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/filelock.h>
18 #include <linux/security.h>
19 #include <linux/evm.h>
20 #include <linux/ima.h>
25 * setattr_should_drop_sgid - determine whether the setgid bit needs to be
27 * @idmap: idmap of the mount @inode was found from
28 * @inode: inode to check
30 * This function determines whether the setgid bit needs to be removed.
31 * We retain backwards compatibility and require setgid bit to be removed
32 * unconditionally if S_IXGRP is set. Otherwise we have the exact same
33 * requirements as setattr_prepare() and setattr_copy().
35 * Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
37 int setattr_should_drop_sgid(struct mnt_idmap
*idmap
,
38 const struct inode
*inode
)
40 umode_t mode
= inode
->i_mode
;
42 if (!(mode
& S_ISGID
))
45 return ATTR_KILL_SGID
;
46 if (!in_group_or_capable(idmap
, inode
, i_gid_into_vfsgid(idmap
, inode
)))
47 return ATTR_KILL_SGID
;
50 EXPORT_SYMBOL(setattr_should_drop_sgid
);
53 * setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
55 * @idmap: idmap of the mount @inode was found from
56 * @inode: inode to check
58 * This function determines whether the set{g,u}id bits need to be removed.
59 * If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the
60 * setgid bit needs to be removed ATTR_KILL_SGID is returned. If both
61 * set{g,u}id bits need to be removed the corresponding mask of both flags is
64 * Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
65 * to remove, 0 otherwise.
67 int setattr_should_drop_suidgid(struct mnt_idmap
*idmap
,
70 umode_t mode
= inode
->i_mode
;
73 /* suid always must be killed */
74 if (unlikely(mode
& S_ISUID
))
75 kill
= ATTR_KILL_SUID
;
77 kill
|= setattr_should_drop_sgid(idmap
, inode
);
79 if (unlikely(kill
&& !capable(CAP_FSETID
) && S_ISREG(mode
)))
84 EXPORT_SYMBOL(setattr_should_drop_suidgid
);
87 * chown_ok - verify permissions to chown inode
88 * @idmap: idmap of the mount @inode was found from
89 * @inode: inode to check permissions on
90 * @ia_vfsuid: uid to chown @inode to
92 * If the inode has been found through an idmapped mount the idmap of
93 * the vfsmount must be passed through @idmap. This function will then
94 * take care to map the inode according to @idmap before checking
95 * permissions. On non-idmapped mounts or if permission checking is to be
96 * performed on the raw inode simply pass @nop_mnt_idmap.
98 static bool chown_ok(struct mnt_idmap
*idmap
,
99 const struct inode
*inode
, vfsuid_t ia_vfsuid
)
101 vfsuid_t vfsuid
= i_uid_into_vfsuid(idmap
, inode
);
102 if (vfsuid_eq_kuid(vfsuid
, current_fsuid()) &&
103 vfsuid_eq(ia_vfsuid
, vfsuid
))
105 if (capable_wrt_inode_uidgid(idmap
, inode
, CAP_CHOWN
))
107 if (!vfsuid_valid(vfsuid
) &&
108 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
114 * chgrp_ok - verify permissions to chgrp inode
115 * @idmap: idmap of the mount @inode was found from
116 * @inode: inode to check permissions on
117 * @ia_vfsgid: gid to chown @inode to
119 * If the inode has been found through an idmapped mount the idmap of
120 * the vfsmount must be passed through @idmap. This function will then
121 * take care to map the inode according to @idmap before checking
122 * permissions. On non-idmapped mounts or if permission checking is to be
123 * performed on the raw inode simply pass @nop_mnt_idmap.
