Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16

Linux/fs/open.c

  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 
 34 #include "internal.h"
 35 
 36 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
 37         struct file *filp)
 38 {
 39         int ret;
 40         struct iattr newattrs;
 41 
 42         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
 43         if (length < 0)
 44                 return -EINVAL;
 45 
 46         newattrs.ia_size = length;
 47         newattrs.ia_valid = ATTR_SIZE | time_attrs;
 48         if (filp) {
 49                 newattrs.ia_file = filp;
 50                 newattrs.ia_valid |= ATTR_FILE;
 51         }
 52 
 53         /* Remove suid/sgid on truncate too */
 54         ret = should_remove_suid(dentry);
 55         if (ret)
 56                 newattrs.ia_valid |= ret | ATTR_FORCE;
 57 
 58         mutex_lock(&dentry->d_inode->i_mutex);
 59         ret = notify_change(dentry, &newattrs);
 60         mutex_unlock(&dentry->d_inode->i_mutex);
 61         return ret;
 62 }
 63 
 64 static long do_sys_truncate(const char __user *pathname, loff_t length)
 65 {
 66         struct path path;
 67         struct inode *inode;
 68         int error;
 69 
 70         error = -EINVAL;
 71         if (length < 0) /* sorry, but loff_t says... */
 72                 goto out;
 73 
 74         error = user_path(pathname, &path);
 75         if (error)
 76                 goto out;
 77         inode = path.dentry->d_inode;
 78 
 79         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
 80         error = -EISDIR;
 81         if (S_ISDIR(inode->i_mode))
 82                 goto dput_and_out;
 83 
 84         error = -EINVAL;
 85         if (!S_ISREG(inode->i_mode))
 86                 goto dput_and_out;
 87 
 88         error = mnt_want_write(path.mnt);
 89         if (error)
 90                 goto dput_and_out;
 91 
 92         error = inode_permission(inode, MAY_WRITE);
 93         if (error)
 94                 goto mnt_drop_write_and_out;
 95 
 96         error = -EPERM;
 97         if (IS_APPEND(inode))
 98                 goto mnt_drop_write_and_out;
 99 
100         error = get_write_access(inode);
101         if (error)
102                 goto mnt_drop_write_and_out;
103 
104         /*
105          * Make sure that there are no leases.  get_write_access() protects
106          * against the truncate racing with a lease-granting setlease().
107          */
108         error = break_lease(inode, O_WRONLY);
109         if (error)
110                 goto put_write_and_out;
111 
112         error = locks_verify_truncate(inode, NULL, length);
113         if (!error)
114                 error = security_path_truncate(&path);
115         if (!error)
116                 error = do_truncate(path.dentry, length, 0, NULL);
117 
118 put_write_and_out:
119         put_write_access(inode);
120 mnt_drop_write_and_out:
121         mnt_drop_write(path.mnt);
122 dput_and_out:
123         path_put(&path);
124 out:
125         return error;
126 }
127 
128 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
129 {
130         return do_sys_truncate(path, length);
131 }
132 
133 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
134 {
135         struct inode * inode;
136         struct dentry *dentry;
137         struct file * file;
138         int error;
139 
140         error = -EINVAL;
141         if (length < 0)
142                 goto out;
143         error = -EBADF;
144         file = fget(fd);
145         if (!file)
146                 goto out;
147 
148         /* explicitly opened as large or we are on 64-bit box */
149         if (file->f_flags & O_LARGEFILE)
150                 small = 0;
151 
152         dentry = file->f_path.dentry;
153         inode = dentry->d_inode;
154         error = -EINVAL;
155         if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
156                 goto out_putf;
157 
158         error = -EINVAL;
159         /* Cannot ftruncate over 2^31 bytes without large file support */
160         if (small && length > MAX_NON_LFS)
161                 goto out_putf;
162 
163         error = -EPERM;
164         if (IS_APPEND(inode))
165                 goto out_putf;
166 
167         error = locks_verify_truncate(inode, file, length);
168         if (!error)
169                 error = security_path_truncate(&file->f_path);
170         if (!error)
171                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
172 out_putf:
173         fput(file);
174 out:
175         return error;
176 }
177 
178 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
179 {
180         long ret = do_sys_ftruncate(fd, length, 1);
181         /* avoid REGPARM breakage on x86: */
182         asmlinkage_protect(2, ret, fd, length);
183         return ret;
184 }
185 
186 /* LFS versions of truncate are only needed on 32 bit machines */
187 #if BITS_PER_LONG == 32
188 SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
189 {
190         return do_sys_truncate(path, length);
