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Linux/fs/open.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/fs/open.c
  4  *
  5  *  Copyright (C) 1991, 1992  Linus Torvalds
  6  */
  7 
  8 #include <linux/string.h>
  9 #include <linux/mm.h>
 10 #include <linux/file.h>
 11 #include <linux/fdtable.h>
 12 #include <linux/fsnotify.h>
 13 #include <linux/module.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/securebits.h>
 19 #include <linux/security.h>
 20 #include <linux/mount.h>
 21 #include <linux/fcntl.h>
 22 #include <linux/slab.h>
 23 #include <linux/uaccess.h>
 24 #include <linux/fs.h>
 25 #include <linux/personality.h>
 26 #include <linux/pagemap.h>
 27 #include <linux/syscalls.h>
 28 #include <linux/rcupdate.h>
 29 #include <linux/audit.h>
 30 #include <linux/falloc.h>
 31 #include <linux/fs_struct.h>
 32 #include <linux/ima.h>
 33 #include <linux/dnotify.h>
 34 #include <linux/compat.h>
 35 
 36 #include "internal.h"
 37 
 38 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
 39         struct file *filp)
 40 {
 41         int ret;
 42         struct iattr newattrs;
 43 
 44         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
 45         if (length < 0)
 46                 return -EINVAL;
 47 
 48         newattrs.ia_size = length;
 49         newattrs.ia_valid = ATTR_SIZE | time_attrs;
 50         if (filp) {
 51                 newattrs.ia_file = filp;
 52                 newattrs.ia_valid |= ATTR_FILE;
 53         }
 54 
 55         /* Remove suid, sgid, and file capabilities on truncate too */
 56         ret = dentry_needs_remove_privs(dentry);
 57         if (ret < 0)
 58                 return ret;
 59         if (ret)
 60                 newattrs.ia_valid |= ret | ATTR_FORCE;
 61 
 62         inode_lock(dentry->d_inode);
 63         /* Note any delegations or leases have already been broken: */
 64         ret = notify_change(dentry, &newattrs, NULL);
 65         inode_unlock(dentry->d_inode);
 66         return ret;
 67 }
 68 
 69 long vfs_truncate(const struct path *path, loff_t length)
 70 {
 71         struct inode *inode;
 72         long error;
 73 
 74         inode = path->dentry->d_inode;
 75 
 76         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
 77         if (S_ISDIR(inode->i_mode))
 78                 return -EISDIR;
 79         if (!S_ISREG(inode->i_mode))
 80                 return -EINVAL;
 81 
 82         error = mnt_want_write(path->mnt);
 83         if (error)
 84                 goto out;
 85 
 86         error = inode_permission(inode, MAY_WRITE);
 87         if (error)
 88                 goto mnt_drop_write_and_out;
 89 
 90         error = -EPERM;
 91         if (IS_APPEND(inode))
 92                 goto mnt_drop_write_and_out;
 93 
 94         error = get_write_access(inode);
 95         if (error)
 96                 goto mnt_drop_write_and_out;
 97 
 98         /*
 99          * Make sure that there are no leases.  get_write_access() protects
100          * against the truncate racing with a lease-granting setlease().
101          */
102         error = break_lease(inode, O_WRONLY);
103         if (error)
104                 goto put_write_and_out;
105 
106         error = locks_verify_truncate(inode, NULL, length);
107         if (!error)
108                 error = security_path_truncate(path);
109         if (!error)
110                 error = do_truncate(path->dentry, length, 0, NULL);
111 
112 put_write_and_out:
113         put_write_access(inode);
114 mnt_drop_write_and_out:
115         mnt_drop_write(path->mnt);
116 out:
117         return error;
118 }
119 EXPORT_SYMBOL_GPL(vfs_truncate);
120 
121 long do_sys_truncate(const char __user *pathname, loff_t length)
122 {
123         unsigned int lookup_flags = LOOKUP_FOLLOW;
124         struct path path;
125         int error;
126 
127         if (length < 0) /* sorry, but loff_t says... */
128                 return -EINVAL;
129 
130 retry:
131         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
132         if (!error) {
133                 error = vfs_truncate(&path, length);
134                 path_put(&path);
135         }
136         if (retry_estale(error, lookup_flags)) {
137                 lookup_flags |= LOOKUP_REVAL;
138                 goto retry;
139         }
140         return error;
141 }
142 
143 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
144 {
145         return do_sys_truncate(path, length);
146 }
147 
148 #ifdef CONFIG_COMPAT
149 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
150 {
151         return do_sys_truncate(path, length);
152 }
153 #endif
154 
155 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
156 {
157         struct inode *inode;
158         struct dentry *dentry;
159         struct fd f;
160         int error;
161 
162         error = -EINVAL;
163         if (length < 0)
164                 goto out;
165         error = -EBADF;
166         f = fdget(fd);
167         if (!f.file)
168                 goto out;
169 
170         /* explicitly opened as large or we are on 64-bit box */
171         if (f.file->f_flags & O_LARGEFILE)
172                 small = 0;
173 
174         dentry = f.file->f_path.dentry;
175         inode = dentry->d_inode;
176         error = -EINVAL;
177         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
178                 goto out_putf;
179 
180         error = -EINVAL;
181         /* Cannot ftruncate over 2^31 bytes without large file support */
182         if (small && length > MAX_NON_LFS)
183                 goto out_putf;
184 
185         error = -EPERM;
186         /* Check IS_APPEND on real upper inode */
187         if (IS_APPEND(file_inode(f.file)))
188                 goto out_putf;
189 
190         sb_start_write(inode->i_sb);
191         error = locks_verify_truncate(inode, f.file, length);
192         if (!error)
193                 error = security_path_truncate(&f.file->f_path);
194         if (!error)
195                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
196         sb_end_write(inode->i_sb);