125 static bool chgrp_ok(struct mnt_idmap
*idmap
,
126 const struct inode
*inode
, vfsgid_t ia_vfsgid
)
128 vfsgid_t vfsgid
= i_gid_into_vfsgid(idmap
, inode
);
129 vfsuid_t vfsuid
= i_uid_into_vfsuid(idmap
, inode
);
130 if (vfsuid_eq_kuid(vfsuid
, current_fsuid())) {
131 if (vfsgid_eq(ia_vfsgid
, vfsgid
))
133 if (vfsgid_in_group_p(ia_vfsgid
))
136 if (capable_wrt_inode_uidgid(idmap
, inode
, CAP_CHOWN
))
138 if (!vfsgid_valid(vfsgid
) &&
139 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
145 * setattr_prepare - check if attribute changes to a dentry are allowed
146 * @idmap: idmap of the mount the inode was found from
147 * @dentry: dentry to check
148 * @attr: attributes to change
150 * Check if we are allowed to change the attributes contained in @attr
151 * in the given dentry. This includes the normal unix access permission
152 * checks, as well as checks for rlimits and others. The function also clears
153 * SGID bit from mode if user is not allowed to set it. Also file capabilities
154 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
156 * If the inode has been found through an idmapped mount the idmap of
157 * the vfsmount must be passed through @idmap. This function will then
158 * take care to map the inode according to @idmap before checking
159 * permissions. On non-idmapped mounts or if permission checking is to be
160 * performed on the raw inode simply passs @nop_mnt_idmap.
162 * Should be called as the first thing in ->setattr implementations,
163 * possibly after taking additional locks.
165 int setattr_prepare(struct mnt_idmap
*idmap
, struct dentry
*dentry
,
168 struct inode
*inode
= d_inode(dentry
);
169 unsigned int ia_valid
= attr
->ia_valid
;
172 * First check size constraints. These can't be overriden using
175 if (ia_valid
& ATTR_SIZE
) {
176 int error
= inode_newsize_ok(inode
, attr
->ia_size
);
181 /* If force is set do it anyway. */
182 if (ia_valid
& ATTR_FORCE
)
185 /* Make sure a caller can chown. */
186 if ((ia_valid
& ATTR_UID
) &&
187 !chown_ok(idmap
, inode
, attr
->ia_vfsuid
))
190 /* Make sure caller can chgrp. */
191 if ((ia_valid
& ATTR_GID
) &&
192 !chgrp_ok(idmap
, inode
, attr
->ia_vfsgid
))
195 /* Make sure a caller can chmod. */
196 if (ia_valid
& ATTR_MODE
) {
199 if (!inode_owner_or_capable(idmap
, inode
))
202 if (ia_valid
& ATTR_GID
)
203 vfsgid
= attr
->ia_vfsgid
;
205 vfsgid
= i_gid_into_vfsgid(idmap
, inode
);
207 /* Also check the setgid bit! */
208 if (!in_group_or_capable(idmap
, inode
, vfsgid
))
209 attr
->ia_mode
&= ~S_ISGID
;
212 /* Check for setting the inode time. */
213 if (ia_valid
& (ATTR_MTIME_SET
| ATTR_ATIME_SET
| ATTR_TIMES_SET
)) {
214 if (!inode_owner_or_capable(idmap
, inode
))
219 /* User has permission for the change */
220 if (ia_valid
& ATTR_KILL_PRIV
) {
223 error
= security_inode_killpriv(idmap
, dentry
);
230 EXPORT_SYMBOL(setattr_prepare
);
233 * inode_newsize_ok - may this inode be truncated to a given size
234 * @inode: the inode to be truncated
235 * @offset: the new size to assign to the inode
237 * inode_newsize_ok must be called with i_mutex held.
239 * inode_newsize_ok will check filesystem limits and ulimits to check that the
240 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
241 * when necessary. Caller must not proceed with inode size change if failure is
242 * returned. @inode must be a file (not directory), with appropriate
243 * permissions to allow truncate (inode_newsize_ok does NOT check these
246 * Return: 0 on success, -ve errno on failure
248 int inode_newsize_ok(const struct inode
*inode
, loff_t offset
)
252 if (inode
->i_size
< offset
) {
255 limit
= rlimit(RLIMIT_FSIZE
);
256 if (limit
!= RLIM_INFINITY
&& offset
> limit
)
258 if (offset
> inode
->i_sb
->s_maxbytes
)
262 * truncation of in-use swapfiles is disallowed - it would
263 * cause subsequent swapout to scribble on the now-freed
266 if (IS_SWAPFILE(inode
))
272 send_sig(SIGXFSZ
, current
, 0);
276 EXPORT_SYMBOL(inode_newsize_ok
);
279 * setattr_copy - copy simple metadata updates into the generic inode
280 * @idmap: idmap of the mount the inode was found from
281 * @inode: the inode to be updated
282 * @attr: the new attributes
284 * setattr_copy must be called with i_mutex held.
