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/buffer_head.h>
  14 #include <linux/writeback.h>
  15 #include <linux/backing-dev.h>
  16 #include <linux/blkdev.h>
  17 #include <linux/fsnotify.h>
  18 #include <linux/security.h>
  19 #include "fat.h"
  20
  21 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
  22 {
  23         u32 attr;
  24
  25         mutex_lock(&inode->i_mutex);
  26         attr = fat_make_attrs(inode);
  27         mutex_unlock(&inode->i_mutex);
  28
  29         return put_user(attr, user_attr);
  30 }
  31
  32 static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
  33 {
  34         struct inode *inode = file->f_path.dentry->d_inode;
  35         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  36         int is_dir = S_ISDIR(inode->i_mode);
  37         u32 attr, oldattr;
  38         struct iattr ia;
  39         int err;
  40
  41         err = get_user(attr, user_attr);
  42         if (err)
  43                 goto out;
  44
  45         mutex_lock(&inode->i_mutex);
  46         err = mnt_want_write(file->f_path.mnt);
  47         if (err)
  48                 goto out_unlock_inode;
  49
  50         /*
  51          * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
  52          * prevents the user from turning us into a VFAT
  53          * longname entry.  Also, we obviously can't set
  54          * any of the NTFS attributes in the high 24 bits.
  55          */
  56         attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
  57         /* Merge in ATTR_VOLUME and ATTR_DIR */
  58         attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
  59                 (is_dir ? ATTR_DIR : 0);
  60         oldattr = fat_make_attrs(inode);
  61
  62         /* Equivalent to a chmod() */
  63         ia.ia_valid = ATTR_MODE | ATTR_CTIME;
  64         ia.ia_ctime = current_fs_time(inode->i_sb);
  65         if (is_dir)
  66                 ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
  67         else {
  68                 ia.ia_mode = fat_make_mode(sbi, attr,
  69                         S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
  70         }
  71
  72         /* The root directory has no attributes */
  73         if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
  74                 err = -EINVAL;
  75                 goto out_drop_write;
  76         }
  77
  78         if (sbi->options.sys_immutable &&
  79             ((attr | oldattr) & ATTR_SYS) &&
  80             !capable(CAP_LINUX_IMMUTABLE)) {
  81                 err = -EPERM;
  82                 goto out_drop_write;
  83         }
  84
  85         /*
  86          * The security check is questionable...  We single
  87          * out the RO attribute for checking by the security
  88          * module, just because it maps to a file mode.
  89          */
  90         err = security_inode_setattr(file->f_path.dentry, &ia);
  91         if (err)
  92                 goto out_drop_write;
  93
  94         /* This MUST be done before doing anything irreversible... */
  95         err = fat_setattr(file->f_path.dentry, &ia);
  96         if (err)
  97                 goto out_drop_write;
  98
  99         fsnotify_change(file->f_path.dentry, ia.ia_valid);
 100         if (sbi->options.sys_immutable) {
 101                 if (attr & ATTR_SYS)
 102                         inode->i_flags |= S_IMMUTABLE;
 103                 else
 104                         inode->i_flags &= S_IMMUTABLE;
 105         }
 106
 107         fat_save_attrs(inode, attr);
 108         mark_inode_dirty(inode);
 109 out_drop_write:
 110         mnt_drop_write(file->f_path.mnt);
 111 out_unlock_inode:
 112         mutex_unlock(&inode->i_mutex);
 113 out:
 114         return err;
 115 }
 116
 117 int fat_generic_ioctl(struct inode *inode, struct file *filp,
 118                       unsigned int cmd, unsigned long arg)
 119 {
 120         u32 __user *user_attr = (u32 __user *)arg;
 121
 122         switch (cmd) {
 123         case FAT_IOCTL_GET_ATTRIBUTES:
 124                 return fat_ioctl_get_attributes(inode, user_attr);
 125         case FAT_IOCTL_SET_ATTRIBUTES:
 126                 return fat_ioctl_set_attributes(filp, user_attr);
 127         default:
 128                 return -ENOTTY; /* Inappropriate ioctl for device */
 129         }
 130 }
 131
 132 static int fat_file_release(struct inode *inode, struct file *filp)
 133 {
 134         if ((filp->f_mode & FMODE_WRITE) &&
 135              MSDOS_SB(inode->i_sb)->options.flush) {
 136                 fat_flush_inodes(inode->i_sb, inode, NULL);
 137                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 138         }
 139         return 0;
