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/buffer_head.h>
14 #include <linux/writeback.h>
15 #include <linux/backing-dev.h>
16 #include <linux/blkdev.h>
17 #include <linux/fsnotify.h>
18 #include <linux/security.h>
19 #include "fat.h"
20
fat_generic_ioctl(struct inode * inode,struct file * filp,unsigned int cmd,unsigned long arg)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 mutex_lock(&inode->i_mutex);
33 attr = fat_make_attrs(inode);
34 mutex_unlock(&inode->i_mutex);
35
36 return put_user(attr, user_attr);
37 }
38 case FAT_IOCTL_SET_ATTRIBUTES:
39 {
40 u32 attr, oldattr;
41 int err, is_dir = S_ISDIR(inode->i_mode);
42 struct iattr ia;
43
44 err = get_user(attr, user_attr);
45 if (err)
46 return err;
47
48 mutex_lock(&inode->i_mutex);
49
50 err = mnt_want_write(filp->f_path.mnt);
51 if (err)
52 goto up_no_drop_write;
53
54 /*
55 * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
56 * prevents the user from turning us into a VFAT
57 * longname entry. Also, we obviously can't set
58 * any of the NTFS attributes in the high 24 bits.
59 */
60 attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
61 /* Merge in ATTR_VOLUME and ATTR_DIR */
62 attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
63 (is_dir ? ATTR_DIR : 0);
64 oldattr = fat_make_attrs(inode);
65
66 /* Equivalent to a chmod() */
67 ia.ia_valid = ATTR_MODE | ATTR_CTIME;
68 ia.ia_ctime = current_fs_time(inode->i_sb);
69 if (is_dir)
70 ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
71 else {
72 ia.ia_mode = fat_make_mode(sbi, attr,
73 S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
74 }
75
76 /* The root directory has no attributes */
77 if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
78 err = -EINVAL;
79 goto up;
80 }
81
82 if (sbi->options.sys_immutable) {
83 if ((attr | oldattr) & ATTR_SYS) {
84 if (!capable(CAP_LINUX_IMMUTABLE)) {
85 err = -EPERM;
86 goto up;
87 }
88 }
89 }
90
91 /*
92 * The security check is questionable... We single
93 * out the RO attribute for checking by the security
94 * module, just because it maps to a file mode.
95 */
96 err = security_inode_setattr(filp->f_path.dentry, &ia);
97 if (err)
98 goto up;
99
100 /* This MUST be done before doing anything irreversible... */
101 err = fat_setattr(filp->f_path.dentry, &ia);
102 if (err)
103 goto up;
104
105 fsnotify_change(filp->f_path.dentry, ia.ia_valid);
106 if (sbi->options.sys_immutable) {
107 if (attr & ATTR_SYS)
108 inode->i_flags |= S_IMMUTABLE;
109 else
110 inode->i_flags &= S_IMMUTABLE;
111 }
112
113 fat_save_attrs(inode, attr);
114 mark_inode_dirty(inode);
115 up:
116 mnt_drop_write(filp->f_path.mnt);
117 up_no_drop_write:
118 mutex_unlock(&inode->i_mutex);
119 return err;
120 }
121 default:
122 return -ENOTTY; /* Inappropriate ioctl for device */
123 }
124 }
125
fat_file_release(struct inode * inode,struct file * filp)126 static int fat_file_release(struct inode *inode, struct file *filp)
127 {
128 if ((filp->f_mode & FMODE_WRITE) &&
129 MSDOS_SB(inode->i_sb)->options.flush) {
130 fat_flush_inodes(inode->i_sb, inode, NULL);
131 congestion_wait(WRITE, HZ/10);
132 }
133 return 0;
134 }
135
136 const struct file_operations fat_file_operations = {
137 .llseek = generic_file_llseek,
138 .read = do_sync_read,
139 .write = do_sync_write,
140 .aio_read = generic_file_aio_read,
141 .aio_write = generic_file_aio_write,
142 .mmap = generic_file_mmap,
143 .release = fat_file_release,
144 .ioctl = fat_generic_ioctl,
145 .fsync = file_fsync,
146 .splice_read = generic_file_splice_read,
147 };
148
fat_cont_expand(struct inode * inode,loff_t size)149 static int fat_cont_expand(struct inode *inode, loff_t size)
150 {
151 struct address_space *mapping = inode->i_mapping;
152 loff_t start = inode->i_size, count = size - inode->i_size;
153 int err;
154
