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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 
do_truncate2(struct vfsmount * mnt,struct dentry * dentry,loff_t length,unsigned int time_attrs,struct file * filp)37 int do_truncate2(struct vfsmount *mnt, struct dentry *dentry, loff_t length,
38 		unsigned int time_attrs, 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, and file capabilities on truncate too */
55 	ret = dentry_needs_remove_privs(dentry);
56 	if (ret < 0)
57 		return ret;
58 	if (ret)
59 		newattrs.ia_valid |= ret | ATTR_FORCE;
60 
61 	inode_lock(dentry->d_inode);
62 	/* Note any delegations or leases have already been broken: */
63 	ret = notify_change2(mnt, dentry, &newattrs, NULL);
64 	inode_unlock(dentry->d_inode);
65 	return ret;
66 }
do_truncate(struct dentry * dentry,loff_t length,unsigned int time_attrs,struct file * filp)67 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
68 	struct file *filp)
69 {
70 	return do_truncate2(NULL, dentry, length, time_attrs, filp);
71 }
72 
vfs_truncate(const struct path * path,loff_t length)73 long vfs_truncate(const struct path *path, loff_t length)
74 {
75 	struct inode *inode;
76 	struct vfsmount *mnt;
77 	struct dentry *upperdentry;
78 	long error;
79 
80 	inode = path->dentry->d_inode;
81 	mnt = path->mnt;
82 
83 	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
84 	if (S_ISDIR(inode->i_mode))
85 		return -EISDIR;
86 	if (!S_ISREG(inode->i_mode))
87 		return -EINVAL;
88 
89 	error = mnt_want_write(path->mnt);
90 	if (error)
91 		goto out;
92 
93 	error = inode_permission2(mnt, inode, MAY_WRITE);
94 	if (error)
95 		goto mnt_drop_write_and_out;
96 
97 	error = -EPERM;
98 	if (IS_APPEND(inode))
99 		goto mnt_drop_write_and_out;
100 
101 	/*
102 	 * If this is an overlayfs then do as if opening the file so we get
103 	 * write access on the upper inode, not on the overlay inode.  For
104 	 * non-overlay filesystems d_real() is an identity function.
105 	 */
106 	upperdentry = d_real(path->dentry, NULL, O_WRONLY);
107 	error = PTR_ERR(upperdentry);
108 	if (IS_ERR(upperdentry))
109 		goto mnt_drop_write_and_out;
110 
111 	error = get_write_access(upperdentry->d_inode);
112 	if (error)
113 		goto mnt_drop_write_and_out;
114 
115 	/*
116 	 * Make sure that there are no leases.  get_write_access() protects
117 	 * against the truncate racing with a lease-granting setlease().
118 	 */
119 	error = break_lease(inode, O_WRONLY);
120 	if (error)
121 		goto put_write_and_out;
122 
123 	error = locks_verify_truncate(inode, NULL, length);
124 	if (!error)
125 		error = security_path_truncate(path);
126 	if (!error)
127 		error = do_truncate2(mnt, path->dentry, length, 0, NULL);
128 
129 put_write_and_out:
130 	put_write_access(upperdentry->d_inode);
131 mnt_drop_write_and_out:
132 	mnt_drop_write(path->mnt);
133 out:
134 	return error;
135 }
136 EXPORT_SYMBOL_GPL(vfs_truncate);
137 
do_sys_truncate(const char __user * pathname,loff_t length)138 static long do_sys_truncate(const char __user *pathname, loff_t length)
139 {
140 	unsigned int lookup_flags = LOOKUP_FOLLOW;
141 	struct path path;
142 	int error;
143 
144 	if (length < 0)	/* sorry, but loff_t says... */
145 		return -EINVAL;
146 
147 retry:
148 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
149 	if (!error) {
150 		error = vfs_truncate(&path, length);
151 		path_put(&path);
152 	}
153 	if (retry_estale(error, lookup_flags)) {
154 		lookup_flags |= LOOKUP_REVAL;
155 		goto retry;
156 	}
157 	return error;
158 }
159 
SYSCALL_DEFINE2(truncate,const char __user *,path,long,length)160 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
161 {
162 	return do_sys_truncate(path, length);
163 }
164 
165 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(truncate,const char __user *,path,compat_off_t,length)166 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
167 {
168 	return do_sys_truncate(path, length);
169 }
170 #endif
171 
do_sys_ftruncate(unsigned int fd,loff_t length,int small)172 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
173 {
174 	struct inode *inode;
175 	struct dentry *dentry;
176 	struct vfsmount *mnt;
177 	struct fd f;
178 	int error;
179 
180 	error = -EINVAL;
181 	if (length < 0)
182 		goto out;
183 	error = -EBADF;
184 	f = fdget(fd);
185 	if (!f.file)
186 		goto out;
187 
188 	/* explicitly opened as large or we are on 64-bit box */
189 	if (f.file->f_flags & O_LARGEFILE)
190 		small = 0;
191 