191 }
192 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
193 asmlinkage long SyS_truncate64(long path, loff_t length)
194 {
195         return SYSC_truncate64((const char __user *) path, length);
196 }
197 SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
198 #endif
199 
200 SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
201 {
202         long ret = do_sys_ftruncate(fd, length, 0);
203         /* avoid REGPARM breakage on x86: */
204         asmlinkage_protect(2, ret, fd, length);
205         return ret;
206 }
207 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
208 asmlinkage long SyS_ftruncate64(long fd, loff_t length)
209 {
210         return SYSC_ftruncate64((unsigned int) fd, length);
211 }
212 SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
213 #endif
214 #endif /* BITS_PER_LONG == 32 */
215 
216 
217 int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
218 {
219         struct inode *inode = file->f_path.dentry->d_inode;
220         long ret;
221 
222         if (offset < 0 || len <= 0)
223                 return -EINVAL;
224 
225         /* Return error if mode is not supported */
226         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
227                 return -EOPNOTSUPP;
228 
229         /* Punch hole must have keep size set */
230         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
231             !(mode & FALLOC_FL_KEEP_SIZE))
232                 return -EOPNOTSUPP;
233 
234         if (!(file->f_mode & FMODE_WRITE))
235                 return -EBADF;
236 
237         /* It's not possible punch hole on append only file */
238         if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
239                 return -EPERM;
240 
241         if (IS_IMMUTABLE(inode))
242                 return -EPERM;
243 
244         /*
245          * Revalidate the write permissions, in case security policy has
246          * changed since the files were opened.
247          */
248         ret = security_file_permission(file, MAY_WRITE);
249         if (ret)
250                 return ret;
251 
252         if (S_ISFIFO(inode->i_mode))
253                 return -ESPIPE;
254 
255         /*
256          * Let individual file system decide if it supports preallocation
257          * for directories or not.
258          */
259         if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
260                 return -ENODEV;
261 
262         /* Check for wrap through zero too */
263         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
264                 return -EFBIG;
265 
266         if (!file->f_op->fallocate)
267                 return -EOPNOTSUPP;
268 
269         return file->f_op->fallocate(file, mode, offset, len);
270 }
271 
272 SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
273 {
274         struct file *file;
275         int error = -EBADF;
276 
277         file = fget(fd);
278         if (file) {
279                 error = do_fallocate(file, mode, offset, len);
280                 fput(file);
281         }
282 
283         return error;
284 }
285 
286 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
287 asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
288 {
289         return SYSC_fallocate((int)fd, (int)mode, offset, len);
290 }
291 SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
292 #endif
293 
294 /*
295  * access() needs to use the real uid/gid, not the effective uid/gid.
296  * We do this by temporarily clearing all FS-related capabilities and
297  * switching the fsuid/fsgid around to the real ones.
298  */
299 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
300 {
301         const struct cred *old_cred;
302         struct cred *override_cred;
303         struct path path;
304         struct inode *inode;
305         int res;
306 
307         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
308                 return -EINVAL;
309 
310         override_cred = prepare_creds();
311         if (!override_cred)
312                 return -ENOMEM;
313 
314         override_cred->fsuid = override_cred->uid;
315         override_cred->fsgid = override_cred->gid;
316 
317         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
318                 /* Clear the capabilities if we switch to a non-root user */
319                 if (override_cred->uid)
320                         cap_clear(override_cred->cap_effective);
321                 else
322                         override_cred->cap_effective =
323                                 override_cred->cap_permitted;
324         }
325 
326         old_cred = override_creds(override_cred);
327 
328         res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
329         if (res)
330                 goto out;
331 
332         inode = path.dentry->d_inode;
333 
334         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
335                 /*
336                  * MAY_EXEC on regular files is denied if the fs is mounted
337                  * with the "noexec" flag.