155 err = generic_cont_expand_simple(inode, size);
156 if (err)
157 goto out;
158
159 inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
160 mark_inode_dirty(inode);
161 if (IS_SYNC(inode))
162 err = sync_page_range_nolock(inode, mapping, start, count);
163 out:
164 return err;
165 }
166
167 /* Free all clusters after the skip'th cluster. */
fat_free(struct inode * inode,int skip)168 static int fat_free(struct inode *inode, int skip)
169 {
170 struct super_block *sb = inode->i_sb;
171 int err, wait, free_start, i_start, i_logstart;
172
173 if (MSDOS_I(inode)->i_start == 0)
174 return 0;
175
176 fat_cache_inval_inode(inode);
177
178 wait = IS_DIRSYNC(inode);
179 i_start = free_start = MSDOS_I(inode)->i_start;
180 i_logstart = MSDOS_I(inode)->i_logstart;
181
182 /* First, we write the new file size. */
183 if (!skip) {
184 MSDOS_I(inode)->i_start = 0;
185 MSDOS_I(inode)->i_logstart = 0;
186 }
187 MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
188 inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
189 if (wait) {
190 err = fat_sync_inode(inode);
191 if (err) {
192 MSDOS_I(inode)->i_start = i_start;
193 MSDOS_I(inode)->i_logstart = i_logstart;
194 return err;
195 }
196 } else
197 mark_inode_dirty(inode);
198
199 /* Write a new EOF, and get the remaining cluster chain for freeing. */
200 if (skip) {
201 struct fat_entry fatent;
202 int ret, fclus, dclus;
203
204 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
205 if (ret < 0)
206 return ret;
207 else if (ret == FAT_ENT_EOF)
208 return 0;
209
210 fatent_init(&fatent);
211 ret = fat_ent_read(inode, &fatent, dclus);
212 if (ret == FAT_ENT_EOF) {
213 fatent_brelse(&fatent);
214 return 0;
215 } else if (ret == FAT_ENT_FREE) {
216 fat_fs_error(sb,
217 "%s: invalid cluster chain (i_pos %lld)",
218 __func__, MSDOS_I(inode)->i_pos);
219 ret = -EIO;
220 } else if (ret > 0) {
221 err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
222 if (err)
223 ret = err;
224 }
225 fatent_brelse(&fatent);
226 if (ret < 0)
227 return ret;
228
229 free_start = ret;
230 }
231 inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
232
233 /* Freeing the remained cluster chain */
234 return fat_free_clusters(inode, free_start);
235 }
236
fat_truncate(struct inode * inode)237 void fat_truncate(struct inode *inode)
238 {
239 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
240 const unsigned int cluster_size = sbi->cluster_size;
241 int nr_clusters;
242
243 /*
244 * This protects against truncating a file bigger than it was then
245 * trying to write into the hole.
246 */
247 if (MSDOS_I(inode)->mmu_private > inode->i_size)
248 MSDOS_I(inode)->mmu_private = inode->i_size;
249
250 nr_clusters = (inode->i_size + (cluster_size - 1)) >> sbi->cluster_bits;
251
252 fat_free(inode, nr_clusters);
253 fat_flush_inodes(inode->i_sb, inode, NULL);
254 }
255
fat_getattr(struct vfsmount * mnt,struct dentry * dentry,struct kstat * stat)256 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
257 {
258 struct inode *inode = dentry->d_inode;
259 generic_fillattr(inode, stat);
260 stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
261 return 0;
262 }
263 EXPORT_SYMBOL_GPL(fat_getattr);
264
fat_sanitize_mode(const struct msdos_sb_info * sbi,struct inode * inode,umode_t * mode_ptr)265 static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
266 struct inode *inode, umode_t *mode_ptr)
267 {
268 mode_t mask, perm;
269
270 /*
271 * Note, the basic check is already done by a caller of
272 * (attr->ia_mode & ~FAT_VALID_MODE)
273 */
274
275 if (S_ISREG(inode->i_mode))
276 mask = sbi->options.fs_fmask;
277 else
278 mask = sbi->options.fs_dmask;
279
280 perm = *mode_ptr & ~(S_IFMT | mask);
281
282 /*
283 * Of the r and x bits, all (subject to umask) must be present. Of the
284 * w bits, either all (subject to umask) or none must be present.