192 	dentry = f.file->f_path.dentry;
193 	mnt = f.file->f_path.mnt;
194 	inode = dentry->d_inode;
195 	error = -EINVAL;
196 	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
197 		goto out_putf;
198 
199 	error = -EINVAL;
200 	/* Cannot ftruncate over 2^31 bytes without large file support */
201 	if (small && length > MAX_NON_LFS)
202 		goto out_putf;
203 
204 	error = -EPERM;
205 	if (IS_APPEND(inode))
206 		goto out_putf;
207 
208 	sb_start_write(inode->i_sb);
209 	error = locks_verify_truncate(inode, f.file, length);
210 	if (!error)
211 		error = security_path_truncate(&f.file->f_path);
212 	if (!error)
213 		error = do_truncate2(mnt, dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
214 	sb_end_write(inode->i_sb);
215 out_putf:
216 	fdput(f);
217 out:
218 	return error;
219 }
220 
SYSCALL_DEFINE2(ftruncate,unsigned int,fd,unsigned long,length)221 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
222 {
223 	return do_sys_ftruncate(fd, length, 1);
224 }
225 
226 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(ftruncate,unsigned int,fd,compat_ulong_t,length)227 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
228 {
229 	return do_sys_ftruncate(fd, length, 1);
230 }
231 #endif
232 
233 /* LFS versions of truncate are only needed on 32 bit machines */
234 #if BITS_PER_LONG == 32
SYSCALL_DEFINE2(truncate64,const char __user *,path,loff_t,length)235 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
236 {
237 	return do_sys_truncate(path, length);
238 }
239 
SYSCALL_DEFINE2(ftruncate64,unsigned int,fd,loff_t,length)240 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
241 {
242 	return do_sys_ftruncate(fd, length, 0);
243 }
244 #endif /* BITS_PER_LONG == 32 */
245 
246 
vfs_fallocate(struct file * file,int mode,loff_t offset,loff_t len)247 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
248 {
249 	struct inode *inode = file_inode(file);
250 	long ret;
251 
252 	if (offset < 0 || len <= 0)
253 		return -EINVAL;
254 
255 	/* Return error if mode is not supported */
256 	if (mode & ~FALLOC_FL_SUPPORTED_MASK)
257 		return -EOPNOTSUPP;
258 
259 	/* Punch hole and zero range are mutually exclusive */
260 	if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
261 	    (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
262 		return -EOPNOTSUPP;
263 
264 	/* Punch hole must have keep size set */
265 	if ((mode & FALLOC_FL_PUNCH_HOLE) &&
266 	    !(mode & FALLOC_FL_KEEP_SIZE))
267 		return -EOPNOTSUPP;
268 
269 	/* Collapse range should only be used exclusively. */
270 	if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
271 	    (mode & ~FALLOC_FL_COLLAPSE_RANGE))
272 		return -EINVAL;
273 
274 	/* Insert range should only be used exclusively. */
275 	if ((mode & FALLOC_FL_INSERT_RANGE) &&
276 	    (mode & ~FALLOC_FL_INSERT_RANGE))
277 		return -EINVAL;
278 
279 	/* Unshare range should only be used with allocate mode. */
280 	if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
281 	    (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
282 		return -EINVAL;
283 
284 	if (!(file->f_mode & FMODE_WRITE))
285 		return -EBADF;
286 
287 	/*
288 	 * We can only allow pure fallocate on append only files
289 	 */
290 	if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
291 		return -EPERM;
292 
293 	if (IS_IMMUTABLE(inode))
294 		return -EPERM;
295 
296 	/*
297 	 * We cannot allow any fallocate operation on an active swapfile
298 	 */
299 	if (IS_SWAPFILE(inode))
300 		return -ETXTBSY;
301 
302 	/*
303 	 * Revalidate the write permissions, in case security policy has
304 	 * changed since the files were opened.
305 	 */
306 	ret = security_file_permission(file, MAY_WRITE);
307 	if (ret)
308 		return ret;
309 
310 	if (S_ISFIFO(inode->i_mode))
311 		return -ESPIPE;
312 
313 	/*
314 	 * Let individual file system decide if it supports preallocation
315 	 * for directories or not.
316 	 */
317 	if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode) &&
318 	    !S_ISBLK(inode->i_mode))
319 		return -ENODEV;
320 
321 	/* Check for wrap through zero too */
322 	if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
323 		return -EFBIG;
324 
325 	if (!file->f_op->fallocate)
326 		return -EOPNOTSUPP;
327 
328 	sb_start_write(inode->i_sb);
329 	ret = file->f_op->fallocate(file, mode, offset, len);
330 
331 	/*
332 	 * Create inotify and fanotify events.
333 	 *
334 	 * To keep the logic simple always create events if fallocate succeeds.
