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Linux/fs/fat/file.c

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  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 
 21 static long fat_fallocate(struct file *file, int mode,
 22                           loff_t offset, loff_t len);
 23 
 24 static 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 
 35 static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
 36 {
 37         struct inode *inode = file_inode(file);
 38         struct msdos_sb_info *sbi = MSDOS_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, attr, S_IRWXUGO);
 70         else {
 71                 ia.ia_mode = fat_make_mode(sbi, 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(file->f_path.dentry, &ia);
 94         if (err)
 95                 goto out_unlock_inode;
 96 
 97         /* This MUST be done before doing anything irreversible... */
 98         err = fat_setattr(file_mnt_user_ns(file), file->f_path.dentry, &ia);
 99         if (err)
100                 goto out_unlock_inode;
101 
102         fsnotify_change(file->f_path.dentry, ia.ia_valid);
103         if (sbi->options.sys_immutable) {
104                 if (attr & ATTR_SYS)
105                         inode->i_flags |= S_IMMUTABLE;
106                 else
107                         inode->i_flags &= ~S_IMMUTABLE;
108         }
109 
110         fat_save_attrs(inode, attr);
111         mark_inode_dirty(inode);
112 out_unlock_inode:
113         inode_unlock(inode);
114         mnt_drop_write_file(file);
115 out:
116         return err;
117 }
118 
119 static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
120 {
121         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
122         return put_user(sbi->vol_id, user_attr);
123 }
124 
125 static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
126 {
127         struct super_block *sb = inode->i_sb;
128         struct fstrim_range __user *user_range;
129         struct fstrim_range range;
130         struct request_queue *q = bdev_get_queue(sb->s_bdev);
131         int err;
132 
133         if (!capable(CAP_SYS_ADMIN))
134                 return -EPERM;
135 
136         if (!blk_queue_discard(q))
137                 return -EOPNOTSUPP;
138 
139         user_range = (struct fstrim_range __user *)arg;
140         if (copy_from_user(&range, user_range, sizeof(range)))
141                 return -EFAULT;
142 
143         range.minlen = max_t(unsigned int, range.minlen,
144                              q->limits.discard_granularity);
145 
146         err = fat_trim_fs(inode, &range);
147         if (err < 0)
148                 return err;
149 
150         if (copy_to_user(user_range, &range, sizeof(range)))
151                 return -EFAULT;
152 
153         return 0;
154 }
155 
156 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
157 {
158         struct inode *inode = file_inode(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(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 
175 static int fat_file_release(struct inode *inode, struct file *filp)
176 {
177         if ((filp->f_mode & FMODE_WRITE) &&
178              MSDOS_SB(inode->i_sb)->options.flush) {
179                 fat_flush_inodes(inode->i_sb, inode, NULL);
180                 congestion_wait(BLK_RW_ASYNC, HZ/10);
181         }
182         return 0;
183 }
184 
185 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
186 {
187         struct inode *inode = filp->f_mapping->host;
188         int err;
189 
190         err = __generic_file_fsync(filp, start, end, datasync);
191         if (err)
192                 return err;
193 
194         err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
195         if (err)
196                 return err;
197 
198         return blkdev_issue_flush(inode->i_sb->s_bdev);
199 }
200 
201 
202 const struct file_operations fat_file_operations = {
203         .llseek         = generic_file_llseek,
204         .read_iter      = generic_file_read_iter,
205         .write_iter     = generic_file_write_iter,
206         .mmap           = generic_file_mmap,
207         .release        = fat_file_release,
208         .unlocked_ioctl = fat_generic_ioctl,
209         .compat_ioctl   = compat_ptr_ioctl,
210         .fsync          = fat_file_fsync,
211         .splice_read    = generic_file_splice_read,
212         .splice_write   = iter_file_splice_write,
213         .fallocate      = fat_fallocate,
214 };
215 
216 static int fat_cont_expand(struct inode *inode, loff_t size)
217 {
218         struct address_space *mapping = inode->i_mapping;
219         loff_t start = inode->i_size, count = size - inode->i_size;
220         int err;
221 
222         err = generic_cont_expand_simple(inode, size);
223         if (err)
224                 goto out;
225 
226         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
227         mark_inode_dirty(inode);
228         if (IS_SYNC(inode)) {
229                 int err2;
230 
231                 /*
232                  * Opencode syncing since we don't have a file open to use
233                  * standard fsync path.
234                  */
235                 err = filemap_fdatawrite_range(mapping, start,
236                                                start + count - 1);
237                 err2 = sync_mapping_buffers(mapping);
238                 if (!err)
239                         err = err2;
240                 err2 = write_inode_now(inode, 1);
241                 if (!err)
242                         err = err2;
243                 if (!err) {
244                         err =  filemap_fdatawait_range(mapping, start,
245                                                        start + count - 1);
246                 }
247         }
248 out:
249         return err;
250 }
251 
252 /*
253  * Preallocate space for a file. This implements fat's fallocate file
254  * operation, which gets called from sys_fallocate system call. User
255  * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
256  * we just allocate clusters without zeroing them out. Otherwise we
257  * allocate and zero out clusters via an expanding truncate.
