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 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET) 317 318 int fat_setattr(struct dentry *dentry, struct iattr *attr) 319 { 320 struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb); 321 struct inode *inode = dentry->d_inode; 322 int error = 0; 323 unsigned int ia_valid; 324 325 /* 326 * Expand the file. Since inode_setattr() updates ->i_size 327 * before calling the ->truncate(), but FAT needs to fill the 328 * hole before it. 329 */ 330 if (attr->ia_valid & ATTR_SIZE) { 331 if (attr->ia_size > inode->i_size) { 332 error = fat_cont_expand(inode, attr->ia_size); 333 if (error || attr->ia_valid == ATTR_SIZE) 334 goto out; 335 attr->ia_valid &= ~ATTR_SIZE; 336 } 337 } 338 339 /* Check for setting the inode time. */ 340 ia_valid = attr->ia_valid; 341 if (ia_valid & TIMES_SET_FLAGS) { 342 if (fat_allow_set_time(sbi, inode)) 343 attr->ia_valid &= ~TIMES_SET_FLAGS; 344 } 345 346 error = inode_change_ok(inode, attr); 347 attr->ia_valid = ia_valid; 348 if (error) { 349 if (sbi->options.quiet) 350 error = 0; 351 goto out; 352 } 353 354 if (((attr->ia_valid & ATTR_UID) && 355 (attr->ia_uid != sbi->options.fs_uid)) || 356 ((attr->ia_valid & ATTR_GID) && 357 (attr->ia_gid != sbi->options.fs_gid)) || 358 ((attr->ia_valid & ATTR_MODE) && 359 (attr->ia_mode & ~MSDOS_VALID_MODE))) 360 error = -EPERM; 361 362 if (error) { 363 if (sbi->options.quiet) 364 error = 0; 365 goto out; 366 } 367 368 /* 369 * We don't return -EPERM here. Yes, strange, but this is too 370 * old behavior. 371 */ 372 if (attr->ia_valid & ATTR_MODE) { 373 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0) 374 attr->ia_valid &= ~ATTR_MODE; 375 } 376 377 error = inode_setattr(inode, attr); 378 out: 379 return error; 380 } 381 EXPORT_SYMBOL_GPL(fat_setattr); 382 383 const struct inode_operations fat_file_inode_operations = { 384 .truncate = fat_truncate, 385 .setattr = fat_setattr, 386 .getattr = fat_getattr, 387 }; 388