335 	 * This implies that events are even created if the file size remains
336 	 * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
337 	 */
338 	if (ret == 0)
339 		fsnotify_modify(file);
340 
341 	sb_end_write(inode->i_sb);
342 	return ret;
343 }
344 EXPORT_SYMBOL_GPL(vfs_fallocate);
345 
SYSCALL_DEFINE4(fallocate,int,fd,int,mode,loff_t,offset,loff_t,len)346 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
347 {
348 	struct fd f = fdget(fd);
349 	int error = -EBADF;
350 
351 	if (f.file) {
352 		error = vfs_fallocate(f.file, mode, offset, len);
353 		fdput(f);
354 	}
355 	return error;
356 }
357 
358 /*
359  * access() needs to use the real uid/gid, not the effective uid/gid.
360  * We do this by temporarily clearing all FS-related capabilities and
361  * switching the fsuid/fsgid around to the real ones.
362  */
SYSCALL_DEFINE3(faccessat,int,dfd,const char __user *,filename,int,mode)363 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
364 {
365 	const struct cred *old_cred;
366 	struct cred *override_cred;
367 	struct path path;
368 	struct inode *inode;
369 	struct vfsmount *mnt;
370 	int res;
371 	unsigned int lookup_flags = LOOKUP_FOLLOW;
372 
373 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
374 		return -EINVAL;
375 
376 	override_cred = prepare_creds();
377 	if (!override_cred)
378 		return -ENOMEM;
379 
380 	override_cred->fsuid = override_cred->uid;
381 	override_cred->fsgid = override_cred->gid;
382 
383 	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
384 		/* Clear the capabilities if we switch to a non-root user */
385 		kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
386 		if (!uid_eq(override_cred->uid, root_uid))
387 			cap_clear(override_cred->cap_effective);
388 		else
389 			override_cred->cap_effective =
390 				override_cred->cap_permitted;
391 	}
392 
393 	old_cred = override_creds(override_cred);
394 retry:
395 	res = user_path_at(dfd, filename, lookup_flags, &path);
396 	if (res)
397 		goto out;
398 
399 	inode = d_backing_inode(path.dentry);
400 	mnt = path.mnt;
401 
402 	if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
403 		/*
404 		 * MAY_EXEC on regular files is denied if the fs is mounted
405 		 * with the "noexec" flag.
406 		 */
407 		res = -EACCES;
408 		if (path_noexec(&path))
409 			goto out_path_release;
410 	}
411 
412 	res = inode_permission2(mnt, inode, mode | MAY_ACCESS);
413 	/* SuS v2 requires we report a read only fs too */
414 	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
415 		goto out_path_release;
416 	/*
417 	 * This is a rare case where using __mnt_is_readonly()
418 	 * is OK without a mnt_want/drop_write() pair.  Since
419 	 * no actual write to the fs is performed here, we do
420 	 * not need to telegraph to that to anyone.
421 	 *
422 	 * By doing this, we accept that this access is
423 	 * inherently racy and know that the fs may change
424 	 * state before we even see this result.
425 	 */
426 	if (__mnt_is_readonly(path.mnt))
427 		res = -EROFS;
428 
429 out_path_release:
430 	path_put(&path);
431 	if (retry_estale(res, lookup_flags)) {
432 		lookup_flags |= LOOKUP_REVAL;
433 		goto retry;
434 	}
435 out:
436 	revert_creds(old_cred);
437 	put_cred(override_cred);
438 	return res;
439 }
440 
SYSCALL_DEFINE2(access,const char __user *,filename,int,mode)441 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
442 {
443 	return sys_faccessat(AT_FDCWD, filename, mode);
444 }
445 
SYSCALL_DEFINE1(chdir,const char __user *,filename)446 SYSCALL_DEFINE1(chdir, const char __user *, filename)
447 {
448 	struct path path;
449 	int error;
450 	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
451 retry:
452 	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
453 	if (error)
454 		goto out;
455 
456 	error = inode_permission2(path.mnt, path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
457 	if (error)
458 		goto dput_and_out;
459 
460 	set_fs_pwd(current->fs, &path);
461 
462 dput_and_out:
463 	path_put(&path);
464 	if (retry_estale(error, lookup_flags)) {
465 		lookup_flags |= LOOKUP_REVAL;
466 		goto retry;
467 	}
468 out:
469 	return error;
470 }
471 
SYSCALL_DEFINE1(fchdir,unsigned int,fd)472 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
473 {
474 	struct fd f = fdget_raw(fd);
475 	struct inode *inode;
476 	struct vfsmount *mnt;
477 	int error = -EBADF;
478 
479 	error = -EBADF;
480 	if (!f.file)
481 		goto out;
482 
483 	inode = file_inode(f.file);
484 	mnt = f.file->f_path.mnt;
485 
486 	error = -ENOTDIR;
487 	if (!S_ISDIR(inode->i_mode))
488 		goto out_putf;
489 
