xref: /openbmc/linux/fs/open.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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/quotaops.h>
11 #include <linux/fsnotify.h>
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/tty.h>
15 #include <linux/namei.h>
16 #include <linux/backing-dev.h>
17 #include <linux/capability.h>
18 #include <linux/security.h>
19 #include <linux/mount.h>
20 #include <linux/vfs.h>
21 #include <linux/fcntl.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 
30 int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
31 {
32 	int retval = -ENODEV;
33 
34 	if (dentry) {
35 		retval = -ENOSYS;
36 		if (dentry->d_sb->s_op->statfs) {
37 			memset(buf, 0, sizeof(*buf));
38 			retval = security_sb_statfs(dentry);
39 			if (retval)
40 				return retval;
41 			retval = dentry->d_sb->s_op->statfs(dentry, buf);
42 			if (retval == 0 && buf->f_frsize == 0)
43 				buf->f_frsize = buf->f_bsize;
44 		}
45 	}
46 	return retval;
47 }
48 
49 EXPORT_SYMBOL(vfs_statfs);
50 
51 static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf)
52 {
53 	struct kstatfs st;
54 	int retval;
55 
56 	retval = vfs_statfs(dentry, &st);
57 	if (retval)
58 		return retval;
59 
60 	if (sizeof(*buf) == sizeof(st))
61 		memcpy(buf, &st, sizeof(st));
62 	else {
63 		if (sizeof buf->f_blocks == 4) {
64 			if ((st.f_blocks | st.f_bfree | st.f_bavail) &
65 			    0xffffffff00000000ULL)
66 				return -EOVERFLOW;
67 			/*
68 			 * f_files and f_ffree may be -1; it's okay to stuff
69 			 * that into 32 bits
70 			 */
71 			if (st.f_files != -1 &&
72 			    (st.f_files & 0xffffffff00000000ULL))
73 				return -EOVERFLOW;
74 			if (st.f_ffree != -1 &&
75 			    (st.f_ffree & 0xffffffff00000000ULL))
76 				return -EOVERFLOW;
77 		}
78 
79 		buf->f_type = st.f_type;
80 		buf->f_bsize = st.f_bsize;
81 		buf->f_blocks = st.f_blocks;
82 		buf->f_bfree = st.f_bfree;
83 		buf->f_bavail = st.f_bavail;
84 		buf->f_files = st.f_files;
85 		buf->f_ffree = st.f_ffree;
86 		buf->f_fsid = st.f_fsid;
87 		buf->f_namelen = st.f_namelen;
88 		buf->f_frsize = st.f_frsize;
89 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
90 	}
91 	return 0;
92 }
93 
94 static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf)
95 {
96 	struct kstatfs st;
97 	int retval;
98 
99 	retval = vfs_statfs(dentry, &st);
100 	if (retval)
101 		return retval;
102 
103 	if (sizeof(*buf) == sizeof(st))
104 		memcpy(buf, &st, sizeof(st));
105 	else {
106 		buf->f_type = st.f_type;
107 		buf->f_bsize = st.f_bsize;
108 		buf->f_blocks = st.f_blocks;
109 		buf->f_bfree = st.f_bfree;
110 		buf->f_bavail = st.f_bavail;
111 		buf->f_files = st.f_files;
112 		buf->f_ffree = st.f_ffree;
113 		buf->f_fsid = st.f_fsid;
114 		buf->f_namelen = st.f_namelen;
115 		buf->f_frsize = st.f_frsize;
116 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
117 	}
118 	return 0;
119 }
120 
121 asmlinkage long sys_statfs(const char __user * path, struct statfs __user * buf)
122 {
123 	struct nameidata nd;
124 	int error;
125 
126 	error = user_path_walk(path, &nd);
127 	if (!error) {
128 		struct statfs tmp;
129 		error = vfs_statfs_native(nd.dentry, &tmp);
