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git.ipfire.org Git - people/ms/linux.git/blob - fs/attr.c
1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 * changes by Thomas Schoebel-Theuer
9 #include <linux/export.h>
10 #include <linux/time.h>
12 #include <linux/string.h>
13 #include <linux/sched/signal.h>
14 #include <linux/capability.h>
15 #include <linux/fsnotify.h>
16 #include <linux/fcntl.h>
17 #include <linux/security.h>
18 #include <linux/evm.h>
19 #include <linux/ima.h>
22 * chown_ok - verify permissions to chown inode
23 * @mnt_userns: user namespace of the mount @inode was found from
24 * @inode: inode to check permissions on
25 * @uid: uid to chown @inode to
27 * If the inode has been found through an idmapped mount the user namespace of
28 * the vfsmount must be passed through @mnt_userns. This function will then
29 * take care to map the inode according to @mnt_userns before checking
30 * permissions. On non-idmapped mounts or if permission checking is to be
31 * performed on the raw inode simply passs init_user_ns.
33 static bool chown_ok(struct user_namespace
*mnt_userns
,
34 const struct inode
*inode
,
37 kuid_t kuid
= i_uid_into_mnt(mnt_userns
, inode
);
38 if (uid_eq(current_fsuid(), kuid
) && uid_eq(uid
, inode
->i_uid
))
40 if (capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_CHOWN
))
42 if (uid_eq(kuid
, INVALID_UID
) &&
43 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
49 * chgrp_ok - verify permissions to chgrp inode
50 * @mnt_userns: user namespace of the mount @inode was found from
51 * @inode: inode to check permissions on
52 * @gid: gid to chown @inode to
54 * If the inode has been found through an idmapped mount the user namespace of
55 * the vfsmount must be passed through @mnt_userns. This function will then
56 * take care to map the inode according to @mnt_userns before checking
57 * permissions. On non-idmapped mounts or if permission checking is to be
58 * performed on the raw inode simply passs init_user_ns.
60 static bool chgrp_ok(struct user_namespace
*mnt_userns
,
61 const struct inode
*inode
, kgid_t gid
)
63 kgid_t kgid
= i_gid_into_mnt(mnt_userns
, inode
);
64 if (uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns
, inode
))) {
67 if (gid_eq(gid
, inode
->i_gid
))
69 mapped_gid
= mapped_kgid_fs(mnt_userns
, i_user_ns(inode
), gid
);
70 if (in_group_p(mapped_gid
))
73 if (capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_CHOWN
))
75 if (gid_eq(kgid
, INVALID_GID
) &&
76 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
82 * setattr_prepare - check if attribute changes to a dentry are allowed
83 * @mnt_userns: user namespace of the mount the inode was found from
84 * @dentry: dentry to check
85 * @attr: attributes to change
87 * Check if we are allowed to change the attributes contained in @attr
88 * in the given dentry. This includes the normal unix access permission
89 * checks, as well as checks for rlimits and others. The function also clears
90 * SGID bit from mode if user is not allowed to set it. Also file capabilities
91 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
93 * If the inode has been found through an idmapped mount the user namespace of
94 * the vfsmount must be passed through @mnt_userns. This function will then
95 * take care to map the inode according to @mnt_userns before checking
96 * permissions. On non-idmapped mounts or if permission checking is to be
97 * performed on the raw inode simply passs init_user_ns.
99 * Should be called as the first thing in ->setattr implementations,
100 * possibly after taking additional locks.
102 int setattr_prepare(struct user_namespace
*mnt_userns
, struct dentry
*dentry
,
105 struct inode
*inode
= d_inode(dentry
);
106 unsigned int ia_valid
= attr
->ia_valid
;
109 * First check size constraints. These can't be overriden using
112 if (ia_valid
& ATTR_SIZE
) {
113 int error
= inode_newsize_ok(inode
, attr
->ia_size
);
118 /* If force is set do it anyway. */
119 if (ia_valid
& ATTR_FORCE
)
122 /* Make sure a caller can chown. */
123 if ((ia_valid
& ATTR_UID
) && !chown_ok(mnt_userns
, inode
, attr
->ia_uid
))
126 /* Make sure caller can chgrp. */
127 if ((ia_valid
& ATTR_GID
) && !chgrp_ok(mnt_userns
, inode
, attr
->ia_gid
))
130 /* Make sure a caller can chmod. */
131 if (ia_valid
& ATTR_MODE
) {
134 if (!inode_owner_or_capable(mnt_userns
, inode
))
137 if (ia_valid
& ATTR_GID
)
138 mapped_gid
= mapped_kgid_fs(mnt_userns
,
139 i_user_ns(inode
), attr
->ia_gid
);
141 mapped_gid
= i_gid_into_mnt(mnt_userns
, inode
);
143 /* Also check the setgid bit! */
144 if (!in_group_p(mapped_gid
) &&
145 !capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_FSETID
))
146 attr
->ia_mode
&= ~S_ISGID
;
149 /* Check for setting the inode time. */
150 if (ia_valid
& (ATTR_MTIME_SET
| ATTR_ATIME_SET
| ATTR_TIMES_SET
)) {
151 if (!inode_owner_or_capable(mnt_userns
, inode
))
156 /* User has permission for the change */
157 if (ia_valid
& ATTR_KILL_PRIV
) {
160 error
= security_inode_killpriv(mnt_userns
, dentry
);
167 EXPORT_SYMBOL(setattr_prepare
);
170 * inode_newsize_ok - may this inode be truncated to a given size
171 * @inode: the inode to be truncated
172 * @offset: the new size to assign to the inode
174 * inode_newsize_ok must be called with i_mutex held.