490 	error = inode_permission2(mnt, inode, MAY_EXEC | MAY_CHDIR);
491 	if (!error)
492 		set_fs_pwd(current->fs, &f.file->f_path);
493 out_putf:
494 	fdput(f);
495 out:
496 	return error;
497 }
498 
SYSCALL_DEFINE1(chroot,const char __user *,filename)499 SYSCALL_DEFINE1(chroot, const char __user *, filename)
500 {
501 	struct path path;
502 	int error;
503 	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
504 retry:
505 	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
506 	if (error)
507 		goto out;
508 
509 	error = inode_permission2(path.mnt, path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
510 	if (error)
511 		goto dput_and_out;
512 
513 	error = -EPERM;
514 	if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
515 		goto dput_and_out;
516 	error = security_path_chroot(&path);
517 	if (error)
518 		goto dput_and_out;
519 
520 	set_fs_root(current->fs, &path);
521 	error = 0;
522 dput_and_out:
523 	path_put(&path);
524 	if (retry_estale(error, lookup_flags)) {
525 		lookup_flags |= LOOKUP_REVAL;
526 		goto retry;
527 	}
528 out:
529 	return error;
530 }
531 
chmod_common(const struct path * path,umode_t mode)532 static int chmod_common(const struct path *path, umode_t mode)
533 {
534 	struct inode *inode = path->dentry->d_inode;
535 	struct inode *delegated_inode = NULL;
536 	struct iattr newattrs;
537 	int error;
538 
539 	error = mnt_want_write(path->mnt);
540 	if (error)
541 		return error;
542 retry_deleg:
543 	inode_lock(inode);
544 	error = security_path_chmod(path, mode);
545 	if (error)
546 		goto out_unlock;
547 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
548 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
549 	error = notify_change2(path->mnt, path->dentry, &newattrs, &delegated_inode);
550 out_unlock:
551 	inode_unlock(inode);
552 	if (delegated_inode) {
553 		error = break_deleg_wait(&delegated_inode);
554 		if (!error)
555 			goto retry_deleg;
556 	}
557 	mnt_drop_write(path->mnt);
558 	return error;
559 }
560 
SYSCALL_DEFINE2(fchmod,unsigned int,fd,umode_t,mode)561 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
562 {
563 	struct fd f = fdget(fd);
564 	int err = -EBADF;
565 
566 	if (f.file) {
567 		audit_file(f.file);
568 		err = chmod_common(&f.file->f_path, mode);
569 		fdput(f);
570 	}
571 	return err;
572 }
573 
SYSCALL_DEFINE3(fchmodat,int,dfd,const char __user *,filename,umode_t,mode)574 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
575 {
576 	struct path path;
577 	int error;
578 	unsigned int lookup_flags = LOOKUP_FOLLOW;
579 retry:
580 	error = user_path_at(dfd, filename, lookup_flags, &path);
581 	if (!error) {
582 		error = chmod_common(&path, mode);
583 		path_put(&path);
584 		if (retry_estale(error, lookup_flags)) {
585 			lookup_flags |= LOOKUP_REVAL;
586 			goto retry;
587 		}
588 	}
589 	return error;
590 }
591 
SYSCALL_DEFINE2(chmod,const char __user *,filename,umode_t,mode)592 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
593 {
594 	return sys_fchmodat(AT_FDCWD, filename, mode);
595 }
596 
chown_common(const struct path * path,uid_t user,gid_t group)597 static int chown_common(const struct path *path, uid_t user, gid_t group)
598 {
599 	struct inode *inode = path->dentry->d_inode;
600 	struct inode *delegated_inode = NULL;
601 	int error;
602 	struct iattr newattrs;
603 	kuid_t uid;
604 	kgid_t gid;
605 
606 	uid = make_kuid(current_user_ns(), user);
607 	gid = make_kgid(current_user_ns(), group);
608 
609 retry_deleg:
610 	newattrs.ia_valid =  ATTR_CTIME;
611 	if (user != (uid_t) -1) {
612 		if (!uid_valid(uid))
613 			return -EINVAL;
614 		newattrs.ia_valid |= ATTR_UID;
615 		newattrs.ia_uid = uid;
616 	}
617 	if (group != (gid_t) -1) {
618 		if (!gid_valid(gid))
619 			return -EINVAL;
620 		newattrs.ia_valid |= ATTR_GID;
621 		newattrs.ia_gid = gid;
622 	}
623 	if (!S_ISDIR(inode->i_mode))
624 		newattrs.ia_valid |=
625 			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
626 	inode_lock(inode);
627 	error = security_path_chown(path, uid, gid);
628 	if (!error)
629 		error = notify_change2(path->mnt, path->dentry, &newattrs, &delegated_inode);
630 	inode_unlock(inode);
631 	if (delegated_inode) {
632 		error = break_deleg_wait(&delegated_inode);
633 		if (!error)
634 			goto retry_deleg;
635 	}
636 	return error;
637 }
638 
SYSCALL_DEFINE5(fchownat,int,dfd,const char __user *,filename,uid_t,user,gid_t,group,int,flag)639 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
640 		gid_t, group, int, flag)
641 {
642 	struct path path;
643 	int error = -EINVAL;
644 	int lookup_flags;
645 
646 	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