130 		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
131 			error = -EFAULT;
132 		path_release(&nd);
133 	}
134 	return error;
135 }
136 
137 
138 asmlinkage long sys_statfs64(const char __user *path, size_t sz, struct statfs64 __user *buf)
139 {
140 	struct nameidata nd;
141 	long error;
142 
143 	if (sz != sizeof(*buf))
144 		return -EINVAL;
145 	error = user_path_walk(path, &nd);
146 	if (!error) {
147 		struct statfs64 tmp;
148 		error = vfs_statfs64(nd.dentry, &tmp);
149 		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
150 			error = -EFAULT;
151 		path_release(&nd);
152 	}
153 	return error;
154 }
155 
156 
157 asmlinkage long sys_fstatfs(unsigned int fd, struct statfs __user * buf)
158 {
159 	struct file * file;
160 	struct statfs tmp;
161 	int error;
162 
163 	error = -EBADF;
164 	file = fget(fd);
165 	if (!file)
166 		goto out;
167 	error = vfs_statfs_native(file->f_path.dentry, &tmp);
168 	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
169 		error = -EFAULT;
170 	fput(file);
171 out:
172 	return error;
173 }
174 
175 asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz, struct statfs64 __user *buf)
176 {
177 	struct file * file;
178 	struct statfs64 tmp;
179 	int error;
180 
181 	if (sz != sizeof(*buf))
182 		return -EINVAL;
183 
184 	error = -EBADF;
185 	file = fget(fd);
186 	if (!file)
187 		goto out;
188 	error = vfs_statfs64(file->f_path.dentry, &tmp);
189 	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
190 		error = -EFAULT;
191 	fput(file);
192 out:
193 	return error;
194 }
195 
196 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
197 	struct file *filp)
198 {
199 	int err;
200 	struct iattr newattrs;
201 
202 	/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
203 	if (length < 0)
204 		return -EINVAL;
205 
206 	newattrs.ia_size = length;
207 	newattrs.ia_valid = ATTR_SIZE | time_attrs;
208 	if (filp) {
209 		newattrs.ia_file = filp;
210 		newattrs.ia_valid |= ATTR_FILE;
211 	}
212 
213 	/* Remove suid/sgid on truncate too */
214 	newattrs.ia_valid |= should_remove_suid(dentry);
215 
216 	mutex_lock(&dentry->d_inode->i_mutex);
217 	err = notify_change(dentry, &newattrs);
218 	mutex_unlock(&dentry->d_inode->i_mutex);
219 	return err;
220 }
221 
222 static long do_sys_truncate(const char __user * path, loff_t length)
223 {
224 	struct nameidata nd;
225 	struct inode * inode;
226 	int error;
227 
228 	error = -EINVAL;
229 	if (length < 0)	/* sorry, but loff_t says... */
230 		goto out;
231 
232 	error = user_path_walk(path, &nd);
233 	if (error)
234 		goto out;
235 	inode = nd.dentry->d_inode;
236 
237 	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
238 	error = -EISDIR;
239 	if (S_ISDIR(inode->i_mode))
240 		goto dput_and_out;
241 
242 	error = -EINVAL;
243 	if (!S_ISREG(inode->i_mode))
244 		goto dput_and_out;
245 
246 	error = vfs_permission(&nd, MAY_WRITE);
247 	if (error)
248 		goto dput_and_out;
249 
250 	error = -EROFS;
251 	if (IS_RDONLY(inode))
252 		goto dput_and_out;
253 
254 	error = -EPERM;
255 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
256 		goto dput_and_out;
257 
258 	/*
259 	 * Make sure that there are no leases.
