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                 int err2;
 181
 182                 /*
 183                  * Opencode syncing since we don't have a file open to use
 184                  * standard fsync path.
 185                  */
 186                 err = filemap_fdatawrite_range(mapping, start,
 187                                                start + count - 1);
 188                 err2 = sync_mapping_buffers(mapping);
 189                 if (!err)
 190                         err = err2;
 191                 err2 = write_inode_now(inode, 1);
 192                 if (!err)
 193                         err = err2;
 194                 if (!err) {
 195                         err =  filemap_fdatawait_range(mapping, start,
 196                                                        start + count - 1);
 197                 }
 198         }
 199 out:
 200         return err;
 201 }
 202
 203 /* Free all clusters after the skip'th cluster. */
 204 static int fat_free(struct inode *inode, int skip)
 205 {
 206         struct super_block *sb = inode->i_sb;
 207         int err, wait, free_start, i_start, i_logstart;
 208
 209         if (MSDOS_I(inode)->i_start == 0)
 210                 return 0;
 211
 212         fat_cache_inval_inode(inode);
 213
 214         wait = IS_DIRSYNC(inode);
 215         i_start = free_start = MSDOS_I(inode)->i_start;
 216         i_logstart = MSDOS_I(inode)->i_logstart;
 217
 218         /* First, we write the new file size. */
 219         if (!skip) {
 220                 MSDOS_I(inode)->i_start = 0;
 221                 MSDOS_I(inode)->i_logstart = 0;
 222         }
 223         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 224         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 225         if (wait) {
 226                 err = fat_sync_inode(inode);
 227                 if (err) {
 228                         MSDOS_I(inode)->i_start = i_start;
 229                         MSDOS_I(inode)->i_logstart = i_logstart;
 230                         return err;
 231                 }
 232         } else
 233                 mark_inode_dirty(inode);
 234
 235         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 236         if (skip) {
 237                 struct fat_entry fatent;
 238                 int ret, fclus, dclus;
 239
 240                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 241                 if (ret < 0)
 242                         return ret;
 243                 else if (ret == FAT_ENT_EOF)
 244                         return 0;
 245
 246                 fatent_init(&fatent);
 247                 ret = fat_ent_read(inode, &fatent, dclus);
 248                 if (ret == FAT_ENT_EOF) {
 249                         fatent_brelse(&fatent);
 250                         return 0;
 251                 } else if (ret == FAT_ENT_FREE) {
 252                         fat_fs_error(sb,
 253                                      "%s: invalid cluster chain (i_pos %lld)",
 254                                      __func__, MSDOS_I(inode)->i_pos);
 255                         ret = -EIO;
 256                 } else if (ret > 0) {
 257                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 258                         if (err)
 259                                 ret = err;
 260                 }
 261                 fatent_brelse(&fatent);
 262                 if (ret < 0)
 263                         return ret;
 264
 265                 free_start = ret;
 266         }
 267         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 268
 269         /* Freeing the remained cluster chain */
 270         return fat_free_clusters(inode, free_start);
 271 }
 272
 273 void fat_truncate(struct inode *inode)
 274 {
 275         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 276         const unsigned int cluster_size = sbi->cluster_size;
 277         int nr_clusters;
 278
 279         /*
 280          * This protects against truncating a file bigger than it was then
 281          * trying to write into the hole.
 282          */
 283         if (MSDOS_I(inode)->mmu_private > inode->i_size)
 284                 MSDOS_I(inode)->mmu_private = inode->i_size;
 285
 286         nr_clusters = (inode->i_size + (cluster_size - 1)) >> sbi->cluster_bits;
 287
 288         fat_free(inode, nr_clusters);
 289         fat_flush_inodes(inode->i_sb, inode, NULL);
 290 }
 291
 292 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 293 {
 294         struct inode *inode = dentry->d_inode;
 295         generic_fillattr(inode, stat);
 296         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 297         return 0;
 298 }
 299 EXPORT_SYMBOL_GPL(fat_getattr);
 300
 301 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 302                              struct inode *inode, umode_t *mode_ptr)
 303 {
 304         mode_t mask, perm;
 305
 306         /*
 307          * Note, the basic check is already done by a caller of
 308          * (attr->ia_mode & ~FAT_VALID_MODE)
 309          */
 310
 311         if (S_ISREG(inode->i_mode))
 312                 mask = sbi->options.fs_fmask;
 313         else
 314                 mask = sbi->options.fs_dmask;
 315
 316         perm = *mode_ptr & ~(S_IFMT | mask);
 317
 318         /*
 319          * Of the r and x bits, all (subject to umask) must be present. Of the
 320          * w bits, either all (subject to umask) or none must be present.