338                  */
339                 res = -EACCES;
340                 if (path.mnt->mnt_flags & MNT_NOEXEC)
341                         goto out_path_release;
342         }
343 
344         res = inode_permission(inode, mode | MAY_ACCESS);
345         /* SuS v2 requires we report a read only fs too */
346         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
347                 goto out_path_release;
348         /*
349          * This is a rare case where using __mnt_is_readonly()
350          * is OK without a mnt_want/drop_write() pair.  Since
351          * no actual write to the fs is performed here, we do
352          * not need to telegraph to that to anyone.
353          *
354          * By doing this, we accept that this access is
355          * inherently racy and know that the fs may change
356          * state before we even see this result.
357          */
358         if (__mnt_is_readonly(path.mnt))
359                 res = -EROFS;
360 
361 out_path_release:
362         path_put(&path);
363 out:
364         revert_creds(old_cred);
365         put_cred(override_cred);
366         return res;
367 }
368 
369 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
370 {
371         return sys_faccessat(AT_FDCWD, filename, mode);
372 }
373 
374 SYSCALL_DEFINE1(chdir, const char __user *, filename)
375 {
376         struct path path;
377         int error;
378 
379         error = user_path_dir(filename, &path);
380         if (error)
381                 goto out;
382 
383         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
384         if (error)
385                 goto dput_and_out;
386 
387         set_fs_pwd(current->fs, &path);
388 
389 dput_and_out:
390         path_put(&path);
391 out:
392         return error;
393 }
394 
395 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
396 {
397         struct file *file;
398         struct inode *inode;
399         int error;
400 
401         error = -EBADF;
402         file = fget(fd);
403         if (!file)
404                 goto out;
405 
406         inode = file->f_path.dentry->d_inode;
407 
408         error = -ENOTDIR;
409         if (!S_ISDIR(inode->i_mode))
410                 goto out_putf;
411 
412         error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
413         if (!error)
414                 set_fs_pwd(current->fs, &file->f_path);
415 out_putf:
416         fput(file);
417 out:
418         return error;
419 }
420 
421 SYSCALL_DEFINE1(chroot, const char __user *, filename)
422 {
423         struct path path;
424         int error;
425 
426         error = user_path_dir(filename, &path);
427         if (error)
428                 goto out;
429 
430         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
431         if (error)
432                 goto dput_and_out;
433 
434         error = -EPERM;
435         if (!capable(CAP_SYS_CHROOT))
436                 goto dput_and_out;
437         error = security_path_chroot(&path);
438         if (error)
439                 goto dput_and_out;
440 
441         set_fs_root(current->fs, &path);
442         error = 0;
443 dput_and_out:
444         path_put(&path);
445 out:
446         return error;
447 }
448 
449 SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode)
450 {
451         struct inode * inode;
452         struct dentry * dentry;
453         struct file * file;
454         int err = -EBADF;
455         struct iattr newattrs;
456 
457         file = fget(fd);
458         if (!file)
459                 goto out;
460 
461         dentry = file->f_path.dentry;
462         inode = dentry->d_inode;
463 
464         audit_inode(NULL, dentry);
465 
466         err = mnt_want_write_file(file);
467         if (err)
468                 goto out_putf;
469         mutex_lock(&inode->i_mutex);
470         err = security_path_chmod(dentry, file->f_vfsmnt, mode);
471         if (err)
472                 goto out_unlock;
473         if (mode == (mode_t) -1)
474                 mode = inode->i_mode;
475         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
476         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
477         err = notify_change(dentry, &newattrs);
478 out_unlock:
479         mutex_unlock(&inode->i_mutex);
480         mnt_drop_write(file->f_path.mnt);
481 out_putf:
482         fput(file);
483 out:
484         return err;
485 }
486 
487 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, mode_t, mode)
488 {
489         struct path path;
490         struct inode *inode;
491         int error;
492         struct iattr newattrs;
493 
494         error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
495         if (error)