286 * setattr_copy updates the inode's metadata with that specified
287 * in attr on idmapped mounts. Necessary permission checks to determine
288 * whether or not the S_ISGID property needs to be removed are performed with
289 * the correct idmapped mount permission helpers.
290 * Noticeably missing is inode size update, which is more complex
291 * as it requires pagecache updates.
293 * If the inode has been found through an idmapped mount the idmap of
294 * the vfsmount must be passed through @idmap. This function will then
295 * take care to map the inode according to @idmap before checking
296 * permissions. On non-idmapped mounts or if permission checking is to be
297 * performed on the raw inode simply pass @nop_mnt_idmap.
299 * The inode is not marked as dirty after this operation. The rationale is
300 * that for "simple" filesystems, the struct inode is the inode storage.
301 * The caller is free to mark the inode dirty afterwards if needed.
303 void setattr_copy(struct mnt_idmap
*idmap
, struct inode
*inode
,
304 const struct iattr
*attr
)
306 unsigned int ia_valid
= attr
->ia_valid
;
308 i_uid_update(idmap
, attr
, inode
);
309 i_gid_update(idmap
, attr
, inode
);
310 if (ia_valid
& ATTR_ATIME
)
311 inode_set_atime_to_ts(inode
, attr
->ia_atime
);
312 if (ia_valid
& ATTR_MTIME
)
313 inode_set_mtime_to_ts(inode
, attr
->ia_mtime
);
314 if (ia_valid
& ATTR_CTIME
)
315 inode_set_ctime_to_ts(inode
, attr
->ia_ctime
);
316 if (ia_valid
& ATTR_MODE
) {
317 umode_t mode
= attr
->ia_mode
;
318 if (!in_group_or_capable(idmap
, inode
,
319 i_gid_into_vfsgid(idmap
, inode
)))
321 inode
->i_mode
= mode
;
324 EXPORT_SYMBOL(setattr_copy
);
326 int may_setattr(struct mnt_idmap
*idmap
, struct inode
*inode
,
327 unsigned int ia_valid
)
331 if (ia_valid
& (ATTR_MODE
| ATTR_UID
| ATTR_GID
| ATTR_TIMES_SET
)) {
332 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
337 * If utimes(2) and friends are called with times == NULL (or both
338 * times are UTIME_NOW), then we need to check for write permission
340 if (ia_valid
& ATTR_TOUCH
) {
341 if (IS_IMMUTABLE(inode
))
344 if (!inode_owner_or_capable(idmap
, inode
)) {
345 error
= inode_permission(idmap
, inode
, MAY_WRITE
);
352 EXPORT_SYMBOL(may_setattr
);
355 * notify_change - modify attributes of a filesytem object
356 * @idmap: idmap of the mount the inode was found from
357 * @dentry: object affected
358 * @attr: new attributes
359 * @delegated_inode: returns inode, if the inode is delegated
361 * The caller must hold the i_mutex on the affected object.
363 * If notify_change discovers a delegation in need of breaking,
364 * it will return -EWOULDBLOCK and return a reference to the inode in
365 * delegated_inode. The caller should then break the delegation and
366 * retry. Because breaking a delegation may take a long time, the
367 * caller should drop the i_mutex before doing so.
369 * Alternatively, a caller may pass NULL for delegated_inode. This may
370 * be appropriate for callers that expect the underlying filesystem not
371 * to be NFS exported. Also, passing NULL is fine for callers holding
372 * the file open for write, as there can be no conflicting delegation in
375 * If the inode has been found through an idmapped mount the idmap of
376 * the vfsmount must be passed through @idmap. This function will then
377 * take care to map the inode according to @idmap before checking
378 * permissions. On non-idmapped mounts or if permission checking is to be
379 * performed on the raw inode simply pass @nop_mnt_idmap.
