1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/fat/file.c
4 *
5 * Written 1992,1993 by Werner Almesberger
6 *
7 * regular file handling primitives for fat-based filesystems
8 */
9
10#include <linux/capability.h>
11#include <linux/module.h>
12#include <linux/compat.h>
13#include <linux/mount.h>
14#include <linux/blkdev.h>
15#include <linux/backing-dev.h>
16#include <linux/fsnotify.h>
17#include <linux/security.h>
18#include <linux/falloc.h>
19#include "fat.h"
20
21static long fat_fallocate(struct file *file, int mode,
22 loff_t offset, loff_t len);
23
24static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
25{
26 u32 attr;
27
28 inode_lock_shared(inode);
29 attr = fat_make_attrs(inode);
30 inode_unlock_shared(inode);
31
32 return put_user(attr, user_attr);
33}
34
35static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
36{
37 struct inode *inode = file_inode(f: file);
38 struct msdos_sb_info *sbi = MSDOS_SB(sb: inode->i_sb);
39 int is_dir = S_ISDIR(inode->i_mode);
40 u32 attr, oldattr;
41 struct iattr ia;
42 int err;
43
44 err = get_user(attr, user_attr);
45 if (err)
46 goto out;
47
48 err = mnt_want_write_file(file);
49 if (err)
50 goto out;
51 inode_lock(inode);
52
53 /*
54 * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
55 * prevents the user from turning us into a VFAT
56 * longname entry. Also, we obviously can't set
57 * any of the NTFS attributes in the high 24 bits.
58 */
59 attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
60 /* Merge in ATTR_VOLUME and ATTR_DIR */
61 attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
62 (is_dir ? ATTR_DIR : 0);
63 oldattr = fat_make_attrs(inode);
64
65 /* Equivalent to a chmod() */
66 ia.ia_valid = ATTR_MODE | ATTR_CTIME;
67 ia.ia_ctime = current_time(inode);
68 if (is_dir)
69 ia.ia_mode = fat_make_mode(sbi, attrs: attr, S_IRWXUGO);
70 else {
71 ia.ia_mode = fat_make_mode(sbi, attrs: attr,
72 S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
73 }
74
75 /* The root directory has no attributes */
76 if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
77 err = -EINVAL;
78 goto out_unlock_inode;
79 }
80
81 if (sbi->options.sys_immutable &&
82 ((attr | oldattr) & ATTR_SYS) &&
83 !capable(CAP_LINUX_IMMUTABLE)) {
84 err = -EPERM;
85 goto out_unlock_inode;
86 }
87
88 /*
89 * The security check is questionable... We single
90 * out the RO attribute for checking by the security
91 * module, just because it maps to a file mode.
92 */
93 err = security_inode_setattr(idmap: file_mnt_idmap(file),
94 dentry: file->f_path.dentry, attr: &ia);
95 if (err)
96 goto out_unlock_inode;
97
98 /* This MUST be done before doing anything irreversible... */
99 err = fat_setattr(idmap: file_mnt_idmap(file), dentry: file->f_path.dentry, attr: &ia);
100 if (err)
101 goto out_unlock_inode;
102
103 fsnotify_change(dentry: file->f_path.dentry, ia_valid: ia.ia_valid);
104 if (sbi->options.sys_immutable) {
105 if (attr & ATTR_SYS)
106 inode->i_flags |= S_IMMUTABLE;
107 else
108 inode->i_flags &= ~S_IMMUTABLE;
109 }
110
111 fat_save_attrs(inode, attrs: attr);
112 mark_inode_dirty(inode);
113out_unlock_inode:
114 inode_unlock(inode);
115 mnt_drop_write_file(file);
116out:
117 return err;
118}
119
120static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