496                 goto out;
497         inode = path.dentry->d_inode;
498 
499         error = mnt_want_write(path.mnt);
500         if (error)
501                 goto dput_and_out;
502         mutex_lock(&inode->i_mutex);
503         error = security_path_chmod(path.dentry, path.mnt, mode);
504         if (error)
505                 goto out_unlock;
506         if (mode == (mode_t) -1)
507                 mode = inode->i_mode;
508         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
509         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
510         error = notify_change(path.dentry, &newattrs);
511 out_unlock:
512         mutex_unlock(&inode->i_mutex);
513         mnt_drop_write(path.mnt);
514 dput_and_out:
515         path_put(&path);
516 out:
517         return error;
518 }
519 
520 SYSCALL_DEFINE2(chmod, const char __user *, filename, mode_t, mode)
521 {
522         return sys_fchmodat(AT_FDCWD, filename, mode);
523 }
524 
525 static int chown_common(struct path *path, uid_t user, gid_t group)
526 {
527         struct inode *inode = path->dentry->d_inode;
528         int error;
529         struct iattr newattrs;
530 
531         newattrs.ia_valid =  ATTR_CTIME;
532         if (user != (uid_t) -1) {
533                 newattrs.ia_valid |= ATTR_UID;
534                 newattrs.ia_uid = user;
535         }
536         if (group != (gid_t) -1) {
537                 newattrs.ia_valid |= ATTR_GID;
538                 newattrs.ia_gid = group;
539         }
540         if (!S_ISDIR(inode->i_mode))
541                 newattrs.ia_valid |=
542                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
543         mutex_lock(&inode->i_mutex);
544         error = security_path_chown(path, user, group);
545         if (!error)
546                 error = notify_change(path->dentry, &newattrs);
547         mutex_unlock(&inode->i_mutex);
548 
549         return error;
550 }
551 
552 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
553 {
554         struct path path;
555         int error;
556 
557         error = user_path(filename, &path);
558         if (error)
559                 goto out;
560         error = mnt_want_write(path.mnt);
561         if (error)
562                 goto out_release;
563         error = chown_common(&path, user, group);
564         mnt_drop_write(path.mnt);
565 out_release:
566         path_put(&path);
567 out:
568         return error;
569 }
570 
571 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
572                 gid_t, group, int, flag)
573 {
574         struct path path;
575         int error = -EINVAL;
576         int lookup_flags;
577 
578         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
579                 goto out;
580 
581         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
582         if (flag & AT_EMPTY_PATH)
583                 lookup_flags |= LOOKUP_EMPTY;
584         error = user_path_at(dfd, filename, lookup_flags, &path);
585         if (error)
586                 goto out;
587         error = mnt_want_write(path.mnt);
588         if (error)
589                 goto out_release;
590         error = chown_common(&path, user, group);
591         mnt_drop_write(path.mnt);
592 out_release:
593         path_put(&path);
594 out:
595         return error;
596 }
597 
598 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
599 {
600         struct path path;
601         int error;
602 
603         error = user_lpath(filename, &path);
604         if (error)
605                 goto out;
606         error = mnt_want_write(path.mnt);
607         if (error)
608                 goto out_release;
609         error = chown_common(&path, user, group);
610         mnt_drop_write(path.mnt);
611 out_release:
612         path_put(&path);
613 out:
614         return error;
615 }
616 
617 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
618 {
619         struct file * file;
620         int error = -EBADF;
621         struct dentry * dentry;
622 
623         file = fget(fd);
624         if (!file)
625                 goto out;
626 
627         error = mnt_want_write_file(file);
628         if (error)
629                 goto out_fput;
630         dentry = file->f_path.dentry;
631         audit_inode(NULL, dentry);
632         error = chown_common(&file->f_path, user, group);
633         mnt_drop_write(file->f_path.mnt);
634 out_fput:
635         fput(file);
636 out:
637         return error;
638 }
639 
640 /*
641  * You have to be very careful that these write
642  * counts get cleaned up in error cases and
643  * upon __fput().  This should probably never
644  * be called outside of __dentry_open().
