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TOMOYO Linux Cross Reference
Linux/fs/fat/file.c

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  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/compat.h>
 12 #include <linux/mount.h>
 13 #include <linux/blkdev.h>
 14 #include <linux/backing-dev.h>
 15 #include <linux/fsnotify.h>
 16 #include <linux/security.h>
 17 #include <linux/falloc.h>
 18 #include "fat.h"
 19 
 20 static long fat_fallocate(struct file *file, int mode,
 21                           loff_t offset, loff_t len);
 22 
 23 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
 24 {
 25         u32 attr;
 26 
 27         inode_lock(inode);
 28         attr = fat_make_attrs(inode);
 29         inode_unlock(inode);
 30 
 31         return put_user(attr, user_attr);
 32 }
 33 
 34 static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
 35 {
 36         struct inode *inode = file_inode(file);
 37         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 38         int is_dir = S_ISDIR(inode->i_mode);
 39         u32 attr, oldattr;
 40         struct iattr ia;
 41         int err;
 42 
 43         err = get_user(attr, user_attr);
 44         if (err)
 45                 goto out;
 46 
 47         err = mnt_want_write_file(file);
 48         if (err)
 49                 goto out;
 50         inode_lock(inode);
 51 
 52         /*
 53          * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
 54          * prevents the user from turning us into a VFAT
 55          * longname entry.  Also, we obviously can't set
 56          * any of the NTFS attributes in the high 24 bits.
 57          */
 58         attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
 59         /* Merge in ATTR_VOLUME and ATTR_DIR */
 60         attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
 61                 (is_dir ? ATTR_DIR : 0);
 62         oldattr = fat_make_attrs(inode);
 63 
 64         /* Equivalent to a chmod() */
 65         ia.ia_valid = ATTR_MODE | ATTR_CTIME;
 66         ia.ia_ctime = current_fs_time(inode->i_sb);
 67         if (is_dir)
 68                 ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
 69         else {
 70                 ia.ia_mode = fat_make_mode(sbi, attr,
 71                         S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
 72         }
 73 
 74         /* The root directory has no attributes */
 75         if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
 76                 err = -EINVAL;
 77                 goto out_unlock_inode;
 78         }
 79 
 80         if (sbi->options.sys_immutable &&
 81             ((attr | oldattr) & ATTR_SYS) &&
 82             !capable(CAP_LINUX_IMMUTABLE)) {
 83                 err = -EPERM;
 84                 goto out_unlock_inode;
 85         }
 86 
 87         /*
 88          * The security check is questionable...  We single
 89          * out the RO attribute for checking by the security
 90          * module, just because it maps to a file mode.
 91          */
 92         err = security_inode_setattr(file->f_path.dentry, &ia);
 93         if (err)
 94                 goto out_unlock_inode;
 95 
 96         /* This MUST be done before doing anything irreversible... */
 97         err = fat_setattr(file->f_path.dentry, &ia);
 98         if (err)
 99                 goto out_unlock_inode;
100 
101         fsnotify_change(file->f_path.dentry, ia.ia_valid);
102         if (sbi->options.sys_immutable) {
103                 if (attr & ATTR_SYS)
104                         inode->i_flags |= S_IMMUTABLE;
105                 else
106                         inode->i_flags &= ~S_IMMUTABLE;
107         }
108 
109         fat_save_attrs(inode, attr);
110         mark_inode_dirty(inode);
111 out_unlock_inode:
112         inode_unlock(inode);
113         mnt_drop_write_file(file);
114 out:
115         return err;
116 }
117 
118 static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
119 {
120         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
