Root/fs/open.c

Source at commit 9845c1745d3d531a5b9544f5322c62bfb4d4e9bc created 1 year 3 months ago.
By Xiangfu, rtc: jz4740 fix hwclock give time out
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
449static int chmod_common(struct path *path, umode_t mode)
450{
451    struct inode *inode = path->dentry->d_inode;
452    struct iattr newattrs;
453    int error;
454
455    error = mnt_want_write(path->mnt);
456    if (error)
457        return error;
458    mutex_lock(&inode->i_mutex);
459    error = security_path_chmod(path->dentry, path->mnt, mode);
460    if (error)
461        goto out_unlock;
462    newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
463    newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
464    error = notify_change(path->dentry, &newattrs);
465out_unlock:
466    mutex_unlock(&inode->i_mutex);
467    mnt_drop_write(path->mnt);
468    return error;
469}
470
471SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode)
472{
473    struct file * file;
474    int err = -EBADF;
475
476    file = fget(fd);
477    if (file) {
478        audit_inode(NULL, file->f_path.dentry);
479        err = chmod_common(&file->f_path, mode);
480        fput(file);
481    }
482    return err;
483}
484
485SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, mode_t, mode)
486{
487    struct path path;
488    int error;
489
490    error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
491    if (!error) {
492        error = chmod_common(&path, mode);
493        path_put(&path);
494    }
495    return error;
496}
497
498SYSCALL_DEFINE2(chmod, const char __user *, filename, mode_t, mode)
499{
500    return sys_fchmodat(AT_FDCWD, filename, mode);
501}
502
503static int chown_common(struct path *path, uid_t user, gid_t group)
504{
505    struct inode *inode = path->dentry->d_inode;
506    int error;
507    struct iattr newattrs;
508
509    newattrs.ia_valid = ATTR_CTIME;
510    if (user != (uid_t) -1) {
511        newattrs.ia_valid |= ATTR_UID;
512        newattrs.ia_uid = user;
513    }
514    if (group != (gid_t) -1) {
515        newattrs.ia_valid |= ATTR_GID;
516        newattrs.ia_gid = group;
517    }
518    if (!S_ISDIR(inode->i_mode))
519        newattrs.ia_valid |=
520            ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
521    mutex_lock(&inode->i_mutex);
522    error = security_path_chown(path, user, group);
523    if (!error)
524        error = notify_change(path->dentry, &newattrs);
525    mutex_unlock(&inode->i_mutex);
526
527    return error;
528}
529
530SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
531{
532    struct path path;
533    int error;
534
535    error = user_path(filename, &path);
536    if (error)
537        goto out;
538    error = mnt_want_write(path.mnt);
539    if (error)
540        goto out_release;
541    error = chown_common(&path, user, group);
542    mnt_drop_write(path.mnt);
543out_release:
544    path_put(&path);
545out:
546    return error;
547}
548
549SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
550        gid_t, group, int, flag)
551{
552    struct path path;
553    int error = -EINVAL;
554    int lookup_flags;
555
556    if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
557        goto out;
558
559    lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
560    if (flag & AT_EMPTY_PATH)
561        lookup_flags |= LOOKUP_EMPTY;
562    error = user_path_at(dfd, filename, lookup_flags, &path);
563    if (error)
564        goto out;
565    error = mnt_want_write(path.mnt);
566    if (error)
567        goto out_release;
568    error = chown_common(&path, user, group);
569    mnt_drop_write(path.mnt);
570out_release:
571    path_put(&path);
572out:
573    return error;
574}
575
576SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
577{
578    struct path path;
579    int error;
580
581    error = user_lpath(filename, &path);
582    if (error)
583        goto out;
584    error = mnt_want_write(path.mnt);
585    if (error)
586        goto out_release;
587    error = chown_common(&path, user, group);
588    mnt_drop_write(path.mnt);
589out_release:
590    path_put(&path);
591out:
592    return error;
593}
594
595SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
596{
597    struct file * file;
598    int error = -EBADF;
599    struct dentry * dentry;
600
601    file = fget(fd);
602    if (!file)
603        goto out;
604
605    error = mnt_want_write_file(file);
606    if (error)
607        goto out_fput;
608    dentry = file->f_path.dentry;
609    audit_inode(NULL, dentry);
610    error = chown_common(&file->f_path, user, group);
611    mnt_drop_write(file->f_path.mnt);
612out_fput:
613    fput(file);
614out:
615    return error;
616}
617
618/*
619 * You have to be very careful that these write
620 * counts get cleaned up in error cases and
621 * upon __fput(). This should probably never
622 * be called outside of __dentry_open().
