xref: /openbmc/linux/fs/open.c (revision 6774def6)
1 /*
2  *  linux/fs/open.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6 
7 #include <linux/string.h>
8 #include <linux/mm.h>
9 #include <linux/file.h>
10 #include <linux/fdtable.h>
11 #include <linux/fsnotify.h>
12 #include <linux/module.h>
13 #include <linux/tty.h>
14 #include <linux/namei.h>
15 #include <linux/backing-dev.h>
16 #include <linux/capability.h>
17 #include <linux/securebits.h>
18 #include <linux/security.h>
19 #include <linux/mount.h>
20 #include <linux/fcntl.h>
21 #include <linux/slab.h>
22 #include <asm/uaccess.h>
23 #include <linux/fs.h>
24 #include <linux/personality.h>
25 #include <linux/pagemap.h>
26 #include <linux/syscalls.h>
27 #include <linux/rcupdate.h>
28 #include <linux/audit.h>
29 #include <linux/falloc.h>
30 #include <linux/fs_struct.h>
31 #include <linux/ima.h>
32 #include <linux/dnotify.h>
33 #include <linux/compat.h>
34 
35 #include "internal.h"
36 
37 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
38 	struct file *filp)
39 {
40 	int ret;
41 	struct iattr newattrs;
42 
43 	/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
44 	if (length < 0)
45 		return -EINVAL;
46 
47 	newattrs.ia_size = length;
48 	newattrs.ia_valid = ATTR_SIZE | time_attrs;
49 	if (filp) {
50 		newattrs.ia_file = filp;
51 		newattrs.ia_valid |= ATTR_FILE;
52 	}
53 
54 	/* Remove suid/sgid on truncate too */
55 	ret = should_remove_suid(dentry);
56 	if (ret)
57 		newattrs.ia_valid |= ret | ATTR_FORCE;
58 
59 	mutex_lock(&dentry->d_inode->i_mutex);
60 	/* Note any delegations or leases have already been broken: */
61 	ret = notify_change(dentry, &newattrs, NULL);
62 	mutex_unlock(&dentry->d_inode->i_mutex);
63 	return ret;
64 }
65 
66 long vfs_truncate(struct path *path, loff_t length)
67 {
68 	struct inode *inode;
69 	long error;
70 
71 	inode = path->dentry->d_inode;
72 
73 	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
74 	if (S_ISDIR(inode->i_mode))
75 		return -EISDIR;
76 	if (!S_ISREG(inode->i_mode))
77 		return -EINVAL;
78 
79 	error = mnt_want_write(path->mnt);
80 	if (error)
81 		goto out;
82 
83 	error = inode_permission(inode, MAY_WRITE);
84 	if (error)
85 		goto mnt_drop_write_and_out;
86 
87 	error = -EPERM;
88 	if (IS_APPEND(inode))
89 		goto mnt_drop_write_and_out;
90 
91 	error = get_write_access(inode);
92 	if (error)
93 		goto mnt_drop_write_and_out;
94 
95 	/*
96 	 * Make sure that there are no leases.  get_write_access() protects
97 	 * against the truncate racing with a lease-granting setlease().