 140 }
 141
 142 int fat_file_fsync(struct file *filp, struct dentry *dentry, int datasync)
 143 {
 144         struct inode *inode = dentry->d_inode;
 145         int res, err;
 146
 147         res = simple_fsync(filp, dentry, datasync);
 148         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
 149
 150         return res ? res : err;
 151 }
 152
 153
 154 const struct file_operations fat_file_operations = {
 155         .llseek         = generic_file_llseek,
 156         .read           = do_sync_read,
 157         .write          = do_sync_write,
 158         .aio_read       = generic_file_aio_read,
 159         .aio_write      = generic_file_aio_write,
 160         .mmap           = generic_file_mmap,
 161         .release        = fat_file_release,
 162         .ioctl          = fat_generic_ioctl,
 163         .fsync          = fat_file_fsync,
 164         .splice_read    = generic_file_splice_read,
 165 };
 166
 167 static int fat_cont_expand(struct inode *inode, loff_t size)
 168 {
 169         struct address_space *mapping = inode->i_mapping;
 170         loff_t start = inode->i_size, count = size - inode->i_size;
 171         int err;
 172
 173         err = generic_cont_expand_simple(inode, size);
 174         if (err)
 175                 goto out;
 176
 177         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 178         mark_inode_dirty(inode);
 179         if (IS_SYNC(inode))
 180                 err = sync_page_range_nolock(inode, mapping, start, count);
 181 out:
 182         return err;
 183 }
 184
 185 /* Free all clusters after the skip'th cluster. */
 186 static int fat_free(struct inode *inode, int skip)
 187 {
 188         struct super_block *sb = inode->i_sb;
 189         int err, wait, free_start, i_start, i_logstart;
 190
 191         if (MSDOS_I(inode)->i_start == 0)
 192                 return 0;
 193
 194         fat_cache_inval_inode(inode);
 195
 196         wait = IS_DIRSYNC(inode);
 197         i_start = free_start = MSDOS_I(inode)->i_start;
 198         i_logstart = MSDOS_I(inode)->i_logstart;
 199
 200         /* First, we write the new file size. */
 201         if (!skip) {
 202                 MSDOS_I(inode)->i_start = 0;
 203                 MSDOS_I(inode)->i_logstart = 0;
 204         }
 205         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 206         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 207         if (wait) {
 208                 err = fat_sync_inode(inode);
 209                 if (err) {
 210                         MSDOS_I(inode)->i_start = i_start;
 211                         MSDOS_I(inode)->i_logstart = i_logstart;
 212                         return err;
 213                 }
 214         } else
 215                 mark_inode_dirty(inode);
 216
 217         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 218         if (skip) {
 219                 struct fat_entry fatent;
 220                 int ret, fclus, dclus;
 221
 222                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 223                 if (ret < 0)
 224                         return ret;
 225                 else if (ret == FAT_ENT_EOF)
 226                         return 0;
 227
 228                 fatent_init(&fatent);
 229                 ret = fat_ent_read(inode, &fatent, dclus);
 230                 if (ret == FAT_ENT_EOF) {
 231                         fatent_brelse(&fatent);
 232                         return 0;
 233                 } else if (ret == FAT_ENT_FREE) {
 234                         fat_fs_error(sb,
 235                                      "%s: invalid cluster chain (i_pos %lld)",
 236                                      __func__, MSDOS_I(inode)->i_pos);
 237                         ret = -EIO;
 238                 } else if (ret > 0) {
 239                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 240                         if (err)
 241                                 ret = err;
 242                 }
 243                 fatent_brelse(&fatent);
 244                 if (ret < 0)
 245                         return ret;
 246
 247                 free_start = ret;
 248         }
 249         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 250
 251         /* Freeing the remained cluster chain */
 252         return fat_free_clusters(inode, free_start);
 253 }
 254
 255 void fat_truncate(struct inode *inode)
 256 {
 257         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 258         const unsigned int cluster_size = sbi->cluster_size;
 259         int nr_clusters;
 260
 261         /*
 262          * This protects against truncating a file bigger than it was then
 263          * trying to write into the hole.
