fs/fat/file.c

   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_shared(inode);
  29         attr = fat_make_attrs(inode);
  30         inode_unlock_shared(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_mnt_user_ns(file),
  94                                      file->f_path.dentry, &ia);
  95         if (err)
  96                 goto out_unlock_inode;
  97
  98         /* This MUST be done before doing anything irreversible... */
  99         err = fat_setattr(file_mnt_user_ns(file), file->f_path.dentry, &ia);
 100         if (err)
 101                 goto out_unlock_inode;
 102
 103         fsnotify_change(file->f_path.dentry, ia.ia_valid);
 104         if (sbi->options.sys_immutable) {
 105                 if (attr & ATTR_SYS)
 106                         inode->i_flags |= S_IMMUTABLE;
 107                 else
 108                         inode->i_flags &= ~S_IMMUTABLE;
 109         }
 110
 111         fat_save_attrs(inode, attr);
 112         mark_inode_dirty(inode);
 113 out_unlock_inode:
 114         inode_unlock(inode);
 115         mnt_drop_write_file(file);
 116 out:
 117         return err;
 118 }
 119
 120 static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
 121 {
 122         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 123         return put_user(sbi->vol_id, user_attr);
 124 }
 125
 126 static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 127 {
 128         struct super_block *sb = inode->i_sb;
 129         struct fstrim_range __user *user_range;
 130         struct fstrim_range range;
 131         int err;
 132
 133         if (!capable(CAP_SYS_ADMIN))
 134                 return -EPERM;
 135
 136         if (!bdev_max_discard_sectors(sb->s_bdev))
 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                              bdev_discard_granularity(sb->s_bdev));
 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 static int fat_file_release(struct inode *inode, struct file *filp)
 176 {
 177         if ((filp->f_mode & FMODE_WRITE) &&
 178             MSDOS_SB(inode->i_sb)->options.flush) {
 179                 fat_flush_inodes(inode->i_sb, inode, NULL);
 180                 set_current_state(TASK_UNINTERRUPTIBLE);
 181                 io_schedule_timeout(HZ/10);
 182         }
 183         return 0;
 184 }
 185
 186 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 187 {
 188         struct inode *inode = filp->f_mapping->host;
 189         int err;
 190
 191         err = __generic_file_fsync(filp, start, end, datasync);
 192         if (err)
 193                 return err;
 194
 195         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
 196         if (err)
 197                 return err;
 198
 199         return blkdev_issue_flush(inode->i_sb->s_bdev);
 200 }
 201
 202
 203 const struct file_operations fat_file_operations = {
 204         .llseek         = generic_file_llseek,
 205         .read_iter      = generic_file_read_iter,
 206         .write_iter     = generic_file_write_iter,
 207         .mmap           = generic_file_mmap,
 208         .release        = fat_file_release,
 209         .unlocked_ioctl = fat_generic_ioctl,
 210         .compat_ioctl   = compat_ptr_ioctl,
 211         .fsync          = fat_file_fsync,
 212         .splice_read    = generic_file_splice_read,
 213         .splice_write   = iter_file_splice_write,
 214         .fallocate      = fat_fallocate,
 215 };
 216
 217 static int fat_cont_expand(struct inode *inode, loff_t size)
 218 {
 219         struct address_space *mapping = inode->i_mapping;
 220         loff_t start = inode->i_size, count = size - inode->i_size;
 221         int err;
 222
 223         err = generic_cont_expand_simple(inode, size);
 224         if (err)
 225                 goto out;
 226
 227         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 228         mark_inode_dirty(inode);
 229         if (IS_SYNC(inode)) {
 230                 int err2;
 231
 232                 /*
 233                  * Opencode syncing since we don't have a file open to use
 234                  * standard fsync path.
