root/fs/fat/file.c

DEFINITIONS

1. fat_ioctl_get_attributes
2. fat_ioctl_set_attributes
3. fat_ioctl_get_volume_id
4. fat_ioctl_fitrim
5. fat_generic_ioctl
6. fat_generic_compat_ioctl
7. fat_file_release
8. fat_file_fsync
9. fat_cont_expand
10. fat_fallocate
11. fat_free
12. fat_truncate_blocks
13. fat_getattr
14. fat_sanitize_mode
15. fat_allow_set_time
16. fat_setattr

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/fat/file.c
   4  *
   5  *  Written 1992,1993 by Werner Almesberger
   6  *
   7  *  regular file handling primitives for fat-based filesystems
   8  */
   9 
  10 #include <linux/capability.h>
  11 #include <linux/module.h>
  12 #include <linux/compat.h>
  13 #include <linux/mount.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/backing-dev.h>
  16 #include <linux/fsnotify.h>
  17 #include <linux/security.h>
  18 #include <linux/falloc.h>
  19 #include "fat.h"
  20 
  21 static long fat_fallocate(struct file *file, int mode,
  22                           loff_t offset, loff_t len);
  23 
  24 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
  25 {
  26         u32 attr;
  27 
  28         inode_lock(inode);
  29         attr = fat_make_attrs(inode);
  30         inode_unlock(inode);
  31 
  32         return put_user(attr, user_attr);
  33 }
  34 
  35 static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
  36 {
  37         struct inode *inode = file_inode(file);
  38         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  39         int is_dir = S_ISDIR(inode->i_mode);
  40         u32 attr, oldattr;
  41         struct iattr ia;
  42         int err;
  43 
  44         err = get_user(attr, user_attr);
  45         if (err)
  46                 goto out;
  47 
  48         err = mnt_want_write_file(file);
  49         if (err)
  50                 goto out;
  51         inode_lock(inode);
  52 
  53         /*
  54          * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
  55          * prevents the user from turning us into a VFAT
  56          * longname entry.  Also, we obviously can't set
  57          * any of the NTFS attributes in the high 24 bits.
  58          */
  59         attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
  60         /* Merge in ATTR_VOLUME and ATTR_DIR */
  61         attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
  62                 (is_dir ? ATTR_DIR : 0);
  63         oldattr = fat_make_attrs(inode);
  64 
  65         /* Equivalent to a chmod() */
  66         ia.ia_valid = ATTR_MODE | ATTR_CTIME;
  67         ia.ia_ctime = current_time(inode);
  68         if (is_dir)
  69                 ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
  70         else {
  71                 ia.ia_mode = fat_make_mode(sbi, attr,
  72                         S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
  73         }
  74 
  75         /* The root directory has no attributes */
  76         if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
  77                 err = -EINVAL;
  78                 goto out_unlock_inode;
  79         }
  80 
  81         if (sbi->options.sys_immutable &&
  82             ((attr | oldattr) & ATTR_SYS) &&
  83             !capable(CAP_LINUX_IMMUTABLE)) {
  84                 err = -EPERM;
  85                 goto out_unlock_inode;
  86         }
  87 
  88         /*
  89          * The security check is questionable...  We single
  90          * out the RO attribute for checking by the security
  91          * module, just because it maps to a file mode.