 264          */
 265         if (MSDOS_I(inode)->mmu_private > inode->i_size)
 266                 MSDOS_I(inode)->mmu_private = inode->i_size;
 267
 268         nr_clusters = (inode->i_size + (cluster_size - 1)) >> sbi->cluster_bits;
 269
 270         fat_free(inode, nr_clusters);
 271         fat_flush_inodes(inode->i_sb, inode, NULL);
 272 }
 273
 274 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 275 {
 276         struct inode *inode = dentry->d_inode;
 277         generic_fillattr(inode, stat);
 278         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 279         return 0;
 280 }
 281 EXPORT_SYMBOL_GPL(fat_getattr);
 282
 283 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 284                              struct inode *inode, umode_t *mode_ptr)
 285 {
 286         mode_t mask, perm;
 287
 288         /*
 289          * Note, the basic check is already done by a caller of
 290          * (attr->ia_mode & ~FAT_VALID_MODE)
 291          */
 292
 293         if (S_ISREG(inode->i_mode))
 294                 mask = sbi->options.fs_fmask;
 295         else
 296                 mask = sbi->options.fs_dmask;
 297
 298         perm = *mode_ptr & ~(S_IFMT | mask);
 299
 300         /*
 301          * Of the r and x bits, all (subject to umask) must be present. Of the
 302          * w bits, either all (subject to umask) or none must be present.
 303          *
 304          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 305          */
 306         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 307                 return -EPERM;
 308         if (fat_mode_can_hold_ro(inode)) {
 309                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 310                         return -EPERM;
 311         } else {
 312                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
 313                         return -EPERM;
 314         }
 315
 316         *mode_ptr &= S_IFMT | perm;
 317
 318         return 0;
 319 }
 320
 321 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 322 {
 323         mode_t allow_utime = sbi->options.allow_utime;
 324
 325         if (current_fsuid() != inode->i_uid) {
 326                 if (in_group_p(inode->i_gid))
 327                         allow_utime >>= 3;
 328                 if (allow_utime & MAY_WRITE)
 329                         return 1;
 330         }
 331
 332         /* use a default check */
 333         return 0;
 334 }
 335
 336 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
 337 /* valid file mode bits */
 338 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
 339
 340 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 341 {
 342         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 343         struct inode *inode = dentry->d_inode;
 344         unsigned int ia_valid;
 345         int error;
 346
 347         /*
 348          * Expand the file. Since inode_setattr() updates ->i_size
 349          * before calling the ->truncate(), but FAT needs to fill the
 350          * hole before it.
 351          */
 352         if (attr->ia_valid & ATTR_SIZE) {
 353                 if (attr->ia_size > inode->i_size) {
 354                         error = fat_cont_expand(inode, attr->ia_size);
 355                         if (error || attr->ia_valid == ATTR_SIZE)
 356                                 goto out;
 357                         attr->ia_valid &= ~ATTR_SIZE;
 358                 }
 359         }
 360
 361         /* Check for setting the inode time. */
 362         ia_valid = attr->ia_valid;
 363         if (ia_valid & TIMES_SET_FLAGS) {
 364                 if (fat_allow_set_time(sbi, inode))
 365                         attr->ia_valid &= ~TIMES_SET_FLAGS;
 366         }
 367
 368         error = inode_change_ok(inode, attr);
 369         attr->ia_valid = ia_valid;
 370         if (error) {
 371                 if (sbi->options.quiet)
 372                         error = 0;
 373                 goto out;
 374         }
 375
 376         if (((attr->ia_valid & ATTR_UID) &&
 377              (attr->ia_uid != sbi->options.fs_uid)) ||
 378             ((attr->ia_valid & ATTR_GID) &&
 379              (attr->ia_gid != sbi->options.fs_gid)) ||
 380             ((attr->ia_valid & ATTR_MODE) &&
 381              (attr->ia_mode & ~FAT_VALID_MODE)))
 382                 error = -EPERM;
 383
 384         if (error) {
 385                 if (sbi->options.quiet)
 386                         error = 0;
 387                 goto out;
 388         }
 389
 390         /*
 391          * We don't return -EPERM here. Yes, strange, but this is too
 392          * old behavior.
 393          */
 394         if (attr->ia_valid & ATTR_MODE) {
 395                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 396                         attr->ia_valid &= ~ATTR_MODE;
 397         }
 398
 399         if (attr->ia_valid)
 400                 error = inode_setattr(inode, attr);
 401 out:
 402         return error;
 403 }
 404 EXPORT_SYMBOL_GPL(fat_setattr);
 405
 406 const struct inode_operations fat_file_inode_operations = {
 407         .truncate       = fat_truncate,
 408         .setattr        = fat_setattr,
 409         .getattr        = fat_getattr,
 410 };