Root/fs/xattr.c

Source at commit 9845c1745d3d531a5b9544f5322c62bfb4d4e9bc created 1 year 2 months ago.
By Xiangfu, rtc: jz4740 fix hwclock give time out
1/*
2  File: fs/xattr.c
3
4  Extended attribute handling.
5
6  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
7  Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
8  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
9 */
10#include <linux/fs.h>
11#include <linux/slab.h>
12#include <linux/file.h>
13#include <linux/xattr.h>
14#include <linux/mount.h>
15#include <linux/namei.h>
16#include <linux/security.h>
17#include <linux/evm.h>
18#include <linux/syscalls.h>
19#include <linux/module.h>
20#include <linux/fsnotify.h>
21#include <linux/audit.h>
22#include <asm/uaccess.h>
23
24
25/*
26 * Check permissions for extended attribute access. This is a bit complicated
27 * because different namespaces have very different rules.
28 */
29static int
30xattr_permission(struct inode *inode, const char *name, int mask)
31{
32    /*
33     * We can never set or remove an extended attribute on a read-only
34     * filesystem or on an immutable / append-only inode.
35     */
36    if (mask & MAY_WRITE) {
37        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
38            return -EPERM;
39    }
40
41    /*
42     * No restriction for security.* and system.* from the VFS. Decision
43     * on these is left to the underlying filesystem / security module.
44     */
45    if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
46        !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
47        return 0;
48
49    /*
50     * The trusted.* namespace can only be accessed by privileged users.
51     */
52    if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
53        if (!capable(CAP_SYS_ADMIN))
54            return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
55        return 0;
56    }
57
58    /*
59     * In the user.* namespace, only regular files and directories can have
60     * extended attributes. For sticky directories, only the owner and
61     * privileged users can write attributes.
62     */
63    if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
64        if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
65            return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
66        if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
67            (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
68            return -EPERM;
69    }
70
71    return inode_permission(inode, mask);
72}
73
74/**
75 * __vfs_setxattr_noperm - perform setxattr operation without performing
76 * permission checks.
77 *
78 * @dentry - object to perform setxattr on
79 * @name - xattr name to set
80 * @value - value to set @name to
81 * @size - size of @value
82 * @flags - flags to pass into filesystem operations
83 *
84 * returns the result of the internal setxattr or setsecurity operations.
85 *
86 * This function requires the caller to lock the inode's i_mutex before it
87 * is executed. It also assumes that the caller will make the appropriate
88 * permission checks.
89 */
90int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
91        const void *value, size_t size, int flags)
92{
93    struct inode *inode = dentry->d_inode;
94    int error = -EOPNOTSUPP;
95    int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
96                   XATTR_SECURITY_PREFIX_LEN);
97
98    if (issec)
99        inode->i_flags &= ~S_NOSEC;
100    if (inode->i_op->setxattr) {
101        error = inode->i_op->setxattr(dentry, name, value, size, flags);
102        if (!error) {
103            fsnotify_xattr(dentry);
104            security_inode_post_setxattr(dentry, name, value,
105                             size, flags);
106        }
107    } else if (issec) {
108        const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
109        error = security_inode_setsecurity(inode, suffix, value,
110                           size, flags);
111        if (!error)
112            fsnotify_xattr(dentry);
113    }
114
115    return error;
116}
117
118
119int
120vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
121        size_t size, int flags)
122{
123    struct inode *inode = dentry->d_inode;
124    int error;
125
126    error = xattr_permission(inode, name, MAY_WRITE);
127    if (error)
128        return error;
129
130    mutex_lock(&inode->i_mutex);
131    error = security_inode_setxattr(dentry, name, value, size, flags);
132    if (error)
133        goto out;
134
135    error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
136
137out:
138    mutex_unlock(&inode->i_mutex);
139    return error;
140}
141EXPORT_SYMBOL_GPL(vfs_setxattr);
142
143ssize_t
144xattr_getsecurity(struct inode *inode, const char *name, void *value,
145            size_t size)
146{
147    void *buffer = NULL;
148    ssize_t len;
149
150    if (!value || !size) {
151        len = security_inode_getsecurity(inode, name, &buffer, false);
152        goto out_noalloc;
153    }
154
155    len = security_inode_getsecurity(inode, name, &buffer, true);
156    if (len < 0)
157        return len;
158    if (size < len) {
159        len = -ERANGE;
160        goto out;
161    }
162    memcpy(value, buffer, len);
163out:
164    security_release_secctx(buffer, len);
165out_noalloc:
166    return len;
167}
168EXPORT_SYMBOL_GPL(xattr_getsecurity);
169
170/*
171 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
172 *
173 * Allocate memory, if not already allocated, or re-allocate correct size,
174 * before retrieving the extended attribute.