381 int notify_change(struct mnt_idmap
*idmap
, struct dentry
*dentry
,
382 struct iattr
*attr
, struct inode
**delegated_inode
)
384 struct inode
*inode
= dentry
->d_inode
;
385 umode_t mode
= inode
->i_mode
;
387 struct timespec64 now
;
388 unsigned int ia_valid
= attr
->ia_valid
;
390 WARN_ON_ONCE(!inode_is_locked(inode
));
392 error
= may_setattr(idmap
, inode
, ia_valid
);
396 if ((ia_valid
& ATTR_MODE
)) {
398 * Don't allow changing the mode of symlinks:
400 * (1) The vfs doesn't take the mode of symlinks into account
401 * during permission checking.
402 * (2) This has never worked correctly. Most major filesystems
403 * did return EOPNOTSUPP due to interactions with POSIX ACLs
404 * but did still updated the mode of the symlink.
405 * This inconsistency led system call wrapper providers such
406 * as libc to block changing the mode of symlinks with
407 * EOPNOTSUPP already.
408 * (3) To even do this in the first place one would have to use
409 * specific file descriptors and quite some effort.
411 if (S_ISLNK(inode
->i_mode
))
414 /* Flag setting protected by i_mutex */
415 if (is_sxid(attr
->ia_mode
))
416 inode
->i_flags
&= ~S_NOSEC
;
419 now
= current_time(inode
);
421 attr
->ia_ctime
= now
;
422 if (!(ia_valid
& ATTR_ATIME_SET
))
423 attr
->ia_atime
= now
;
425 attr
->ia_atime
= timestamp_truncate(attr
->ia_atime
, inode
);
426 if (!(ia_valid
& ATTR_MTIME_SET
))
427 attr
->ia_mtime
= now
;
429 attr
->ia_mtime
= timestamp_truncate(attr
->ia_mtime
, inode
);
431 if (ia_valid
& ATTR_KILL_PRIV
) {
432 error
= security_inode_need_killpriv(dentry
);
436 ia_valid
= attr
->ia_valid
&= ~ATTR_KILL_PRIV
;
440 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
441 * that the function has the ability to reinterpret a mode change
442 * that's due to these bits. This adds an implicit restriction that
443 * no function will ever call notify_change with both ATTR_MODE and
444 * ATTR_KILL_S*ID set.
446 if ((ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
)) &&
447 (ia_valid
& ATTR_MODE
))
450 if (ia_valid
& ATTR_KILL_SUID
) {
451 if (mode
& S_ISUID
) {
452 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
453 attr
->ia_mode
= (inode
->i_mode
& ~S_ISUID
);
456 if (ia_valid
& ATTR_KILL_SGID
) {
457 if (mode
& S_ISGID
) {
458 if (!(ia_valid
& ATTR_MODE
)) {
459 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
460 attr
->ia_mode
= inode
->i_mode
;
462 attr
->ia_mode
&= ~S_ISGID
;
465 if (!(attr
->ia_valid
& ~(ATTR_KILL_SUID
| ATTR_KILL_SGID
)))
469 * Verify that uid/gid changes are valid in the target
470 * namespace of the superblock.
472 if (ia_valid
& ATTR_UID
&&
473 !vfsuid_has_fsmapping(idmap
, inode
->i_sb
->s_user_ns
,
476 if (ia_valid
& ATTR_GID
&&
477 !vfsgid_has_fsmapping(idmap
, inode
->i_sb
->s_user_ns
,
481 /* Don't allow modifications of files with invalid uids or
482 * gids unless those uids & gids are being made valid.
484 if (!(ia_valid
& ATTR_UID
) &&
485 !vfsuid_valid(i_uid_into_vfsuid(idmap
, inode
)))
487 if (!(ia_valid
& ATTR_GID
) &&
488 !vfsgid_valid(i_gid_into_vfsgid(idmap
, inode
)))
491 error
= security_inode_setattr(idmap
, dentry
, attr
);
494 error
= try_break_deleg(inode
, delegated_inode
);
498 if (inode
->i_op
->setattr
)
499 error
= inode
->i_op
->setattr(idmap
, dentry
, attr
);
501 error
= simple_setattr(idmap
, dentry
, attr
);
504 fsnotify_change(dentry
, ia_valid
);
505 ima_inode_post_setattr(idmap
, dentry
);
506 evm_inode_post_setattr(dentry
, ia_valid
);
511 EXPORT_SYMBOL(notify_change
);