121         return put_user(sbi->vol_id, user_attr);
122 }
123 
124 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
125 {
126         struct inode *inode = file_inode(filp);
127         u32 __user *user_attr = (u32 __user *)arg;
128 
129         switch (cmd) {
130         case FAT_IOCTL_GET_ATTRIBUTES:
131                 return fat_ioctl_get_attributes(inode, user_attr);
132         case FAT_IOCTL_SET_ATTRIBUTES:
133                 return fat_ioctl_set_attributes(filp, user_attr);
134         case FAT_IOCTL_GET_VOLUME_ID:
135                 return fat_ioctl_get_volume_id(inode, user_attr);
136         default:
137                 return -ENOTTY; /* Inappropriate ioctl for device */
138         }
139 }
140 
141 #ifdef CONFIG_COMPAT
142 static long fat_generic_compat_ioctl(struct file *filp, unsigned int cmd,
143                                       unsigned long arg)
144 
145 {
146         return fat_generic_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
147 }
148 #endif
149 
150 static int fat_file_release(struct inode *inode, struct file *filp)
151 {
152         if ((filp->f_mode & FMODE_WRITE) &&
153              MSDOS_SB(inode->i_sb)->options.flush) {
154                 fat_flush_inodes(inode->i_sb, inode, NULL);
155                 congestion_wait(BLK_RW_ASYNC, HZ/10);
156         }
157         return 0;
158 }
159 
160 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
161 {
162         struct inode *inode = filp->f_mapping->host;
163         int res, err;
164 
165         res = generic_file_fsync(filp, start, end, datasync);
166         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
167 
168         return res ? res : err;
169 }
170 
171 
172 const struct file_operations fat_file_operations = {
173         .llseek         = generic_file_llseek,
174         .read_iter      = generic_file_read_iter,
175         .write_iter     = generic_file_write_iter,
176         .mmap           = generic_file_mmap,
177         .release        = fat_file_release,
178         .unlocked_ioctl = fat_generic_ioctl,
179 #ifdef CONFIG_COMPAT
180         .compat_ioctl   = fat_generic_compat_ioctl,
181 #endif
182         .fsync          = fat_file_fsync,
183         .splice_read    = generic_file_splice_read,
184         .fallocate      = fat_fallocate,
185 };
186 
187 static int fat_cont_expand(struct inode *inode, loff_t size)
188 {
189         struct address_space *mapping = inode->i_mapping;
190         loff_t start = inode->i_size, count = size - inode->i_size;
191         int err;
192 
193         err = generic_cont_expand_simple(inode, size);
194         if (err)
195                 goto out;
196 
197         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
198         mark_inode_dirty(inode);
199         if (IS_SYNC(inode)) {
200                 int err2;
201 
202                 /*
203                  * Opencode syncing since we don't have a file open to use
204                  * standard fsync path.
205                  */
206                 err = filemap_fdatawrite_range(mapping, start,
207                                                start + count - 1);
208                 err2 = sync_mapping_buffers(mapping);
209                 if (!err)
210                         err = err2;
211                 err2 = write_inode_now(inode, 1);
212                 if (!err)
213                         err = err2;
214                 if (!err) {
215                         err =  filemap_fdatawait_range(mapping, start,
216                                                        start + count - 1);
217                 }
218         }
219 out:
220         return err;
221 }
222 
223 /*
224  * Preallocate space for a file. This implements fat's fallocate file
225  * operation, which gets called from sys_fallocate system call. User
226  * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
227  * we just allocate clusters without zeroing them out. Otherwise we
228  * allocate and zero out clusters via an expanding truncate.