98 	 */
99 	error = break_lease(inode, O_WRONLY);
100 	if (error)
101 		goto put_write_and_out;
102 
103 	error = locks_verify_truncate(inode, NULL, length);
104 	if (!error)
105 		error = security_path_truncate(path);
106 	if (!error)
107 		error = do_truncate(path->dentry, length, 0, NULL);
108 
109 put_write_and_out:
110 	put_write_access(inode);
111 mnt_drop_write_and_out:
112 	mnt_drop_write(path->mnt);
113 out:
114 	return error;
115 }
116 EXPORT_SYMBOL_GPL(vfs_truncate);
117 
118 static long do_sys_truncate(const char __user *pathname, loff_t length)
119 {
120 	unsigned int lookup_flags = LOOKUP_FOLLOW;
121 	struct path path;
122 	int error;
123 
124 	if (length < 0)	/* sorry, but loff_t says... */
125 		return -EINVAL;
126 
127 retry:
128 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
129 	if (!error) {
130 		error = vfs_truncate(&path, length);
131 		path_put(&path);
132 	}
133 	if (retry_estale(error, lookup_flags)) {
134 		lookup_flags |= LOOKUP_REVAL;
135 		goto retry;
136 	}
137 	return error;
138 }
139 
140 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
141 {
142 	return do_sys_truncate(path, length);
143 }
144 
145 #ifdef CONFIG_COMPAT
146 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
147 {
148 	return do_sys_truncate(path, length);
149 }
150 #endif
151 
152 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
153 {
154 	struct inode *inode;
155 	struct dentry *dentry;
156 	struct fd f;
157 	int error;
158 
159 	error = -EINVAL;
160 	if (length < 0)
161 		goto out;
162 	error = -EBADF;
163 	f = fdget(fd);
164 	if (!f.file)
165 		goto out;
166 
167 	/* explicitly opened as large or we are on 64-bit box */
168 	if (f.file->f_flags & O_LARGEFILE)
169 		small = 0;
170 
171 	dentry = f.file->f_path.dentry;
172 	inode = dentry->d_inode;
173 	error = -EINVAL;
174 	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
175 		goto out_putf;
176 
177 	error = -EINVAL;
178 	/* Cannot ftruncate over 2^31 bytes without large file support */
179 	if (small && length > MAX_NON_LFS)
180 		goto out_putf;
181 
182 	error = -EPERM;
183 	if (IS_APPEND(inode))
184 		goto out_putf;
185 
186 	sb_start_write(inode->i_sb);
187 	error = locks_verify_truncate(inode, f.file, length);
188 	if (!error)
189 		error = security_path_truncate(&f.file->f_path);
190 	if (!error)
191 		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
192 	sb_end_write(inode->i_sb);
193 out_putf:
194 	fdput(f);
195 out:
196 	return error;
197 }
198 
199 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
200 {
201 	return do_sys_ftruncate(fd, length, 1);
202 }
203 
204 #ifdef CONFIG_COMPAT
205 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
206 {
207 	return do_sys_ftruncate(fd, length, 1);
208 }
209 #endif
210 
211 /* LFS versions of truncate are only needed on 32 bit machines */
212 #if BITS_PER_LONG == 32
213 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
214 {
215 	return do_sys_truncate(path, length);
216 }
217 
218 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
219 {
220 	return do_sys_ftruncate(fd, length, 0);
221 }
222 #endif /* BITS_PER_LONG == 32 */
223 
224 
225 int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
226 {
227 	struct inode *inode = file_inode(file);
228 	long ret;
229 
230 	if (offset < 0 || len <= 0)
231 		return -EINVAL;
232 
233 	/* Return error if mode is not supported */
234 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
235 		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
236 		return -EOPNOTSUPP;
237 
238 	/* Punch hole and zero range are mutually exclusive */
239 	if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
240 	    (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
241 		return -EOPNOTSUPP;
242 
243 	/* Punch hole must have keep size set */
244 	if ((mode & FALLOC_FL_PUNCH_HOLE) &&
245 	    !(mode & FALLOC_FL_KEEP_SIZE))
246 		return -EOPNOTSUPP;
247 
248 	/* Collapse range should only be used exclusively. */
249 	if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
250 	    (mode & ~FALLOC_FL_COLLAPSE_RANGE))
251 		return -EINVAL;
252 
253 	if (!(file->f_mode & FMODE_WRITE))
254 		return -EBADF;
255 
256 	/*
257 	 * We can only allow pure fallocate on append only files
258 	 */
259 	if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
260 		return -EPERM;
261 
262 	if (IS_IMMUTABLE(inode))
263 		return -EPERM;
264 
265 	/*
266 	 * We cannot allow any fallocate operation on an active swapfile
267 	 */
268 	if (IS_SWAPFILE(inode))
269 		return -ETXTBSY;
270 
271 	/*
272 	 * Revalidate the write permissions, in case security policy has
273 	 * changed since the files were opened.
274 	 */
275 	ret = security_file_permission(file, MAY_WRITE);
276 	if (ret)
277 		return ret;
278 
279 	if (S_ISFIFO(inode->i_mode))
280 		return -ESPIPE;
281 
282 	/*
283 	 * Let individual file system decide if it supports preallocation
284 	 * for directories or not.
