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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>
21 static bool chown_ok(const struct inode
*inode
, kuid_t uid
)
23 if (uid_eq(current_fsuid(), inode
->i_uid
) &&
24 uid_eq(uid
, inode
->i_uid
))
26 if (capable_wrt_inode_uidgid(inode
, CAP_CHOWN
))
28 if (uid_eq(inode
->i_uid
, INVALID_UID
) &&
29 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
34 static bool chgrp_ok(const struct inode
*inode
, kgid_t gid
)
36 if (uid_eq(current_fsuid(), inode
->i_uid
) &&
37 (in_group_p(gid
) || gid_eq(gid
, inode
->i_gid
)))
39 if (capable_wrt_inode_uidgid(inode
, CAP_CHOWN
))
41 if (gid_eq(inode
->i_gid
, INVALID_GID
) &&
42 ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
48 * setattr_prepare - check if attribute changes to a dentry are allowed
49 * @dentry: dentry to check
50 * @attr: attributes to change
52 * Check if we are allowed to change the attributes contained in @attr
53 * in the given dentry. This includes the normal unix access permission
54 * checks, as well as checks for rlimits and others. The function also clears
55 * SGID bit from mode if user is not allowed to set it. Also file capabilities
56 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
58 * Should be called as the first thing in ->setattr implementations,
59 * possibly after taking additional locks.
61 int setattr_prepare(struct dentry
*dentry
, struct iattr
*attr
)
63 struct inode
*inode
= d_inode(dentry
);
64 unsigned int ia_valid
= attr
->ia_valid
;
67 * First check size constraints. These can't be overriden using
70 if (ia_valid
& ATTR_SIZE
) {
71 int error
= inode_newsize_ok(inode
, attr
->ia_size
);
76 /* If force is set do it anyway. */
77 if (ia_valid
& ATTR_FORCE
)
80 /* Make sure a caller can chown. */
81 if ((ia_valid
& ATTR_UID
) && !chown_ok(inode
, attr
->ia_uid
))
84 /* Make sure caller can chgrp. */
85 if ((ia_valid
& ATTR_GID
) && !chgrp_ok(inode
, attr
->ia_gid
))
88 /* Make sure a caller can chmod. */
89 if (ia_valid
& ATTR_MODE
) {
90 if (!inode_owner_or_capable(inode
))
92 /* Also check the setgid bit! */
93 if (!in_group_p((ia_valid
& ATTR_GID
) ? attr
->ia_gid
:
95 !capable_wrt_inode_uidgid(inode
, CAP_FSETID
))
96 attr
->ia_mode
&= ~S_ISGID
;
99 /* Check for setting the inode time. */
100 if (ia_valid
& (ATTR_MTIME_SET
| ATTR_ATIME_SET
| ATTR_TIMES_SET
)) {
101 if (!inode_owner_or_capable(inode
))
106 /* User has permission for the change */
107 if (ia_valid
& ATTR_KILL_PRIV
) {
110 error
= security_inode_killpriv(dentry
);
117 EXPORT_SYMBOL(setattr_prepare
);
120 * inode_newsize_ok - may this inode be truncated to a given size
121 * @inode: the inode to be truncated
122 * @offset: the new size to assign to the inode
124 * inode_newsize_ok must be called with i_mutex held.
126 * inode_newsize_ok will check filesystem limits and ulimits to check that the
127 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
128 * when necessary. Caller must not proceed with inode size change if failure is
129 * returned. @inode must be a file (not directory), with appropriate
130 * permissions to allow truncate (inode_newsize_ok does NOT check these
133 * Return: 0 on success, -ve errno on failure
135 int inode_newsize_ok(const struct inode
*inode
, loff_t offset
)
137 if (inode
->i_size
< offset
) {
140 limit
= rlimit(RLIMIT_FSIZE
);
141 if (limit
!= RLIM_INFINITY
&& offset
> limit
)
143 if (offset
> inode
->i_sb
->s_maxbytes
)
147 * truncation of in-use swapfiles is disallowed - it would
148 * cause subsequent swapout to scribble on the now-freed
151 if (IS_SWAPFILE(inode
))
157 send_sig(SIGXFSZ
, current
, 0);
161 EXPORT_SYMBOL(inode_newsize_ok
);
164 * setattr_copy - copy simple metadata updates into the generic inode
165 * @inode: the inode to be updated
166 * @attr: the new attributes
168 * setattr_copy must be called with i_mutex held.
170 * setattr_copy updates the inode's metadata with that specified
171 * in attr. Noticeably missing is inode size update, which is more complex
172 * as it requires pagecache updates.
174 * The inode is not marked as dirty after this operation. The rationale is
175 * that for "simple" filesystems, the struct inode is the inode storage.
176 * The caller is free to mark the inode dirty afterwards if needed.