260 	 */
261 	error = break_lease(inode, FMODE_WRITE);
262 	if (error)
263 		goto dput_and_out;
264 
265 	error = get_write_access(inode);
266 	if (error)
267 		goto dput_and_out;
268 
269 	error = locks_verify_truncate(inode, NULL, length);
270 	if (!error) {
271 		DQUOT_INIT(inode);
272 		error = do_truncate(nd.dentry, length, 0, NULL);
273 	}
274 	put_write_access(inode);
275 
276 dput_and_out:
277 	path_release(&nd);
278 out:
279 	return error;
280 }
281 
282 asmlinkage long sys_truncate(const char __user * path, unsigned long length)
283 {
284 	/* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
285 	return do_sys_truncate(path, (long)length);
286 }
287 
288 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
289 {
290 	struct inode * inode;
291 	struct dentry *dentry;
292 	struct file * file;
293 	int error;
294 
295 	error = -EINVAL;
296 	if (length < 0)
297 		goto out;
298 	error = -EBADF;
299 	file = fget(fd);
300 	if (!file)
301 		goto out;
302 
303 	/* explicitly opened as large or we are on 64-bit box */
304 	if (file->f_flags & O_LARGEFILE)
305 		small = 0;
306 
307 	dentry = file->f_path.dentry;
308 	inode = dentry->d_inode;
309 	error = -EINVAL;
310 	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
311 		goto out_putf;
312 
313 	error = -EINVAL;
314 	/* Cannot ftruncate over 2^31 bytes without large file support */
315 	if (small && length > MAX_NON_LFS)
316 		goto out_putf;
317 
318 	error = -EPERM;
319 	if (IS_APPEND(inode))
320 		goto out_putf;
321 
322 	error = locks_verify_truncate(inode, file, length);
323 	if (!error)
324 		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
325 out_putf:
326 	fput(file);
327 out:
328 	return error;
329 }
330 
331 asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
332 {
333 	long ret = do_sys_ftruncate(fd, length, 1);
334 	/* avoid REGPARM breakage on x86: */
335 	prevent_tail_call(ret);
336 	return ret;
337 }
338 
339 /* LFS versions of truncate are only needed on 32 bit machines */
340 #if BITS_PER_LONG == 32
341 asmlinkage long sys_truncate64(const char __user * path, loff_t length)
342 {
343 	return do_sys_truncate(path, length);
344 }
345 
346 asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
347 {
348 	long ret = do_sys_ftruncate(fd, length, 0);
349 	/* avoid REGPARM breakage on x86: */
350 	prevent_tail_call(ret);
351 	return ret;
352 }
353 #endif
354 
355 /*
356  * access() needs to use the real uid/gid, not the effective uid/gid.
357  * We do this by temporarily clearing all FS-related capabilities and
358  * switching the fsuid/fsgid around to the real ones.
359  */
360 asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
361 {
362 	struct nameidata nd;
363 	int old_fsuid, old_fsgid;
364 	kernel_cap_t old_cap;
365 	int res;
366 
367 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
368 		return -EINVAL;
369 
370 	old_fsuid = current->fsuid;
371 	old_fsgid = current->fsgid;
372 	old_cap = current->cap_effective;
373 
374 	current->fsuid = current->uid;
375 	current->fsgid = current->gid;
376 
377 	/*
378 	 * Clear the capabilities if we switch to a non-root user
379 	 *
380 	 * FIXME: There is a race here against sys_capset.  The
381 	 * capabilities can change yet we will restore the old
382 	 * value below.  We should hold task_capabilities_lock,
383 	 * but we cannot because user_path_walk can sleep.
384 	 */
385 	if (current->uid)
386 		cap_clear(current->cap_effective);
387 	else
388 		current->cap_effective = current->cap_permitted;
389 
390 	res = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW|LOOKUP_ACCESS, &nd);
391 	if (res)
392 		goto out;
393 
394 	res = vfs_permission(&nd, mode);
395 	/* SuS v2 requires we report a read only fs too */
396 	if(res || !(mode & S_IWOTH) ||
397 	   special_file(nd.dentry->d_inode->i_mode))
398 		goto out_path_release;
399 
400 	if(IS_RDONLY(nd.dentry->d_inode))
401 		res = -EROFS;
402 
403 out_path_release:
404 	path_release(&nd);
405 out:
406 	current->fsuid = old_fsuid;
407 	current->fsgid = old_fsgid;
408 	current->cap_effective = old_cap;
409 
410 	return res;
411 }
412 