645  */
646 static inline int __get_file_write_access(struct inode *inode,
647                                           struct vfsmount *mnt)
648 {
649         int error;
650         error = get_write_access(inode);
651         if (error)
652                 return error;
653         /*
654          * Do not take mount writer counts on
655          * special files since no writes to
656          * the mount itself will occur.
657          */
658         if (!special_file(inode->i_mode)) {
659                 /*
660                  * Balanced in __fput()
661                  */
662                 error = mnt_want_write(mnt);
663                 if (error)
664                         put_write_access(inode);
665         }
666         return error;
667 }
668 
669 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
670                                         struct file *f,
671                                         int (*open)(struct inode *, struct file *),
672                                         const struct cred *cred)
673 {
674         static const struct file_operations empty_fops = {};
675         struct inode *inode;
676         int error;
677 
678         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
679                                 FMODE_PREAD | FMODE_PWRITE;
680 
681         if (unlikely(f->f_flags & O_PATH))
682                 f->f_mode = FMODE_PATH;
683 
684         inode = dentry->d_inode;
685         if (f->f_mode & FMODE_WRITE) {
686                 error = __get_file_write_access(inode, mnt);
687                 if (error)
688                         goto cleanup_file;
689                 if (!special_file(inode->i_mode))
690                         file_take_write(f);
691         }
692 
693         f->f_mapping = inode->i_mapping;
694         f->f_path.dentry = dentry;
695         f->f_path.mnt = mnt;
696         f->f_pos = 0;
697         file_sb_list_add(f, inode->i_sb);
698 
699         if (unlikely(f->f_mode & FMODE_PATH)) {
700                 f->f_op = &empty_fops;
701                 return f;
702         }
703 
704         f->f_op = fops_get(inode->i_fop);
705 
706         error = security_dentry_open(f, cred);
707         if (error)
708                 goto cleanup_all;
709 
710         if (!open && f->f_op)
711                 open = f->f_op->open;
712         if (open) {
713                 error = open(inode, f);
714                 if (error)
715                         goto cleanup_all;
716         }
717         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
718                 i_readcount_inc(inode);
719 
720         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
721 
722         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
723 
724         /* NB: we're sure to have correct a_ops only after f_op->open */
725         if (f->f_flags & O_DIRECT) {
726                 if (!f->f_mapping->a_ops ||
727                     ((!f->f_mapping->a_ops->direct_IO) &&
728                     (!f->f_mapping->a_ops->get_xip_mem))) {
729                         fput(f);
730                         f = ERR_PTR(-EINVAL);
731                 }
732         }
733 
734         return f;
735 
736 cleanup_all:
737         fops_put(f->f_op);
738         if (f->f_mode & FMODE_WRITE) {
739                 put_write_access(inode);
740                 if (!special_file(inode->i_mode)) {
741                         /*
742                          * We don't consider this a real
743                          * mnt_want/drop_write() pair
744                          * because it all happenend right
745                          * here, so just reset the state.
746                          */
747                         file_reset_write(f);
748                         mnt_drop_write(mnt);
749                 }
750         }
751         file_sb_list_del(f);
752         f->f_path.dentry = NULL;
753         f->f_path.mnt = NULL;
754 cleanup_file:
755         put_filp(f);
756         dput(dentry);
757         mntput(mnt);
758         return ERR_PTR(error);
759 }
760 
761 /**
762  * lookup_instantiate_filp - instantiates the open intent filp
763  * @nd: pointer to nameidata
764  * @dentry: pointer to dentry
765  * @open: open callback
766  *
767  * Helper for filesystems that want to use lookup open intents and pass back
768  * a fully instantiated struct file to the caller.
769  * This function is meant to be called from within a filesystem's
770  * lookup method.
771  * Beware of calling it for non-regular files! Those ->open methods might block
772  * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
773  * leading to a deadlock, as nobody can open that fifo anymore, because
774  * another process to open fifo will block on locked parent when doing lookup).