121{
122 struct msdos_sb_info *sbi = MSDOS_SB(sb: inode->i_sb);
123 return put_user(sbi->vol_id, user_attr);
124}
125
126static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
127{
128 struct super_block *sb = inode->i_sb;
129 struct fstrim_range __user *user_range;
130 struct fstrim_range range;
131 int err;
132
133 if (!capable(CAP_SYS_ADMIN))
134 return -EPERM;
135
136 if (!bdev_max_discard_sectors(bdev: sb->s_bdev))
137 return -EOPNOTSUPP;
138
139 user_range = (struct fstrim_range __user *)arg;
140 if (copy_from_user(to: &range, from: user_range, n: sizeof(range)))
141 return -EFAULT;
142
143 range.minlen = max_t(unsigned int, range.minlen,
144 bdev_discard_granularity(sb->s_bdev));
145
146 err = fat_trim_fs(inode, range: &range);
147 if (err < 0)
148 return err;
149
150 if (copy_to_user(to: user_range, from: &range, n: sizeof(range)))
151 return -EFAULT;
152
153 return 0;
154}
155
156long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
157{
158 struct inode *inode = file_inode(f: filp);
159 u32 __user *user_attr = (u32 __user *)arg;
160
161 switch (cmd) {
162 case FAT_IOCTL_GET_ATTRIBUTES:
163 return fat_ioctl_get_attributes(inode, user_attr);
164 case FAT_IOCTL_SET_ATTRIBUTES:
165 return fat_ioctl_set_attributes(file: filp, user_attr);
166 case FAT_IOCTL_GET_VOLUME_ID:
167 return fat_ioctl_get_volume_id(inode, user_attr);
168 case FITRIM:
169 return fat_ioctl_fitrim(inode, arg);
170 default:
171 return -ENOTTY; /* Inappropriate ioctl for device */
172 }
173}
174
175static int fat_file_release(struct inode *inode, struct file *filp)
176{
177 if ((filp->f_mode & FMODE_WRITE) &&
178 MSDOS_SB(sb: inode->i_sb)->options.flush) {
179 fat_flush_inodes(sb: inode->i_sb, i1: inode, NULL);
180 set_current_state(TASK_UNINTERRUPTIBLE);
181 io_schedule_timeout(HZ/10);
182 }
183 return 0;
184}
185
186int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
187{
188 struct inode *inode = filp->f_mapping->host;
189 int err;
190
191 err = __generic_file_fsync(filp, start, end, datasync);
192 if (err)
193 return err;
194
195 err = sync_mapping_buffers(mapping: MSDOS_SB(sb: inode->i_sb)->fat_inode->i_mapping);
196 if (err)
197 return err;
198
199 return blkdev_issue_flush(bdev: inode->i_sb->s_bdev);
200}
201
202
203const struct file_operations fat_file_operations = {
204 .llseek = generic_file_llseek,
205 .read_iter = generic_file_read_iter,
206 .write_iter = generic_file_write_iter,
207 .mmap_prepare = generic_file_mmap_prepare,
208 .release = fat_file_release,
209 .unlocked_ioctl = fat_generic_ioctl,
210 .compat_ioctl = compat_ptr_ioctl,
211 .fsync = fat_file_fsync,
212 .splice_read = filemap_splice_read,
213 .splice_write = iter_file_splice_write,
214 .fallocate = fat_fallocate,
215};
216
217static int fat_cont_expand(struct inode *inode, loff_t size)
218{
219 struct address_space *mapping = inode->i_mapping;
220 loff_t start = inode->i_size, count = size - inode->i_size;
221 int err;
222
223 err = generic_cont_expand_simple(inode, size);
224 if (err)
225 goto out;
226
227 fat_truncate_time(inode, NULL, flags: S_CTIME|S_MTIME);
228 mark_inode_dirty(inode);
229 if (IS_SYNC(inode)) {
230 int err2;
231
232 /*
233 * Opencode syncing since we don't have a file open to use
234 * standard fsync path.