258  */
259 static long fat_fallocate(struct file *file, int mode,
260                           loff_t offset, loff_t len)
261 {
262         int nr_cluster; /* Number of clusters to be allocated */
263         loff_t mm_bytes; /* Number of bytes to be allocated for file */
264         loff_t ondisksize; /* block aligned on-disk size in bytes*/
265         struct inode *inode = file->f_mapping->host;
266         struct super_block *sb = inode->i_sb;
267         struct msdos_sb_info *sbi = MSDOS_SB(sb);
268         int err = 0;
269 
270         /* No support for hole punch or other fallocate flags. */
271         if (mode & ~FALLOC_FL_KEEP_SIZE)
272                 return -EOPNOTSUPP;
273 
274         /* No support for dir */
275         if (!S_ISREG(inode->i_mode))
276                 return -EOPNOTSUPP;
277 
278         inode_lock(inode);
279         if (mode & FALLOC_FL_KEEP_SIZE) {
280                 ondisksize = inode->i_blocks << 9;
281                 if ((offset + len) <= ondisksize)
282                         goto error;
283 
284                 /* First compute the number of clusters to be allocated */
285                 mm_bytes = offset + len - ondisksize;
286                 nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
287                         sbi->cluster_bits;
288 
289                 /* Start the allocation.We are not zeroing out the clusters */
290                 while (nr_cluster-- > 0) {
291                         err = fat_add_cluster(inode);
292                         if (err)
293                                 goto error;
294                 }
295         } else {
296                 if ((offset + len) <= i_size_read(inode))
297                         goto error;
298 
299                 /* This is just an expanding truncate */
300                 err = fat_cont_expand(inode, (offset + len));
301         }
302 
303 error:
304         inode_unlock(inode);
305         return err;
306 }
307 
308 /* Free all clusters after the skip'th cluster. */
309 static int fat_free(struct inode *inode, int skip)
310 {
311         struct super_block *sb = inode->i_sb;
312         int err, wait, free_start, i_start, i_logstart;
313 
314         if (MSDOS_I(inode)->i_start == 0)
315                 return 0;
316 
317         fat_cache_inval_inode(inode);
318 
319         wait = IS_DIRSYNC(inode);
320         i_start = free_start = MSDOS_I(inode)->i_start;
321         i_logstart = MSDOS_I(inode)->i_logstart;
322 
323         /* First, we write the new file size. */
324         if (!skip) {
325                 MSDOS_I(inode)->i_start = 0;
326                 MSDOS_I(inode)->i_logstart = 0;
327         }
328         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
329         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
330         if (wait) {
331                 err = fat_sync_inode(inode);
332                 if (err) {
333                         MSDOS_I(inode)->i_start = i_start;
334                         MSDOS_I(inode)->i_logstart = i_logstart;
335                         return err;
336                 }
337         } else
338                 mark_inode_dirty(inode);
339 
340         /* Write a new EOF, and get the remaining cluster chain for freeing. */
341         if (skip) {
342                 struct fat_entry fatent;
343                 int ret, fclus, dclus;
344 
345                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
346                 if (ret < 0)
347                         return ret;
348                 else if (ret == FAT_ENT_EOF)
349                         return 0;
350 
351                 fatent_init(&fatent);
352                 ret = fat_ent_read(inode, &fatent, dclus);
353                 if (ret == FAT_ENT_EOF) {
354                         fatent_brelse(&fatent);
355                         return 0;
356                 } else if (ret == FAT_ENT_FREE) {
357                         fat_fs_error(sb,
358                                      "%s: invalid cluster chain (i_pos %lld)",
359                                      __func__, MSDOS_I(inode)->i_pos);
360                         ret = -EIO;
361                 } else if (ret > 0) {
362                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
363                         if (err)
364                                 ret = err;
365                 }
366                 fatent_brelse(&fatent);
367                 if (ret < 0)
368                         return ret;
369 
370                 free_start = ret;
371         }
372         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
373 
374         /* Freeing the remained cluster chain */
375         return fat_free_clusters(inode, free_start);
376 }
377 
378 void fat_truncate_blocks(struct inode *inode, loff_t offset)
379 {
380         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
381         const unsigned int cluster_size = sbi->cluster_size;
382         int nr_clusters;
383 
384         /*
385          * This protects against truncating a file bigger than it was then
386          * trying to write into the hole.