647 		goto out;
648 
649 	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
650 	if (flag & AT_EMPTY_PATH)
651 		lookup_flags |= LOOKUP_EMPTY;
652 retry:
653 	error = user_path_at(dfd, filename, lookup_flags, &path);
654 	if (error)
655 		goto out;
656 	error = mnt_want_write(path.mnt);
657 	if (error)
658 		goto out_release;
659 	error = chown_common(&path, user, group);
660 	mnt_drop_write(path.mnt);
661 out_release:
662 	path_put(&path);
663 	if (retry_estale(error, lookup_flags)) {
664 		lookup_flags |= LOOKUP_REVAL;
665 		goto retry;
666 	}
667 out:
668 	return error;
669 }
670 
SYSCALL_DEFINE3(chown,const char __user *,filename,uid_t,user,gid_t,group)671 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
672 {
673 	return sys_fchownat(AT_FDCWD, filename, user, group, 0);
674 }
675 
SYSCALL_DEFINE3(lchown,const char __user *,filename,uid_t,user,gid_t,group)676 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
677 {
678 	return sys_fchownat(AT_FDCWD, filename, user, group,
679 			    AT_SYMLINK_NOFOLLOW);
680 }
681 
SYSCALL_DEFINE3(fchown,unsigned int,fd,uid_t,user,gid_t,group)682 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
683 {
684 	struct fd f = fdget(fd);
685 	int error = -EBADF;
686 
687 	if (!f.file)
688 		goto out;
689 
690 	error = mnt_want_write_file(f.file);
691 	if (error)
692 		goto out_fput;
693 	audit_file(f.file);
694 	error = chown_common(&f.file->f_path, user, group);
695 	mnt_drop_write_file(f.file);
696 out_fput:
697 	fdput(f);
698 out:
699 	return error;
700 }
701 
open_check_o_direct(struct file * f)702 int open_check_o_direct(struct file *f)
703 {
704 	/* NB: we're sure to have correct a_ops only after f_op->open */
705 	if (f->f_flags & O_DIRECT) {
706 		if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
707 			return -EINVAL;
708 	}
709 	return 0;
710 }
711 
do_dentry_open(struct file * f,struct inode * inode,int (* open)(struct inode *,struct file *),const struct cred * cred)712 static int do_dentry_open(struct file *f,
713 			  struct inode *inode,
714 			  int (*open)(struct inode *, struct file *),
715 			  const struct cred *cred)
716 {
717 	static const struct file_operations empty_fops = {};
718 	int error;
719 
720 	f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
721 				FMODE_PREAD | FMODE_PWRITE;
722 
723 	path_get(&f->f_path);
724 	f->f_inode = inode;
725 	f->f_mapping = inode->i_mapping;
726 
727 	if (unlikely(f->f_flags & O_PATH)) {
728 		f->f_mode = FMODE_PATH;
729 		f->f_op = &empty_fops;
730 		return 0;
731 	}
732 
733 	if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
734 		error = get_write_access(inode);
735 		if (unlikely(error))
736 			goto cleanup_file;
737 		error = __mnt_want_write(f->f_path.mnt);
738 		if (unlikely(error)) {
739 			put_write_access(inode);
740 			goto cleanup_file;
741 		}
742 		f->f_mode |= FMODE_WRITER;
743 	}
744 
745 	/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
746 	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
747 		f->f_mode |= FMODE_ATOMIC_POS;
748 
749 	f->f_op = fops_get(inode->i_fop);
750 	if (unlikely(WARN_ON(!f->f_op))) {
751 		error = -ENODEV;
752 		goto cleanup_all;
753 	}
754 
755 	error = security_file_open(f, cred);
756 	if (error)
757 		goto cleanup_all;
758 
759 	error = break_lease(locks_inode(f), f->f_flags);
760 	if (error)
761 		goto cleanup_all;
762 
763 	if (!open)
764 		open = f->f_op->open;
765 	if (open) {
766 		error = open(inode, f);
767 		if (error)
768 			goto cleanup_all;
769 	}
770 	if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
771 		i_readcount_inc(inode);
772 	if ((f->f_mode & FMODE_READ) &&
773 	     likely(f->f_op->read || f->f_op->read_iter))
774 		f->f_mode |= FMODE_CAN_READ;
775 	if ((f->f_mode & FMODE_WRITE) &&
776 	     likely(f->f_op->write || f->f_op->write_iter))
777 		f->f_mode |= FMODE_CAN_WRITE;
778 
779 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
780 
781 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
782 
783 	return 0;
784 
785 cleanup_all:
786 	fops_put(f->f_op);
787 	if (f->f_mode & FMODE_WRITER) {
788 		put_write_access(inode);
789 		__mnt_drop_write(f->f_path.mnt);
790 	}
791 cleanup_file:
792 	path_put(&f->f_path);
793 	f->f_path.mnt = NULL;
794 	f->f_path.dentry = NULL;
795 	f->f_inode = NULL;
796 	return error;
797 }
798 
799 /**
800  * finish_open - finish opening a file
801  * @file: file pointer
802  * @dentry: pointer to dentry
803  * @open: open callback
804  * @opened: state of open
805  *
806  * This can be used to finish opening a file passed to i_op->atomic_open().