413 asmlinkage long sys_access(const char __user *filename, int mode)
414 {
415 	return sys_faccessat(AT_FDCWD, filename, mode);
416 }
417 
418 asmlinkage long sys_chdir(const char __user * filename)
419 {
420 	struct nameidata nd;
421 	int error;
422 
423 	error = __user_walk(filename,
424 			    LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);
425 	if (error)
426 		goto out;
427 
428 	error = vfs_permission(&nd, MAY_EXEC);
429 	if (error)
430 		goto dput_and_out;
431 
432 	set_fs_pwd(current->fs, nd.mnt, nd.dentry);
433 
434 dput_and_out:
435 	path_release(&nd);
436 out:
437 	return error;
438 }
439 
440 asmlinkage long sys_fchdir(unsigned int fd)
441 {
442 	struct file *file;
443 	struct dentry *dentry;
444 	struct inode *inode;
445 	struct vfsmount *mnt;
446 	int error;
447 
448 	error = -EBADF;
449 	file = fget(fd);
450 	if (!file)
451 		goto out;
452 
453 	dentry = file->f_path.dentry;
454 	mnt = file->f_path.mnt;
455 	inode = dentry->d_inode;
456 
457 	error = -ENOTDIR;
458 	if (!S_ISDIR(inode->i_mode))
459 		goto out_putf;
460 
461 	error = file_permission(file, MAY_EXEC);
462 	if (!error)
463 		set_fs_pwd(current->fs, mnt, dentry);
464 out_putf:
465 	fput(file);
466 out:
467 	return error;
468 }
469 
470 asmlinkage long sys_chroot(const char __user * filename)
471 {
472 	struct nameidata nd;
473 	int error;
474 
475 	error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
476 	if (error)
477 		goto out;
478 
479 	error = vfs_permission(&nd, MAY_EXEC);
480 	if (error)
481 		goto dput_and_out;
482 
483 	error = -EPERM;
484 	if (!capable(CAP_SYS_CHROOT))
485 		goto dput_and_out;
486 
487 	set_fs_root(current->fs, nd.mnt, nd.dentry);
488 	set_fs_altroot();
489 	error = 0;
490 dput_and_out:
491 	path_release(&nd);
492 out:
493 	return error;
494 }
495 
496 asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
497 {
498 	struct inode * inode;
499 	struct dentry * dentry;
500 	struct file * file;
501 	int err = -EBADF;
502 	struct iattr newattrs;
503 
504 	file = fget(fd);
505 	if (!file)
506 		goto out;
507 
508 	dentry = file->f_path.dentry;
509 	inode = dentry->d_inode;
510 
511 	audit_inode(NULL, inode);
512 
513 	err = -EROFS;
514 	if (IS_RDONLY(inode))
515 		goto out_putf;
516 	err = -EPERM;
517 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
518 		goto out_putf;
519 	mutex_lock(&inode->i_mutex);
520 	if (mode == (mode_t) -1)
521 		mode = inode->i_mode;
522 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
523 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
524 	err = notify_change(dentry, &newattrs);
525 	mutex_unlock(&inode->i_mutex);
526 
527 out_putf:
528 	fput(file);
529 out:
530 	return err;
531 }
532 
533 asmlinkage long sys_fchmodat(int dfd, const char __user *filename,
534 			     mode_t mode)
535 {
536 	struct nameidata nd;
537 	struct inode * inode;
538 	int error;
539 	struct iattr newattrs;
540 
541 	error = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW, &nd);
542 	if (error)
543 		goto out;
544 	inode = nd.dentry->d_inode;
545 
546 	error = -EROFS;
547 	if (IS_RDONLY(inode))
548 		goto dput_and_out;
549 
550 	error = -EPERM;
551 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
552 		goto dput_and_out;
553 
554 	mutex_lock(&inode->i_mutex);
555 	if (mode == (mode_t) -1)
556 		mode = inode->i_mode;
557 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
558 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
559 	error = notify_change(nd.dentry, &newattrs);
560 	mutex_unlock(&inode->i_mutex);
561 
562 dput_and_out:
563 	path_release(&nd);
564 out:
565 	return error;
566 }
567 
568 asmlinkage long sys_chmod(const char __user *filename, mode_t mode)
569 {
570 	return sys_fchmodat(AT_FDCWD, filename, mode);
571 }
572 
573 static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
574 {
575 	struct inode * inode;
576 	int error;
577 	struct iattr newattrs;
578 
579 	error = -ENOENT;
580 	if (!(inode = dentry->d_inode)) {
581 		printk(KERN_ERR "chown_common: NULL inode\n");
582 		goto out;
583 	}
584 	error = -EROFS;
585 	if (IS_RDONLY(inode))
586 		goto out;
587 	error = -EPERM;
