xref: /openbmc/linux/fs/fat/file.c (revision cf1788fb)
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_mnt_idmap(file),
94  				     file->f_path.dentry, &ia);
95  	if (err)
96  		goto out_unlock_inode;
97  
98  	/* This MUST be done before doing anything irreversible... */
99  	err = fat_setattr(file_mnt_idmap(file), file->f_path.dentry, &ia);
100  	if (err)
101  		goto out_unlock_inode;
102  
103  	fsnotify_change(file->f_path.dentry, 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, attr);
112  	mark_inode_dirty(inode);
113  out_unlock_inode:
114  	inode_unlock(inode);
115  	mnt_drop_write_file(file);
116  out:
117  	return err;
118  }
119  
120  static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
121  {
122  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
123  	return put_user(sbi->vol_id, user_attr);
124  }
125  
126  static 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(sb->s_bdev))
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  			     bdev_discard_granularity(sb->s_bdev));
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  		set_current_state(TASK_UNINTERRUPTIBLE);
181  		io_schedule_timeout(HZ/10);
182  	}
183  	return 0;
184  }
185  
186  int 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(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
196  	if (err)
197  		return err;
198  
199  	return blkdev_issue_flush(inode->i_sb->s_bdev);
200  }
201  
202  
203  const 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		= generic_file_mmap,
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  
217  static 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, 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  					       start + count - 1);
238  		err2 = sync_mapping_buffers(mapping);
239  		if (!err)
240  			err = err2;
241  		err2 = write_inode_now(inode, 1);
242  		if (!err)
243  			err = err2;
244  		if (!err) {
245  			err =  filemap_fdatawait_range(mapping, start,
246  						       start + count - 1);
247  		}
248  	}
249  out:
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   */
260  static 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, (offset + len));
302  	}
303  
304  error:
305  	inode_unlock(inode);
306  	return err;
307  }
308  
309  /* Free all clusters after the skip'th cluster. */
310  static 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, 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, skip - 1, &fclus, &dclus);
347  		if (ret < 0)
348  			return ret;
349  		else if (ret == FAT_ENT_EOF)
350  			return 0;
351  
352  		fatent_init(&fatent);
353  		ret = fat_ent_read(inode, &fatent, dclus);
354  		if (ret == FAT_ENT_EOF) {
355  			fatent_brelse(&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, FAT_ENT_EOF, wait);
364  			if (err)
365  				ret = err;
366  		}
367  		fatent_brelse(&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, free_start);
377  }
378  
379  void fat_truncate_blocks(struct inode *inode, loff_t offset)
380  {
381  	struct msdos_sb_info *sbi = MSDOS_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, nr_clusters);
395  	fat_flush_inodes(inode->i_sb, inode, NULL);
396  }
397  
398  int 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(path->dentry);
402  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
403  
404  	generic_fillattr(idmap, 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  }
419  EXPORT_SYMBOL_GPL(fat_getattr);
420  
421  static 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  
459  static 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(i_uid_into_vfsuid(idmap, inode),
465  			    current_fsuid())) {
466  		if (vfsgid_in_group_p(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  
480  int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
481  		struct iattr *attr)
482  {
483  	struct msdos_sb_info *sbi = MSDOS_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, 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(from_vfsuid(idmap, i_user_ns(inode), attr->ia_vfsuid),
522  		      sbi->options.fs_uid))) ||
523  	    ((attr->ia_valid & ATTR_GID) &&
524  	     (!gid_eq(from_vfsgid(idmap, i_user_ns(inode), attr->ia_vfsgid),
525  		      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, &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, attr->ia_size);
547  		if (error)
548  			goto out;
549  		down_write(&MSDOS_I(inode)->truncate_lock);
550  		truncate_setsize(inode, attr->ia_size);
551  		fat_truncate_blocks(inode, attr->ia_size);
552  		up_write(&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, &attr->ia_atime, S_ATIME);
561  	if (attr->ia_valid & ATTR_CTIME)
562  		fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
563  	if (attr->ia_valid & ATTR_MTIME)
564  		fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
565  	attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
566  
567  	setattr_copy(idmap, inode, attr);
568  	mark_inode_dirty(inode);
569  out:
570  	return error;
571  }
572  EXPORT_SYMBOL_GPL(fat_setattr);
573  
574  const struct inode_operations fat_file_inode_operations = {
575  	.setattr	= fat_setattr,
576  	.getattr	= fat_getattr,
577  	.update_time	= fat_update_time,
578  };
579