178 void setattr_copy(struct inode
*inode
, const struct iattr
*attr
)
180 unsigned int ia_valid
= attr
->ia_valid
;
182 if (ia_valid
& ATTR_UID
)
183 inode
->i_uid
= attr
->ia_uid
;
184 if (ia_valid
& ATTR_GID
)
185 inode
->i_gid
= attr
->ia_gid
;
186 if (ia_valid
& ATTR_ATIME
) {
187 inode
->i_atime
= timestamp_truncate(attr
->ia_atime
,
190 if (ia_valid
& ATTR_MTIME
) {
191 inode
->i_mtime
= timestamp_truncate(attr
->ia_mtime
,
194 if (ia_valid
& ATTR_CTIME
) {
195 inode
->i_ctime
= timestamp_truncate(attr
->ia_ctime
,
198 if (ia_valid
& ATTR_MODE
) {
199 umode_t mode
= attr
->ia_mode
;
201 if (!in_group_p(inode
->i_gid
) &&
202 !capable_wrt_inode_uidgid(inode
, CAP_FSETID
))
204 inode
->i_mode
= mode
;
207 EXPORT_SYMBOL(setattr_copy
);
210 * notify_change - modify attributes of a filesytem object
211 * @dentry: object affected
212 * @attr: new attributes
213 * @delegated_inode: returns inode, if the inode is delegated
215 * The caller must hold the i_mutex on the affected object.
217 * If notify_change discovers a delegation in need of breaking,
218 * it will return -EWOULDBLOCK and return a reference to the inode in
219 * delegated_inode. The caller should then break the delegation and
220 * retry. Because breaking a delegation may take a long time, the
221 * caller should drop the i_mutex before doing so.
223 * Alternatively, a caller may pass NULL for delegated_inode. This may
224 * be appropriate for callers that expect the underlying filesystem not
225 * to be NFS exported. Also, passing NULL is fine for callers holding
226 * the file open for write, as there can be no conflicting delegation in
229 int notify_change(struct dentry
* dentry
, struct iattr
* attr
, struct inode
**delegated_inode
)
231 struct inode
*inode
= dentry
->d_inode
;
232 umode_t mode
= inode
->i_mode
;
234 struct timespec64 now
;
235 unsigned int ia_valid
= attr
->ia_valid
;
237 WARN_ON_ONCE(!inode_is_locked(inode
));
239 if (ia_valid
& (ATTR_MODE
| ATTR_UID
| ATTR_GID
| ATTR_TIMES_SET
)) {
240 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
245 * If utimes(2) and friends are called with times == NULL (or both
246 * times are UTIME_NOW), then we need to check for write permission
248 if (ia_valid
& ATTR_TOUCH
) {
249 if (IS_IMMUTABLE(inode
))
252 if (!inode_owner_or_capable(inode
)) {
253 error
= inode_permission(inode
, MAY_WRITE
);
259 if ((ia_valid
& ATTR_MODE
)) {
260 umode_t amode
= attr
->ia_mode
;
261 /* Flag setting protected by i_mutex */
263 inode
->i_flags
&= ~S_NOSEC
;
266 now
= current_time(inode
);
268 attr
->ia_ctime
= now
;
269 if (!(ia_valid
& ATTR_ATIME_SET
))
270 attr
->ia_atime
= now
;
271 if (!(ia_valid
& ATTR_MTIME_SET
))
272 attr
->ia_mtime
= now
;
273 if (ia_valid
& ATTR_KILL_PRIV
) {
274 error
= security_inode_need_killpriv(dentry
);
278 ia_valid
= attr
->ia_valid
&= ~ATTR_KILL_PRIV
;
282 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
283 * that the function has the ability to reinterpret a mode change
284 * that's due to these bits. This adds an implicit restriction that
285 * no function will ever call notify_change with both ATTR_MODE and
286 * ATTR_KILL_S*ID set.
288 if ((ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
)) &&
289 (ia_valid
& ATTR_MODE
))
292 if (ia_valid
& ATTR_KILL_SUID
) {
293 if (mode
& S_ISUID
) {
294 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
295 attr
->ia_mode
= (inode
->i_mode
& ~S_ISUID
);
298 if (ia_valid
& ATTR_KILL_SGID
) {
299 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
)) {
300 if (!(ia_valid
& ATTR_MODE
)) {
301 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
302 attr
->ia_mode
= inode
->i_mode
;
304 attr
->ia_mode
&= ~S_ISGID
;
307 if (!(attr
->ia_valid
& ~(ATTR_KILL_SUID
| ATTR_KILL_SGID
)))
311 * Verify that uid/gid changes are valid in the target
312 * namespace of the superblock.
314 if (ia_valid
& ATTR_UID
&&
315 !kuid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_uid
))
317 if (ia_valid
& ATTR_GID
&&
318 !kgid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_gid
))
321 /* Don't allow modifications of files with invalid uids or
322 * gids unless those uids & gids are being made valid.
324 if (!(ia_valid
& ATTR_UID
) && !uid_valid(inode
->i_uid
))
326 if (!(ia_valid
& ATTR_GID
) && !gid_valid(inode
->i_gid
))
329 error
= security_inode_setattr(dentry
, attr
);
332 error
= try_break_deleg(inode
, delegated_inode
);
336 if (inode
->i_op
->setattr
)
337 error
= inode
->i_op
->setattr(dentry
, attr
);
339 error
= simple_setattr(dentry
, attr
);
342 fsnotify_change(dentry
, ia_valid
);
343 ima_inode_post_setattr(dentry
);
344 evm_inode_post_setattr(dentry
, ia_valid
);
349 EXPORT_SYMBOL(notify_change
);