807  *
808  * If the open callback is set to NULL, then the standard f_op->open()
809  * filesystem callback is substituted.
810  *
811  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
812  * the return value of d_splice_alias(), then the caller needs to perform dput()
813  * on it after finish_open().
814  *
815  * On successful return @file is a fully instantiated open file.  After this, if
816  * an error occurs in ->atomic_open(), it needs to clean up with fput().
817  *
818  * Returns zero on success or -errno if the open failed.
819  */
finish_open(struct file * file,struct dentry * dentry,int (* open)(struct inode *,struct file *),int * opened)820 int finish_open(struct file *file, struct dentry *dentry,
821 		int (*open)(struct inode *, struct file *),
822 		int *opened)
823 {
824 	int error;
825 	BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
826 
827 	file->f_path.dentry = dentry;
828 	error = do_dentry_open(file, d_backing_inode(dentry), open,
829 			       current_cred());
830 	if (!error)
831 		*opened |= FILE_OPENED;
832 
833 	return error;
834 }
835 EXPORT_SYMBOL(finish_open);
836 
837 /**
838  * finish_no_open - finish ->atomic_open() without opening the file
839  *
840  * @file: file pointer
841  * @dentry: dentry or NULL (as returned from ->lookup())
842  *
843  * This can be used to set the result of a successful lookup in ->atomic_open().
844  *
845  * NB: unlike finish_open() this function does consume the dentry reference and
846  * the caller need not dput() it.
847  *
848  * Returns "1" which must be the return value of ->atomic_open() after having
849  * called this function.
850  */
finish_no_open(struct file * file,struct dentry * dentry)851 int finish_no_open(struct file *file, struct dentry *dentry)
852 {
853 	file->f_path.dentry = dentry;
854 	return 1;
855 }
856 EXPORT_SYMBOL(finish_no_open);
857 
file_path(struct file * filp,char * buf,int buflen)858 char *file_path(struct file *filp, char *buf, int buflen)
859 {
860 	return d_path(&filp->f_path, buf, buflen);
861 }
862 EXPORT_SYMBOL(file_path);
863 
864 /**
865  * vfs_open - open the file at the given path
866  * @path: path to open
867  * @file: newly allocated file with f_flag initialized
868  * @cred: credentials to use
869  */
vfs_open(const struct path * path,struct file * file,const struct cred * cred)870 int vfs_open(const struct path *path, struct file *file,
871 	     const struct cred *cred)
872 {
873 	struct dentry *dentry = d_real(path->dentry, NULL, file->f_flags);
874 
875 	if (IS_ERR(dentry))
876 		return PTR_ERR(dentry);
877 
878 	file->f_path = *path;
879 	return do_dentry_open(file, d_backing_inode(dentry), NULL, cred);
880 }
881 
dentry_open(const struct path * path,int flags,const struct cred * cred)882 struct file *dentry_open(const struct path *path, int flags,
883 			 const struct cred *cred)
884 {
885 	int error;
886 	struct file *f;
887 
888 	validate_creds(cred);
889 
890 	/* We must always pass in a valid mount pointer. */
891 	BUG_ON(!path->mnt);
892 
893 	f = get_empty_filp();
894 	if (!IS_ERR(f)) {
895 		f->f_flags = flags;
896 		error = vfs_open(path, f, cred);
897 		if (!error) {
898 			/* from now on we need fput() to dispose of f */
899 			error = open_check_o_direct(f);
900 			if (error) {
901 				fput(f);
902 				f = ERR_PTR(error);
903 			}
904 		} else {
905 			put_filp(f);
906 			f = ERR_PTR(error);
907 		}
908 	}
909 	return f;
910 }
911 EXPORT_SYMBOL(dentry_open);
912 
build_open_flags(int flags,umode_t mode,struct open_flags * op)913 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
914 {
915 	int lookup_flags = 0;
916 	int acc_mode = ACC_MODE(flags);
917 
918 	/*
919 	 * Clear out all open flags we don't know about so that we don't report
920 	 * them in fcntl(F_GETFD) or similar interfaces.