387          */
388         if (MSDOS_I(inode)->mmu_private > offset)
389                 MSDOS_I(inode)->mmu_private = offset;
390 
391         nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
392 
393         fat_free(inode, nr_clusters);
394         fat_flush_inodes(inode->i_sb, inode, NULL);
395 }
396 
397 int fat_getattr(struct user_namespace *mnt_userns, const struct path *path,
398                 struct kstat *stat, u32 request_mask, unsigned int flags)
399 {
400         struct inode *inode = d_inode(path->dentry);
401         generic_fillattr(mnt_userns, inode, stat);
402         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
403 
404         if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
405                 /* Use i_pos for ino. This is used as fileid of nfs. */
406                 stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
407         }
408         return 0;
409 }
410 EXPORT_SYMBOL_GPL(fat_getattr);
411 
412 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
413                              struct inode *inode, umode_t *mode_ptr)
414 {
415         umode_t mask, perm;
416 
417         /*
418          * Note, the basic check is already done by a caller of
419          * (attr->ia_mode & ~FAT_VALID_MODE)
420          */
421 
422         if (S_ISREG(inode->i_mode))
423                 mask = sbi->options.fs_fmask;
424         else
425                 mask = sbi->options.fs_dmask;
426 
427         perm = *mode_ptr & ~(S_IFMT | mask);
428 
429         /*
430          * Of the r and x bits, all (subject to umask) must be present. Of the
431          * w bits, either all (subject to umask) or none must be present.
432          *
433          * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
434          */
435         if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
436                 return -EPERM;
437         if (fat_mode_can_hold_ro(inode)) {
438                 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
439                         return -EPERM;
440         } else {
441                 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
442                         return -EPERM;
443         }
444 
445         *mode_ptr &= S_IFMT | perm;
446 
447         return 0;
448 }
449 
450 static int fat_allow_set_time(struct user_namespace *mnt_userns,
451                               struct msdos_sb_info *sbi, struct inode *inode)
452 {
453         umode_t allow_utime = sbi->options.allow_utime;
454 
455         if (!uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode))) {
456                 if (in_group_p(i_gid_into_mnt(mnt_userns, inode)))
457                         allow_utime >>= 3;
458                 if (allow_utime & MAY_WRITE)
459                         return 1;
460         }
461 
462         /* use a default check */
463         return 0;
464 }
465 
466 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
467 /* valid file mode bits */
468 #define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)
469 
470 int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
471                 struct iattr *attr)
472 {
473         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
474         struct inode *inode = d_inode(dentry);
475         unsigned int ia_valid;
476         int error;
477 
478         /* Check for setting the inode time. */
479         ia_valid = attr->ia_valid;
480         if (ia_valid & TIMES_SET_FLAGS) {
481                 if (fat_allow_set_time(mnt_userns, sbi, inode))
482                         attr->ia_valid &= ~TIMES_SET_FLAGS;
483         }
484 
485         error = setattr_prepare(mnt_userns, dentry, attr);
486         attr->ia_valid = ia_valid;
487         if (error) {
488                 if (sbi->options.quiet)
489                         error = 0;
490                 goto out;
491         }
492 
493         /*
494          * Expand the file. Since inode_setattr() updates ->i_size
495          * before calling the ->truncate(), but FAT needs to fill the
496          * hole before it. XXX: this is no longer true with new truncate
497          * sequence.
498          */
499         if (attr->ia_valid & ATTR_SIZE) {
500                 inode_dio_wait(inode);
501 
502                 if (attr->ia_size > inode->i_size) {
503                         error = fat_cont_expand(inode, attr->ia_size);
504                         if (error || attr->ia_valid == ATTR_SIZE)
505                                 goto out;
506                         attr->ia_valid &= ~ATTR_SIZE;
507                 }
508         }
509 
510         if (((attr->ia_valid & ATTR_UID) &&
511              (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
512             ((attr->ia_valid & ATTR_GID) &&
513              (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
514             ((attr->ia_valid & ATTR_MODE) &&
515              (attr->ia_mode & ~FAT_VALID_MODE)))
516                 error = -EPERM;
517 
518         if (error) {
519                 if (sbi->options.quiet)
520                         error = 0;
521                 goto out;
522         }
523 
524         /*
525          * We don't return -EPERM here. Yes, strange, but this is too
526          * old behavior.
527          */
528         if (attr->ia_valid & ATTR_MODE) {
529                 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
530                         attr->ia_valid &= ~ATTR_MODE;
531         }
532 
533         if (attr->ia_valid & ATTR_SIZE) {
534                 error = fat_block_truncate_page(inode, attr->ia_size);
535                 if (error)
536                         goto out;
537                 down_write(&MSDOS_I(inode)->truncate_lock);
538                 truncate_setsize(inode, attr->ia_size);
539                 fat_truncate_blocks(inode, attr->ia_size);
540                 up_write(&MSDOS_I(inode)->truncate_lock);
541         }
542 
543         /*
544          * setattr_copy can't truncate these appropriately, so we'll
545          * copy them ourselves
546          */
547         if (attr->ia_valid & ATTR_ATIME)
548                 fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
549         if (attr->ia_valid & ATTR_CTIME)
550                 fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
551         if (attr->ia_valid & ATTR_MTIME)
552                 fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
553         attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
554 
555         setattr_copy(mnt_userns, inode, attr);
556         mark_inode_dirty(inode);
557 out:
558         return error;
559 }
560 EXPORT_SYMBOL_GPL(fat_setattr);
561 
562 const struct inode_operations fat_file_inode_operations = {
563         .setattr        = fat_setattr,
564         .getattr        = fat_getattr,
565         .update_time    = fat_update_time,
566 };
567 

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