285 *
286 * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
287 */
288 if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
289 return -EPERM;
290 if (fat_mode_can_hold_ro(inode)) {
291 if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
292 return -EPERM;
293 } else {
294 if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
295 return -EPERM;
296 }
297
298 *mode_ptr &= S_IFMT | perm;
299
300 return 0;
301 }
302
fat_allow_set_time(struct msdos_sb_info * sbi,struct inode * inode)303 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
304 {
305 mode_t allow_utime = sbi->options.allow_utime;
306
307 if (current_fsuid() != inode->i_uid) {
308 if (in_group_p(inode->i_gid))
309 allow_utime >>= 3;
310 if (allow_utime & MAY_WRITE)
311 return 1;
312 }
313
314 /* use a default check */
315 return 0;
316 }
317
318 #define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
319 /* valid file mode bits */
320 #define FAT_VALID_MODE (S_IFREG | S_IFDIR | S_IRWXUGO)
321
fat_setattr(struct dentry * dentry,struct iattr * attr)322 int fat_setattr(struct dentry *dentry, struct iattr *attr)
323 {
324 struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
325 struct inode *inode = dentry->d_inode;
326 unsigned int ia_valid;
327 int error;
328
329 /*
330 * Expand the file. Since inode_setattr() updates ->i_size
331 * before calling the ->truncate(), but FAT needs to fill the
332 * hole before it.
333 */
334 if (attr->ia_valid & ATTR_SIZE) {
335 if (attr->ia_size > inode->i_size) {
336 error = fat_cont_expand(inode, attr->ia_size);
337 if (error || attr->ia_valid == ATTR_SIZE)
338 goto out;
339 attr->ia_valid &= ~ATTR_SIZE;
340 }
341 }
342
343 /* Check for setting the inode time. */
344 ia_valid = attr->ia_valid;
345 if (ia_valid & TIMES_SET_FLAGS) {
346 if (fat_allow_set_time(sbi, inode))
347 attr->ia_valid &= ~TIMES_SET_FLAGS;
348 }
349
350 error = inode_change_ok(inode, attr);
351 attr->ia_valid = ia_valid;
352 if (error) {
353 if (sbi->options.quiet)
354 error = 0;
355 goto out;
356 }
357
358 if (((attr->ia_valid & ATTR_UID) &&
359 (attr->ia_uid != sbi->options.fs_uid)) ||
360 ((attr->ia_valid & ATTR_GID) &&
361 (attr->ia_gid != sbi->options.fs_gid)) ||
362 ((attr->ia_valid & ATTR_MODE) &&
363 (attr->ia_mode & ~FAT_VALID_MODE)))
364 error = -EPERM;
365
366 if (error) {
367 if (sbi->options.quiet)
368 error = 0;
369 goto out;
370 }
371
372 /*
373 * We don't return -EPERM here. Yes, strange, but this is too
374 * old behavior.
375 */
376 if (attr->ia_valid & ATTR_MODE) {
377 if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
378 attr->ia_valid &= ~ATTR_MODE;
379 }
380
381 if (attr->ia_valid)
382 error = inode_setattr(inode, attr);
383 out:
384 return error;
385 }
386 EXPORT_SYMBOL_GPL(fat_setattr);
387
388 const struct inode_operations fat_file_inode_operations = {
389 .truncate = fat_truncate,
390 .setattr = fat_setattr,
391 .getattr = fat_getattr,
392 };
393