235 */
236 err = filemap_fdatawrite_range(mapping, start,
237 end: start + count - 1);
238 err2 = sync_mapping_buffers(mapping);
239 if (!err)
240 err = err2;
241 err2 = write_inode_now(inode, sync: 1);
242 if (!err)
243 err = err2;
244 if (!err) {
245 err = filemap_fdatawait_range(mapping, lstart: start,
246 lend: start + count - 1);
247 }
248 }
249out:
250 return err;
251}
252
253/*
254 * Preallocate space for a file. This implements fat's fallocate file
255 * operation, which gets called from sys_fallocate system call. User
256 * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
257 * we just allocate clusters without zeroing them out. Otherwise we
258 * allocate and zero out clusters via an expanding truncate.
259 */
260static long fat_fallocate(struct file *file, int mode,
261 loff_t offset, loff_t len)
262{
263 int nr_cluster; /* Number of clusters to be allocated */
264 loff_t mm_bytes; /* Number of bytes to be allocated for file */
265 loff_t ondisksize; /* block aligned on-disk size in bytes*/
266 struct inode *inode = file->f_mapping->host;
267 struct super_block *sb = inode->i_sb;
268 struct msdos_sb_info *sbi = MSDOS_SB(sb);
269 int err = 0;
270
271 /* No support for hole punch or other fallocate flags. */
272 if (mode & ~FALLOC_FL_KEEP_SIZE)
273 return -EOPNOTSUPP;
274
275 /* No support for dir */
276 if (!S_ISREG(inode->i_mode))
277 return -EOPNOTSUPP;
278
279 inode_lock(inode);
280 if (mode & FALLOC_FL_KEEP_SIZE) {
281 ondisksize = inode->i_blocks << 9;
282 if ((offset + len) <= ondisksize)
283 goto error;
284
285 /* First compute the number of clusters to be allocated */
286 mm_bytes = offset + len - ondisksize;
287 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
288 sbi->cluster_bits;
289
290 /* Start the allocation.We are not zeroing out the clusters */
291 while (nr_cluster-- > 0) {
292 err = fat_add_cluster(inode);
293 if (err)
294 goto error;
295 }
296 } else {
297 if ((offset + len) <= i_size_read(inode))
298 goto error;
299
300 /* This is just an expanding truncate */
301 err = fat_cont_expand(inode, size: (offset + len));
302 }
303
304error:
305 inode_unlock(inode);
306 return err;
307}
308
309/* Free all clusters after the skip'th cluster. */
310static int fat_free(struct inode *inode, int skip)
311{
312 struct super_block *sb = inode->i_sb;
313 int err, wait, free_start, i_start, i_logstart;
314
315 if (MSDOS_I(inode)->i_start == 0)
316 return 0;
317
318 fat_cache_inval_inode(inode);
319
320 wait = IS_DIRSYNC(inode);
321 i_start = free_start = MSDOS_I(inode)->i_start;
322 i_logstart = MSDOS_I(inode)->i_logstart;
323
324 /* First, we write the new file size. */
325 if (!skip) {
326 MSDOS_I(inode)->i_start = 0;
327 MSDOS_I(inode)->i_logstart = 0;
328 }
329 MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
330 fat_truncate_time(inode, NULL, flags: S_CTIME|S_MTIME);
331 if (wait) {
332 err = fat_sync_inode(inode);
333 if (err) {
334 MSDOS_I(inode)->i_start = i_start;
335 MSDOS_I(inode)->i_logstart = i_logstart;
336 return err;
337 }
338 } else
339 mark_inode_dirty(inode);
340
341 /* Write a new EOF, and get the remaining cluster chain for freeing. */
342 if (skip) {
343 struct fat_entry fatent;
344 int ret, fclus, dclus;
345
346 ret = fat_get_cluster(inode, cluster: skip - 1, fclus: &fclus, dclus: &dclus);
347 if (ret < 0)
348 return ret;
349 else if (ret == FAT_ENT_EOF)
350 return 0;
351
352 fatent_init(fatent: &fatent);
353 ret = fat_ent_read(inode, fatent: &fatent, entry: dclus);
354 if (ret == FAT_ENT_EOF) {
355 fatent_brelse(fatent: &fatent);
356 return 0;
357 } else if (ret == FAT_ENT_FREE) {
358 fat_fs_error(sb,
359 "%s: invalid cluster chain (i_pos %lld)",
360 __func__, MSDOS_I(inode)->i_pos);
361 ret = -EIO;
362 } else if (ret > 0) {
363 err = fat_ent_write(inode, fatent: &fatent, FAT_ENT_EOF, wait);
364 if (err)
365 ret = err;
366 }
367 fatent_brelse(fatent: &fatent);
368 if (ret < 0)
369 return ret;
370
371 free_start = ret;
372 }
373 inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
374
375 /* Freeing the remained cluster chain */
376 return fat_free_clusters(inode, cluster: free_start);
377}
378
379void fat_truncate_blocks(struct inode *inode, loff_t offset)
380{
381 struct msdos_sb_info *sbi = MSDOS_SB(sb: inode->i_sb);
382 const unsigned int cluster_size = sbi->cluster_size;
383 int nr_clusters;
384
385 /*
386 * This protects against truncating a file bigger than it was then
387 * trying to write into the hole.