197 out_putf:
198         fdput(f);
199 out:
200         return error;
201 }
202 
203 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
204 {
205         return do_sys_ftruncate(fd, length, 1);
206 }
207 
208 #ifdef CONFIG_COMPAT
209 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
210 {
211         return do_sys_ftruncate(fd, length, 1);
212 }
213 #endif
214 
215 /* LFS versions of truncate are only needed on 32 bit machines */
216 #if BITS_PER_LONG == 32
217 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
218 {
219         return do_sys_truncate(path, length);
220 }
221 
222 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
223 {
224         return do_sys_ftruncate(fd, length, 0);
225 }
226 #endif /* BITS_PER_LONG == 32 */
227 
228 
229 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
230 {
231         struct inode *inode = file_inode(file);
232         long ret;
233 
234         if (offset < 0 || len <= 0)
235                 return -EINVAL;
236 
237         /* Return error if mode is not supported */
238         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
239                 return -EOPNOTSUPP;
240 
241         /* Punch hole and zero range are mutually exclusive */
242         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
243             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
244                 return -EOPNOTSUPP;
245 
246         /* Punch hole must have keep size set */
247         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
248             !(mode & FALLOC_FL_KEEP_SIZE))
249                 return -EOPNOTSUPP;
250 
251         /* Collapse range should only be used exclusively. */
252         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
253             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
254                 return -EINVAL;
255 
256         /* Insert range should only be used exclusively. */
257         if ((mode & FALLOC_FL_INSERT_RANGE) &&
258             (mode & ~FALLOC_FL_INSERT_RANGE))
259                 return -EINVAL;
260 
261         /* Unshare range should only be used with allocate mode. */
262         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
263             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
264                 return -EINVAL;
265 
266         if (!(file->f_mode & FMODE_WRITE))
267                 return -EBADF;
268 
269         /*
270          * We can only allow pure fallocate on append only files
271          */
272         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
273                 return -EPERM;
274 
275         if (IS_IMMUTABLE(inode))
276                 return -EPERM;
277 
278         /*
279          * We cannot allow any fallocate operation on an active swapfile
280          */
281         if (IS_SWAPFILE(inode))
282                 return -ETXTBSY;
283 
284         /*
285          * Revalidate the write permissions, in case security policy has
286          * changed since the files were opened.
287          */
288         ret = security_file_permission(file, MAY_WRITE);
289         if (ret)
290                 return ret;
291 
292         if (S_ISFIFO(inode->i_mode))
293                 return -ESPIPE;
294 
295         if (S_ISDIR(inode->i_mode))
296                 return -EISDIR;
297 
298         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
299                 return -ENODEV;
300 
301         /* Check for wrap through zero too */
302         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
303                 return -EFBIG;
304 
305         if (!file->f_op->fallocate)
306                 return -EOPNOTSUPP;
307 
308         file_start_write(file);
309         ret = file->f_op->fallocate(file, mode, offset, len);
310 
311         /*
312          * Create inotify and fanotify events.
313          *
314          * To keep the logic simple always create events if fallocate succeeds.
315          * This implies that events are even created if the file size remains
316          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
317          */
318         if (ret == 0)
319                 fsnotify_modify(file);
320 
321         file_end_write(file);
322         return ret;
323 }
324 EXPORT_SYMBOL_GPL(vfs_fallocate);
325 
326 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
327 {
328         struct fd f = fdget(fd);
329         int error = -EBADF;
330 
331         if (f.file) {
332                 error = vfs_fallocate(f.file, mode, offset, len);
333                 fdput(f);
334         }
335         return error;
336 }
337 
338 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
339 {
340         return ksys_fallocate(fd, mode, offset, len);
341 }
342 
343 /*
344  * access() needs to use the real uid/gid, not the effective uid/gid.
345  * We do this by temporarily clearing all FS-related capabilities and
346  * switching the fsuid/fsgid around to the real ones.
347  */
348 static const struct cred *access_override_creds(void)
349 {
350         const struct cred *old_cred;
351         struct cred *override_cred;
352 
353         override_cred = prepare_creds();
354         if (!override_cred)
355                 return NULL;
356 
357         override_cred->fsuid = override_cred->uid;
358         override_cred->fsgid = override_cred->gid;
359 
360         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
361                 /* Clear the capabilities if we switch to a non-root user */
362                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
363                 if (!uid_eq(override_cred->uid, root_uid))
364                         cap_clear(override_cred->cap_effective);
365                 else
366                         override_cred->cap_effective =
367                                 override_cred->cap_permitted;
368         }
369 
370         /*
371          * The new set of credentials can *only* be used in
372          * task-synchronous circumstances, and does not need
373          * RCU freeing, unless somebody then takes a separate
374          * reference to it.