588 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
589 		goto out;
590 	newattrs.ia_valid =  ATTR_CTIME;
591 	if (user != (uid_t) -1) {
592 		newattrs.ia_valid |= ATTR_UID;
593 		newattrs.ia_uid = user;
594 	}
595 	if (group != (gid_t) -1) {
596 		newattrs.ia_valid |= ATTR_GID;
597 		newattrs.ia_gid = group;
598 	}
599 	if (!S_ISDIR(inode->i_mode))
600 		newattrs.ia_valid |= ATTR_KILL_SUID|ATTR_KILL_SGID;
601 	mutex_lock(&inode->i_mutex);
602 	error = notify_change(dentry, &newattrs);
603 	mutex_unlock(&inode->i_mutex);
604 out:
605 	return error;
606 }
607 
608 asmlinkage long sys_chown(const char __user * filename, uid_t user, gid_t group)
609 {
610 	struct nameidata nd;
611 	int error;
612 
613 	error = user_path_walk(filename, &nd);
614 	if (error)
615 		goto out;
616 	error = chown_common(nd.dentry, user, group);
617 	path_release(&nd);
618 out:
619 	return error;
620 }
621 
622 asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user,
623 			     gid_t group, int flag)
624 {
625 	struct nameidata nd;
626 	int error = -EINVAL;
627 	int follow;
628 
629 	if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
630 		goto out;
631 
632 	follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
633 	error = __user_walk_fd(dfd, filename, follow, &nd);
634 	if (error)
635 		goto out;
636 	error = chown_common(nd.dentry, user, group);
637 	path_release(&nd);
638 out:
639 	return error;
640 }
641 
642 asmlinkage long sys_lchown(const char __user * filename, uid_t user, gid_t group)
643 {
644 	struct nameidata nd;
645 	int error;
646 
647 	error = user_path_walk_link(filename, &nd);
648 	if (error)
649 		goto out;
650 	error = chown_common(nd.dentry, user, group);
651 	path_release(&nd);
652 out:
653 	return error;
654 }
655 
656 
657 asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group)
658 {
659 	struct file * file;
660 	int error = -EBADF;
661 	struct dentry * dentry;
662 
663 	file = fget(fd);
664 	if (!file)
665 		goto out;
666 
667 	dentry = file->f_path.dentry;
668 	audit_inode(NULL, dentry->d_inode);
669 	error = chown_common(dentry, user, group);
670 	fput(file);
671 out:
672 	return error;
673 }
674 
675 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
676 					int flags, struct file *f,
677 					int (*open)(struct inode *, struct file *))
678 {
679 	struct inode *inode;
680 	int error;
681 
682 	f->f_flags = flags;
683 	f->f_mode = ((flags+1) & O_ACCMODE) | FMODE_LSEEK |
684 				FMODE_PREAD | FMODE_PWRITE;
685 	inode = dentry->d_inode;
686 	if (f->f_mode & FMODE_WRITE) {
687 		error = get_write_access(inode);
688 		if (error)
689 			goto cleanup_file;
690 	}
691 
692 	f->f_mapping = inode->i_mapping;
693 	f->f_path.dentry = dentry;
694 	f->f_path.mnt = mnt;
695 	f->f_pos = 0;
696 	f->f_op = fops_get(inode->i_fop);
697 	file_move(f, &inode->i_sb->s_files);
698 
699 	if (!open && f->f_op)
700 		open = f->f_op->open;
701 	if (open) {
702 		error = open(inode, f);
703 		if (error)
704 			goto cleanup_all;
705 	}
706 
707 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
708 
709 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
710 
711 	/* NB: we're sure to have correct a_ops only after f_op->open */
712 	if (f->f_flags & O_DIRECT) {
713 		if (!f->f_mapping->a_ops ||
714 		    ((!f->f_mapping->a_ops->direct_IO) &&
715 		    (!f->f_mapping->a_ops->get_xip_page))) {
716 			fput(f);
717 			f = ERR_PTR(-EINVAL);
718 		}
719 	}
720 
721 	return f;
722 
723 cleanup_all:
724 	fops_put(f->f_op);
725 	if (f->f_mode & FMODE_WRITE)
726 		put_write_access(inode);
727 	file_kill(f);
728 	f->f_path.dentry = NULL;
729 	f->f_path.mnt = NULL;
730 cleanup_file:
731 	put_filp(f);
732 	dput(dentry);
733 	mntput(mnt);
734 	return ERR_PTR(error);
735 }
736 
737 /*
738  * Note that while the flag value (low two bits) for sys_open means:
739  *	00 - read-only
740  *	01 - write-only
741  *	10 - read-write
742  *	11 - special
743  * it is changed into
744  *	00 - no permissions needed
745  *	01 - read-permission
746  *	10 - write-permission
747  *	11 - read-write
748  * for the internal routines (ie open_namei()/follow_link() etc). 00 is
749  * used by symlinks.