285 	 */
286 	if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
287 		return -ENODEV;
288 
289 	/* Check for wrap through zero too */
290 	if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
291 		return -EFBIG;
292 
293 	if (!file->f_op->fallocate)
294 		return -EOPNOTSUPP;
295 
296 	sb_start_write(inode->i_sb);
297 	ret = file->f_op->fallocate(file, mode, offset, len);
298 	sb_end_write(inode->i_sb);
299 	return ret;
300 }
301 
302 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
303 {
304 	struct fd f = fdget(fd);
305 	int error = -EBADF;
306 
307 	if (f.file) {
308 		error = do_fallocate(f.file, mode, offset, len);
309 		fdput(f);
310 	}
311 	return error;
312 }
313 
314 /*
315  * access() needs to use the real uid/gid, not the effective uid/gid.
316  * We do this by temporarily clearing all FS-related capabilities and
317  * switching the fsuid/fsgid around to the real ones.
318  */
319 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
320 {
321 	const struct cred *old_cred;
322 	struct cred *override_cred;
323 	struct path path;
324 	struct inode *inode;
325 	int res;
326 	unsigned int lookup_flags = LOOKUP_FOLLOW;
327 
328 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
329 		return -EINVAL;
330 
331 	override_cred = prepare_creds();
332 	if (!override_cred)
333 		return -ENOMEM;
334 
335 	override_cred->fsuid = override_cred->uid;
336 	override_cred->fsgid = override_cred->gid;
337 
338 	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
339 		/* Clear the capabilities if we switch to a non-root user */
340 		kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
341 		if (!uid_eq(override_cred->uid, root_uid))
342 			cap_clear(override_cred->cap_effective);
343 		else
344 			override_cred->cap_effective =
345 				override_cred->cap_permitted;
346 	}
347 
348 	old_cred = override_creds(override_cred);
349 retry:
350 	res = user_path_at(dfd, filename, lookup_flags, &path);
351 	if (res)
352 		goto out;
353 
354 	inode = path.dentry->d_inode;
355 
356 	if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
357 		/*
358 		 * MAY_EXEC on regular files is denied if the fs is mounted
359 		 * with the "noexec" flag.
360 		 */
361 		res = -EACCES;
362 		if (path.mnt->mnt_flags & MNT_NOEXEC)
363 			goto out_path_release;
364 	}
365 
366 	res = inode_permission(inode, mode | MAY_ACCESS);
367 	/* SuS v2 requires we report a read only fs too */
368 	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
369 		goto out_path_release;
370 	/*
371 	 * This is a rare case where using __mnt_is_readonly()
372 	 * is OK without a mnt_want/drop_write() pair.  Since
373 	 * no actual write to the fs is performed here, we do
374 	 * not need to telegraph to that to anyone.
375 	 *
376 	 * By doing this, we accept that this access is
377 	 * inherently racy and know that the fs may change
378 	 * state before we even see this result.
379 	 */
380 	if (__mnt_is_readonly(path.mnt))
381 		res = -EROFS;
382 
383 out_path_release:
384 	path_put(&path);
385 	if (retry_estale(res, lookup_flags)) {
386 		lookup_flags |= LOOKUP_REVAL;
387 		goto retry;
388 	}
389 out:
390 	revert_creds(old_cred);
391 	put_cred(override_cred);
392 	return res;
393 }
394 
395 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
396 {
397 	return sys_faccessat(AT_FDCWD, filename, mode);
398 }
399 
400 SYSCALL_DEFINE1(chdir, const char __user *, filename)
401 {
402 	struct path path;
403 	int error;
404 	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
405 retry:
406 	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
407 	if (error)
408 		goto out;
409 
410 	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
411 	if (error)
412 		goto dput_and_out;
413 
414 	set_fs_pwd(current->fs, &path);
415 
416 dput_and_out:
417 	path_put(&path);
418 	if (retry_estale(error, lookup_flags)) {
419 		lookup_flags |= LOOKUP_REVAL;
420 		goto retry;
421 	}
422 out:
423 	return error;
424 }
425 
426 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
427 {
428 	struct fd f = fdget_raw(fd);
429 	struct inode *inode;
430 	int error = -EBADF;
431 
432 	error = -EBADF;
433 	if (!f.file)
434 		goto out;
435 
436 	inode = file_inode(f.file);
437 
438 	error = -ENOTDIR;
439 	if (!S_ISDIR(inode->i_mode))