375          *
376          * NOTE! This is _only_ true because this credential
377          * is used purely for override_creds() that installs
378          * it as the subjective cred. Other threads will be
379          * accessing ->real_cred, not the subjective cred.
380          *
381          * If somebody _does_ make a copy of this (using the
382          * 'get_current_cred()' function), that will clear the
383          * non_rcu field, because now that other user may be
384          * expecting RCU freeing. But normal thread-synchronous
385          * cred accesses will keep things non-RCY.
386          */
387         override_cred->non_rcu = 1;
388 
389         old_cred = override_creds(override_cred);
390 
391         /* override_cred() gets its own ref */
392         put_cred(override_cred);
393 
394         return old_cred;
395 }
396 
397 static long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
398 {
399         struct path path;
400         struct inode *inode;
401         int res;
402         unsigned int lookup_flags = LOOKUP_FOLLOW;
403         const struct cred *old_cred = NULL;
404 
405         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
406                 return -EINVAL;
407 
408         if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
409                 return -EINVAL;
410 
411         if (flags & AT_SYMLINK_NOFOLLOW)
412                 lookup_flags &= ~LOOKUP_FOLLOW;
413         if (flags & AT_EMPTY_PATH)
414                 lookup_flags |= LOOKUP_EMPTY;
415 
416         if (!(flags & AT_EACCESS)) {
417                 old_cred = access_override_creds();
418                 if (!old_cred)
419                         return -ENOMEM;
420         }
421 
422 retry:
423         res = user_path_at(dfd, filename, lookup_flags, &path);
424         if (res)
425                 goto out;
426 
427         inode = d_backing_inode(path.dentry);
428 
429         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
430                 /*
431                  * MAY_EXEC on regular files is denied if the fs is mounted
432                  * with the "noexec" flag.
433                  */
434                 res = -EACCES;
435                 if (path_noexec(&path))
436                         goto out_path_release;
437         }
438 
439         res = inode_permission(inode, mode | MAY_ACCESS);
440         /* SuS v2 requires we report a read only fs too */
441         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
442                 goto out_path_release;
443         /*
444          * This is a rare case where using __mnt_is_readonly()
445          * is OK without a mnt_want/drop_write() pair.  Since
446          * no actual write to the fs is performed here, we do
447          * not need to telegraph to that to anyone.
448          *
449          * By doing this, we accept that this access is
450          * inherently racy and know that the fs may change
451          * state before we even see this result.
452          */
453         if (__mnt_is_readonly(path.mnt))
454                 res = -EROFS;
455 
456 out_path_release:
457         path_put(&path);
458         if (retry_estale(res, lookup_flags)) {
459                 lookup_flags |= LOOKUP_REVAL;
460                 goto retry;
461         }
462 out:
463         if (old_cred)
464                 revert_creds(old_cred);
465 
466         return res;
467 }
468 
469 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
470 {
471         return do_faccessat(dfd, filename, mode, 0);
472 }
473 
474 SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
475                 int, flags)
476 {
477         return do_faccessat(dfd, filename, mode, flags);
478 }
479 
480 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
481 {
482         return do_faccessat(AT_FDCWD, filename, mode, 0);
483 }
484 
485 SYSCALL_DEFINE1(chdir, const char __user *, filename)
486 {
487         struct path path;
488         int error;
489         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
490 retry:
491         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
492         if (error)
493                 goto out;
494 
495         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
496         if (error)
497                 goto dput_and_out;
498 
499         set_fs_pwd(current->fs, &path);
500 
501 dput_and_out:
502         path_put(&path);
503         if (retry_estale(error, lookup_flags)) {
504                 lookup_flags |= LOOKUP_REVAL;
505                 goto retry;
506         }
507 out:
508         return error;
509 }
510 
511 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
512 {
513         struct fd f = fdget_raw(fd);
514         int error;
515 
516         error = -EBADF;
517         if (!f.file)
518                 goto out;
519 
520         error = -ENOTDIR;
521         if (!d_can_lookup(f.file->f_path.dentry))
522                 goto out_putf;
523 
524         error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
525         if (!error)
526                 set_fs_pwd(current->fs, &f.file->f_path);
527 out_putf:
528         fdput(f);
529 out:
530         return error;
531 }
532 
533 SYSCALL_DEFINE1(chroot, const char __user *, filename)
534 {
535         struct path path;
536         int error;
537         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
538 retry:
539         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
540         if (error)
541                 goto out;
542 
543         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
544         if (error)
545                 goto dput_and_out;
546 
547         error = -EPERM;
548         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
549                 goto dput_and_out;
550         error = security_path_chroot(&path);
551         if (error)
552                 goto dput_and_out;
553 
554         set_fs_root(current->fs, &path);
555         error = 0;