  92          */
  93         err = security_inode_setattr(file->f_path.dentry, &ia);
  94         if (err)
  95                 goto out_unlock_inode;
  96 
  97         /* This MUST be done before doing anything irreversible... */
  98         err = fat_setattr(file->f_path.dentry, &ia);
  99         if (err)
 100                 goto out_unlock_inode;
 101 
 102         fsnotify_change(file->f_path.dentry, ia.ia_valid);
 103         if (sbi->options.sys_immutable) {
 104                 if (attr & ATTR_SYS)
 105                         inode->i_flags |= S_IMMUTABLE;
 106                 else
 107                         inode->i_flags &= ~S_IMMUTABLE;
 108         }
 109 
 110         fat_save_attrs(inode, attr);
 111         mark_inode_dirty(inode);
 112 out_unlock_inode:
 113         inode_unlock(inode);
 114         mnt_drop_write_file(file);
 115 out:
 116         return err;
 117 }
 118 
 119 static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
 120 {
 121         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 122         return put_user(sbi->vol_id, user_attr);
 123 }
 124 
 125 static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 126 {
 127         struct super_block *sb = inode->i_sb;
 128         struct fstrim_range __user *user_range;
 129         struct fstrim_range range;
 130         struct request_queue *q = bdev_get_queue(sb->s_bdev);
 131         int err;
 132 
 133         if (!capable(CAP_SYS_ADMIN))
 134                 return -EPERM;
 135 
 136         if (!blk_queue_discard(q))
 137                 return -EOPNOTSUPP;
 138 
 139         user_range = (struct fstrim_range __user *)arg;
 140         if (copy_from_user(&range, user_range, sizeof(range)))
 141                 return -EFAULT;
 142 
 143         range.minlen = max_t(unsigned int, range.minlen,
 144                              q->limits.discard_granularity);
 145 
 146         err = fat_trim_fs(inode, &range);
 147         if (err < 0)
 148                 return err;
 149 
 150         if (copy_to_user(user_range, &range, sizeof(range)))
 151                 return -EFAULT;
 152 
 153         return 0;
 154 }
 155 
 156 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 157 {
 158         struct inode *inode = file_inode(filp);
 159         u32 __user *user_attr = (u32 __user *)arg;
 160 
 161         switch (cmd) {
 162         case FAT_IOCTL_GET_ATTRIBUTES:
 163                 return fat_ioctl_get_attributes(inode, user_attr);
 164         case FAT_IOCTL_SET_ATTRIBUTES:
 165                 return fat_ioctl_set_attributes(filp, user_attr);
 166         case FAT_IOCTL_GET_VOLUME_ID:
 167                 return fat_ioctl_get_volume_id(inode, user_attr);
 168         case FITRIM:
 169                 return fat_ioctl_fitrim(inode, arg);
 170         default:
 171                 return -ENOTTY; /* Inappropriate ioctl for device */
 172         }
 173 }
 174 
 175 #ifdef CONFIG_COMPAT
 176 static long fat_generic_compat_ioctl(struct file *filp, unsigned int cmd,
 177                                       unsigned long arg)
 178 
 179 {
 180         return fat_generic_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 181 }
 182 #endif
 183 
 184 static int fat_file_release(struct inode *inode, struct file *filp)
 185 {
 186         if ((filp->f_mode & FMODE_WRITE) &&
 187              MSDOS_SB(inode->i_sb)->options.flush) {
 188                 fat_flush_inodes(inode->i_sb, inode, NULL);
 189                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 190         }
 191         return 0;
 192 }
 193 
 194 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 195 {
 196         struct inode *inode = filp->f_mapping->host;
 197         int err;
 198 
 199         err = __generic_file_fsync(filp, start, end, datasync);
 200         if (err)
 201                 return err;
 202 
 203         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
 204         if (err)
 205                 return err;
 206 
 207         return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 208 }
 209 
 210 
 211 const struct file_operations fat_file_operations = {
 212         .llseek         = generic_file_llseek,
 213         .read_iter      = generic_file_read_iter,
 214         .write_iter     = generic_file_write_iter,
 215         .mmap           = generic_file_mmap,
 216         .release        = fat_file_release,
 217         .unlocked_ioctl = fat_generic_ioctl,
 218 #ifdef CONFIG_COMPAT
 219         .compat_ioctl   = fat_generic_compat_ioctl,
 220 #endif
 221         .fsync          = fat_file_fsync,
 222         .splice_read    = generic_file_splice_read,
 223         .splice_write   = iter_file_splice_write,
 224         .fallocate      = fat_fallocate,
 225 };
 226 
 227 static int fat_cont_expand(struct inode *inode, loff_t size)
 228 {
 229         struct address_space *mapping = inode->i_mapping;
 230         loff_t start = inode->i_size, count = size - inode->i_size;
 231         int err;
 232 
 233         err = generic_cont_expand_simple(inode, size);
 234         if (err)
 235                 goto out;
 236 
 237         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 238         mark_inode_dirty(inode);
 239         if (IS_SYNC(inode)) {
 240                 int err2;
 241 
 242                 /*
 243                  * Opencode syncing since we don't have a file open to use
 244                  * standard fsync path.