175 *
176 * Returns the result of alloc, if failed, or the getxattr operation.
177 */
178ssize_t
179vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
180           size_t xattr_size, gfp_t flags)
181{
182    struct inode *inode = dentry->d_inode;
183    char *value = *xattr_value;
184    int error;
185
186    error = xattr_permission(inode, name, MAY_READ);
187    if (error)
188        return error;
189
190    if (!inode->i_op->getxattr)
191        return -EOPNOTSUPP;
192
193    error = inode->i_op->getxattr(dentry, name, NULL, 0);
194    if (error < 0)
195        return error;
196
197    if (!value || (error > xattr_size)) {
198        value = krealloc(*xattr_value, error + 1, flags);
199        if (!value)
200            return -ENOMEM;
201        memset(value, 0, error + 1);
202    }
203
204    error = inode->i_op->getxattr(dentry, name, value, error);
205    *xattr_value = value;
206    return error;
207}
208
209/* Compare an extended attribute value with the given value */
210int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
211          const char *value, size_t size, gfp_t flags)
212{
213    char *xattr_value = NULL;
214    int rc;
215
216    rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
217    if (rc < 0)
218        return rc;
219
220    if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
221        rc = -EINVAL;
222    else
223        rc = 0;
224    kfree(xattr_value);
225    return rc;
226}
227
228ssize_t
229vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
230{
231    struct inode *inode = dentry->d_inode;
232    int error;
233
234    error = xattr_permission(inode, name, MAY_READ);
235    if (error)
236        return error;
237
238    error = security_inode_getxattr(dentry, name);
239    if (error)
240        return error;
241
242    if (!strncmp(name, XATTR_SECURITY_PREFIX,
243                XATTR_SECURITY_PREFIX_LEN)) {
244        const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
245        int ret = xattr_getsecurity(inode, suffix, value, size);
246        /*
247         * Only overwrite the return value if a security module
248         * is actually active.
249         */
250        if (ret == -EOPNOTSUPP)
251            goto nolsm;
252        return ret;
253    }
254nolsm:
255    if (inode->i_op->getxattr)
256        error = inode->i_op->getxattr(dentry, name, value, size);
257    else
258        error = -EOPNOTSUPP;
259
260    return error;
261}
262EXPORT_SYMBOL_GPL(vfs_getxattr);
263
264ssize_t
265vfs_listxattr(struct dentry *d, char *list, size_t size)
266{
267    ssize_t error;
268
269    error = security_inode_listxattr(d);
270    if (error)
271        return error;
272    error = -EOPNOTSUPP;
273    if (d->d_inode->i_op->listxattr) {
274        error = d->d_inode->i_op->listxattr(d, list, size);
275    } else {
276        error = security_inode_listsecurity(d->d_inode, list, size);
277        if (size && error > size)
278            error = -ERANGE;
279    }
280    return error;
281}
282EXPORT_SYMBOL_GPL(vfs_listxattr);
283
284int
285vfs_removexattr(struct dentry *dentry, const char *name)
286{
287    struct inode *inode = dentry->d_inode;
288    int error;
289
290    if (!inode->i_op->removexattr)
291        return -EOPNOTSUPP;
292
293    error = xattr_permission(inode, name, MAY_WRITE);
294    if (error)
295        return error;
296
297    error = security_inode_removexattr(dentry, name);
298    if (error)
299        return error;
300
301    mutex_lock(&inode->i_mutex);
302    error = inode->i_op->removexattr(dentry, name);
303    mutex_unlock(&inode->i_mutex);
304
305    if (!error) {
306        fsnotify_xattr(dentry);
307        evm_inode_post_removexattr(dentry, name);
308    }
309    return error;
310}
311EXPORT_SYMBOL_GPL(vfs_removexattr);
312
313
314/*
315 * Extended attribute SET operations
316 */
317static long
318setxattr(struct dentry *d, const char __user *name, const void __user *value,
319     size_t size, int flags)
320{
321    int error;
322    void *kvalue = NULL;
323    char kname[XATTR_NAME_MAX + 1];
324
325    if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
326        return -EINVAL;
327
328    error = strncpy_from_user(kname, name, sizeof(kname));
