Root/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
36int 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
64static 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
118put_write_and_out:
119    put_write_access(inode);
120mnt_drop_write_and_out:
121    mnt_drop_write(path.mnt);
122dput_and_out:
123    path_put(&path);
124out:
125    return error;
126}
127
128SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
129{
130    return do_sys_truncate(path, length);
131}
132
133static 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);
172out_putf:
173    fput(file);
174out:
175    return error;
176}
177
178SYSCALL_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
188SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
189{
190    return do_sys_truncate(path, length);
191}
192#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
193asmlinkage long SyS_truncate64(long path, loff_t length)
194{
195    return SYSC_truncate64((const char __user *) path, length);
196}
197SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
198#endif
199
200SYSCALL_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
208asmlinkage long SyS_ftruncate64(long fd, loff_t length)
209{
210    return SYSC_ftruncate64((unsigned int) fd, length);
211}
212SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
213#endif
214#endif /* BITS_PER_LONG == 32 */
215
216
217int 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
272SYSCALL_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
287asmlinkage 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}
291SYSCALL_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 */
299SYSCALL_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
361out_path_release:
362    path_put(&path);
363out:
364    revert_creds(old_cred);
365    put_cred(override_cred);
366    return res;
367}
368
369SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
370{
371    return sys_faccessat(AT_FDCWD, filename, mode);
372}
373
374SYSCALL_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
389dput_and_out:
390    path_put(&path);
391out:
392    return error;
393}
394
395SYSCALL_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);
415out_putf:
416    fput(file);
417out:
418    return error;
419}
420
421SYSCALL_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;
443dput_and_out:
444    path_put(&path);
445out:
446    return error;
447}
448
449SYSCALL_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);
478out_unlock:
479    mutex_unlock(&inode->i_mutex);
480    mnt_drop_write(file->f_path.mnt);
481out_putf:
482    fput(file);
483out:
484    return err;
485}
486
487SYSCALL_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);
511out_unlock:
512    mutex_unlock(&inode->i_mutex);
513    mnt_drop_write(path.mnt);
514dput_and_out:
515    path_put(&path);
516out:
517    return error;
518}
519
520SYSCALL_DEFINE2(chmod, const char __user *, filename, mode_t, mode)
521{
522    return sys_fchmodat(AT_FDCWD, filename, mode);
523}
524
525static 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
552SYSCALL_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);
565out_release:
566    path_put(&path);
567out:
568    return error;
569}
570
571SYSCALL_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);
592out_release:
593    path_put(&path);
594out:
595    return error;
596}
597
598SYSCALL_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);
611out_release:
612    path_put(&path);
613out:
614    return error;
615}
616
617SYSCALL_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);
634out_fput:
635    fput(file);
636out:
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 */
646static 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
669static 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
736cleanup_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;
754cleanup_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 */
780struct 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);
792out:
793    return nd->intent.open.file;
794out_err:
795    release_open_intent(nd);
796    nd->intent.open.file = (struct file *)dentry;
797    goto out;
798}
799EXPORT_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 */
808struct 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 */
830struct 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}
852EXPORT_SYMBOL(dentry_open);
853
854static 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
862void 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
870EXPORT_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
885void 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
896EXPORT_SYMBOL(fd_install);
897
898static 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 */
969struct 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}
975EXPORT_SYMBOL(filp_open);
976
977struct 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}
989EXPORT_SYMBOL(file_open_root);
990
991long 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
1015SYSCALL_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
1028SYSCALL_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 */
1048SYSCALL_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 */
1059int 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
1079EXPORT_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 */
1086SYSCALL_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
1115out_unlock:
1116    spin_unlock(&files->file_lock);
1117    return -EBADF;
1118}
1119EXPORT_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 */
1125SYSCALL_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 */
1140int 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
1147EXPORT_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 */
1155int nonseekable_open(struct inode *inode, struct file *filp)
1156{
1157    filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1158    return 0;
1159}
1160
1161EXPORT_SYMBOL(nonseekable_open);
1162

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