 245                  */
 246                 err = filemap_fdatawrite_range(mapping, start,
 247                                                start + count - 1);
 248                 err2 = sync_mapping_buffers(mapping);
 249                 if (!err)
 250                         err = err2;
 251                 err2 = write_inode_now(inode, 1);
 252                 if (!err)
 253                         err = err2;
 254                 if (!err) {
 255                         err =  filemap_fdatawait_range(mapping, start,
 256                                                        start + count - 1);
 257                 }
 258         }
 259 out:
 260         return err;
 261 }
 262 
 263 /*
 264  * Preallocate space for a file. This implements fat's fallocate file
 265  * operation, which gets called from sys_fallocate system call. User
 266  * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
 267  * we just allocate clusters without zeroing them out. Otherwise we
 268  * allocate and zero out clusters via an expanding truncate.
 269  */
 270 static long fat_fallocate(struct file *file, int mode,
 271                           loff_t offset, loff_t len)
 272 {
 273         int nr_cluster; /* Number of clusters to be allocated */
 274         loff_t mm_bytes; /* Number of bytes to be allocated for file */
 275         loff_t ondisksize; /* block aligned on-disk size in bytes*/
 276         struct inode *inode = file->f_mapping->host;
 277         struct super_block *sb = inode->i_sb;
 278         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 279         int err = 0;
 280 
 281         /* No support for hole punch or other fallocate flags. */
 282         if (mode & ~FALLOC_FL_KEEP_SIZE)
 283                 return -EOPNOTSUPP;
 284 
 285         /* No support for dir */
 286         if (!S_ISREG(inode->i_mode))
 287                 return -EOPNOTSUPP;
 288 
 289         inode_lock(inode);
 290         if (mode & FALLOC_FL_KEEP_SIZE) {
 291                 ondisksize = inode->i_blocks << 9;
 292                 if ((offset + len) <= ondisksize)
 293                         goto error;
 294 
 295                 /* First compute the number of clusters to be allocated */
 296                 mm_bytes = offset + len - ondisksize;
 297                 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
 298                         sbi->cluster_bits;
 299 
 300                 /* Start the allocation.We are not zeroing out the clusters */
 301                 while (nr_cluster-- > 0) {
 302                         err = fat_add_cluster(inode);
 303                         if (err)
 304                                 goto error;
 305                 }
 306         } else {
 307                 if ((offset + len) <= i_size_read(inode))
 308                         goto error;
 309 
 310                 /* This is just an expanding truncate */
 311                 err = fat_cont_expand(inode, (offset + len));
 312         }
 313 
 314 error:
 315         inode_unlock(inode);
 316         return err;
 317 }
 318 
 319 /* Free all clusters after the skip'th cluster. */
 320 static int fat_free(struct inode *inode, int skip)
 321 {
 322         struct super_block *sb = inode->i_sb;
 323         int err, wait, free_start, i_start, i_logstart;
 324 
 325         if (MSDOS_I(inode)->i_start == 0)
 326                 return 0;
 327 
 328         fat_cache_inval_inode(inode);
 329 
 330         wait = IS_DIRSYNC(inode);
 331         i_start = free_start = MSDOS_I(inode)->i_start;
 332         i_logstart = MSDOS_I(inode)->i_logstart;
 333 
 334         /* First, we write the new file size. */
 335         if (!skip) {
 336                 MSDOS_I(inode)->i_start = 0;
 337                 MSDOS_I(inode)->i_logstart = 0;
 338         }
 339         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 340         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 341         if (wait) {
