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/mount.h>
  12 #include <linux/time.h>
  13 #include <linux/msdos_fs.h>
  14 #include <linux/buffer_head.h>
  15 #include <linux/writeback.h>
  16 #include <linux/backing-dev.h>
  17 #include <linux/blkdev.h>
  18 #include <linux/fsnotify.h>
  19 #include <linux/security.h>
  20
  21 int fat_generic_ioctl(struct inode *inode, struct file *filp,
  22                       unsigned int cmd, unsigned long arg)
  23 {
  24         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  25         u32 __user *user_attr = (u32 __user *)arg;
  26
  27         switch (cmd) {
  28         case FAT_IOCTL_GET_ATTRIBUTES:
  29         {
  30                 u32 attr;
  31
  32                 if (inode->i_ino == MSDOS_ROOT_INO)
  33                         attr = ATTR_DIR;
  34                 else
  35                         attr = fat_attr(inode);
  36
  37                 return put_user(attr, user_attr);
  38         }
  39         case FAT_IOCTL_SET_ATTRIBUTES:
  40         {
  41                 u32 attr, oldattr;
  42                 int err, is_dir = S_ISDIR(inode->i_mode);
  43                 struct iattr ia;
  44
  45                 err = get_user(attr, user_attr);
  46                 if (err)
  47                         return err;
  48
  49                 mutex_lock(&inode->i_mutex);
  50
  51                 err = mnt_want_write(filp->f_path.mnt);
  52                 if (err)
  53                         goto up_no_drop_write;
  54
  55                 /*
  56                  * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
  57                  * prevents the user from turning us into a VFAT
  58                  * longname entry.  Also, we obviously can't set
  59                  * any of the NTFS attributes in the high 24 bits.
  60                  */
  61                 attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
  62                 /* Merge in ATTR_VOLUME and ATTR_DIR */
  63                 attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
  64                         (is_dir ? ATTR_DIR : 0);
  65                 oldattr = fat_attr(inode);
  66
  67                 /* Equivalent to a chmod() */
  68                 ia.ia_valid = ATTR_MODE | ATTR_CTIME;
  69                 ia.ia_ctime = current_fs_time(inode->i_sb);
  70                 if (is_dir) {
  71                         ia.ia_mode = MSDOS_MKMODE(attr,
  72                                 S_IRWXUGO & ~sbi->options.fs_dmask)
  73                                 | S_IFDIR;
  74                 } else {
  75                         ia.ia_mode = MSDOS_MKMODE(attr,
  76                                 (S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO))
  77                                 & ~sbi->options.fs_fmask)
  78                                 | S_IFREG;
  79                 }
  80
  81                 /* The root directory has no attributes */
  82                 if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
  83                         err = -EINVAL;
  84                         goto up;
  85                 }
  86
  87                 if (sbi->options.sys_immutable) {
  88                         if ((attr | oldattr) & ATTR_SYS) {
  89                                 if (!capable(CAP_LINUX_IMMUTABLE)) {
  90                                         err = -EPERM;
  91                                         goto up;
  92                                 }
  93                         }
  94                 }
  95
  96                 /*
  97                  * The security check is questionable...  We single
  98                  * out the RO attribute for checking by the security
  99                  * module, just because it maps to a file mode.