 235                  */
 236                 err = filemap_fdatawrite_range(mapping, start,
 237                                                start + count - 1);
 238                 err2 = sync_mapping_buffers(mapping);
 239                 if (!err)
 240                         err = err2;
 241                 err2 = write_inode_now(inode, 1);
 242                 if (!err)
 243                         err = err2;
 244                 if (!err) {
 245                         err =  filemap_fdatawait_range(mapping, start,
 246                                                        start + count - 1);
 247                 }
 248         }
 249 out:
 250         return err;
 251 }
 252
 253 /*
 254  * Preallocate space for a file. This implements fat's fallocate file
 255  * operation, which gets called from sys_fallocate system call. User
 256  * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
 257  * we just allocate clusters without zeroing them out. Otherwise we
 258  * allocate and zero out clusters via an expanding truncate.
 259  */
 260 static long fat_fallocate(struct file *file, int mode,
 261                           loff_t offset, loff_t len)
 262 {
 263         int nr_cluster; /* Number of clusters to be allocated */
 264         loff_t mm_bytes; /* Number of bytes to be allocated for file */
 265         loff_t ondisksize; /* block aligned on-disk size in bytes*/
 266         struct inode *inode = file->f_mapping->host;
 267         struct super_block *sb = inode->i_sb;
 268         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 269         int err = 0;
 270
 271         /* No support for hole punch or other fallocate flags. */
 272         if (mode & ~FALLOC_FL_KEEP_SIZE)
 273                 return -EOPNOTSUPP;
 274
 275         /* No support for dir */
 276         if (!S_ISREG(inode->i_mode))
 277                 return -EOPNOTSUPP;
 278
 279         inode_lock(inode);
 280         if (mode & FALLOC_FL_KEEP_SIZE) {
 281                 ondisksize = inode->i_blocks << 9;
 282                 if ((offset + len) <= ondisksize)
 283                         goto error;
 284
 285                 /* First compute the number of clusters to be allocated */
 286                 mm_bytes = offset + len - ondisksize;
 287                 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
 288                         sbi->cluster_bits;
 289
 290                 /* Start the allocation.We are not zeroing out the clusters */
 291                 while (nr_cluster-- > 0) {
 292                         err = fat_add_cluster(inode);
 293                         if (err)
 294                                 goto error;
 295                 }
 296         } else {
 297                 if ((offset + len) <= i_size_read(inode))
 298                         goto error;
 299
 300                 /* This is just an expanding truncate */
 301                 err = fat_cont_expand(inode, (offset + len));
 302         }
 303
 304 error:
 305         inode_unlock(inode);
 306         return err;
 307 }
 308
 309 /* Free all clusters after the skip'th cluster. */
 310 static int fat_free(struct inode *inode, int skip)
 311 {
 312         struct super_block *sb = inode->i_sb;
 313         int err, wait, free_start, i_start, i_logstart;
 314
 315         if (MSDOS_I(inode)->i_start == 0)
 316                 return 0;
 317
 318         fat_cache_inval_inode(inode);
 319
 320         wait = IS_DIRSYNC(inode);
 321         i_start = free_start = MSDOS_I(inode)->i_start;
 322         i_logstart = MSDOS_I(inode)->i_logstart;
 323
 324         /* First, we write the new file size. */
 325         if (!skip) {
 326                 MSDOS_I(inode)->i_start = 0;
 327                 MSDOS_I(inode)->i_logstart = 0;
 328         }
 329         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 330         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 331         if (wait) {
 332                 err = fat_sync_inode(inode);
 333                 if (err) {
 334                         MSDOS_I(inode)->i_start = i_start;
 335                         MSDOS_I(inode)->i_logstart = i_logstart;
 336                         return err;
 337                 }
 338         } else
 339                 mark_inode_dirty(inode);
 340
 341         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 342         if (skip) {
 343                 struct fat_entry fatent;
 344                 int ret, fclus, dclus;
 345
 346                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 347                 if (ret < 0)
 348                         return ret;
 349                 else if (ret == FAT_ENT_EOF)
 350                         return 0;
 351
 352                 fatent_init(&fatent);
 353                 ret = fat_ent_read(inode, &fatent, dclus);
 354                 if (ret == FAT_ENT_EOF) {
 355                         fatent_brelse(&fatent);
 356                         return 0;
 357                 } else if (ret == FAT_ENT_FREE) {
 358                         fat_fs_error(sb,
 359                                      "%s: invalid cluster chain (i_pos %lld)",
 360                                      __func__, MSDOS_I(inode)->i_pos);
 361                         ret = -EIO;
 362                 } else if (ret > 0) {
 363                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 364                         if (err)
 365                                 ret = err;
 366                 }
 367                 fatent_brelse(&fatent);
 368                 if (ret < 0)
 369                         return ret;
 370
 371                 free_start = ret;
 372         }
 373         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 374
 375         /* Freeing the remained cluster chain */
 376         return fat_free_clusters(inode, free_start);
 377 }
 378
 379 void fat_truncate_blocks(struct inode *inode, loff_t offset)
 380 {
 381         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 382         const unsigned int cluster_size = sbi->cluster_size;
 383         int nr_clusters;
 384
 385         /*
 386          * This protects against truncating a file bigger than it was then
 387          * trying to write into the hole.