 342                 err = fat_sync_inode(inode);
 343                 if (err) {
 344                         MSDOS_I(inode)->i_start = i_start;
 345                         MSDOS_I(inode)->i_logstart = i_logstart;
 346                         return err;
 347                 }
 348         } else
 349                 mark_inode_dirty(inode);
 350 
 351         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 352         if (skip) {
 353                 struct fat_entry fatent;
 354                 int ret, fclus, dclus;
 355 
 356                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 357                 if (ret < 0)
 358                         return ret;
 359                 else if (ret == FAT_ENT_EOF)
 360                         return 0;
 361 
 362                 fatent_init(&fatent);
 363                 ret = fat_ent_read(inode, &fatent, dclus);
 364                 if (ret == FAT_ENT_EOF) {
 365                         fatent_brelse(&fatent);
 366                         return 0;
 367                 } else if (ret == FAT_ENT_FREE) {
 368                         fat_fs_error(sb,
 369                                      "%s: invalid cluster chain (i_pos %lld)",
 370                                      __func__, MSDOS_I(inode)->i_pos);
 371                         ret = -EIO;
 372                 } else if (ret > 0) {
 373                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 374                         if (err)
 375                                 ret = err;
 376                 }
 377                 fatent_brelse(&fatent);
 378                 if (ret < 0)
 379                         return ret;
 380 
 381                 free_start = ret;
 382         }
 383         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 384 
 385         /* Freeing the remained cluster chain */
 386         return fat_free_clusters(inode, free_start);
 387 }
 388 
 389 void fat_truncate_blocks(struct inode *inode, loff_t offset)
 390 {
 391         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 392         const unsigned int cluster_size = sbi->cluster_size;
 393         int nr_clusters;
 394 
 395         /*
 396          * This protects against truncating a file bigger than it was then
 397          * trying to write into the hole.
 398          */
 399         if (MSDOS_I(inode)->mmu_private > offset)
 400                 MSDOS_I(inode)->mmu_private = offset;
 401 
 402         nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
 403 
 404         fat_free(inode, nr_clusters);
 405         fat_flush_inodes(inode->i_sb, inode, NULL);
 406 }
 407 
 408 int fat_getattr(const struct path *path, struct kstat *stat,
 409                 u32 request_mask, unsigned int flags)
 410 {
 411         struct inode *inode = d_inode(path->dentry);
 412         generic_fillattr(inode, stat);
 413         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 414 
 415         if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
 416                 /* Use i_pos for ino. This is used as fileid of nfs. */
 417                 stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
 418         }
 419         return 0;
 420 }
 421 EXPORT_SYMBOL_GPL(fat_getattr);
 422 
 423 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 424                              struct inode *inode, umode_t *mode_ptr)
 425 {
 426         umode_t mask, perm;
 427 
 428         /*
 429          * Note, the basic check is already done by a caller of
 430          * (attr->ia_mode & ~FAT_VALID_MODE)
 431          */
 432 
 433         if (S_ISREG(inode->i_mode))
 434                 mask = sbi->options.fs_fmask;
 435         else
 436                 mask = sbi->options.fs_dmask;
 437 
 438         perm = *mode_ptr & ~(S_IFMT | mask);
 439 
 440         /*
 441          * Of the r and x bits, all (subject to umask) must be present. Of the
 442          * w bits, either all (subject to umask) or none must be present.