388 */
389 if (MSDOS_I(inode)->mmu_private > offset)
390 MSDOS_I(inode)->mmu_private = offset;
391
392 nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
393
394 fat_free(inode, skip: nr_clusters);
395 fat_flush_inodes(sb: inode->i_sb, i1: inode, NULL);
396}
397
398int fat_getattr(struct mnt_idmap *idmap, const struct path *path,
399 struct kstat *stat, u32 request_mask, unsigned int flags)
400{
401 struct inode *inode = d_inode(dentry: path->dentry);
402 struct msdos_sb_info *sbi = MSDOS_SB(sb: inode->i_sb);
403
404 generic_fillattr(idmap, request_mask, inode, stat);
405 stat->blksize = sbi->cluster_size;
406
407 if (sbi->options.nfs == FAT_NFS_NOSTALE_RO) {
408 /* Use i_pos for ino. This is used as fileid of nfs. */
409 stat->ino = fat_i_pos_read(sbi, inode);
410 }
411
412 if (sbi->options.isvfat && request_mask & STATX_BTIME) {
413 stat->result_mask |= STATX_BTIME;
414 stat->btime = MSDOS_I(inode)->i_crtime;
415 }
416
417 return 0;
418}
419EXPORT_SYMBOL_GPL(fat_getattr);
420
421static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
422 struct inode *inode, umode_t *mode_ptr)
423{
424 umode_t mask, perm;
425
426 /*
427 * Note, the basic check is already done by a caller of
428 * (attr->ia_mode & ~FAT_VALID_MODE)
429 */
430
431 if (S_ISREG(inode->i_mode))
432 mask = sbi->options.fs_fmask;
433 else
434 mask = sbi->options.fs_dmask;
435
436 perm = *mode_ptr & ~(S_IFMT | mask);
437
438 /*
439 * Of the r and x bits, all (subject to umask) must be present. Of the
440 * w bits, either all (subject to umask) or none must be present.
441 *
442 * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
443 */
444 if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
445 return -EPERM;
446 if (fat_mode_can_hold_ro(inode)) {
447 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
448 return -EPERM;
449 } else {
450 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
451 return -EPERM;
452 }
453
454 *mode_ptr &= S_IFMT | perm;
455
456 return 0;
457}
458
459static int fat_allow_set_time(struct mnt_idmap *idmap,
460 struct msdos_sb_info *sbi, struct inode *inode)
461{
462 umode_t allow_utime = sbi->options.allow_utime;
463
464 if (!vfsuid_eq_kuid(vfsuid: i_uid_into_vfsuid(idmap, inode),
465 current_fsuid())) {
466 if (vfsgid_in_group_p(vfsgid: i_gid_into_vfsgid(idmap, inode)))
467 allow_utime >>= 3;
468 if (allow_utime & MAY_WRITE)
469 return 1;
470 }
471
472 /* use a default check */
473 return 0;
474}
475
476#define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
477/* valid file mode bits */
478#define FAT_VALID_MODE (S_IFREG | S_IFDIR | S_IRWXUGO)
479
480int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
481 struct iattr *attr)
482{
483 struct msdos_sb_info *sbi = MSDOS_SB(sb: dentry->d_sb);
484 struct inode *inode = d_inode(dentry);
485 unsigned int ia_valid;
486 int error;
487
488 /* Check for setting the inode time. */
489 ia_valid = attr->ia_valid;
490 if (ia_valid & TIMES_SET_FLAGS) {
491 if (fat_allow_set_time(idmap, sbi, inode))
492 attr->ia_valid &= ~TIMES_SET_FLAGS;
493 }
494
495 error = setattr_prepare(idmap, dentry, attr);
496 attr->ia_valid = ia_valid;
497 if (error) {
498 if (sbi->options.quiet)
499 error = 0;
500 goto out;
501 }
502
503 /*
504 * Expand the file. Since inode_setattr() updates ->i_size
505 * before calling the ->truncate(), but FAT needs to fill the
506 * hole before it. XXX: this is no longer true with new truncate
507 * sequence.