556 dput_and_out:
557         path_put(&path);
558         if (retry_estale(error, lookup_flags)) {
559                 lookup_flags |= LOOKUP_REVAL;
560                 goto retry;
561         }
562 out:
563         return error;
564 }
565 
566 int chmod_common(const struct path *path, umode_t mode)
567 {
568         struct inode *inode = path->dentry->d_inode;
569         struct inode *delegated_inode = NULL;
570         struct iattr newattrs;
571         int error;
572 
573         error = mnt_want_write(path->mnt);
574         if (error)
575                 return error;
576 retry_deleg:
577         inode_lock(inode);
578         error = security_path_chmod(path, mode);
579         if (error)
580                 goto out_unlock;
581         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
582         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
583         error = notify_change(path->dentry, &newattrs, &delegated_inode);
584 out_unlock:
585         inode_unlock(inode);
586         if (delegated_inode) {
587                 error = break_deleg_wait(&delegated_inode);
588                 if (!error)
589                         goto retry_deleg;
590         }
591         mnt_drop_write(path->mnt);
592         return error;
593 }
594 
595 int vfs_fchmod(struct file *file, umode_t mode)
596 {
597         audit_file(file);
598         return chmod_common(&file->f_path, mode);
599 }
600 
601 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
602 {
603         struct fd f = fdget(fd);
604         int err = -EBADF;
605 
606         if (f.file) {
607                 err = vfs_fchmod(f.file, mode);
608                 fdput(f);
609         }
610         return err;
611 }
612 
613 static int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
614 {
615         struct path path;
616         int error;
617         unsigned int lookup_flags = LOOKUP_FOLLOW;
618 retry:
619         error = user_path_at(dfd, filename, lookup_flags, &path);
620         if (!error) {
621                 error = chmod_common(&path, mode);
622                 path_put(&path);
623                 if (retry_estale(error, lookup_flags)) {
624                         lookup_flags |= LOOKUP_REVAL;
625                         goto retry;
626                 }
627         }
628         return error;
629 }
630 
631 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
632                 umode_t, mode)
633 {
634         return do_fchmodat(dfd, filename, mode);
635 }
636 
637 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
638 {
639         return do_fchmodat(AT_FDCWD, filename, mode);
640 }
641 
642 int chown_common(const struct path *path, uid_t user, gid_t group)
643 {
644         struct inode *inode = path->dentry->d_inode;
645         struct inode *delegated_inode = NULL;
646         int error;
647         struct iattr newattrs;
648         kuid_t uid;
649         kgid_t gid;
650 
651         uid = make_kuid(current_user_ns(), user);
652         gid = make_kgid(current_user_ns(), group);
653 
654 retry_deleg:
655         newattrs.ia_valid =  ATTR_CTIME;
656         if (user != (uid_t) -1) {
657                 if (!uid_valid(uid))
658                         return -EINVAL;
659                 newattrs.ia_valid |= ATTR_UID;
660                 newattrs.ia_uid = uid;
661         }
662         if (group != (gid_t) -1) {
663                 if (!gid_valid(gid))
664                         return -EINVAL;
665                 newattrs.ia_valid |= ATTR_GID;
666                 newattrs.ia_gid = gid;
667         }
668         if (!S_ISDIR(inode->i_mode))
669                 newattrs.ia_valid |=
670                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
671         inode_lock(inode);
672         error = security_path_chown(path, uid, gid);
673         if (!error)
674                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
675         inode_unlock(inode);
676         if (delegated_inode) {
677                 error = break_deleg_wait(&delegated_inode);
678                 if (!error)
679                         goto retry_deleg;
680         }
681         return error;
682 }
683 
684 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
685                 int flag)
686 {
687         struct path path;
688         int error = -EINVAL;
689         int lookup_flags;
690 
691         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
692                 goto out;
693 
694         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
695         if (flag & AT_EMPTY_PATH)
696                 lookup_flags |= LOOKUP_EMPTY;
697 retry:
698         error = user_path_at(dfd, filename, lookup_flags, &path);
699         if (error)
700                 goto out;
701         error = mnt_want_write(path.mnt);
702         if (error)
703                 goto out_release;
704         error = chown_common(&path, user, group);
705         mnt_drop_write(path.mnt);
706 out_release:
707         path_put(&path);
708         if (retry_estale(error, lookup_flags)) {
709                 lookup_flags |= LOOKUP_REVAL;
710                 goto retry;
711         }
712 out:
713         return error;
714 }
715 
716 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
717                 gid_t, group, int, flag)
718 {
719         return do_fchownat(dfd, filename, user, group, flag);
720 }
721 
722 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
723 {
724         return do_fchownat(AT_FDCWD, filename, user, group, 0);
725 }
726 
727 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
728 {
729         return do_fchownat(AT_FDCWD, filename, user, group,
730                            AT_SYMLINK_NOFOLLOW);
731 }
732 
733 int vfs_fchown(struct file *file, uid_t user, gid_t group)
734 {
735         int error;
736 
737         error = mnt_want_write_file(file);
738         if (error)
739                 return error;
740         audit_file(file);