 100                  */
 101                 err = security_inode_setattr(filp->f_path.dentry, &ia);
 102                 if (err)
 103                         goto up;
 104
 105                 /* This MUST be done before doing anything irreversible... */
 106                 err = fat_setattr(filp->f_path.dentry, &ia);
 107                 if (err)
 108                         goto up;
 109
 110                 fsnotify_change(filp->f_path.dentry, ia.ia_valid);
 111                 if (sbi->options.sys_immutable) {
 112                         if (attr & ATTR_SYS)
 113                                 inode->i_flags |= S_IMMUTABLE;
 114                         else
 115                                 inode->i_flags &= S_IMMUTABLE;
 116                 }
 117
 118                 MSDOS_I(inode)->i_attrs = attr & ATTR_UNUSED;
 119                 mark_inode_dirty(inode);
 120 up:
 121                 mnt_drop_write(filp->f_path.mnt);
 122 up_no_drop_write:
 123                 mutex_unlock(&inode->i_mutex);
 124                 return err;
 125         }
 126         default:
 127                 return -ENOTTY; /* Inappropriate ioctl for device */
 128         }
 129 }
 130
 131 static int fat_file_release(struct inode *inode, struct file *filp)
 132 {
 133         if ((filp->f_mode & FMODE_WRITE) &&
 134              MSDOS_SB(inode->i_sb)->options.flush) {
 135                 fat_flush_inodes(inode->i_sb, inode, NULL);
 136                 congestion_wait(WRITE, HZ/10);
 137         }
 138         return 0;
 139 }
 140
 141 const struct file_operations fat_file_operations = {
 142         .llseek         = generic_file_llseek,
 143         .read           = do_sync_read,
 144         .write          = do_sync_write,
 145         .aio_read       = generic_file_aio_read,
 146         .aio_write      = generic_file_aio_write,
 147         .mmap           = generic_file_mmap,
 148         .release        = fat_file_release,
 149         .ioctl          = fat_generic_ioctl,
 150         .fsync          = file_fsync,
 151         .splice_read    = generic_file_splice_read,
 152 };
 153
 154 static int fat_cont_expand(struct inode *inode, loff_t size)
 155 {
 156         struct address_space *mapping = inode->i_mapping;
 157         loff_t start = inode->i_size, count = size - inode->i_size;
 158         int err;
 159
 160         err = generic_cont_expand_simple(inode, size);
 161         if (err)
 162                 goto out;
 163
 164         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 165         mark_inode_dirty(inode);
 166         if (IS_SYNC(inode))
 167                 err = sync_page_range_nolock(inode, mapping, start, count);
 168 out:
 169         return err;
 170 }
 171
 172 /* Free all clusters after the skip'th cluster. */
 173 static int fat_free(struct inode *inode, int skip)
 174 {
 175         struct super_block *sb = inode->i_sb;
 176         int err, wait, free_start, i_start, i_logstart;
 177
 178         if (MSDOS_I(inode)->i_start == 0)
 179                 return 0;
 180
 181         fat_cache_inval_inode(inode);
 182
 183         wait = IS_DIRSYNC(inode);
 184         i_start = free_start = MSDOS_I(inode)->i_start;
 185         i_logstart = MSDOS_I(inode)->i_logstart;
 186
 187         /* First, we write the new file size. */
 188         if (!skip) {
 189                 MSDOS_I(inode)->i_start = 0;
 190                 MSDOS_I(inode)->i_logstart = 0;
 191         }
 192         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 193         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 194         if (wait) {
 195                 err = fat_sync_inode(inode);
 196                 if (err) {
 197                         MSDOS_I(inode)->i_start = i_start;
 198                         MSDOS_I(inode)->i_logstart = i_logstart;
 199                         return err;
 200                 }
 201         } else
 202                 mark_inode_dirty(inode);
 203
 204         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 205         if (skip) {
 206                 struct fat_entry fatent;
 207                 int ret, fclus, dclus;
 208
 209                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 210                 if (ret < 0)
 211                         return ret;
 212                 else if (ret == FAT_ENT_EOF)
 213                         return 0;
 214
 215                 fatent_init(&fatent);
 216                 ret = fat_ent_read(inode, &fatent, dclus);
 217                 if (ret == FAT_ENT_EOF) {
 218                         fatent_brelse(&fatent);
 219                         return 0;
 220                 } else if (ret == FAT_ENT_FREE) {
 221                         fat_fs_panic(sb,
 222                                      "%s: invalid cluster chain (i_pos %lld)",
 223                                      __func__, MSDOS_I(inode)->i_pos);
 224                         ret = -EIO;
 225                 } else if (ret > 0) {
 226                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 227                         if (err)
 228                                 ret = err;
 229                 }
 230                 fatent_brelse(&fatent);
 231                 if (ret < 0)
 232                         return ret;
 233
 234                 free_start = ret;
 235         }
 236         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 237
 238         /* Freeing the remained cluster chain */
 239         return fat_free_clusters(inode, free_start);
 240 }
 241
 242 void fat_truncate(struct inode *inode)
 243 {
 244         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 245         const unsigned int cluster_size = sbi->cluster_size;
 246         int nr_clusters;
 247
 248         /*
 249          * This protects against truncating a file bigger than it was then
 250          * trying to write into the hole.