329    if (error == 0 || error == sizeof(kname))
330        error = -ERANGE;
331    if (error < 0)
332        return error;
333
334    if (size) {
335        if (size > XATTR_SIZE_MAX)
336            return -E2BIG;
337        kvalue = memdup_user(value, size);
338        if (IS_ERR(kvalue))
339            return PTR_ERR(kvalue);
340    }
341
342    error = vfs_setxattr(d, kname, kvalue, size, flags);
343    kfree(kvalue);
344    return error;
345}
346
347SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
348        const char __user *, name, const void __user *, value,
349        size_t, size, int, flags)
350{
351    struct path path;
352    int error;
353
354    error = user_path(pathname, &path);
355    if (error)
356        return error;
357    error = mnt_want_write(path.mnt);
358    if (!error) {
359        error = setxattr(path.dentry, name, value, size, flags);
360        mnt_drop_write(path.mnt);
361    }
362    path_put(&path);
363    return error;
364}
365
366SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
367        const char __user *, name, const void __user *, value,
368        size_t, size, int, flags)
369{
370    struct path path;
371    int error;
372
373    error = user_lpath(pathname, &path);
374    if (error)
375        return error;
376    error = mnt_want_write(path.mnt);
377    if (!error) {
378        error = setxattr(path.dentry, name, value, size, flags);
379        mnt_drop_write(path.mnt);
380    }
381    path_put(&path);
382    return error;
383}
384
385SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
386        const void __user *,value, size_t, size, int, flags)
387{
388    struct file *f;
389    struct dentry *dentry;
390    int error = -EBADF;
391
392    f = fget(fd);
393    if (!f)
394        return error;
395    dentry = f->f_path.dentry;
396    audit_inode(NULL, dentry);
397    error = mnt_want_write_file(f);
398    if (!error) {
399        error = setxattr(dentry, name, value, size, flags);
400        mnt_drop_write(f->f_path.mnt);
401    }
402    fput(f);
403    return error;
404}
405
406/*
407 * Extended attribute GET operations
408 */
409static ssize_t
410getxattr(struct dentry *d, const char __user *name, void __user *value,
411     size_t size)
412{
413    ssize_t error;
414    void *kvalue = NULL;
415    char kname[XATTR_NAME_MAX + 1];
416
417    error = strncpy_from_user(kname, name, sizeof(kname));
418    if (error == 0 || error == sizeof(kname))
419        error = -ERANGE;
420    if (error < 0)
421        return error;
422
423    if (size) {
424        if (size > XATTR_SIZE_MAX)
425            size = XATTR_SIZE_MAX;
426        kvalue = kzalloc(size, GFP_KERNEL);
427        if (!kvalue)
428            return -ENOMEM;
429    }
430
431    error = vfs_getxattr(d, kname, kvalue, size);
432    if (error > 0) {
433        if (size && copy_to_user(value, kvalue, error))
434            error = -EFAULT;
435    } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
436        /* The file system tried to returned a value bigger
437           than XATTR_SIZE_MAX bytes. Not possible. */
438        error = -E2BIG;
439    }
440    kfree(kvalue);
441    return error;
442}
443
444SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
445        const char __user *, name, void __user *, value, size_t, size)
446{
447    struct path path;
448    ssize_t error;
449
450    error = user_path(pathname, &path);
451    if (error)
452        return error;
453    error = getxattr(path.dentry, name, value, size);
454    path_put(&path);
455    return error;
456}
457
458SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
459        const char __user *, name, void __user *, value, size_t, size)
460{
461    struct path path;
462    ssize_t error;
463
464    error = user_lpath(pathname, &path);
465    if (error)
466        return error;
467    error = getxattr(path.dentry, name, value, size);
468    path_put(&path);
469    return error;
470}
471
472SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
473        void __user *, value, size_t, size)
474{
475    struct file *f;
476    ssize_t error = -EBADF;
477
478    f = fget(fd);
479    if (!f)
480        return error;
481    audit_inode(NULL, f->f_path.dentry);