741         error = chown_common(&file->f_path, user, group);
742         mnt_drop_write_file(file);
743         return error;
744 }
745 
746 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
747 {
748         struct fd f = fdget(fd);
749         int error = -EBADF;
750 
751         if (f.file) {
752                 error = vfs_fchown(f.file, user, group);
753                 fdput(f);
754         }
755         return error;
756 }
757 
758 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
759 {
760         return ksys_fchown(fd, user, group);
761 }
762 
763 static int do_dentry_open(struct file *f,
764                           struct inode *inode,
765                           int (*open)(struct inode *, struct file *))
766 {
767         static const struct file_operations empty_fops = {};
768         int error;
769 
770         path_get(&f->f_path);
771         f->f_inode = inode;
772         f->f_mapping = inode->i_mapping;
773         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
774         f->f_sb_err = file_sample_sb_err(f);
775 
776         if (unlikely(f->f_flags & O_PATH)) {
777                 f->f_mode = FMODE_PATH | FMODE_OPENED;
778                 f->f_op = &empty_fops;
779                 return 0;
780         }
781 
782         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
783                 error = get_write_access(inode);
784                 if (unlikely(error))
785                         goto cleanup_file;
786                 error = __mnt_want_write(f->f_path.mnt);
787                 if (unlikely(error)) {
788                         put_write_access(inode);
789                         goto cleanup_file;
790                 }
791                 f->f_mode |= FMODE_WRITER;
792         }
793 
794         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
795         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
796                 f->f_mode |= FMODE_ATOMIC_POS;
797 
798         f->f_op = fops_get(inode->i_fop);
799         if (WARN_ON(!f->f_op)) {
800                 error = -ENODEV;
801                 goto cleanup_all;
802         }
803 
804         error = security_file_open(f);
805         if (error)
806                 goto cleanup_all;
807 
808         error = break_lease(locks_inode(f), f->f_flags);
809         if (error)
810                 goto cleanup_all;
811 
812         /* normally all 3 are set; ->open() can clear them if needed */
813         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
814         if (!open)
815                 open = f->f_op->open;
816         if (open) {
817                 error = open(inode, f);
818                 if (error)
819                         goto cleanup_all;
820         }
821         f->f_mode |= FMODE_OPENED;
822         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
823                 i_readcount_inc(inode);
824         if ((f->f_mode & FMODE_READ) &&
825              likely(f->f_op->read || f->f_op->read_iter))
826                 f->f_mode |= FMODE_CAN_READ;
827         if ((f->f_mode & FMODE_WRITE) &&
828              likely(f->f_op->write || f->f_op->write_iter))
829                 f->f_mode |= FMODE_CAN_WRITE;
830 
831         f->f_write_hint = WRITE_LIFE_NOT_SET;
832         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
833 
834         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
835 
836         /* NB: we're sure to have correct a_ops only after f_op->open */
837         if (f->f_flags & O_DIRECT) {
838                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
839                         return -EINVAL;
840         }
841 
842         /*
843          * XXX: Huge page cache doesn't support writing yet. Drop all page
844          * cache for this file before processing writes.
845          */
846         if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))
847                 truncate_pagecache(inode, 0);
848 
849         return 0;
850 
851 cleanup_all:
852         if (WARN_ON_ONCE(error > 0))
853                 error = -EINVAL;
854         fops_put(f->f_op);
855         if (f->f_mode & FMODE_WRITER) {
856                 put_write_access(inode);
857                 __mnt_drop_write(f->f_path.mnt);
858         }
859 cleanup_file:
860         path_put(&f->f_path);
861         f->f_path.mnt = NULL;
862         f->f_path.dentry = NULL;
863         f->f_inode = NULL;
864         return error;
865 }
866 
867 /**
868  * finish_open - finish opening a file
869  * @file: file pointer
870  * @dentry: pointer to dentry
871  * @open: open callback
872  * @opened: state of open
873  *
874  * This can be used to finish opening a file passed to i_op->atomic_open().
875  *
876  * If the open callback is set to NULL, then the standard f_op->open()
877  * filesystem callback is substituted.
878  *
879  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
880  * the return value of d_splice_alias(), then the caller needs to perform dput()
881  * on it after finish_open().
882  *
883  * Returns zero on success or -errno if the open failed.
884  */
885 int finish_open(struct file *file, struct dentry *dentry,
886                 int (*open)(struct inode *, struct file *))
887 {
888         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
889 
890         file->f_path.dentry = dentry;
891         return do_dentry_open(file, d_backing_inode(dentry), open);
892 }
893 EXPORT_SYMBOL(finish_open);
894 
895 /**
896  * finish_no_open - finish ->atomic_open() without opening the file
897  *
898  * @file: file pointer
899  * @dentry: dentry or NULL (as returned from ->lookup())
900  *
901  * This can be used to set the result of a successful lookup in ->atomic_open().
902  *
903  * NB: unlike finish_open() this function does consume the dentry reference and
904  * the caller need not dput() it.
905  *
906  * Returns "" which must be the return value of ->atomic_open() after having
907  * called this function.