440 		goto out_putf;
441 
442 	error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
443 	if (!error)
444 		set_fs_pwd(current->fs, &f.file->f_path);
445 out_putf:
446 	fdput(f);
447 out:
448 	return error;
449 }
450 
451 SYSCALL_DEFINE1(chroot, const char __user *, filename)
452 {
453 	struct path path;
454 	int error;
455 	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
456 retry:
457 	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
458 	if (error)
459 		goto out;
460 
461 	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
462 	if (error)
463 		goto dput_and_out;
464 
465 	error = -EPERM;
466 	if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
467 		goto dput_and_out;
468 	error = security_path_chroot(&path);
469 	if (error)
470 		goto dput_and_out;
471 
472 	set_fs_root(current->fs, &path);
473 	error = 0;
474 dput_and_out:
475 	path_put(&path);
476 	if (retry_estale(error, lookup_flags)) {
477 		lookup_flags |= LOOKUP_REVAL;
478 		goto retry;
479 	}
480 out:
481 	return error;
482 }
483 
484 static int chmod_common(struct path *path, umode_t mode)
485 {
486 	struct inode *inode = path->dentry->d_inode;
487 	struct inode *delegated_inode = NULL;
488 	struct iattr newattrs;
489 	int error;
490 
491 	error = mnt_want_write(path->mnt);
492 	if (error)
493 		return error;
494 retry_deleg:
495 	mutex_lock(&inode->i_mutex);
496 	error = security_path_chmod(path, mode);
497 	if (error)
498 		goto out_unlock;
499 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
500 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
501 	error = notify_change(path->dentry, &newattrs, &delegated_inode);
502 out_unlock:
503 	mutex_unlock(&inode->i_mutex);
504 	if (delegated_inode) {
505 		error = break_deleg_wait(&delegated_inode);
506 		if (!error)
507 			goto retry_deleg;
508 	}
509 	mnt_drop_write(path->mnt);
510 	return error;
511 }
512 
513 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
514 {
515 	struct fd f = fdget(fd);
516 	int err = -EBADF;
517 
518 	if (f.file) {
519 		audit_inode(NULL, f.file->f_path.dentry, 0);
520 		err = chmod_common(&f.file->f_path, mode);
521 		fdput(f);
522 	}
523 	return err;
524 }
525 
526 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
527 {
528 	struct path path;
529 	int error;
530 	unsigned int lookup_flags = LOOKUP_FOLLOW;
531 retry:
532 	error = user_path_at(dfd, filename, lookup_flags, &path);
533 	if (!error) {
534 		error = chmod_common(&path, mode);
535 		path_put(&path);
536 		if (retry_estale(error, lookup_flags)) {
537 			lookup_flags |= LOOKUP_REVAL;
538 			goto retry;
539 		}
540 	}
541 	return error;
542 }
543 
544 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
545 {
546 	return sys_fchmodat(AT_FDCWD, filename, mode);
547 }
548 
549 static int chown_common(struct path *path, uid_t user, gid_t group)
550 {
551 	struct inode *inode = path->dentry->d_inode;
552 	struct inode *delegated_inode = NULL;
553 	int error;
554 	struct iattr newattrs;
555 	kuid_t uid;
556 	kgid_t gid;
557 
558 	uid = make_kuid(current_user_ns(), user);
559 	gid = make_kgid(current_user_ns(), group);
560 
561 	newattrs.ia_valid =  ATTR_CTIME;
562 	if (user != (uid_t) -1) {
563 		if (!uid_valid(uid))
564 			return -EINVAL;
565 		newattrs.ia_valid |= ATTR_UID;
566 		newattrs.ia_uid = uid;
567 	}
568 	if (group != (gid_t) -1) {
569 		if (!gid_valid(gid))
570 			return -EINVAL;
571 		newattrs.ia_valid |= ATTR_GID;
572 		newattrs.ia_gid = gid;
573 	}
574 	if (!S_ISDIR(inode->i_mode))
575 		newattrs.ia_valid |=
576 			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
577 retry_deleg:
578 	mutex_lock(&inode->i_mutex);
579 	error = security_path_chown(path, uid, gid);
580 	if (!error)
581 		error = notify_change(path->dentry, &newattrs, &delegated_inode);
582 	mutex_unlock(&inode->i_mutex);
583 	if (delegated_inode) {
584 		error = break_deleg_wait(&delegated_inode);
585 		if (!error)
586 			goto retry_deleg;
587 	}
588 	return error;
589 }
590 
591 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
592 		gid_t, group, int, flag)
593 {
594 	struct path path;
595 	int error = -EINVAL;
596 	int lookup_flags;
597 
598 	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
599 		goto out;
600 
601 	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