 321          *
 322          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 323          */
 324         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 325                 return -EPERM;
 326         if (fat_mode_can_hold_ro(inode)) {
 327                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
 328                         return -EPERM;
 329         } else {
 330                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
 331                         return -EPERM;
 332         }
 333
 334         *mode_ptr &= S_IFMT | perm;
 335
 336         return 0;
 337 }
 338
 339 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 340 {
 341         mode_t allow_utime = sbi->options.allow_utime;
 342
 343         if (current_fsuid() != inode->i_uid) {
 344                 if (in_group_p(inode->i_gid))
 345                         allow_utime >>= 3;
 346                 if (allow_utime & MAY_WRITE)
 347                         return 1;
 348         }
 349
 350         /* use a default check */
 351         return 0;
 352 }
 353
 354 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
 355 /* valid file mode bits */
 356 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
 357
 358 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 359 {
 360         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 361         struct inode *inode = dentry->d_inode;
 362         unsigned int ia_valid;
 363         int error;
 364
 365         /*
 366          * Expand the file. Since inode_setattr() updates ->i_size
 367          * before calling the ->truncate(), but FAT needs to fill the
 368          * hole before it.
 369          */
 370         if (attr->ia_valid & ATTR_SIZE) {
 371                 if (attr->ia_size > inode->i_size) {
 372                         error = fat_cont_expand(inode, attr->ia_size);
 373                         if (error || attr->ia_valid == ATTR_SIZE)
 374                                 goto out;
 375                         attr->ia_valid &= ~ATTR_SIZE;
 376                 }
 377         }
 378
 379         /* Check for setting the inode time. */
 380         ia_valid = attr->ia_valid;
 381         if (ia_valid & TIMES_SET_FLAGS) {
 382                 if (fat_allow_set_time(sbi, inode))
 383                         attr->ia_valid &= ~TIMES_SET_FLAGS;
 384         }
 385
 386         error = inode_change_ok(inode, attr);
 387         attr->ia_valid = ia_valid;
 388         if (error) {
 389                 if (sbi->options.quiet)
 390                         error = 0;
 391                 goto out;
 392         }
 393
 394         if (((attr->ia_valid & ATTR_UID) &&
 395              (attr->ia_uid != sbi->options.fs_uid)) ||
 396             ((attr->ia_valid & ATTR_GID) &&
 397              (attr->ia_gid != sbi->options.fs_gid)) ||
 398             ((attr->ia_valid & ATTR_MODE) &&
 399              (attr->ia_mode & ~FAT_VALID_MODE)))
 400                 error = -EPERM;
 401
 402         if (error) {
 403                 if (sbi->options.quiet)
 404                         error = 0;
 405                 goto out;
 406         }
 407
 408         /*
 409          * We don't return -EPERM here. Yes, strange, but this is too
 410          * old behavior.
 411          */
 412         if (attr->ia_valid & ATTR_MODE) {
 413                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
 414                         attr->ia_valid &= ~ATTR_MODE;
 415         }
 416
 417         if (attr->ia_valid)
 418                 error = inode_setattr(inode, attr);
 419 out:
 420         return error;
 421 }
 422 EXPORT_SYMBOL_GPL(fat_setattr);
 423
 424 const struct inode_operations fat_file_inode_operations = {
 425         .truncate       = fat_truncate,
 426         .setattr        = fat_setattr,
 427         .getattr        = fat_getattr,
 428 };