750  */
751 static struct file *do_filp_open(int dfd, const char *filename, int flags,
752 				 int mode)
753 {
754 	int namei_flags, error;
755 	struct nameidata nd;
756 
757 	namei_flags = flags;
758 	if ((namei_flags+1) & O_ACCMODE)
759 		namei_flags++;
760 
761 	error = open_namei(dfd, filename, namei_flags, mode, &nd);
762 	if (!error)
763 		return nameidata_to_filp(&nd, flags);
764 
765 	return ERR_PTR(error);
766 }
767 
768 struct file *filp_open(const char *filename, int flags, int mode)
769 {
770 	return do_filp_open(AT_FDCWD, filename, flags, mode);
771 }
772 EXPORT_SYMBOL(filp_open);
773 
774 /**
775  * lookup_instantiate_filp - instantiates the open intent filp
776  * @nd: pointer to nameidata
777  * @dentry: pointer to dentry
778  * @open: open callback
779  *
780  * Helper for filesystems that want to use lookup open intents and pass back
781  * a fully instantiated struct file to the caller.
782  * This function is meant to be called from within a filesystem's
783  * lookup method.
784  * Beware of calling it for non-regular files! Those ->open methods might block
785  * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
786  * leading to a deadlock, as nobody can open that fifo anymore, because
787  * another process to open fifo will block on locked parent when doing lookup).
788  * Note that in case of error, nd->intent.open.file is destroyed, but the
789  * path information remains valid.
790  * If the open callback is set to NULL, then the standard f_op->open()
791  * filesystem callback is substituted.
792  */
793 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
794 		int (*open)(struct inode *, struct file *))
795 {
796 	if (IS_ERR(nd->intent.open.file))
797 		goto out;
798 	if (IS_ERR(dentry))
799 		goto out_err;
800 	nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->mnt),
801 					     nd->intent.open.flags - 1,
802 					     nd->intent.open.file,
803 					     open);
804 out:
805 	return nd->intent.open.file;
806 out_err:
807 	release_open_intent(nd);
808 	nd->intent.open.file = (struct file *)dentry;
809 	goto out;
810 }
811 EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
812 
813 /**
814  * nameidata_to_filp - convert a nameidata to an open filp.
815  * @nd: pointer to nameidata
816  * @flags: open flags
817  *
818  * Note that this function destroys the original nameidata
819  */
820 struct file *nameidata_to_filp(struct nameidata *nd, int flags)
821 {
822 	struct file *filp;
823 
824 	/* Pick up the filp from the open intent */
825 	filp = nd->intent.open.file;
826 	/* Has the filesystem initialised the file for us? */
827 	if (filp->f_path.dentry == NULL)
828 		filp = __dentry_open(nd->dentry, nd->mnt, flags, filp, NULL);
829 	else
830 		path_release(nd);
831 	return filp;
832 }
833 
834 /*
835  * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
836  * error.
837  */
838 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
839 {
840 	int error;
841 	struct file *f;
842 
843 	error = -ENFILE;
844 	f = get_empty_filp();
845 	if (f == NULL) {
846 		dput(dentry);
847 		mntput(mnt);
848 		return ERR_PTR(error);
849 	}
850 
851 	return __dentry_open(dentry, mnt, flags, f, NULL);
852 }
853 EXPORT_SYMBOL(dentry_open);
854 
855 /*
856  * Find an empty file descriptor entry, and mark it busy.