602 	if (flag & AT_EMPTY_PATH)
603 		lookup_flags |= LOOKUP_EMPTY;
604 retry:
605 	error = user_path_at(dfd, filename, lookup_flags, &path);
606 	if (error)
607 		goto out;
608 	error = mnt_want_write(path.mnt);
609 	if (error)
610 		goto out_release;
611 	error = chown_common(&path, user, group);
612 	mnt_drop_write(path.mnt);
613 out_release:
614 	path_put(&path);
615 	if (retry_estale(error, lookup_flags)) {
616 		lookup_flags |= LOOKUP_REVAL;
617 		goto retry;
618 	}
619 out:
620 	return error;
621 }
622 
623 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
624 {
625 	return sys_fchownat(AT_FDCWD, filename, user, group, 0);
626 }
627 
628 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
629 {
630 	return sys_fchownat(AT_FDCWD, filename, user, group,
631 			    AT_SYMLINK_NOFOLLOW);
632 }
633 
634 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
635 {
636 	struct fd f = fdget(fd);
637 	int error = -EBADF;
638 
639 	if (!f.file)
640 		goto out;
641 
642 	error = mnt_want_write_file(f.file);
643 	if (error)
644 		goto out_fput;
645 	audit_inode(NULL, f.file->f_path.dentry, 0);
646 	error = chown_common(&f.file->f_path, user, group);
647 	mnt_drop_write_file(f.file);
648 out_fput:
649 	fdput(f);
650 out:
651 	return error;
652 }
653 
654 int open_check_o_direct(struct file *f)
655 {
656 	/* NB: we're sure to have correct a_ops only after f_op->open */
657 	if (f->f_flags & O_DIRECT) {
658 		if (!f->f_mapping->a_ops ||
659 		    ((!f->f_mapping->a_ops->direct_IO) &&
660 		    (!f->f_mapping->a_ops->get_xip_mem))) {
661 			return -EINVAL;
662 		}
663 	}
664 	return 0;
665 }
666 
667 static int do_dentry_open(struct file *f,
668 			  int (*open)(struct inode *, struct file *),
669 			  const struct cred *cred)
670 {
671 	static const struct file_operations empty_fops = {};
672 	struct inode *inode;
673 	int error;
674 
675 	f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
676 				FMODE_PREAD | FMODE_PWRITE;
677 
678 	path_get(&f->f_path);
679 	inode = f->f_inode = f->f_path.dentry->d_inode;
680 	f->f_mapping = inode->i_mapping;
681 
682 	if (unlikely(f->f_flags & O_PATH)) {
683 		f->f_mode = FMODE_PATH;
684 		f->f_op = &empty_fops;
685 		return 0;
686 	}
687 
688 	if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
689 		error = get_write_access(inode);
690 		if (unlikely(error))
691 			goto cleanup_file;
692 		error = __mnt_want_write(f->f_path.mnt);
693 		if (unlikely(error)) {
694 			put_write_access(inode);
695 			goto cleanup_file;
696 		}
697 		f->f_mode |= FMODE_WRITER;
698 	}
699 
700 	/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
701 	if (S_ISREG(inode->i_mode))
702 		f->f_mode |= FMODE_ATOMIC_POS;
703 
704 	f->f_op = fops_get(inode->i_fop);
705 	if (unlikely(WARN_ON(!f->f_op))) {
706 		error = -ENODEV;
707 		goto cleanup_all;
708 	}
709 
710 	error = security_file_open(f, cred);
711 	if (error)
712 		goto cleanup_all;
713 
714 	error = break_lease(inode, f->f_flags);
715 	if (error)
716 		goto cleanup_all;
717 
718 	if (!open)
719 		open = f->f_op->open;
720 	if (open) {
721 		error = open(inode, f);
722 		if (error)
723 			goto cleanup_all;
724 	}
725 	if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
726 		i_readcount_inc(inode);
727 	if ((f->f_mode & FMODE_READ) &&
728 	     likely(f->f_op->read || f->f_op->aio_read || f->f_op->read_iter))
729 		f->f_mode |= FMODE_CAN_READ;
730 	if ((f->f_mode & FMODE_WRITE) &&
731 	     likely(f->f_op->write || f->f_op->aio_write || f->f_op->write_iter))
732 		f->f_mode |= FMODE_CAN_WRITE;
733 
734 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
735 
736 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
737 
738 	return 0;
739 
740 cleanup_all:
741 	fops_put(f->f_op);
742 	if (f->f_mode & FMODE_WRITER) {
743 		put_write_access(inode);
744 		__mnt_drop_write(f->f_path.mnt);
745 	}
746 cleanup_file:
747 	path_put(&f->f_path);
748 	f->f_path.mnt = NULL;
749 	f->f_path.dentry = NULL;
750 	f->f_inode = NULL;
751 	return error;
752 }
753 
754 /**
755  * finish_open - finish opening a file
756  * @file: file pointer
757  * @dentry: pointer to dentry
758  * @open: open callback
759  * @opened: state of open
760  *
761  * This can be used to finish opening a file passed to i_op->atomic_open().