921 	 */
922 	flags &= VALID_OPEN_FLAGS;
923 
924 	if (flags & (O_CREAT | __O_TMPFILE))
925 		op->mode = (mode & S_IALLUGO) | S_IFREG;
926 	else
927 		op->mode = 0;
928 
929 	/* Must never be set by userspace */
930 	flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
931 
932 	/*
933 	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
934 	 * check for O_DSYNC if the need any syncing at all we enforce it's
935 	 * always set instead of having to deal with possibly weird behaviour
936 	 * for malicious applications setting only __O_SYNC.
937 	 */
938 	if (flags & __O_SYNC)
939 		flags |= O_DSYNC;
940 
941 	if (flags & __O_TMPFILE) {
942 		if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
943 			return -EINVAL;
944 		if (!(acc_mode & MAY_WRITE))
945 			return -EINVAL;
946 	} else if (flags & O_PATH) {
947 		/*
948 		 * If we have O_PATH in the open flag. Then we
949 		 * cannot have anything other than the below set of flags
950 		 */
951 		flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
952 		acc_mode = 0;
953 	}
954 
955 	op->open_flag = flags;
956 
957 	/* O_TRUNC implies we need access checks for write permissions */
958 	if (flags & O_TRUNC)
959 		acc_mode |= MAY_WRITE;
960 
961 	/* Allow the LSM permission hook to distinguish append
962 	   access from general write access. */
963 	if (flags & O_APPEND)
964 		acc_mode |= MAY_APPEND;
965 
966 	op->acc_mode = acc_mode;
967 
968 	op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
969 
970 	if (flags & O_CREAT) {
971 		op->intent |= LOOKUP_CREATE;
972 		if (flags & O_EXCL)
973 			op->intent |= LOOKUP_EXCL;
974 	}
975 
976 	if (flags & O_DIRECTORY)
977 		lookup_flags |= LOOKUP_DIRECTORY;
978 	if (!(flags & O_NOFOLLOW))
979 		lookup_flags |= LOOKUP_FOLLOW;
980 	op->lookup_flags = lookup_flags;
981 	return 0;
982 }
983 
984 /**
985  * file_open_name - open file and return file pointer
986  *
987  * @name:	struct filename containing path to open
988  * @flags:	open flags as per the open(2) second argument
989  * @mode:	mode for the new file if O_CREAT is set, else ignored
990  *
991  * This is the helper to open a file from kernelspace if you really
992  * have to.  But in generally you should not do this, so please move
993  * along, nothing to see here..
994  */
file_open_name(struct filename * name,int flags,umode_t mode)995 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
996 {
997 	struct open_flags op;
998 	int err = build_open_flags(flags, mode, &op);
999 	return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
1000 }
1001 
1002 /**
1003  * filp_open - open file and return file pointer
1004  *
1005  * @filename:	path to open
1006  * @flags:	open flags as per the open(2) second argument
1007  * @mode:	mode for the new file if O_CREAT is set, else ignored
1008  *
1009  * This is the helper to open a file from kernelspace if you really
1010  * have to.  But in generally you should not do this, so please move
1011  * along, nothing to see here..
1012  */
filp_open(const char * filename,int flags,umode_t mode)1013 struct file *filp_open(const char *filename, int flags, umode_t mode)
1014 {
1015 	struct filename *name = getname_kernel(filename);
1016 	struct file *file = ERR_CAST(name);
1017 
1018 	if (!IS_ERR(name)) {
1019 		file = file_open_name(name, flags, mode);
1020 		putname(name);
1021 	}
1022 	return file;
1023 }
1024 EXPORT_SYMBOL(filp_open);
1025 
file_open_root(struct dentry * dentry,struct vfsmount * mnt,const char * filename,int flags,umode_t mode)1026 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1027 			    const char *filename, int flags, umode_t mode)
1028 {
1029 	struct open_flags op;
1030 	int err = build_open_flags(flags, mode, &op);
1031 	if (err)
1032 		return ERR_PTR(err);
1033 	return do_file_open_root(dentry, mnt, filename, &op);
1034 }
1035 EXPORT_SYMBOL(file_open_root);
1036 
filp_clone_open(struct file * oldfile)1037 struct file *filp_clone_open(struct file *oldfile)
1038 {
1039 	struct file *file;
1040 	int retval;
1041 
1042 	file = get_empty_filp();
1043 	if (IS_ERR(file))
1044 		return file;
1045 
1046 	file->f_flags = oldfile->f_flags;
1047 	retval = vfs_open(&oldfile->f_path, file, oldfile->f_cred);
1048 	if (retval) {
1049 		put_filp(file);
1050 		return ERR_PTR(retval);
1051 	}
1052 
1053 	return file;
1054 }
1055 EXPORT_SYMBOL(filp_clone_open);
1056 