857  */
858 int get_unused_fd(void)
859 {
860 	struct files_struct * files = current->files;
861 	int fd, error;
862 	struct fdtable *fdt;
863 
864   	error = -EMFILE;
865 	spin_lock(&files->file_lock);
866 
867 repeat:
868 	fdt = files_fdtable(files);
869 	fd = find_next_zero_bit(fdt->open_fds->fds_bits, fdt->max_fds,
870 				files->next_fd);
871 
872 	/*
873 	 * N.B. For clone tasks sharing a files structure, this test
874 	 * will limit the total number of files that can be opened.
875 	 */
876 	if (fd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
877 		goto out;
878 
879 	/* Do we need to expand the fd array or fd set?  */
880 	error = expand_files(files, fd);
881 	if (error < 0)
882 		goto out;
883 
884 	if (error) {
885 		/*
886 	 	 * If we needed to expand the fs array we
887 		 * might have blocked - try again.
888 		 */
889 		error = -EMFILE;
890 		goto repeat;
891 	}
892 
893 	FD_SET(fd, fdt->open_fds);
894 	FD_CLR(fd, fdt->close_on_exec);
895 	files->next_fd = fd + 1;
896 #if 1
897 	/* Sanity check */
898 	if (fdt->fd[fd] != NULL) {
899 		printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd);
900 		fdt->fd[fd] = NULL;
901 	}
902 #endif
903 	error = fd;
904 
905 out:
906 	spin_unlock(&files->file_lock);
907 	return error;
908 }
909 
910 EXPORT_SYMBOL(get_unused_fd);
911 
912 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
913 {
914 	struct fdtable *fdt = files_fdtable(files);
915 	__FD_CLR(fd, fdt->open_fds);
916 	if (fd < files->next_fd)
917 		files->next_fd = fd;
918 }
919 
920 void fastcall put_unused_fd(unsigned int fd)
921 {
922 	struct files_struct *files = current->files;
923 	spin_lock(&files->file_lock);
924 	__put_unused_fd(files, fd);
925 	spin_unlock(&files->file_lock);
926 }
927 
928 EXPORT_SYMBOL(put_unused_fd);
929 
930 /*
931  * Install a file pointer in the fd array.
932  *
933  * The VFS is full of places where we drop the files lock between
934  * setting the open_fds bitmap and installing the file in the file
935  * array.  At any such point, we are vulnerable to a dup2() race
936  * installing a file in the array before us.  We need to detect this and
937  * fput() the struct file we are about to overwrite in this case.
938  *
939  * It should never happen - if we allow dup2() do it, _really_ bad things
940  * will follow.
941  */
942 
943 void fastcall fd_install(unsigned int fd, struct file * file)
944 {
945 	struct files_struct *files = current->files;
946 	struct fdtable *fdt;
947 	spin_lock(&files->file_lock);
948 	fdt = files_fdtable(files);
949 	BUG_ON(fdt->fd[fd] != NULL);
950 	rcu_assign_pointer(fdt->fd[fd], file);
951 	spin_unlock(&files->file_lock);
952 }
953 
954 EXPORT_SYMBOL(fd_install);
955 
956 long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
957 {
958 	char *tmp = getname(filename);
959 	int fd = PTR_ERR(tmp);
960 
961 	if (!IS_ERR(tmp)) {
962 		fd = get_unused_fd();
963 		if (fd >= 0) {
964 			struct file *f = do_filp_open(dfd, tmp, flags, mode);
965 			if (IS_ERR(f)) {
966 				put_unused_fd(fd);
967 				fd = PTR_ERR(f);
968 			} else {
969 				fsnotify_open(f->f_path.dentry);
970 				fd_install(fd, f);
971 			}
972 		}
973 		putname(tmp);
974 	}
975 	return fd;
976 }
977 
978 asmlinkage long sys_open(const char __user *filename, int flags, int mode)
979 {
980 	long ret;
981 
982 	if (force_o_largefile())
983 		flags |= O_LARGEFILE;
984 
985 	ret = do_sys_open(AT_FDCWD, filename, flags, mode);
986 	/* avoid REGPARM breakage on x86: */
987 	prevent_tail_call(ret);
988 	return ret;
989 }
990 EXPORT_SYMBOL_GPL(sys_open);
991 
992 asmlinkage long sys_openat(int dfd, const char __user *filename, int flags,
993 			   int mode)
994 {
995 	long ret;
996 
997 	if (force_o_largefile())
998 		flags |= O_LARGEFILE;
999 
1000 	ret = do_sys_open(dfd, filename, flags, mode);
1001 	/* avoid REGPARM breakage on x86: */
1002 	prevent_tail_call(ret);
1003 	return ret;
1004 }
1005 
1006 #ifndef __alpha__
1007 
1008 /*
1009  * For backward compatibility?  Maybe this should be moved
1010  * into arch/i386 instead?