 251          */
 252         if (MSDOS_I(inode)->mmu_private > inode->i_size)
 253                 MSDOS_I(inode)->mmu_private = inode->i_size;
 254
 255         nr_clusters = (inode->i_size + (cluster_size - 1)) >> sbi->cluster_bits;
 256
 257         fat_free(inode, nr_clusters);
 258         fat_flush_inodes(inode->i_sb, inode, NULL);
 259 }
 260
 261 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 262 {
 263         struct inode *inode = dentry->d_inode;
 264         generic_fillattr(inode, stat);
 265         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 266         return 0;
 267 }
 268 EXPORT_SYMBOL_GPL(fat_getattr);
 269
 270 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 271                              struct inode *inode, umode_t *mode_ptr)
 272 {
 273         mode_t mask, perm;
 274
 275         /*
 276          * Note, the basic check is already done by a caller of
 277          * (attr->ia_mode & ~MSDOS_VALID_MODE)
 278          */
 279
 280         if (S_ISREG(inode->i_mode))
 281                 mask = sbi->options.fs_fmask;
 282         else
 283                 mask = sbi->options.fs_dmask;
 284
 285         perm = *mode_ptr & ~(S_IFMT | mask);
 286
 287         /*
 288          * Of the r and x bits, all (subject to umask) must be present. Of the
 289          * w bits, either all (subject to umask) or none must be present.
 290          */
 291         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 292                 return -EPERM;
 293         if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 294                 return -EPERM;
 295
 296         *mode_ptr &= S_IFMT | perm;
 297
 298         return 0;
 299 }
 300
 301 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 302 {
 303         mode_t allow_utime = sbi->options.allow_utime;
 304
 305         if (current->fsuid != inode->i_uid) {
 306                 if (in_group_p(inode->i_gid))
 307                         allow_utime >>= 3;
 308                 if (allow_utime & MAY_WRITE)
 309                         return 1;
 310         }
 311
 312         /* use a default check */
 313         return 0;
 314 }
 315
 316 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 317 {
 318         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 319         struct inode *inode = dentry->d_inode;
 320         int error = 0;
 321         unsigned int ia_valid;
 322
 323         /*
 324          * Expand the file. Since inode_setattr() updates ->i_size
 325          * before calling the ->truncate(), but FAT needs to fill the
 326          * hole before it.
 327          */
 328         if (attr->ia_valid & ATTR_SIZE) {
 329                 if (attr->ia_size > inode->i_size) {
 330                         error = fat_cont_expand(inode, attr->ia_size);
 331                         if (error || attr->ia_valid == ATTR_SIZE)
 332                                 goto out;
 333                         attr->ia_valid &= ~ATTR_SIZE;
 334                 }
 335         }
 336
 337         /* Check for setting the inode time. */
 338         ia_valid = attr->ia_valid;
 339         if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
 340                 if (fat_allow_set_time(sbi, inode))
 341                         attr->ia_valid &= ~(ATTR_MTIME_SET | ATTR_ATIME_SET);
 342         }
 343
 344         error = inode_change_ok(inode, attr);
 345         attr->ia_valid = ia_valid;
 346         if (error) {
 347                 if (sbi->options.quiet)
 348                         error = 0;
 349                 goto out;
 350         }
 351
 352         if (((attr->ia_valid & ATTR_UID) &&
 353              (attr->ia_uid != sbi->options.fs_uid)) ||
 354             ((attr->ia_valid & ATTR_GID) &&
 355              (attr->ia_gid != sbi->options.fs_gid)) ||
 356             ((attr->ia_valid & ATTR_MODE) &&
 357              (attr->ia_mode & ~MSDOS_VALID_MODE)))
 358                 error = -EPERM;
 359
 360         if (error) {
 361                 if (sbi->options.quiet)
 362                         error = 0;
 363                 goto out;
 364         }
 365
 366         /*
 367          * We don't return -EPERM here. Yes, strange, but this is too
 368          * old behavior.
 369          */
 370         if (attr->ia_valid & ATTR_MODE) {
 371                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 372                         attr->ia_valid &= ~ATTR_MODE;
 373         }
 374
 375         error = inode_setattr(inode, attr);
 376 out:
 377         return error;
 378 }
 379 EXPORT_SYMBOL_GPL(fat_setattr);
 380
 381 const struct inode_operations fat_file_inode_operations = {
 382         .truncate       = fat_truncate,
 383         .setattr        = fat_setattr,
 384         .getattr        = fat_getattr,
 385 };