762  *
763  * If the open callback is set to NULL, then the standard f_op->open()
764  * filesystem callback is substituted.
765  *
766  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
767  * the return value of d_splice_alias(), then the caller needs to perform dput()
768  * on it after finish_open().
769  *
770  * On successful return @file is a fully instantiated open file.  After this, if
771  * an error occurs in ->atomic_open(), it needs to clean up with fput().
772  *
773  * Returns zero on success or -errno if the open failed.
774  */
775 int finish_open(struct file *file, struct dentry *dentry,
776 		int (*open)(struct inode *, struct file *),
777 		int *opened)
778 {
779 	int error;
780 	BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
781 
782 	file->f_path.dentry = dentry;
783 	error = do_dentry_open(file, open, current_cred());
784 	if (!error)
785 		*opened |= FILE_OPENED;
786 
787 	return error;
788 }
789 EXPORT_SYMBOL(finish_open);
790 
791 /**
792  * finish_no_open - finish ->atomic_open() without opening the file
793  *
794  * @file: file pointer
795  * @dentry: dentry or NULL (as returned from ->lookup())
796  *
797  * This can be used to set the result of a successful lookup in ->atomic_open().
798  *
799  * NB: unlike finish_open() this function does consume the dentry reference and
800  * the caller need not dput() it.
801  *
802  * Returns "1" which must be the return value of ->atomic_open() after having
803  * called this function.
804  */
805 int finish_no_open(struct file *file, struct dentry *dentry)
806 {
807 	file->f_path.dentry = dentry;
808 	return 1;
809 }
810 EXPORT_SYMBOL(finish_no_open);
811 
812 struct file *dentry_open(const struct path *path, int flags,
813 			 const struct cred *cred)
814 {
815 	int error;
816 	struct file *f;
817 
818 	validate_creds(cred);
819 
820 	/* We must always pass in a valid mount pointer. */
821 	BUG_ON(!path->mnt);
822 
823 	f = get_empty_filp();
824 	if (!IS_ERR(f)) {
825 		f->f_flags = flags;
826 		error = vfs_open(path, f, cred);
827 		if (!error) {
828 			/* from now on we need fput() to dispose of f */
829 			error = open_check_o_direct(f);
830 			if (error) {
831 				fput(f);
832 				f = ERR_PTR(error);
833 			}
834 		} else {
835 			put_filp(f);
836 			f = ERR_PTR(error);
837 		}
838 	}
839 	return f;
840 }
841 EXPORT_SYMBOL(dentry_open);
842 
843 /**
844  * vfs_open - open the file at the given path
845  * @path: path to open
846  * @filp: newly allocated file with f_flag initialized
847  * @cred: credentials to use
848  */
849 int vfs_open(const struct path *path, struct file *filp,
850 	     const struct cred *cred)
851 {
852 	struct inode *inode = path->dentry->d_inode;
853 
854 	if (inode->i_op->dentry_open)
855 		return inode->i_op->dentry_open(path->dentry, filp, cred);
856 	else {
857 		filp->f_path = *path;
858 		return do_dentry_open(filp, NULL, cred);
859 	}
860 }
861 EXPORT_SYMBOL(vfs_open);
862 
863 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
864 {
865 	int lookup_flags = 0;
866 	int acc_mode;
867 
868 	if (flags & (O_CREAT | __O_TMPFILE))
869 		op->mode = (mode & S_IALLUGO) | S_IFREG;
870 	else
871 		op->mode = 0;
872 
873 	/* Must never be set by userspace */
874 	flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
875 
876 	/*
877 	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
878 	 * check for O_DSYNC if the need any syncing at all we enforce it's
879 	 * always set instead of having to deal with possibly weird behaviour
880 	 * for malicious applications setting only __O_SYNC.