775  * Note that in case of error, nd->intent.open.file is destroyed, but the
776  * path information remains valid.
777  * If the open callback is set to NULL, then the standard f_op->open()
778  * filesystem callback is substituted.
779  */
780 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
781                 int (*open)(struct inode *, struct file *))
782 {
783         const struct cred *cred = current_cred();
784 
785         if (IS_ERR(nd->intent.open.file))
786                 goto out;
787         if (IS_ERR(dentry))
788                 goto out_err;
789         nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
790                                              nd->intent.open.file,
791                                              open, cred);
792 out:
793         return nd->intent.open.file;
794 out_err:
795         release_open_intent(nd);
796         nd->intent.open.file = (struct file *)dentry;
797         goto out;
798 }
799 EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
800 
801 /**
802  * nameidata_to_filp - convert a nameidata to an open filp.
803  * @nd: pointer to nameidata
804  * @flags: open flags
805  *
806  * Note that this function destroys the original nameidata
807  */
808 struct file *nameidata_to_filp(struct nameidata *nd)
809 {
810         const struct cred *cred = current_cred();
811         struct file *filp;
812 
813         /* Pick up the filp from the open intent */
814         filp = nd->intent.open.file;
815         nd->intent.open.file = NULL;
816 
817         /* Has the filesystem initialised the file for us? */
818         if (filp->f_path.dentry == NULL) {
819                 path_get(&nd->path);
820                 filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
821                                      NULL, cred);
822         }
823         return filp;
824 }
825 
826 /*
827  * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
828  * error.
829  */
830 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
831                          const struct cred *cred)
832 {
833         int error;
834         struct file *f;
835 
836         validate_creds(cred);
837 
838         /* We must always pass in a valid mount pointer. */
839         BUG_ON(!mnt);
840 
841         error = -ENFILE;
842         f = get_empty_filp();
843         if (f == NULL) {
844                 dput(dentry);
845                 mntput(mnt);
846                 return ERR_PTR(error);
847         }
848 
849         f->f_flags = flags;
850         return __dentry_open(dentry, mnt, f, NULL, cred);
851 }
852 EXPORT_SYMBOL(dentry_open);
853 
854 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
855 {
856         struct fdtable *fdt = files_fdtable(files);
857         __FD_CLR(fd, fdt->open_fds);
858         if (fd < files->next_fd)
859                 files->next_fd = fd;
860 }
861 
862 void put_unused_fd(unsigned int fd)
863 {
864         struct files_struct *files = current->files;
865         spin_lock(&files->file_lock);
866         __put_unused_fd(files, fd);
867         spin_unlock(&files->file_lock);
868 }
869 
870 EXPORT_SYMBOL(put_unused_fd);
871 
872 /*
873  * Install a file pointer in the fd array.
874  *
875  * The VFS is full of places where we drop the files lock between
876  * setting the open_fds bitmap and installing the file in the file
877  * array.  At any such point, we are vulnerable to a dup2() race
878  * installing a file in the array before us.  We need to detect this and
879  * fput() the struct file we are about to overwrite in this case.
880  *
881  * It should never happen - if we allow dup2() do it, _really_ bad things
882  * will follow.
883  */
884 
885 void fd_install(unsigned int fd, struct file *file)
886 {
887         struct files_struct *files = current->files;
888         struct fdtable *fdt;
889         spin_lock(&files->file_lock);
890         fdt = files_fdtable(files);
891         BUG_ON(fdt->fd[fd] != NULL);
892         rcu_assign_pointer(fdt->fd[fd], file);
893         spin_unlock(&files->file_lock);
894 }
895 
896 EXPORT_SYMBOL(fd_install);
897 
898 static inline int build_open_flags(int flags, int mode, struct open_flags *op)
899 {
900         int lookup_flags = 0;
901         int acc_mode;
902 
903         if (!(flags & O_CREAT))
904                 mode = 0;
905         op->mode = mode;
906 
907         /* Must never be set by userspace */
908         flags &= ~FMODE_NONOTIFY;
909 
910         /*
911          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
912          * check for O_DSYNC if the need any syncing at all we enforce it's
913          * always set instead of having to deal with possibly weird behaviour
914          * for malicious applications setting only __O_SYNC.