508 */
509 if (attr->ia_valid & ATTR_SIZE) {
510 inode_dio_wait(inode);
511
512 if (attr->ia_size > inode->i_size) {
513 error = fat_cont_expand(inode, size: attr->ia_size);
514 if (error || attr->ia_valid == ATTR_SIZE)
515 goto out;
516 attr->ia_valid &= ~ATTR_SIZE;
517 }
518 }
519
520 if (((attr->ia_valid & ATTR_UID) &&
521 (!uid_eq(left: from_vfsuid(idmap, fs_userns: i_user_ns(inode), vfsuid: attr->ia_vfsuid),
522 right: sbi->options.fs_uid))) ||
523 ((attr->ia_valid & ATTR_GID) &&
524 (!gid_eq(left: from_vfsgid(idmap, fs_userns: i_user_ns(inode), vfsgid: attr->ia_vfsgid),
525 right: sbi->options.fs_gid))) ||
526 ((attr->ia_valid & ATTR_MODE) &&
527 (attr->ia_mode & ~FAT_VALID_MODE)))
528 error = -EPERM;
529
530 if (error) {
531 if (sbi->options.quiet)
532 error = 0;
533 goto out;
534 }
535
536 /*
537 * We don't return -EPERM here. Yes, strange, but this is too
538 * old behavior.
539 */
540 if (attr->ia_valid & ATTR_MODE) {
541 if (fat_sanitize_mode(sbi, inode, mode_ptr: &attr->ia_mode) < 0)
542 attr->ia_valid &= ~ATTR_MODE;
543 }
544
545 if (attr->ia_valid & ATTR_SIZE) {
546 error = fat_block_truncate_page(inode, from: attr->ia_size);
547 if (error)
548 goto out;
549 down_write(sem: &MSDOS_I(inode)->truncate_lock);
550 truncate_setsize(inode, newsize: attr->ia_size);
551 fat_truncate_blocks(inode, offset: attr->ia_size);
552 up_write(sem: &MSDOS_I(inode)->truncate_lock);
553 }
554
555 /*
556 * setattr_copy can't truncate these appropriately, so we'll
557 * copy them ourselves
558 */
559 if (attr->ia_valid & ATTR_ATIME)
560 fat_truncate_time(inode, now: &attr->ia_atime, flags: S_ATIME);
561 if (attr->ia_valid & ATTR_CTIME)
562 fat_truncate_time(inode, now: &attr->ia_ctime, flags: S_CTIME);
563 if (attr->ia_valid & ATTR_MTIME)
564 fat_truncate_time(inode, now: &attr->ia_mtime, flags: S_MTIME);
565 attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
566
567 setattr_copy(idmap, inode, attr);
568 mark_inode_dirty(inode);
569out:
570 return error;
571}
572EXPORT_SYMBOL_GPL(fat_setattr);
573
574const struct inode_operations fat_file_inode_operations = {
575 .setattr = fat_setattr,
576 .getattr = fat_getattr,
577 .update_time = fat_update_time,
578};
579

source code of linux/fs/fat/file.c