623 */
624static inline int __get_file_write_access(struct inode *inode,
625                      struct vfsmount *mnt)
626{
627    int error;
628    error = get_write_access(inode);
629    if (error)
630        return error;
631    /*
632     * Do not take mount writer counts on
633     * special files since no writes to
634     * the mount itself will occur.
635     */
636    if (!special_file(inode->i_mode)) {
637        /*
638         * Balanced in __fput()
639         */
640        error = mnt_want_write(mnt);
641        if (error)
642            put_write_access(inode);
643    }
644    return error;
645}
646
647static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
648                    struct file *f,
649                    int (*open)(struct inode *, struct file *),
650                    const struct cred *cred)
651{
652    static const struct file_operations empty_fops = {};
653    struct inode *inode;
654    int error;
655
656    f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
657                FMODE_PREAD | FMODE_PWRITE;
658
659    if (unlikely(f->f_flags & O_PATH))
660        f->f_mode = FMODE_PATH;
661
662    inode = dentry->d_inode;
663    if (f->f_mode & FMODE_WRITE) {
664        error = __get_file_write_access(inode, mnt);
665        if (error)
666            goto cleanup_file;
667        if (!special_file(inode->i_mode))
668            file_take_write(f);
669    }
670
671    f->f_mapping = inode->i_mapping;
672    f->f_path.dentry = dentry;
673    f->f_path.mnt = mnt;
674    f->f_pos = 0;
675    file_sb_list_add(f, inode->i_sb);
676
677    if (unlikely(f->f_mode & FMODE_PATH)) {
678        f->f_op = &empty_fops;
679        return f;
680    }
681
682    f->f_op = fops_get(inode->i_fop);
683
684    error = security_dentry_open(f, cred);
685    if (error)
686        goto cleanup_all;
687
688    error = break_lease(inode, f->f_flags);
689    if (error)
690        goto cleanup_all;
691
692    if (!open && f->f_op)
693        open = f->f_op->open;
694    if (open) {
695        error = open(inode, f);
696        if (error)
697            goto cleanup_all;
698    }
699    if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
700        i_readcount_inc(inode);
701
702    f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
703
704    file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
705
706    /* NB: we're sure to have correct a_ops only after f_op->open */
707    if (f->f_flags & O_DIRECT) {
708        if (!f->f_mapping->a_ops ||
709            ((!f->f_mapping->a_ops->direct_IO) &&
710            (!f->f_mapping->a_ops->get_xip_mem))) {
711            fput(f);
712            f = ERR_PTR(-EINVAL);
713        }
714    }
715
716    return f;
717
718cleanup_all:
719    fops_put(f->f_op);
720    if (f->f_mode & FMODE_WRITE) {
721        put_write_access(inode);
722        if (!special_file(inode->i_mode)) {
723            /*
724             * We don't consider this a real
725             * mnt_want/drop_write() pair
726             * because it all happenend right
727             * here, so just reset the state.
728             */
729            file_reset_write(f);
730            mnt_drop_write(mnt);
731        }
732    }
733    file_sb_list_del(f);
734    f->f_path.dentry = NULL;
735    f->f_path.mnt = NULL;
736cleanup_file:
737    put_filp(f);
738    dput(dentry);
739    mntput(mnt);
740    return ERR_PTR(error);
741}
742
743/**
744 * lookup_instantiate_filp - instantiates the open intent filp
745 * @nd: pointer to nameidata
746 * @dentry: pointer to dentry
747 * @open: open callback
748 *
749 * Helper for filesystems that want to use lookup open intents and pass back
750 * a fully instantiated struct file to the caller.