908  */
909 int finish_no_open(struct file *file, struct dentry *dentry)
910 {
911         file->f_path.dentry = dentry;
912         return 0;
913 }
914 EXPORT_SYMBOL(finish_no_open);
915 
916 char *file_path(struct file *filp, char *buf, int buflen)
917 {
918         return d_path(&filp->f_path, buf, buflen);
919 }
920 EXPORT_SYMBOL(file_path);
921 
922 /**
923  * vfs_open - open the file at the given path
924  * @path: path to open
925  * @file: newly allocated file with f_flag initialized
926  * @cred: credentials to use
927  */
928 int vfs_open(const struct path *path, struct file *file)
929 {
930         file->f_path = *path;
931         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
932 }
933 
934 struct file *dentry_open(const struct path *path, int flags,
935                          const struct cred *cred)
936 {
937         int error;
938         struct file *f;
939 
940         validate_creds(cred);
941 
942         /* We must always pass in a valid mount pointer. */
943         BUG_ON(!path->mnt);
944 
945         f = alloc_empty_file(flags, cred);
946         if (!IS_ERR(f)) {
947                 error = vfs_open(path, f);
948                 if (error) {
949                         fput(f);
950                         f = ERR_PTR(error);
951                 }
952         }
953         return f;
954 }
955 EXPORT_SYMBOL(dentry_open);
956 
957 struct file *open_with_fake_path(const struct path *path, int flags,
958                                 struct inode *inode, const struct cred *cred)
959 {
960         struct file *f = alloc_empty_file_noaccount(flags, cred);
961         if (!IS_ERR(f)) {
962                 int error;
963 
964                 f->f_path = *path;
965                 error = do_dentry_open(f, inode, NULL);
966                 if (error) {
967                         fput(f);
968                         f = ERR_PTR(error);
969                 }
970         }
971         return f;
972 }
973 EXPORT_SYMBOL(open_with_fake_path);
974 
975 #define WILL_CREATE(flags)      (flags & (O_CREAT | __O_TMPFILE))
976 #define O_PATH_FLAGS            (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)
977 
978 inline struct open_how build_open_how(int flags, umode_t mode)
979 {
980         struct open_how how = {
981                 .flags = flags & VALID_OPEN_FLAGS,
982                 .mode = mode & S_IALLUGO,
983         };
984 
985         /* O_PATH beats everything else. */
986         if (how.flags & O_PATH)
987                 how.flags &= O_PATH_FLAGS;
988         /* Modes should only be set for create-like flags. */
989         if (!WILL_CREATE(how.flags))
990                 how.mode = 0;
991         return how;
992 }
993 
994 inline int build_open_flags(const struct open_how *how, struct open_flags *op)
995 {
996         int flags = how->flags;
997         int lookup_flags = 0;
998         int acc_mode = ACC_MODE(flags);
999 
1000         /* Must never be set by userspace */
1001         flags &= ~(FMODE_NONOTIFY | O_CLOEXEC);
1002 
1003         /*
1004          * Older syscalls implicitly clear all of the invalid flags or argument
1005          * values before calling build_open_flags(), but openat2(2) checks all
1006          * of its arguments.
1007          */
1008         if (flags & ~VALID_OPEN_FLAGS)
1009                 return -EINVAL;
1010         if (how->resolve & ~VALID_RESOLVE_FLAGS)
1011                 return -EINVAL;
1012 
1013         /* Deal with the mode. */
1014         if (WILL_CREATE(flags)) {
1015                 if (how->mode & ~S_IALLUGO)
1016                         return -EINVAL;
1017                 op->mode = how->mode | S_IFREG;
1018         } else {
1019                 if (how->mode != 0)
1020                         return -EINVAL;
1021                 op->mode = 0;
1022         }
1023 
1024         /*
1025          * In order to ensure programs get explicit errors when trying to use
1026          * O_TMPFILE on old kernels, O_TMPFILE is implemented such that it
1027          * looks like (O_DIRECTORY|O_RDWR & ~O_CREAT) to old kernels. But we
1028          * have to require userspace to explicitly set it.
1029          */
1030         if (flags & __O_TMPFILE) {
1031                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
1032                         return -EINVAL;
1033                 if (!(acc_mode & MAY_WRITE))
1034                         return -EINVAL;
1035         }
1036         if (flags & O_PATH) {
1037                 /* O_PATH only permits certain other flags to be set. */
1038                 if (flags & ~O_PATH_FLAGS)
1039                         return -EINVAL;
1040                 acc_mode = 0;
1041         }
1042 
1043         /*
1044          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
1045          * check for O_DSYNC if the need any syncing at all we enforce it's
1046          * always set instead of having to deal with possibly weird behaviour
1047          * for malicious applications setting only __O_SYNC.