1011  */
1012 asmlinkage long sys_creat(const char __user * pathname, int mode)
1013 {
1014 	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1015 }
1016 
1017 #endif
1018 
1019 /*
1020  * "id" is the POSIX thread ID. We use the
1021  * files pointer for this..
1022  */
1023 int filp_close(struct file *filp, fl_owner_t id)
1024 {
1025 	int retval = 0;
1026 
1027 	if (!file_count(filp)) {
1028 		printk(KERN_ERR "VFS: Close: file count is 0\n");
1029 		return 0;
1030 	}
1031 
1032 	if (filp->f_op && filp->f_op->flush)
1033 		retval = filp->f_op->flush(filp, id);
1034 
1035 	dnotify_flush(filp, id);
1036 	locks_remove_posix(filp, id);
1037 	fput(filp);
1038 	return retval;
1039 }
1040 
1041 EXPORT_SYMBOL(filp_close);
1042 
1043 /*
1044  * Careful here! We test whether the file pointer is NULL before
1045  * releasing the fd. This ensures that one clone task can't release
1046  * an fd while another clone is opening it.
1047  */
1048 asmlinkage long sys_close(unsigned int fd)
1049 {
1050 	struct file * filp;
1051 	struct files_struct *files = current->files;
1052 	struct fdtable *fdt;
1053 	int retval;
1054 
1055 	spin_lock(&files->file_lock);
1056 	fdt = files_fdtable(files);
1057 	if (fd >= fdt->max_fds)
1058 		goto out_unlock;
1059 	filp = fdt->fd[fd];
1060 	if (!filp)
1061 		goto out_unlock;
1062 	rcu_assign_pointer(fdt->fd[fd], NULL);
1063 	FD_CLR(fd, fdt->close_on_exec);
1064 	__put_unused_fd(files, fd);
1065 	spin_unlock(&files->file_lock);
1066 	retval = filp_close(filp, files);
1067 
1068 	/* can't restart close syscall because file table entry was cleared */
1069 	if (unlikely(retval == -ERESTARTSYS ||
1070 		     retval == -ERESTARTNOINTR ||
1071 		     retval == -ERESTARTNOHAND ||
1072 		     retval == -ERESTART_RESTARTBLOCK))
1073 		retval = -EINTR;
1074 
1075 	return retval;
1076 
1077 out_unlock:
1078 	spin_unlock(&files->file_lock);
1079 	return -EBADF;
1080 }
1081 
1082 EXPORT_SYMBOL(sys_close);
1083 
1084 /*
1085  * This routine simulates a hangup on the tty, to arrange that users
1086  * are given clean terminals at login time.
1087  */
1088 asmlinkage long sys_vhangup(void)
1089 {
1090 	if (capable(CAP_SYS_TTY_CONFIG)) {
1091 		/* XXX: this needs locking */
1092 		tty_vhangup(current->signal->tty);
1093 		return 0;
1094 	}
1095 	return -EPERM;
1096 }
1097 
1098 /*
1099  * Called when an inode is about to be open.
1100  * We use this to disallow opening large files on 32bit systems if
1101  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1102  * on this flag in sys_open.
1103  */
1104 int generic_file_open(struct inode * inode, struct file * filp)
1105 {
1106 	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1107 		return -EFBIG;
1108 	return 0;
1109 }
1110 
1111 EXPORT_SYMBOL(generic_file_open);
1112 
1113 /*
1114  * This is used by subsystems that don't want seekable
1115  * file descriptors
1116  */
1117 int nonseekable_open(struct inode *inode, struct file *filp)
1118 {
1119 	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1120 	return 0;
1121 }
1122 
1123 EXPORT_SYMBOL(nonseekable_open);
1124