482    error = getxattr(f->f_path.dentry, name, value, size);
483    fput(f);
484    return error;
485}
486
487/*
488 * Extended attribute LIST operations
489 */
490static ssize_t
491listxattr(struct dentry *d, char __user *list, size_t size)
492{
493    ssize_t error;
494    char *klist = NULL;
495
496    if (size) {
497        if (size > XATTR_LIST_MAX)
498            size = XATTR_LIST_MAX;
499        klist = kmalloc(size, GFP_KERNEL);
500        if (!klist)
501            return -ENOMEM;
502    }
503
504    error = vfs_listxattr(d, klist, size);
505    if (error > 0) {
506        if (size && copy_to_user(list, klist, error))
507            error = -EFAULT;
508    } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
509        /* The file system tried to returned a list bigger
510           than XATTR_LIST_MAX bytes. Not possible. */
511        error = -E2BIG;
512    }
513    kfree(klist);
514    return error;
515}
516
517SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
518        size_t, size)
519{
520    struct path path;
521    ssize_t error;
522
523    error = user_path(pathname, &path);
524    if (error)
525        return error;
526    error = listxattr(path.dentry, list, size);
527    path_put(&path);
528    return error;
529}
530
531SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
532        size_t, size)
533{
534    struct path path;
535    ssize_t error;
536
537    error = user_lpath(pathname, &path);
538    if (error)
539        return error;
540    error = listxattr(path.dentry, list, size);
541    path_put(&path);
542    return error;
543}
544
545SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
546{
547    struct file *f;
548    ssize_t error = -EBADF;
549
550    f = fget(fd);
551    if (!f)
552        return error;
553    audit_inode(NULL, f->f_path.dentry);
554    error = listxattr(f->f_path.dentry, list, size);
555    fput(f);
556    return error;
557}
558
559/*
560 * Extended attribute REMOVE operations
561 */
562static long
563removexattr(struct dentry *d, const char __user *name)
564{
565    int error;
566    char kname[XATTR_NAME_MAX + 1];
567
568    error = strncpy_from_user(kname, name, sizeof(kname));
569    if (error == 0 || error == sizeof(kname))
570        error = -ERANGE;
571    if (error < 0)
572        return error;
573
574    return vfs_removexattr(d, kname);
575}
576
577SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
578        const char __user *, name)
579{
580    struct path path;
581    int error;
582
583    error = user_path(pathname, &path);
584    if (error)
585        return error;
586    error = mnt_want_write(path.mnt);
587    if (!error) {
588        error = removexattr(path.dentry, name);
589        mnt_drop_write(path.mnt);
590    }
591    path_put(&path);
592    return error;
593}
594
595SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
596        const char __user *, name)
597{
598    struct path path;
599    int error;
600
601    error = user_lpath(pathname, &path);
602    if (error)
603        return error;
604    error = mnt_want_write(path.mnt);
605    if (!error) {
606        error = removexattr(path.dentry, name);
607        mnt_drop_write(path.mnt);
608    }
609    path_put(&path);
610    return error;
611}
612
613SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
614{
615    struct file *f;
616    struct dentry *dentry;
617    int error = -EBADF;
618
619    f = fget(fd);
620    if (!f)
621        return error;
622    dentry = f->f_path.dentry;
623    audit_inode(NULL, dentry);
624    error = mnt_want_write_file(f);
625    if (!error) {
626        error = removexattr(dentry, name);
627        mnt_drop_write(f->f_path.mnt);
628    }
629    fput(f);
630    return error;
631}
632
633
634static const char *
635strcmp_prefix(const char *a, const char *a_prefix)
636{
637    while (*a_prefix && *a == *a_prefix) {
638        a++;
639        a_prefix++;
640    }
641    return *a_prefix ? NULL : a;
642}
643
644/*
645 * In order to implement different sets of xattr operations for each xattr
646 * prefix with the generic xattr API, a filesystem should create a
647 * null-terminated array of struct xattr_handler (one for each prefix) and
648 * hang a pointer to it off of the s_xattr field of the superblock.