915          */
916         if (flags & __O_SYNC)
917                 flags |= O_DSYNC;
918 
919         /*
920          * If we have O_PATH in the open flag. Then we
921          * cannot have anything other than the below set of flags
922          */
923         if (flags & O_PATH) {
924                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
925                 acc_mode = 0;
926         } else {
927                 acc_mode = MAY_OPEN | ACC_MODE(flags);
928         }
929 
930         op->open_flag = flags;
931 
932         /* O_TRUNC implies we need access checks for write permissions */
933         if (flags & O_TRUNC)
934                 acc_mode |= MAY_WRITE;
935 
936         /* Allow the LSM permission hook to distinguish append
937            access from general write access. */
938         if (flags & O_APPEND)
939                 acc_mode |= MAY_APPEND;
940 
941         op->acc_mode = acc_mode;
942 
943         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
944 
945         if (flags & O_CREAT) {
946                 op->intent |= LOOKUP_CREATE;
947                 if (flags & O_EXCL)
948                         op->intent |= LOOKUP_EXCL;
949         }
950 
951         if (flags & O_DIRECTORY)
952                 lookup_flags |= LOOKUP_DIRECTORY;
953         if (!(flags & O_NOFOLLOW))
954                 lookup_flags |= LOOKUP_FOLLOW;
955         return lookup_flags;
956 }
957 
958 /**
959  * filp_open - open file and return file pointer
960  *
961  * @filename:   path to open
962  * @flags:      open flags as per the open(2) second argument
963  * @mode:       mode for the new file if O_CREAT is set, else ignored
964  *
965  * This is the helper to open a file from kernelspace if you really
966  * have to.  But in generally you should not do this, so please move
967  * along, nothing to see here..
968  */
969 struct file *filp_open(const char *filename, int flags, int mode)
970 {
971         struct open_flags op;
972         int lookup = build_open_flags(flags, mode, &op);
973         return do_filp_open(AT_FDCWD, filename, &op, lookup);
974 }
975 EXPORT_SYMBOL(filp_open);
976 
977 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
978                             const char *filename, int flags)
979 {
980         struct open_flags op;
981         int lookup = build_open_flags(flags, 0, &op);
982         if (flags & O_CREAT)
983                 return ERR_PTR(-EINVAL);
984         if (!filename && (flags & O_DIRECTORY))
985                 if (!dentry->d_inode->i_op->lookup)
986                         return ERR_PTR(-ENOTDIR);
987         return do_file_open_root(dentry, mnt, filename, &op, lookup);
988 }
989 EXPORT_SYMBOL(file_open_root);
990 
991 long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
992 {
993         struct open_flags op;
994         int lookup = build_open_flags(flags, mode, &op);
995         char *tmp = getname(filename);
996         int fd = PTR_ERR(tmp);
997 
998         if (!IS_ERR(tmp)) {
999                 fd = get_unused_fd_flags(flags);
1000                 if (fd >= 0) {
1001                         struct file *f = do_filp_open(dfd, tmp, &op, lookup);
1002                         if (IS_ERR(f)) {
1003                                 put_unused_fd(fd);
1004                                 fd = PTR_ERR(f);
1005                         } else {
1006                                 fsnotify_open(f);
1007                                 fd_install(fd, f);
1008                         }
1009                 }
1010                 putname(tmp);
1011         }
1012         return fd;
1013 }
1014 
1015 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode)
1016 {
1017         long ret;
1018 
1019         if (force_o_largefile())
1020                 flags |= O_LARGEFILE;
1021 
1022         ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1023         /* avoid REGPARM breakage on x86: */
1024         asmlinkage_protect(3, ret, filename, flags, mode);
1025         return ret;
1026 }
1027 
1028 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1029                 int, mode)
1030 {
1031         long ret;
1032 
1033         if (force_o_largefile())
1034                 flags |= O_LARGEFILE;
1035 
1036         ret = do_sys_open(dfd, filename, flags, mode);
1037         /* avoid REGPARM breakage on x86: */
1038         asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1039         return ret;
1040 }
1041 
1042 #ifndef __alpha__
1043 
1044 /*
1045  * For backward compatibility?  Maybe this should be moved
1046  * into arch/i386 instead?