229  */
230 static long fat_fallocate(struct file *file, int mode,
231                           loff_t offset, loff_t len)
232 {
233         int nr_cluster; /* Number of clusters to be allocated */
234         loff_t mm_bytes; /* Number of bytes to be allocated for file */
235         loff_t ondisksize; /* block aligned on-disk size in bytes*/
236         struct inode *inode = file->f_mapping->host;
237         struct super_block *sb = inode->i_sb;
238         struct msdos_sb_info *sbi = MSDOS_SB(sb);
239         int err = 0;
240 
241         /* No support for hole punch or other fallocate flags. */
242         if (mode & ~FALLOC_FL_KEEP_SIZE)
243                 return -EOPNOTSUPP;
244 
245         /* No support for dir */
246         if (!S_ISREG(inode->i_mode))
247                 return -EOPNOTSUPP;
248 
249         inode_lock(inode);
250         if (mode & FALLOC_FL_KEEP_SIZE) {
251                 ondisksize = inode->i_blocks << 9;
252                 if ((offset + len) <= ondisksize)
253                         goto error;
254 
255                 /* First compute the number of clusters to be allocated */
256                 mm_bytes = offset + len - ondisksize;
257                 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
258                         sbi->cluster_bits;
259 
260                 /* Start the allocation.We are not zeroing out the clusters */
261                 while (nr_cluster-- > 0) {
262                         err = fat_add_cluster(inode);
263                         if (err)
264                                 goto error;
265                 }
266         } else {
267                 if ((offset + len) <= i_size_read(inode))
268                         goto error;
269 
270                 /* This is just an expanding truncate */
271                 err = fat_cont_expand(inode, (offset + len));
272         }
273 
274 error:
275         inode_unlock(inode);
276         return err;
277 }
278 
279 /* Free all clusters after the skip'th cluster. */
280 static int fat_free(struct inode *inode, int skip)
281 {
282         struct super_block *sb = inode->i_sb;
283         int err, wait, free_start, i_start, i_logstart;
284 
285         if (MSDOS_I(inode)->i_start == 0)
286                 return 0;
287 
288         fat_cache_inval_inode(inode);
289 
290         wait = IS_DIRSYNC(inode);
291         i_start = free_start = MSDOS_I(inode)->i_start;
292         i_logstart = MSDOS_I(inode)->i_logstart;
293 
294         /* First, we write the new file size. */
295         if (!skip) {
296                 MSDOS_I(inode)->i_start = 0;
297                 MSDOS_I(inode)->i_logstart = 0;
298         }
299         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
300         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
301         if (wait) {
302                 err = fat_sync_inode(inode);
303                 if (err) {
304                         MSDOS_I(inode)->i_start = i_start;
305                         MSDOS_I(inode)->i_logstart = i_logstart;
306                         return err;
307                 }
308         } else
309                 mark_inode_dirty(inode);
310 
311         /* Write a new EOF, and get the remaining cluster chain for freeing. */
312         if (skip) {
313                 struct fat_entry fatent;
314                 int ret, fclus, dclus;
315 
316                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
317                 if (ret < 0)
318                         return ret;
319                 else if (ret == FAT_ENT_EOF)
320                         return 0;
321 
322                 fatent_init(&fatent);
323                 ret = fat_ent_read(inode, &fatent, dclus);
324                 if (ret == FAT_ENT_EOF) {
325                         fatent_brelse(&fatent);
326                         return 0;
327                 } else if (ret == FAT_ENT_FREE) {
328                         fat_fs_error(sb,
329                                      "%s: invalid cluster chain (i_pos %lld)",
330                                      __func__, MSDOS_I(inode)->i_pos);
331                         ret = -EIO;
332                 } else if (ret > 0) {
333                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
334                         if (err)
335                                 ret = err;
336                 }
337                 fatent_brelse(&fatent);
338                 if (ret < 0)
339                         return ret;
340 
341                 free_start = ret;
342         }
343         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
344 
345         /* Freeing the remained cluster chain */
346         return fat_free_clusters(inode, free_start);
347 }
348 
349 void fat_truncate_blocks(struct inode *inode, loff_t offset)
350 {
351         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
352         const unsigned int cluster_size = sbi->cluster_size;
353         int nr_clusters;
354 
355         /*
356          * This protects against truncating a file bigger than it was then
357          * trying to write into the hole.
358          */
359         if (MSDOS_I(inode)->mmu_private > offset)
360                 MSDOS_I(inode)->mmu_private = offset;
361 
362         nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
363 
364         fat_free(inode, nr_clusters);
365         fat_flush_inodes(inode->i_sb, inode, NULL);
366 }
367 
368 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
369 {
370         struct inode *inode = d_inode(dentry);
371         generic_fillattr(inode, stat);
372         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
373 
374         if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
375                 /* Use i_pos for ino. This is used as fileid of nfs. */
376                 stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
377         }
378         return 0;
379 }
380 EXPORT_SYMBOL_GPL(fat_getattr);
381 
382 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
383                              struct inode *inode, umode_t *mode_ptr)
384 {
385         umode_t mask, perm;
386 
387         /*
388          * Note, the basic check is already done by a caller of
389          * (attr->ia_mode & ~FAT_VALID_MODE)
390          */
391 
392         if (S_ISREG(inode->i_mode))
393                 mask = sbi->options.fs_fmask;
394         else
395                 mask = sbi->options.fs_dmask;
396 
397         perm = *mode_ptr & ~(S_IFMT | mask);
398 
399         /*
400          * Of the r and x bits, all (subject to umask) must be present. Of the
401          * w bits, either all (subject to umask) or none must be present.