1048          */
1049         if (flags & __O_SYNC)
1050                 flags |= O_DSYNC;
1051 
1052         op->open_flag = flags;
1053 
1054         /* O_TRUNC implies we need access checks for write permissions */
1055         if (flags & O_TRUNC)
1056                 acc_mode |= MAY_WRITE;
1057 
1058         /* Allow the LSM permission hook to distinguish append
1059            access from general write access. */
1060         if (flags & O_APPEND)
1061                 acc_mode |= MAY_APPEND;
1062 
1063         op->acc_mode = acc_mode;
1064 
1065         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
1066 
1067         if (flags & O_CREAT) {
1068                 op->intent |= LOOKUP_CREATE;
1069                 if (flags & O_EXCL) {
1070                         op->intent |= LOOKUP_EXCL;
1071                         flags |= O_NOFOLLOW;
1072                 }
1073         }
1074 
1075         if (flags & O_DIRECTORY)
1076                 lookup_flags |= LOOKUP_DIRECTORY;
1077         if (!(flags & O_NOFOLLOW))
1078                 lookup_flags |= LOOKUP_FOLLOW;
1079 
1080         if (how->resolve & RESOLVE_NO_XDEV)
1081                 lookup_flags |= LOOKUP_NO_XDEV;
1082         if (how->resolve & RESOLVE_NO_MAGICLINKS)
1083                 lookup_flags |= LOOKUP_NO_MAGICLINKS;
1084         if (how->resolve & RESOLVE_NO_SYMLINKS)
1085                 lookup_flags |= LOOKUP_NO_SYMLINKS;
1086         if (how->resolve & RESOLVE_BENEATH)
1087                 lookup_flags |= LOOKUP_BENEATH;
1088         if (how->resolve & RESOLVE_IN_ROOT)
1089                 lookup_flags |= LOOKUP_IN_ROOT;
1090 
1091         op->lookup_flags = lookup_flags;
1092         return 0;
1093 }
1094 
1095 /**
1096  * file_open_name - open file and return file pointer
1097  *
1098  * @name:       struct filename containing path to open
1099  * @flags:      open flags as per the open(2) second argument
1100  * @mode:       mode for the new file if O_CREAT is set, else ignored
1101  *
1102  * This is the helper to open a file from kernelspace if you really
1103  * have to.  But in generally you should not do this, so please move
1104  * along, nothing to see here..
1105  */
1106 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1107 {
1108         struct open_flags op;
1109         struct open_how how = build_open_how(flags, mode);
1110         int err = build_open_flags(&how, &op);
1111         if (err)
1112                 return ERR_PTR(err);
1113         return do_filp_open(AT_FDCWD, name, &op);
1114 }
1115 
1116 /**
1117  * filp_open - open file and return file pointer
1118  *
1119  * @filename:   path to open
1120  * @flags:      open flags as per the open(2) second argument
1121  * @mode:       mode for the new file if O_CREAT is set, else ignored
1122  *
1123  * This is the helper to open a file from kernelspace if you really
1124  * have to.  But in generally you should not do this, so please move
1125  * along, nothing to see here..
1126  */
1127 struct file *filp_open(const char *filename, int flags, umode_t mode)
1128 {
1129         struct filename *name = getname_kernel(filename);
1130         struct file *file = ERR_CAST(name);
1131         
1132         if (!IS_ERR(name)) {
1133                 file = file_open_name(name, flags, mode);
1134                 putname(name);
1135         }
1136         return file;
1137 }
1138 EXPORT_SYMBOL(filp_open);
1139 
1140 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1141                             const char *filename, int flags, umode_t mode)
1142 {
1143         struct open_flags op;
1144         struct open_how how = build_open_how(flags, mode);
1145         int err = build_open_flags(&how, &op);
1146         if (err)
1147                 return ERR_PTR(err);
1148         return do_file_open_root(dentry, mnt, filename, &op);
1149 }
1150 EXPORT_SYMBOL(file_open_root);
1151 
1152 static long do_sys_openat2(int dfd, const char __user *filename,
1153                            struct open_how *how)
1154 {
1155         struct open_flags op;
1156         int fd = build_open_flags(how, &op);
1157         struct filename *tmp;
1158 
1159         if (fd)
1160                 return fd;
1161 
1162         tmp = getname(filename);
1163         if (IS_ERR(tmp))
1164                 return PTR_ERR(tmp);
1165 
1166         fd = get_unused_fd_flags(how->flags);
1167         if (fd >= 0) {
1168                 struct file *f = do_filp_open(dfd, tmp, &op);
1169                 if (IS_ERR(f)) {
1170                         put_unused_fd(fd);
1171                         fd = PTR_ERR(f);
1172                 } else {
1173                         fsnotify_open(f);
1174                         fd_install(fd, f);
1175                 }
1176         }
1177         putname(tmp);
1178         return fd;
1179 }
1180 
1181 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1182 {
1183         struct open_how how = build_open_how(flags, mode);
1184         return do_sys_openat2(dfd, filename, &how);
1185 }
1186 
1187 
1188 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1189 {
1190         if (force_o_largefile())
1191                 flags |= O_LARGEFILE;
1192         return do_sys_open(AT_FDCWD, filename, flags, mode);
1193 }
1194 
1195 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1196                 umode_t, mode)
1197 {
1198         if (force_o_largefile())
1199                 flags |= O_LARGEFILE;
1200         return do_sys_open(dfd, filename, flags, mode);
1201 }
1202 
1203 SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
1204                 struct open_how __user *, how, size_t, usize)
1205 {
1206         int err;
1207         struct open_how tmp;
1208 
1209         BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
1210         BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
1211 
1212         if (unlikely(usize < OPEN_HOW_SIZE_VER0))
1213                 return -EINVAL;
1214 
1215         err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
1216         if (err)
1217                 return err;
1218 
1219         /* O_LARGEFILE is only allowed for non-O_PATH. */
1220         if (!(tmp.flags & O_PATH) && force_o_largefile())
1221                 tmp.flags |= O_LARGEFILE;
1222 
1223         return do_sys_openat2(dfd, filename, &tmp);
1224 }
1225 
1226 #ifdef CONFIG_COMPAT
1227 /*
1228  * Exactly like sys_open(), except that it doesn't set the
1229  * O_LARGEFILE flag.