 443          *
 444          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 445          */
 446         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 447                 return -EPERM;
 448         if (fat_mode_can_hold_ro(inode)) {
 449                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 450                         return -EPERM;
 451         } else {
 452                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
 453                         return -EPERM;
 454         }
 455 
 456         *mode_ptr &= S_IFMT | perm;
 457 
 458         return 0;
 459 }
 460 
 461 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 462 {
 463         umode_t allow_utime = sbi->options.allow_utime;
 464 
 465         if (!uid_eq(current_fsuid(), inode->i_uid)) {
 466                 if (in_group_p(inode->i_gid))
 467                         allow_utime >>= 3;
 468                 if (allow_utime & MAY_WRITE)
 469                         return 1;
 470         }
 471 
 472         /* use a default check */
 473         return 0;
 474 }
 475 
 476 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
 477 /* valid file mode bits */
 478 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
 479 
 480 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 481 {
 482         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 483         struct inode *inode = d_inode(dentry);
 484         unsigned int ia_valid;
 485         int error;
 486 
 487         /* Check for setting the inode time. */
 488         ia_valid = attr->ia_valid;
 489         if (ia_valid & TIMES_SET_FLAGS) {
 490                 if (fat_allow_set_time(sbi, inode))
 491                         attr->ia_valid &= ~TIMES_SET_FLAGS;
 492         }
 493 
 494         error = setattr_prepare(dentry, attr);
 495         attr->ia_valid = ia_valid;
 496         if (error) {
 497                 if (sbi->options.quiet)
 498                         error = 0;
 499                 goto out;
 500         }
 501 
 502         /*
 503          * Expand the file. Since inode_setattr() updates ->i_size
 504          * before calling the ->truncate(), but FAT needs to fill the
 505          * hole before it. XXX: this is no longer true with new truncate
 506          * sequence.
 507          */
 508         if (attr->ia_valid & ATTR_SIZE) {
 509                 inode_dio_wait(inode);
 510 
 511                 if (attr->ia_size > inode->i_size) {
 512                         error = fat_cont_expand(inode, attr->ia_size);
 513                         if (error || attr->ia_valid == ATTR_SIZE)
 514                                 goto out;
 515                         attr->ia_valid &= ~ATTR_SIZE;
 516                 }
 517         }
 518 
 519         if (((attr->ia_valid & ATTR_UID) &&
 520              (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
 521             ((attr->ia_valid & ATTR_GID) &&
 522              (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
 523             ((attr->ia_valid & ATTR_MODE) &&
 524              (attr->ia_mode & ~FAT_VALID_MODE)))
 525                 error = -EPERM;
 526 
 527         if (error) {
 528                 if (sbi->options.quiet)
 529                         error = 0;
 530                 goto out;
 531         }
 532 
 533         /*
 534          * We don't return -EPERM here. Yes, strange, but this is too
 535          * old behavior.
 536          */
 537         if (attr->ia_valid & ATTR_MODE) {
 538                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 539                         attr->ia_valid &= ~ATTR_MODE;
 540         }
 541 
 542         if (attr->ia_valid & ATTR_SIZE) {
 543                 error = fat_block_truncate_page(inode, attr->ia_size);
 544                 if (error)
 545                         goto out;
 546                 down_write(&MSDOS_I(inode)->truncate_lock);
 547                 truncate_setsize(inode, attr->ia_size);
 548                 fat_truncate_blocks(inode, attr->ia_size);
 549                 up_write(&MSDOS_I(inode)->truncate_lock);
 550         }
 551 
 552         /*
 553          * setattr_copy can't truncate these appropriately, so we'll
 554          * copy them ourselves
 555          */
 556         if (attr->ia_valid & ATTR_ATIME)
 557                 fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
 558         if (attr->ia_valid & ATTR_CTIME)
 559                 fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
 560         if (attr->ia_valid & ATTR_MTIME)
 561                 fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
 562         attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
 563 
 564         setattr_copy(inode, attr);
 565         mark_inode_dirty(inode);
 566 out:
 567         return error;
 568 }
 569 EXPORT_SYMBOL_GPL(fat_setattr);
 570 
 571 const struct inode_operations fat_file_inode_operations = {
 572         .setattr        = fat_setattr,
 573         .getattr        = fat_getattr,
 574         .update_time    = fat_update_time,
 575 };