402          *
403          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
404          */
405         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
406                 return -EPERM;
407         if (fat_mode_can_hold_ro(inode)) {
408                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
409                         return -EPERM;
410         } else {
411                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
412                         return -EPERM;
413         }
414 
415         *mode_ptr &= S_IFMT | perm;
416 
417         return 0;
418 }
419 
420 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
421 {
422         umode_t allow_utime = sbi->options.allow_utime;
423 
424         if (!uid_eq(current_fsuid(), inode->i_uid)) {
425                 if (in_group_p(inode->i_gid))
426                         allow_utime >>= 3;
427                 if (allow_utime & MAY_WRITE)
428                         return 1;
429         }
430 
431         /* use a default check */
432         return 0;
433 }
434 
435 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
436 /* valid file mode bits */
437 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
438 
439 int fat_setattr(struct dentry *dentry, struct iattr *attr)
440 {
441         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
442         struct inode *inode = d_inode(dentry);
443         unsigned int ia_valid;
444         int error;
445 
446         /* Check for setting the inode time. */
447         ia_valid = attr->ia_valid;
448         if (ia_valid & TIMES_SET_FLAGS) {
449                 if (fat_allow_set_time(sbi, inode))
450                         attr->ia_valid &= ~TIMES_SET_FLAGS;
451         }
452 
453         error = inode_change_ok(inode, attr);
454         attr->ia_valid = ia_valid;
455         if (error) {
456                 if (sbi->options.quiet)
457                         error = 0;
458                 goto out;
459         }
460 
461         /*
462          * Expand the file. Since inode_setattr() updates ->i_size
463          * before calling the ->truncate(), but FAT needs to fill the
464          * hole before it. XXX: this is no longer true with new truncate
465          * sequence.
466          */
467         if (attr->ia_valid & ATTR_SIZE) {
468                 inode_dio_wait(inode);
469 
470                 if (attr->ia_size > inode->i_size) {
471                         error = fat_cont_expand(inode, attr->ia_size);
472                         if (error || attr->ia_valid == ATTR_SIZE)
473                                 goto out;
474                         attr->ia_valid &= ~ATTR_SIZE;
475                 }
476         }
477 
478         if (((attr->ia_valid & ATTR_UID) &&
479              (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
480             ((attr->ia_valid & ATTR_GID) &&
481              (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
482             ((attr->ia_valid & ATTR_MODE) &&
483              (attr->ia_mode & ~FAT_VALID_MODE)))
484                 error = -EPERM;
485 
486         if (error) {
487                 if (sbi->options.quiet)
488                         error = 0;
489                 goto out;
490         }
491 
492         /*
493          * We don't return -EPERM here. Yes, strange, but this is too
494          * old behavior.
495          */
496         if (attr->ia_valid & ATTR_MODE) {
497                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
498                         attr->ia_valid &= ~ATTR_MODE;
499         }
500 
501         if (attr->ia_valid & ATTR_SIZE) {
502                 error = fat_block_truncate_page(inode, attr->ia_size);
503                 if (error)
504                         goto out;
505                 down_write(&MSDOS_I(inode)->truncate_lock);
506                 truncate_setsize(inode, attr->ia_size);
507                 fat_truncate_blocks(inode, attr->ia_size);
508                 up_write(&MSDOS_I(inode)->truncate_lock);
509         }
510 
511         setattr_copy(inode, attr);
512         mark_inode_dirty(inode);
513 out:
514         return error;
515 }
516 EXPORT_SYMBOL_GPL(fat_setattr);
517 
518 const struct inode_operations fat_file_inode_operations = {
519         .setattr        = fat_setattr,
520         .getattr        = fat_getattr,
521 };
522 

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