 388          */
 389         if (MSDOS_I(inode)->mmu_private > offset)
 390                 MSDOS_I(inode)->mmu_private = offset;
 391
 392         nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
 393
 394         fat_free(inode, nr_clusters);
 395         fat_flush_inodes(inode->i_sb, inode, NULL);
 396 }
 397
 398 int fat_getattr(struct user_namespace *mnt_userns, const struct path *path,
 399                 struct kstat *stat, u32 request_mask, unsigned int flags)
 400 {
 401         struct inode *inode = d_inode(path->dentry);
 402         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 403
 404         generic_fillattr(mnt_userns, inode, stat);
 405         stat->blksize = sbi->cluster_size;
 406
 407         if (sbi->options.nfs == FAT_NFS_NOSTALE_RO) {
 408                 /* Use i_pos for ino. This is used as fileid of nfs. */
 409                 stat->ino = fat_i_pos_read(sbi, inode);
 410         }
 411
 412         if (sbi->options.isvfat && request_mask & STATX_BTIME) {
 413                 stat->result_mask |= STATX_BTIME;
 414                 stat->btime = MSDOS_I(inode)->i_crtime;
 415         }
 416
 417         return 0;
 418 }
 419 EXPORT_SYMBOL_GPL(fat_getattr);
 420
 421 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 422                              struct inode *inode, umode_t *mode_ptr)
 423 {
 424         umode_t mask, perm;
 425
 426         /*
 427          * Note, the basic check is already done by a caller of
 428          * (attr->ia_mode & ~FAT_VALID_MODE)
 429          */
 430
 431         if (S_ISREG(inode->i_mode))
 432                 mask = sbi->options.fs_fmask;
 433         else
 434                 mask = sbi->options.fs_dmask;
 435
 436         perm = *mode_ptr & ~(S_IFMT | mask);
 437
 438         /*
 439          * Of the r and x bits, all (subject to umask) must be present. Of the
 440          * w bits, either all (subject to umask) or none must be present.
