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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/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