1230  */
1231 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1232 {
1233         return do_sys_open(AT_FDCWD, filename, flags, mode);
1234 }
1235 
1236 /*
1237  * Exactly like sys_openat(), except that it doesn't set the
1238  * O_LARGEFILE flag.
1239  */
1240 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1241 {
1242         return do_sys_open(dfd, filename, flags, mode);
1243 }
1244 #endif
1245 
1246 #ifndef __alpha__
1247 
1248 /*
1249  * For backward compatibility?  Maybe this should be moved
1250  * into arch/i386 instead?
1251  */
1252 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1253 {
1254         int flags = O_CREAT | O_WRONLY | O_TRUNC;
1255 
1256         if (force_o_largefile())
1257                 flags |= O_LARGEFILE;
1258         return do_sys_open(AT_FDCWD, pathname, flags, mode);
1259 }
1260 #endif
1261 
1262 /*
1263  * "id" is the POSIX thread ID. We use the
1264  * files pointer for this..
1265  */
1266 int filp_close(struct file *filp, fl_owner_t id)
1267 {
1268         int retval = 0;
1269 
1270         if (!file_count(filp)) {
1271                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1272                 return 0;
1273         }
1274 
1275         if (filp->f_op->flush)
1276                 retval = filp->f_op->flush(filp, id);
1277 
1278         if (likely(!(filp->f_mode & FMODE_PATH))) {
1279                 dnotify_flush(filp, id);
1280                 locks_remove_posix(filp, id);
1281         }
1282         fput(filp);
1283         return retval;
1284 }
1285 
1286 EXPORT_SYMBOL(filp_close);
1287 
1288 /*
1289  * Careful here! We test whether the file pointer is NULL before
1290  * releasing the fd. This ensures that one clone task can't release
1291  * an fd while another clone is opening it.
1292  */
1293 SYSCALL_DEFINE1(close, unsigned int, fd)
1294 {
1295         int retval = __close_fd(current->files, fd);
1296 
1297         /* can't restart close syscall because file table entry was cleared */
1298         if (unlikely(retval == -ERESTARTSYS ||
1299                      retval == -ERESTARTNOINTR ||
1300                      retval == -ERESTARTNOHAND ||
1301                      retval == -ERESTART_RESTARTBLOCK))
1302                 retval = -EINTR;
1303 
1304         return retval;
1305 }
1306 
1307 /**
1308  * close_range() - Close all file descriptors in a given range.
1309  *
1310  * @fd:     starting file descriptor to close
1311  * @max_fd: last file descriptor to close
1312  * @flags:  reserved for future extensions
1313  *
1314  * This closes a range of file descriptors. All file descriptors
1315  * from @fd up to and including @max_fd are closed.
1316  * Currently, errors to close a given file descriptor are ignored.
1317  */
1318 SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd,
1319                 unsigned int, flags)
1320 {
1321         return __close_range(fd, max_fd, flags);
1322 }
1323 
1324 /*
1325  * This routine simulates a hangup on the tty, to arrange that users
1326  * are given clean terminals at login time.
1327  */
1328 SYSCALL_DEFINE0(vhangup)
1329 {
1330         if (!ccs_capable(CCS_SYS_VHANGUP))
1331                 return -EPERM;
1332         if (capable(CAP_SYS_TTY_CONFIG)) {
1333                 tty_vhangup_self();
1334                 return 0;
1335         }
1336         return -EPERM;
1337 }
1338 
1339 /*
1340  * Called when an inode is about to be open.
1341  * We use this to disallow opening large files on 32bit systems if
1342  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1343  * on this flag in sys_open.
1344  */
1345 int generic_file_open(struct inode * inode, struct file * filp)
1346 {
1347         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1348                 return -EOVERFLOW;
1349         return 0;
1350 }
1351 
1352 EXPORT_SYMBOL(generic_file_open);
1353 
1354 /*
1355  * This is used by subsystems that don't want seekable
1356  * file descriptors. The function is not supposed to ever fail, the only
1357  * reason it returns an 'int' and not 'void' is so that it can be plugged
1358  * directly into file_operations structure.
1359  */
1360 int nonseekable_open(struct inode *inode, struct file *filp)
1361 {
1362         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1363         return 0;
1364 }
1365 
1366 EXPORT_SYMBOL(nonseekable_open);
1367 
1368 /*
1369  * stream_open is used by subsystems that want stream-like file descriptors.
1370  * Such file descriptors are not seekable and don't have notion of position
1371  * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
1372  * Contrary to file descriptors of other regular files, .read() and .write()
1373  * can run simultaneously.
1374  *
1375  * stream_open never fails and is marked to return int so that it could be
1376  * directly used as file_operations.open .
1377  */
1378 int stream_open(struct inode *inode, struct file *filp)
1379 {
1380         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
1381         filp->f_mode |= FMODE_STREAM;
1382         return 0;
1383 }
1384 
1385 EXPORT_SYMBOL(stream_open);
1386 

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