881 	 */
882 	if (flags & __O_SYNC)
883 		flags |= O_DSYNC;
884 
885 	if (flags & __O_TMPFILE) {
886 		if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
887 			return -EINVAL;
888 		acc_mode = MAY_OPEN | ACC_MODE(flags);
889 		if (!(acc_mode & MAY_WRITE))
890 			return -EINVAL;
891 	} else if (flags & O_PATH) {
892 		/*
893 		 * If we have O_PATH in the open flag. Then we
894 		 * cannot have anything other than the below set of flags
895 		 */
896 		flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
897 		acc_mode = 0;
898 	} else {
899 		acc_mode = MAY_OPEN | ACC_MODE(flags);
900 	}
901 
902 	op->open_flag = flags;
903 
904 	/* O_TRUNC implies we need access checks for write permissions */
905 	if (flags & O_TRUNC)
906 		acc_mode |= MAY_WRITE;
907 
908 	/* Allow the LSM permission hook to distinguish append
909 	   access from general write access. */
910 	if (flags & O_APPEND)
911 		acc_mode |= MAY_APPEND;
912 
913 	op->acc_mode = acc_mode;
914 
915 	op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
916 
917 	if (flags & O_CREAT) {
918 		op->intent |= LOOKUP_CREATE;
919 		if (flags & O_EXCL)
920 			op->intent |= LOOKUP_EXCL;
921 	}
922 
923 	if (flags & O_DIRECTORY)
924 		lookup_flags |= LOOKUP_DIRECTORY;
925 	if (!(flags & O_NOFOLLOW))
926 		lookup_flags |= LOOKUP_FOLLOW;
927 	op->lookup_flags = lookup_flags;
928 	return 0;
929 }
930 
931 /**
932  * file_open_name - open file and return file pointer
933  *
934  * @name:	struct filename containing path to open
935  * @flags:	open flags as per the open(2) second argument
936  * @mode:	mode for the new file if O_CREAT is set, else ignored
937  *
938  * This is the helper to open a file from kernelspace if you really
939  * have to.  But in generally you should not do this, so please move
940  * along, nothing to see here..
941  */
942 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
943 {
944 	struct open_flags op;
945 	int err = build_open_flags(flags, mode, &op);
946 	return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
947 }
948 
949 /**
950  * filp_open - open file and return file pointer
951  *
952  * @filename:	path to open
953  * @flags:	open flags as per the open(2) second argument
954  * @mode:	mode for the new file if O_CREAT is set, else ignored
955  *
956  * This is the helper to open a file from kernelspace if you really
957  * have to.  But in generally you should not do this, so please move
958  * along, nothing to see here..