176 * inode_newsize_ok will check filesystem limits and ulimits to check that the
177 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
178 * when necessary. Caller must not proceed with inode size change if failure is
179 * returned. @inode must be a file (not directory), with appropriate
180 * permissions to allow truncate (inode_newsize_ok does NOT check these
183 * Return: 0 on success, -ve errno on failure
185 int inode_newsize_ok(const struct inode
*inode
, loff_t offset
)
187 if (inode
->i_size
< offset
) {
190 limit
= rlimit(RLIMIT_FSIZE
);
191 if (limit
!= RLIM_INFINITY
&& offset
> limit
)
193 if (offset
> inode
->i_sb
->s_maxbytes
)
197 * truncation of in-use swapfiles is disallowed - it would
198 * cause subsequent swapout to scribble on the now-freed
201 if (IS_SWAPFILE(inode
))
207 send_sig(SIGXFSZ
, current
, 0);
211 EXPORT_SYMBOL(inode_newsize_ok
);
214 * setattr_copy - copy simple metadata updates into the generic inode
215 * @mnt_userns: user namespace of the mount the inode was found from
216 * @inode: the inode to be updated
217 * @attr: the new attributes
219 * setattr_copy must be called with i_mutex held.
221 * setattr_copy updates the inode's metadata with that specified
222 * in attr on idmapped mounts. If file ownership is changed setattr_copy
223 * doesn't map ia_uid and ia_gid. It will asssume the caller has already
224 * provided the intended values. Necessary permission checks to determine
225 * whether or not the S_ISGID property needs to be removed are performed with
226 * the correct idmapped mount permission helpers.
227 * Noticeably missing is inode size update, which is more complex
228 * as it requires pagecache updates.
230 * If the inode has been found through an idmapped mount the user namespace of
231 * the vfsmount must be passed through @mnt_userns. This function will then
232 * take care to map the inode according to @mnt_userns before checking
233 * permissions. On non-idmapped mounts or if permission checking is to be
234 * performed on the raw inode simply passs init_user_ns.
236 * The inode is not marked as dirty after this operation. The rationale is
237 * that for "simple" filesystems, the struct inode is the inode storage.
238 * The caller is free to mark the inode dirty afterwards if needed.
240 void setattr_copy(struct user_namespace
*mnt_userns
, struct inode
*inode
,
241 const struct iattr
*attr
)
243 unsigned int ia_valid
= attr
->ia_valid
;
245 if (ia_valid
& ATTR_UID
)
246 inode
->i_uid
= attr
->ia_uid
;
247 if (ia_valid
& ATTR_GID
)
248 inode
->i_gid
= attr
->ia_gid
;
249 if (ia_valid
& ATTR_ATIME
)
250 inode
->i_atime
= attr
->ia_atime
;
251 if (ia_valid
& ATTR_MTIME
)
252 inode
->i_mtime
= attr
->ia_mtime
;
253 if (ia_valid
& ATTR_CTIME
)
254 inode
->i_ctime
= attr
->ia_ctime
;
255 if (ia_valid
& ATTR_MODE
) {
256 umode_t mode
= attr
->ia_mode
;
257 kgid_t kgid
= i_gid_into_mnt(mnt_userns
, inode
);
258 if (!in_group_p(kgid
) &&
259 !capable_wrt_inode_uidgid(mnt_userns
, inode
, CAP_FSETID
))
261 inode
->i_mode
= mode
;
264 EXPORT_SYMBOL(setattr_copy
);
266 int may_setattr(struct user_namespace
*mnt_userns
, struct inode
*inode
,
267 unsigned int ia_valid
)
271 if (ia_valid
& (ATTR_MODE
| ATTR_UID
| ATTR_GID
| ATTR_TIMES_SET
)) {
272 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
277 * If utimes(2) and friends are called with times == NULL (or both
278 * times are UTIME_NOW), then we need to check for write permission
280 if (ia_valid
& ATTR_TOUCH
) {
281 if (IS_IMMUTABLE(inode
))
284 if (!inode_owner_or_capable(mnt_userns
, inode
)) {
285 error
= inode_permission(mnt_userns
, inode
, MAY_WRITE
);
292 EXPORT_SYMBOL(may_setattr
);
295 * notify_change - modify attributes of a filesytem object
296 * @mnt_userns: user namespace of the mount the inode was found from
297 * @dentry: object affected
298 * @attr: new attributes
299 * @delegated_inode: returns inode, if the inode is delegated
301 * The caller must hold the i_mutex on the affected object.