751 * This function is meant to be called from within a filesystem's
752 * lookup method.
753 * Beware of calling it for non-regular files! Those ->open methods might block
754 * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
755 * leading to a deadlock, as nobody can open that fifo anymore, because
756 * another process to open fifo will block on locked parent when doing lookup).
757 * Note that in case of error, nd->intent.open.file is destroyed, but the
758 * path information remains valid.
759 * If the open callback is set to NULL, then the standard f_op->open()
760 * filesystem callback is substituted.
761 */
762struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
763        int (*open)(struct inode *, struct file *))
764{
765    const struct cred *cred = current_cred();
766
767    if (IS_ERR(nd->intent.open.file))
768        goto out;
769    if (IS_ERR(dentry))
770        goto out_err;
771    nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
772                         nd->intent.open.file,
773                         open, cred);
774out:
775    return nd->intent.open.file;
776out_err:
777    release_open_intent(nd);
778    nd->intent.open.file = ERR_CAST(dentry);
779    goto out;
780}
781EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
782
783/**
784 * nameidata_to_filp - convert a nameidata to an open filp.
785 * @nd: pointer to nameidata
786 * @flags: open flags
787 *
788 * Note that this function destroys the original nameidata
789 */
790struct file *nameidata_to_filp(struct nameidata *nd)
791{
792    const struct cred *cred = current_cred();
793    struct file *filp;
794
795    /* Pick up the filp from the open intent */
796    filp = nd->intent.open.file;
797    nd->intent.open.file = NULL;
798
799    /* Has the filesystem initialised the file for us? */
800    if (filp->f_path.dentry == NULL) {
801        path_get(&nd->path);
802        filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
803                     NULL, cred);
804    }
805    return filp;
806}
807
808/*
809 * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
810 * error.
811 */
812struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
813             const struct cred *cred)
814{
815    int error;
816    struct file *f;
817
818    validate_creds(cred);
819
820    /* We must always pass in a valid mount pointer. */
821    BUG_ON(!mnt);
822
823    error = -ENFILE;
824    f = get_empty_filp();
825    if (f == NULL) {
826        dput(dentry);
827        mntput(mnt);
828        return ERR_PTR(error);
829    }
830
831    f->f_flags = flags;
832    return __dentry_open(dentry, mnt, f, NULL, cred);
833}
834EXPORT_SYMBOL(dentry_open);
835
836static void __put_unused_fd(struct files_struct *files, unsigned int fd)
837{
838    struct fdtable *fdt = files_fdtable(files);
839    __FD_CLR(fd, fdt->open_fds);
840    if (fd < files->next_fd)
841        files->next_fd = fd;
842}
843
844void put_unused_fd(unsigned int fd)
845{
846    struct files_struct *files = current->files;
847    spin_lock(&files->file_lock);
848    __put_unused_fd(files, fd);
849    spin_unlock(&files->file_lock);
850}
851
852EXPORT_SYMBOL(put_unused_fd);
853
854/*
855 * Install a file pointer in the fd array.
856 *
857 * The VFS is full of places where we drop the files lock between
858 * setting the open_fds bitmap and installing the file in the file
859 * array. At any such point, we are vulnerable to a dup2() race
860 * installing a file in the array before us. We need to detect this and
861 * fput() the struct file we are about to overwrite in this case.
862 *
863 * It should never happen - if we allow dup2() do it, _really_ bad things
864 * will follow.
865 */
866
867void fd_install(unsigned int fd, struct file *file)
868{
869    struct files_struct *files = current->files;
870    struct fdtable *fdt;
871    spin_lock(&files->file_lock);
872    fdt = files_fdtable(files);
873    BUG_ON(fdt->fd[fd] != NULL);
874    rcu_assign_pointer(fdt->fd[fd], file);
875    spin_unlock(&files->file_lock);
876}
877
878EXPORT_SYMBOL(fd_install);
879
880static inline int build_open_flags(int flags, int mode, struct open_flags *op)
881{
882    int lookup_flags = 0;
883    int acc_mode;
884
885    if (!(flags & O_CREAT))
886        mode = 0;
887    op->mode = mode;
888
889    /* Must never be set by userspace */
890    flags &= ~FMODE_NONOTIFY;
891
892    /*
893     * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
894     * check for O_DSYNC if the need any syncing at all we enforce it's
895     * always set instead of having to deal with possibly weird behaviour
896     * for malicious applications setting only __O_SYNC.