959  */
960 struct file *filp_open(const char *filename, int flags, umode_t mode)
961 {
962 	struct filename name = {.name = filename};
963 	return file_open_name(&name, flags, mode);
964 }
965 EXPORT_SYMBOL(filp_open);
966 
967 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
968 			    const char *filename, int flags)
969 {
970 	struct open_flags op;
971 	int err = build_open_flags(flags, 0, &op);
972 	if (err)
973 		return ERR_PTR(err);
974 	if (flags & O_CREAT)
975 		return ERR_PTR(-EINVAL);
976 	if (!filename && (flags & O_DIRECTORY))
977 		if (!dentry->d_inode->i_op->lookup)
978 			return ERR_PTR(-ENOTDIR);
979 	return do_file_open_root(dentry, mnt, filename, &op);
980 }
981 EXPORT_SYMBOL(file_open_root);
982 
983 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
984 {
985 	struct open_flags op;
986 	int fd = build_open_flags(flags, mode, &op);
987 	struct filename *tmp;
988 
989 	if (fd)
990 		return fd;
991 
992 	tmp = getname(filename);
993 	if (IS_ERR(tmp))
994 		return PTR_ERR(tmp);
995 
996 	fd = get_unused_fd_flags(flags);
997 	if (fd >= 0) {
998 		struct file *f = do_filp_open(dfd, tmp, &op);
999 		if (IS_ERR(f)) {
1000 			put_unused_fd(fd);
1001 			fd = PTR_ERR(f);
1002 		} else {
1003 			fsnotify_open(f);
1004 			fd_install(fd, f);
1005 		}
1006 	}
1007 	putname(tmp);
1008 	return fd;
1009 }
1010 
1011 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1012 {
1013 	if (force_o_largefile())
1014 		flags |= O_LARGEFILE;
1015 
1016 	return do_sys_open(AT_FDCWD, filename, flags, mode);
1017 }
1018 
1019 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1020 		umode_t, mode)
1021 {
1022 	if (force_o_largefile())
1023 		flags |= O_LARGEFILE;
1024 
1025 	return do_sys_open(dfd, filename, flags, mode);
1026 }
1027 
1028 #ifndef __alpha__
1029 
1030 /*
1031  * For backward compatibility?  Maybe this should be moved
1032  * into arch/i386 instead?
1033  */
1034 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1035 {
1036 	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1037 }
1038 
1039 #endif
1040 
1041 /*
1042  * "id" is the POSIX thread ID. We use the
1043  * files pointer for this..
1044  */
1045 int filp_close(struct file *filp, fl_owner_t id)
1046 {
1047 	int retval = 0;
1048 
1049 	if (!file_count(filp)) {
1050 		printk(KERN_ERR "VFS: Close: file count is 0\n");
1051 		return 0;
1052 	}
1053 
1054 	if (filp->f_op->flush)
1055 		retval = filp->f_op->flush(filp, id);
1056 
1057 	if (likely(!(filp->f_mode & FMODE_PATH))) {
1058 		dnotify_flush(filp, id);
1059 		locks_remove_posix(filp, id);
1060 	}
1061 	fput(filp);
1062 	return retval;
1063 }
1064 
1065 EXPORT_SYMBOL(filp_close);
1066 
1067 /*
1068  * Careful here! We test whether the file pointer is NULL before
1069  * releasing the fd. This ensures that one clone task can't release
1070  * an fd while another clone is opening it.
1071  */
1072 SYSCALL_DEFINE1(close, unsigned int, fd)
1073 {
1074 	int retval = __close_fd(current->files, fd);
1075 
1076 	/* can't restart close syscall because file table entry was cleared */
1077 	if (unlikely(retval == -ERESTARTSYS ||
1078 		     retval == -ERESTARTNOINTR ||
1079 		     retval == -ERESTARTNOHAND ||
1080 		     retval == -ERESTART_RESTARTBLOCK))
1081 		retval = -EINTR;
1082 
1083 	return retval;
1084 }
1085 EXPORT_SYMBOL(sys_close);
1086 
1087 /*
1088  * This routine simulates a hangup on the tty, to arrange that users
1089  * are given clean terminals at login time.
1090  */
1091 SYSCALL_DEFINE0(vhangup)
1092 {
1093 	if (capable(CAP_SYS_TTY_CONFIG)) {
1094 		tty_vhangup_self();
1095 		return 0;
1096 	}
1097 	return -EPERM;
1098 }
1099 
1100 /*
1101  * Called when an inode is about to be open.
1102  * We use this to disallow opening large files on 32bit systems if
1103  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1104  * on this flag in sys_open.
1105  */
1106 int generic_file_open(struct inode * inode, struct file * filp)
1107 {
1108 	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1109 		return -EOVERFLOW;
1110 	return 0;
1111 }
1112 
1113 EXPORT_SYMBOL(generic_file_open);
1114 
1115 /*
1116  * This is used by subsystems that don't want seekable
1117  * file descriptors. The function is not supposed to ever fail, the only
1118  * reason it returns an 'int' and not 'void' is so that it can be plugged
1119  * directly into file_operations structure.
1120  */
1121 int nonseekable_open(struct inode *inode, struct file *filp)
1122 {
1123 	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1124 	return 0;
1125 }
1126 
1127 EXPORT_SYMBOL(nonseekable_open);
1128