303 * If notify_change discovers a delegation in need of breaking,
304 * it will return -EWOULDBLOCK and return a reference to the inode in
305 * delegated_inode. The caller should then break the delegation and
306 * retry. Because breaking a delegation may take a long time, the
307 * caller should drop the i_mutex before doing so.
309 * If file ownership is changed notify_change() doesn't map ia_uid and
310 * ia_gid. It will asssume the caller has already provided the intended values.
312 * Alternatively, a caller may pass NULL for delegated_inode. This may
313 * be appropriate for callers that expect the underlying filesystem not
314 * to be NFS exported. Also, passing NULL is fine for callers holding
315 * the file open for write, as there can be no conflicting delegation in
318 * If the inode has been found through an idmapped mount the user namespace of
319 * the vfsmount must be passed through @mnt_userns. This function will then
320 * take care to map the inode according to @mnt_userns before checking
321 * permissions. On non-idmapped mounts or if permission checking is to be
322 * performed on the raw inode simply passs init_user_ns.
324 int notify_change(struct user_namespace
*mnt_userns
, struct dentry
*dentry
,
325 struct iattr
*attr
, struct inode
**delegated_inode
)
327 struct inode
*inode
= dentry
->d_inode
;
328 umode_t mode
= inode
->i_mode
;
330 struct timespec64 now
;
331 unsigned int ia_valid
= attr
->ia_valid
;
333 WARN_ON_ONCE(!inode_is_locked(inode
));
335 error
= may_setattr(mnt_userns
, inode
, ia_valid
);
339 if ((ia_valid
& ATTR_MODE
)) {
340 umode_t amode
= attr
->ia_mode
;
341 /* Flag setting protected by i_mutex */
343 inode
->i_flags
&= ~S_NOSEC
;
346 now
= current_time(inode
);
348 attr
->ia_ctime
= now
;
349 if (!(ia_valid
& ATTR_ATIME_SET
))
350 attr
->ia_atime
= now
;
352 attr
->ia_atime
= timestamp_truncate(attr
->ia_atime
, inode
);
353 if (!(ia_valid
& ATTR_MTIME_SET
))
354 attr
->ia_mtime
= now
;
356 attr
->ia_mtime
= timestamp_truncate(attr
->ia_mtime
, inode
);
358 if (ia_valid
& ATTR_KILL_PRIV
) {
359 error
= security_inode_need_killpriv(dentry
);
363 ia_valid
= attr
->ia_valid
&= ~ATTR_KILL_PRIV
;
367 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
368 * that the function has the ability to reinterpret a mode change
369 * that's due to these bits. This adds an implicit restriction that
370 * no function will ever call notify_change with both ATTR_MODE and
371 * ATTR_KILL_S*ID set.
373 if ((ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
)) &&
374 (ia_valid
& ATTR_MODE
))
377 if (ia_valid
& ATTR_KILL_SUID
) {
378 if (mode
& S_ISUID
) {
379 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
380 attr
->ia_mode
= (inode
->i_mode
& ~S_ISUID
);
383 if (ia_valid
& ATTR_KILL_SGID
) {
384 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
)) {
385 if (!(ia_valid
& ATTR_MODE
)) {
386 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
387 attr
->ia_mode
= inode
->i_mode
;
389 attr
->ia_mode
&= ~S_ISGID
;
392 if (!(attr
->ia_valid
& ~(ATTR_KILL_SUID
| ATTR_KILL_SGID
)))
396 * Verify that uid/gid changes are valid in the target
397 * namespace of the superblock.
399 if (ia_valid
& ATTR_UID
&&
400 !kuid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_uid
))
402 if (ia_valid
& ATTR_GID
&&
403 !kgid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_gid
))
406 /* Don't allow modifications of files with invalid uids or
407 * gids unless those uids & gids are being made valid.
409 if (!(ia_valid
& ATTR_UID
) &&
410 !uid_valid(i_uid_into_mnt(mnt_userns
, inode
)))
412 if (!(ia_valid
& ATTR_GID
) &&
413 !gid_valid(i_gid_into_mnt(mnt_userns
, inode
)))
416 error
= security_inode_setattr(dentry
, attr
);
419 error
= try_break_deleg(inode
, delegated_inode
);
423 if (inode
->i_op
->setattr
)
424 error
= inode
->i_op
->setattr(mnt_userns
, dentry
, attr
);
426 error
= simple_setattr(mnt_userns
, dentry
, attr
);
429 fsnotify_change(dentry
, ia_valid
);
430 ima_inode_post_setattr(mnt_userns
, dentry
);
431 evm_inode_post_setattr(dentry
, ia_valid
);
436 EXPORT_SYMBOL(notify_change
);