649 *
650 * The generic_fooxattr() functions will use this list to dispatch xattr
651 * operations to the correct xattr_handler.
652 */
653#define for_each_xattr_handler(handlers, handler) \
654        for ((handler) = *(handlers)++; \
655            (handler) != NULL; \
656            (handler) = *(handlers)++)
657
658/*
659 * Find the xattr_handler with the matching prefix.
660 */
661static const struct xattr_handler *
662xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
663{
664    const struct xattr_handler *handler;
665
666    if (!*name)
667        return NULL;
668
669    for_each_xattr_handler(handlers, handler) {
670        const char *n = strcmp_prefix(*name, handler->prefix);
671        if (n) {
672            *name = n;
673            break;
674        }
675    }
676    return handler;
677}
678
679/*
680 * Find the handler for the prefix and dispatch its get() operation.
681 */
682ssize_t
683generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
684{
685    const struct xattr_handler *handler;
686
687    handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
688    if (!handler)
689        return -EOPNOTSUPP;
690    return handler->get(dentry, name, buffer, size, handler->flags);
691}
692
693/*
694 * Combine the results of the list() operation from every xattr_handler in the
695 * list.
696 */
697ssize_t
698generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
699{
700    const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
701    unsigned int size = 0;
702
703    if (!buffer) {
704        for_each_xattr_handler(handlers, handler) {
705            size += handler->list(dentry, NULL, 0, NULL, 0,
706                          handler->flags);
707        }
708    } else {
709        char *buf = buffer;
710
711        for_each_xattr_handler(handlers, handler) {
712            size = handler->list(dentry, buf, buffer_size,
713                         NULL, 0, handler->flags);
714            if (size > buffer_size)
715                return -ERANGE;
716            buf += size;
717            buffer_size -= size;
718        }
719        size = buf - buffer;
720    }
721    return size;
722}
723
724/*
725 * Find the handler for the prefix and dispatch its set() operation.
726 */
727int
728generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
729{
730    const struct xattr_handler *handler;
731
732    if (size == 0)
733        value = ""; /* empty EA, do not remove */
734    handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
735    if (!handler)
736        return -EOPNOTSUPP;
737    return handler->set(dentry, name, value, size, flags, handler->flags);
738}
739
740/*
741 * Find the handler for the prefix and dispatch its set() operation to remove
742 * any associated extended attribute.
743 */
744int
745generic_removexattr(struct dentry *dentry, const char *name)
746{
747    const struct xattr_handler *handler;
748
749    handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
750    if (!handler)
751        return -EOPNOTSUPP;
752    return handler->set(dentry, name, NULL, 0,
753                XATTR_REPLACE, handler->flags);
754}
755
756EXPORT_SYMBOL(generic_getxattr);
757EXPORT_SYMBOL(generic_listxattr);
758EXPORT_SYMBOL(generic_setxattr);
759EXPORT_SYMBOL(generic_removexattr);
760

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