1047  */
1048 SYSCALL_DEFINE2(creat, const char __user *, pathname, int, mode)
1049 {
1050         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1051 }
1052 
1053 #endif
1054 
1055 /*
1056  * "id" is the POSIX thread ID. We use the
1057  * files pointer for this..
1058  */
1059 int filp_close(struct file *filp, fl_owner_t id)
1060 {
1061         int retval = 0;
1062 
1063         if (!file_count(filp)) {
1064                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1065                 return 0;
1066         }
1067 
1068         if (filp->f_op && filp->f_op->flush)
1069                 retval = filp->f_op->flush(filp, id);
1070 
1071         if (likely(!(filp->f_mode & FMODE_PATH))) {
1072                 dnotify_flush(filp, id);
1073                 locks_remove_posix(filp, id);
1074         }
1075         fput(filp);
1076         return retval;
1077 }
1078 
1079 EXPORT_SYMBOL(filp_close);
1080 
1081 /*
1082  * Careful here! We test whether the file pointer is NULL before
1083  * releasing the fd. This ensures that one clone task can't release
1084  * an fd while another clone is opening it.
1085  */
1086 SYSCALL_DEFINE1(close, unsigned int, fd)
1087 {
1088         struct file * filp;
1089         struct files_struct *files = current->files;
1090         struct fdtable *fdt;
1091         int retval;
1092 
1093         spin_lock(&files->file_lock);
1094         fdt = files_fdtable(files);
1095         if (fd >= fdt->max_fds)
1096                 goto out_unlock;
1097         filp = fdt->fd[fd];
1098         if (!filp)
1099                 goto out_unlock;
1100         rcu_assign_pointer(fdt->fd[fd], NULL);
1101         FD_CLR(fd, fdt->close_on_exec);
1102         __put_unused_fd(files, fd);
1103         spin_unlock(&files->file_lock);
1104         retval = filp_close(filp, files);
1105 
1106         /* can't restart close syscall because file table entry was cleared */
1107         if (unlikely(retval == -ERESTARTSYS ||
1108                      retval == -ERESTARTNOINTR ||
1109                      retval == -ERESTARTNOHAND ||
1110                      retval == -ERESTART_RESTARTBLOCK))
1111                 retval = -EINTR;
1112 
1113         return retval;
1114 
1115 out_unlock:
1116         spin_unlock(&files->file_lock);
1117         return -EBADF;
1118 }
1119 EXPORT_SYMBOL(sys_close);
1120 
1121 /*
1122  * This routine simulates a hangup on the tty, to arrange that users
1123  * are given clean terminals at login time.
1124  */
1125 SYSCALL_DEFINE0(vhangup)
1126 {
1127         if (capable(CAP_SYS_TTY_CONFIG)) {
1128                 tty_vhangup_self();
1129                 return 0;
1130         }
1131         return -EPERM;
1132 }
1133 
1134 /*
1135  * Called when an inode is about to be open.
1136  * We use this to disallow opening large files on 32bit systems if
1137  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1138  * on this flag in sys_open.
1139  */
1140 int generic_file_open(struct inode * inode, struct file * filp)
1141 {
1142         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1143                 return -EOVERFLOW;
1144         return 0;
1145 }
1146 
1147 EXPORT_SYMBOL(generic_file_open);
1148 
1149 /*
1150  * This is used by subsystems that don't want seekable
1151  * file descriptors. The function is not supposed to ever fail, the only
1152  * reason it returns an 'int' and not 'void' is so that it can be plugged
1153  * directly into file_operations structure.
1154  */
1155 int nonseekable_open(struct inode *inode, struct file *filp)
1156 {
1157         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1158         return 0;
1159 }
1160 
1161 EXPORT_SYMBOL(nonseekable_open);
1162 

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