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