897     */
898    if (flags & __O_SYNC)
899        flags |= O_DSYNC;
900
901    /*
902     * If we have O_PATH in the open flag. Then we
903     * cannot have anything other than the below set of flags
904     */
905    if (flags & O_PATH) {
906        flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
907        acc_mode = 0;
908    } else {
909        acc_mode = MAY_OPEN | ACC_MODE(flags);
910    }
911
912    op->open_flag = flags;
913
914    /* O_TRUNC implies we need access checks for write permissions */
915    if (flags & O_TRUNC)
916        acc_mode |= MAY_WRITE;
917
918    /* Allow the LSM permission hook to distinguish append
919       access from general write access. */
920    if (flags & O_APPEND)
921        acc_mode |= MAY_APPEND;
922
923    op->acc_mode = acc_mode;
924
925    op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
926
927    if (flags & O_CREAT) {
928        op->intent |= LOOKUP_CREATE;
929        if (flags & O_EXCL)
930            op->intent |= LOOKUP_EXCL;
931    }
932
933    if (flags & O_DIRECTORY)
934        lookup_flags |= LOOKUP_DIRECTORY;
935    if (!(flags & O_NOFOLLOW))
936        lookup_flags |= LOOKUP_FOLLOW;
937    return lookup_flags;
938}
939
940/**
941 * filp_open - open file and return file pointer
942 *
943 * @filename: path to open
944 * @flags: open flags as per the open(2) second argument
945 * @mode: mode for the new file if O_CREAT is set, else ignored
946 *
947 * This is the helper to open a file from kernelspace if you really
948 * have to. But in generally you should not do this, so please move
949 * along, nothing to see here..
950 */
951struct file *filp_open(const char *filename, int flags, int mode)
952{
953    struct open_flags op;
954    int lookup = build_open_flags(flags, mode, &op);
955    return do_filp_open(AT_FDCWD, filename, &op, lookup);
956}
957EXPORT_SYMBOL(filp_open);
958
959struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
960                const char *filename, int flags)
961{
962    struct open_flags op;
963    int lookup = build_open_flags(flags, 0, &op);
964    if (flags & O_CREAT)
965        return ERR_PTR(-EINVAL);
966    if (!filename && (flags & O_DIRECTORY))
967        if (!dentry->d_inode->i_op->lookup)
968            return ERR_PTR(-ENOTDIR);
969    return do_file_open_root(dentry, mnt, filename, &op, lookup);
970}
971EXPORT_SYMBOL(file_open_root);
972
973long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
974{
975    struct open_flags op;
976    int lookup = build_open_flags(flags, mode, &op);
977    char *tmp = getname(filename);
978    int fd = PTR_ERR(tmp);
979
980    if (!IS_ERR(tmp)) {
981        fd = get_unused_fd_flags(flags);
982        if (fd >= 0) {
983            struct file *f = do_filp_open(dfd, tmp, &op, lookup);
984            if (IS_ERR(f)) {
985                put_unused_fd(fd);
986                fd = PTR_ERR(f);
987            } else {
988                fsnotify_open(f);
989                fd_install(fd, f);
990            }
991        }
992        putname(tmp);
993    }
994    return fd;
995}
996
997SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode)
998{
999    long ret;
1000
1001    if (force_o_largefile())
1002        flags |= O_LARGEFILE;
1003
1004    ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1005    /* avoid REGPARM breakage on x86: */
1006    asmlinkage_protect(3, ret, filename, flags, mode);
1007    return ret;
1008}
1009
1010SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1011        int, mode)
1012{
1013    long ret;
1014
1015    if (force_o_largefile())
1016        flags |= O_LARGEFILE;
1017
1018    ret = do_sys_open(dfd, filename, flags, mode);
1019    /* avoid REGPARM breakage on x86: */
1020    asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1021    return ret;
1022}
1023
1024#ifndef __alpha__
1025
1026/*
1027 * For backward compatibility? Maybe this should be moved
1028 * into arch/i386 instead?