do_sys_open(int dfd,const char __user * filename,int flags,umode_t mode)1057 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1058 {
1059 	struct open_flags op;
1060 	int fd = build_open_flags(flags, mode, &op);
1061 	struct filename *tmp;
1062 
1063 	if (fd)
1064 		return fd;
1065 
1066 	tmp = getname(filename);
1067 	if (IS_ERR(tmp))
1068 		return PTR_ERR(tmp);
1069 
1070 	fd = get_unused_fd_flags(flags);
1071 	if (fd >= 0) {
1072 		struct file *f = do_filp_open(dfd, tmp, &op);
1073 		if (IS_ERR(f)) {
1074 			put_unused_fd(fd);
1075 			fd = PTR_ERR(f);
1076 		} else {
1077 			fsnotify_open(f);
1078 			fd_install(fd, f);
1079 		}
1080 	}
1081 	putname(tmp);
1082 	return fd;
1083 }
1084 
SYSCALL_DEFINE3(open,const char __user *,filename,int,flags,umode_t,mode)1085 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1086 {
1087 	if (force_o_largefile())
1088 		flags |= O_LARGEFILE;
1089 
1090 	return do_sys_open(AT_FDCWD, filename, flags, mode);
1091 }
1092 
SYSCALL_DEFINE4(openat,int,dfd,const char __user *,filename,int,flags,umode_t,mode)1093 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1094 		umode_t, mode)
1095 {
1096 	if (force_o_largefile())
1097 		flags |= O_LARGEFILE;
1098 
1099 	return do_sys_open(dfd, filename, flags, mode);
1100 }
1101 
1102 #ifndef __alpha__
1103 
1104 /*
1105  * For backward compatibility?  Maybe this should be moved
1106  * into arch/i386 instead?
1107  */
SYSCALL_DEFINE2(creat,const char __user *,pathname,umode_t,mode)1108 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1109 {
1110 	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1111 }
1112 
1113 #endif
1114 
1115 /*
1116  * "id" is the POSIX thread ID. We use the
1117  * files pointer for this..
1118  */
filp_close(struct file * filp,fl_owner_t id)1119 int filp_close(struct file *filp, fl_owner_t id)
1120 {
1121 	int retval = 0;
1122 
1123 	if (!file_count(filp)) {
1124 		printk(KERN_ERR "VFS: Close: file count is 0\n");
1125 		return 0;
1126 	}
1127 
1128 	if (filp->f_op->flush)
1129 		retval = filp->f_op->flush(filp, id);
1130 
1131 	if (likely(!(filp->f_mode & FMODE_PATH))) {
1132 		dnotify_flush(filp, id);
1133 		locks_remove_posix(filp, id);
1134 	}
1135 	fput(filp);
1136 	return retval;
1137 }
1138 
1139 EXPORT_SYMBOL(filp_close);
1140 
1141 /*
1142  * Careful here! We test whether the file pointer is NULL before
1143  * releasing the fd. This ensures that one clone task can't release
1144  * an fd while another clone is opening it.
1145  */
SYSCALL_DEFINE1(close,unsigned int,fd)1146 SYSCALL_DEFINE1(close, unsigned int, fd)
1147 {
1148 	int retval = __close_fd(current->files, fd);
1149 
1150 	/* can't restart close syscall because file table entry was cleared */
1151 	if (unlikely(retval == -ERESTARTSYS ||
1152 		     retval == -ERESTARTNOINTR ||
1153 		     retval == -ERESTARTNOHAND ||
1154 		     retval == -ERESTART_RESTARTBLOCK))
1155 		retval = -EINTR;
1156 
1157 	return retval;
1158 }
1159 EXPORT_SYMBOL(sys_close);
1160 
1161 /*
1162  * This routine simulates a hangup on the tty, to arrange that users
1163  * are given clean terminals at login time.
1164  */
SYSCALL_DEFINE0(vhangup)1165 SYSCALL_DEFINE0(vhangup)
1166 {
1167 	if (capable(CAP_SYS_TTY_CONFIG)) {
1168 		tty_vhangup_self();
1169 		return 0;
1170 	}
1171 	return -EPERM;
1172 }
1173 
1174 /*
1175  * Called when an inode is about to be open.
1176  * We use this to disallow opening large files on 32bit systems if
1177  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1178  * on this flag in sys_open.
1179  */
generic_file_open(struct inode * inode,struct file * filp)1180 int generic_file_open(struct inode * inode, struct file * filp)
1181 {
1182 	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1183 		return -EOVERFLOW;
1184 	return 0;
1185 }
1186 
1187 EXPORT_SYMBOL(generic_file_open);
1188 
1189 /*
1190  * This is used by subsystems that don't want seekable
1191  * file descriptors. The function is not supposed to ever fail, the only
1192  * reason it returns an 'int' and not 'void' is so that it can be plugged
1193  * directly into file_operations structure.
1194  */
nonseekable_open(struct inode * inode,struct file * filp)1195 int nonseekable_open(struct inode *inode, struct file *filp)
1196 {
1197 	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1198 	return 0;
1199 }
1200 
1201 EXPORT_SYMBOL(nonseekable_open);
1202