 441          *
 442          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 443          */
 444         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 445                 return -EPERM;
 446         if (fat_mode_can_hold_ro(inode)) {
 447                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 448                         return -EPERM;
 449         } else {
 450                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
 451                         return -EPERM;
 452         }
 453
 454         *mode_ptr &= S_IFMT | perm;
 455
 456         return 0;
 457 }
 458
 459 static int fat_allow_set_time(struct user_namespace *mnt_userns,
 460                               struct msdos_sb_info *sbi, struct inode *inode)
 461 {
 462         umode_t allow_utime = sbi->options.allow_utime;
 463
 464         if (!vfsuid_eq_kuid(i_uid_into_vfsuid(mnt_userns, inode),
 465                             current_fsuid())) {
 466                 if (vfsgid_in_group_p(i_gid_into_vfsgid(mnt_userns, inode)))
 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 user_namespace *mnt_userns, struct dentry *dentry,
 481                 struct iattr *attr)
 482 {
 483         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 484         struct inode *inode = d_inode(dentry);
 485         unsigned int ia_valid;
 486         int error;
 487
 488         /* Check for setting the inode time. */
 489         ia_valid = attr->ia_valid;
 490         if (ia_valid & TIMES_SET_FLAGS) {
 491                 if (fat_allow_set_time(mnt_userns, sbi, inode))
 492                         attr->ia_valid &= ~TIMES_SET_FLAGS;
 493         }
 494
 495         error = setattr_prepare(mnt_userns, dentry, attr);
 496         attr->ia_valid = ia_valid;
 497         if (error) {
 498                 if (sbi->options.quiet)
 499                         error = 0;
 500                 goto out;
 501         }
 502
 503         /*
 504          * Expand the file. Since inode_setattr() updates ->i_size
 505          * before calling the ->truncate(), but FAT needs to fill the
 506          * hole before it. XXX: this is no longer true with new truncate
 507          * sequence.
 508          */
 509         if (attr->ia_valid & ATTR_SIZE) {
 510                 inode_dio_wait(inode);
 511
 512                 if (attr->ia_size > inode->i_size) {
 513                         error = fat_cont_expand(inode, attr->ia_size);
 514                         if (error || attr->ia_valid == ATTR_SIZE)
 515                                 goto out;
 516                         attr->ia_valid &= ~ATTR_SIZE;
 517                 }
 518         }
 519
 520         if (((attr->ia_valid & ATTR_UID) &&
 521              (!uid_eq(from_vfsuid(mnt_userns, i_user_ns(inode), attr->ia_vfsuid),
 522                       sbi->options.fs_uid))) ||
 523             ((attr->ia_valid & ATTR_GID) &&
 524              (!gid_eq(from_vfsgid(mnt_userns, i_user_ns(inode), attr->ia_vfsgid),
 525                       sbi->options.fs_gid))) ||
 526             ((attr->ia_valid & ATTR_MODE) &&
 527              (attr->ia_mode & ~FAT_VALID_MODE)))
 528                 error = -EPERM;
 529
 530         if (error) {
 531                 if (sbi->options.quiet)
 532                         error = 0;
 533                 goto out;
 534         }
 535
 536         /*
 537          * We don't return -EPERM here. Yes, strange, but this is too
 538          * old behavior.
 539          */
 540         if (attr->ia_valid & ATTR_MODE) {
 541                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 542                         attr->ia_valid &= ~ATTR_MODE;
 543         }
 544
 545         if (attr->ia_valid & ATTR_SIZE) {
 546                 error = fat_block_truncate_page(inode, attr->ia_size);
 547                 if (error)
 548                         goto out;
 549                 down_write(&MSDOS_I(inode)->truncate_lock);
 550                 truncate_setsize(inode, attr->ia_size);
 551                 fat_truncate_blocks(inode, attr->ia_size);
 552                 up_write(&MSDOS_I(inode)->truncate_lock);
 553         }
 554
 555         /*
 556          * setattr_copy can't truncate these appropriately, so we'll
 557          * copy them ourselves
 558          */
 559         if (attr->ia_valid & ATTR_ATIME)
 560                 fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
 561         if (attr->ia_valid & ATTR_CTIME)
 562                 fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
 563         if (attr->ia_valid & ATTR_MTIME)
 564                 fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
 565         attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
 566
 567         setattr_copy(mnt_userns, inode, attr);
 568         mark_inode_dirty(inode);
 569 out:
 570         return error;
 571 }
 572 EXPORT_SYMBOL_GPL(fat_setattr);
 573
 574 const struct inode_operations fat_file_inode_operations = {
 575         .setattr        = fat_setattr,
 576         .getattr        = fat_getattr,
 577         .update_time    = fat_update_time,
 578 };