1029 */
1030SYSCALL_DEFINE2(creat, const char __user *, pathname, int, mode)
1031{
1032    return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1033}
1034
1035#endif
1036
1037/*
1038 * "id" is the POSIX thread ID. We use the
1039 * files pointer for this..
1040 */
1041int filp_close(struct file *filp, fl_owner_t id)
1042{
1043    int retval = 0;
1044
1045    if (!file_count(filp)) {
1046        printk(KERN_ERR "VFS: Close: file count is 0\n");
1047        return 0;
1048    }
1049
1050    if (filp->f_op && filp->f_op->flush)
1051        retval = filp->f_op->flush(filp, id);
1052
1053    if (likely(!(filp->f_mode & FMODE_PATH))) {
1054        dnotify_flush(filp, id);
1055        locks_remove_posix(filp, id);
1056    }
1057    fput(filp);
1058    return retval;
1059}
1060
1061EXPORT_SYMBOL(filp_close);
1062
1063/*
1064 * Careful here! We test whether the file pointer is NULL before
1065 * releasing the fd. This ensures that one clone task can't release
1066 * an fd while another clone is opening it.
1067 */
1068SYSCALL_DEFINE1(close, unsigned int, fd)
1069{
1070    struct file * filp;
1071    struct files_struct *files = current->files;
1072    struct fdtable *fdt;
1073    int retval;
1074
1075    spin_lock(&files->file_lock);
1076    fdt = files_fdtable(files);
1077    if (fd >= fdt->max_fds)
1078        goto out_unlock;
1079    filp = fdt->fd[fd];
1080    if (!filp)
1081        goto out_unlock;
1082    rcu_assign_pointer(fdt->fd[fd], NULL);
1083    FD_CLR(fd, fdt->close_on_exec);
1084    __put_unused_fd(files, fd);
1085    spin_unlock(&files->file_lock);
1086    retval = filp_close(filp, files);
1087
1088    /* can't restart close syscall because file table entry was cleared */
1089    if (unlikely(retval == -ERESTARTSYS ||
1090             retval == -ERESTARTNOINTR ||
1091             retval == -ERESTARTNOHAND ||
1092             retval == -ERESTART_RESTARTBLOCK))
1093        retval = -EINTR;
1094
1095    return retval;
1096
1097out_unlock:
1098    spin_unlock(&files->file_lock);
1099    return -EBADF;
1100}
1101EXPORT_SYMBOL(sys_close);
1102
1103/*
1104 * This routine simulates a hangup on the tty, to arrange that users
1105 * are given clean terminals at login time.
1106 */
1107SYSCALL_DEFINE0(vhangup)
1108{
1109    if (capable(CAP_SYS_TTY_CONFIG)) {
1110        tty_vhangup_self();
1111        return 0;
1112    }
1113    return -EPERM;
1114}
1115
1116/*
1117 * Called when an inode is about to be open.
1118 * We use this to disallow opening large files on 32bit systems if
1119 * the caller didn't specify O_LARGEFILE. On 64bit systems we force
1120 * on this flag in sys_open.
1121 */
1122int generic_file_open(struct inode * inode, struct file * filp)
1123{
1124    if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1125        return -EOVERFLOW;
1126    return 0;
1127}
1128
1129EXPORT_SYMBOL(generic_file_open);
1130
1131/*
1132 * This is used by subsystems that don't want seekable
1133 * file descriptors. The function is not supposed to ever fail, the only
1134 * reason it returns an 'int' and not 'void' is so that it can be plugged
1135 * directly into file_operations structure.
1136 */
1137int nonseekable_open(struct inode *inode, struct file *filp)
1138{
1139    filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1140    return 0;
1141}
1142
1143EXPORT_SYMBOL(nonseekable_open);
1144

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