID_MODE)
 396          */
 397
 398         if (S_ISREG(inode->i_mode))
 399                 mask = sbi->options.fs_fmask;
 400         else
 401                 mask = sbi->options.fs_dmask;
 402
 403         perm = *mode_ptr & ~(S_IFMT | mask);
 404
 405         /*
 406          * Of the r and x bits, all (subject to umask) must be present. Of the
 407          * w bits, either all (subject to umask) or none must be present.
 408          *
 409          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 410          */
 411         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 412                 return -EPERM;
 413         if (fat_mode_can_hold_ro(inode)) {
 414                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 415                         return -EPERM;
 416         } else {
 417                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
 418                         return -EPERM;
 419         }
 420
 421         *mode_ptr &= S_IFMT | perm;
 422
 423         return 0;
 424 }
 425
 426 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 427 {
 428         umode_t allow_utime = sbi->options.allow_utime;
 429
 430         if (!uid_eq(current_fsuid(), inode->i_uid)) {
 431                 if (in_group_p(inode->i_gid))
 432                         allow_utime >>= 3;
 433                 if (allow_utime & MAY_WRITE)
 434                         return 1;
 435         }
 436
 437         /* use a default check */
 438         return 0;
 439 }
 440
 441 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
 442 /* valid file mode bits */
 443 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
 444
 445 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 446 {
 447         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 448         struct inode *inode = d_inode(dentry);
 449         unsigned int ia_valid;
 450         int error;
 451
 452         /* Check for setting the inode time. */
 453         ia_valid = attr->ia_valid;
 454         if (ia_valid & TIMES_SET_FLAGS) {
 455                 if (fat_allow_set_time(sbi, inode))
 456                         attr->ia_valid &= ~TIMES_SET_FLAGS;
 457         }
 458
 459         error = setattr_prepare(dentry, attr);
 460         attr->ia_valid = ia_valid;
 461         if (error) {
 462                 if (sbi->options.quiet)
 463                         error = 0;
 464                 goto out;
 465         }
 466
 467         /*
 468          * Expand the file. Since inode_setattr() updates ->i_size
 469          * before calling the ->truncate(), but FAT needs to fill the
 470          * hole before it. XXX: this is no longer true with new truncate
 471          * sequence.
 472          */
 473         if (attr->ia_valid & ATTR_SIZE) {
 474                 inode_dio_wait(inode);
 475
 476                 if (attr->ia_size > inode->i_size) {
 477                         error = fat_cont_expand(inode, attr->ia_size);
 478                         if (error || attr->ia_valid == ATTR_SIZE)
 479                                 goto out;
 480                         attr->ia_valid &= ~ATTR_SIZE;
 481                 }
 482         }
 483
 484         if (((attr->ia_valid & ATTR_UID) &&
 485              (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
 486             ((attr->ia_valid & ATTR_GID) &&
 487              (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
 488             ((attr->ia_valid & ATTR_MODE) &&
 489              (attr->ia_mode & ~FAT_VALID_MODE)))
 490                 error = -EPERM;
 491
 492         if (error) {
 493                 if (sbi->options.quiet)
 494                         error = 0;
 495                 goto out;
 496         }
 497
 498         /*
 499          * We don't return -EPERM here. Yes, strange, but this is too
 500          * old behavior.
 501          */
 502         if (attr->ia_valid & ATTR_MODE) {
 503                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 504                         attr->ia_valid &= ~ATTR_MODE;
 505         }
 506
 507         if (attr->ia_valid & ATTR_SIZE) {
 508                 error = fat_block_truncate_page(inode, attr->ia_size);
 509                 if (error)
 510                         goto out;
 511                 down_write(&MSDOS_I(inode)->truncate_lock);
 512                 truncate_setsize(inode, attr->ia_size);
 513                 fat_truncate_blocks(inode, attr->ia_size);
 514                 up_write(&MSDOS_I(inode)->truncate_lock);
 515         }
 516
 517         setattr_copy(inode, attr);
 518         mark_inode_dirty(inode);
 519 out:
 520         return error;
 521 }
 522 EXPORT_SYMBOL_GPL(fat_setattr);
 523
 524 const struct inode_operations fat_file_inode_operations = {
 525         .setattr        = fat_setattr,
 526         .getattr        = fat_getattr,
 527 };