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