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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 (ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
33 static bool chgrp_ok(const struct inode
*inode
, kgid_t gid
)
35 if (uid_eq(current_fsuid(), inode
->i_uid
) &&
36 (in_group_p(gid
) || gid_eq(gid
, inode
->i_gid
)))
38 if (capable_wrt_inode_uidgid(inode
, CAP_CHOWN
))
40 if (ns_capable(inode
->i_sb
->s_user_ns
, CAP_CHOWN
))
46 * setattr_prepare - check if attribute changes to a dentry are allowed
47 * @dentry: dentry to check
48 * @attr: attributes to change
50 * Check if we are allowed to change the attributes contained in @attr
51 * in the given dentry. This includes the normal unix access permission
52 * checks, as well as checks for rlimits and others. The function also clears
53 * SGID bit from mode if user is not allowed to set it. Also file capabilities
54 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
56 * Should be called as the first thing in ->setattr implementations,
57 * possibly after taking additional locks.
59 int setattr_prepare(struct dentry
*dentry
, struct iattr
*attr
)
61 struct inode
*inode
= d_inode(dentry
);
62 unsigned int ia_valid
= attr
->ia_valid
;
65 * First check size constraints. These can't be overriden using
68 if (ia_valid
& ATTR_SIZE
) {
69 int error
= inode_newsize_ok(inode
, attr
->ia_size
);
74 /* If force is set do it anyway. */
75 if (ia_valid
& ATTR_FORCE
)
78 /* Make sure a caller can chown. */
79 if ((ia_valid
& ATTR_UID
) && !chown_ok(inode
, attr
->ia_uid
))
82 /* Make sure caller can chgrp. */
83 if ((ia_valid
& ATTR_GID
) && !chgrp_ok(inode
, attr
->ia_gid
))
86 /* Make sure a caller can chmod. */
87 if (ia_valid
& ATTR_MODE
) {
88 if (!inode_owner_or_capable(inode
))
90 /* Also check the setgid bit! */
91 if (!in_group_p((ia_valid
& ATTR_GID
) ? attr
->ia_gid
:
93 !capable_wrt_inode_uidgid(inode
, CAP_FSETID
))
94 attr
->ia_mode
&= ~S_ISGID
;
97 /* Check for setting the inode time. */
98 if (ia_valid
& (ATTR_MTIME_SET
| ATTR_ATIME_SET
| ATTR_TIMES_SET
)) {
99 if (!inode_owner_or_capable(inode
))
104 /* User has permission for the change */
105 if (ia_valid
& ATTR_KILL_PRIV
) {
108 error
= security_inode_killpriv(dentry
);
115 EXPORT_SYMBOL(setattr_prepare
);
118 * inode_newsize_ok - may this inode be truncated to a given size
119 * @inode: the inode to be truncated
120 * @offset: the new size to assign to the inode
121 * @Returns: 0 on success, -ve errno on failure
123 * inode_newsize_ok must be called with i_mutex held.
125 * inode_newsize_ok will check filesystem limits and ulimits to check that the
126 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
127 * when necessary. Caller must not proceed with inode size change if failure is
128 * returned. @inode must be a file (not directory), with appropriate
129 * permissions to allow truncate (inode_newsize_ok does NOT check these
132 int inode_newsize_ok(const struct inode
*inode
, loff_t offset
)
134 if (inode
->i_size
< offset
) {
137 limit
= rlimit(RLIMIT_FSIZE
);
138 if (limit
!= RLIM_INFINITY
&& offset
> limit
)
140 if (offset
> inode
->i_sb
->s_maxbytes
)
144 * truncation of in-use swapfiles is disallowed - it would
145 * cause subsequent swapout to scribble on the now-freed
148 if (IS_SWAPFILE(inode
))
154 send_sig(SIGXFSZ
, current
, 0);
158 EXPORT_SYMBOL(inode_newsize_ok
);
161 * setattr_copy - copy simple metadata updates into the generic inode
162 * @inode: the inode to be updated
163 * @attr: the new attributes
165 * setattr_copy must be called with i_mutex held.
167 * setattr_copy updates the inode's metadata with that specified
168 * in attr. Noticeably missing is inode size update, which is more complex
169 * as it requires pagecache updates.
171 * The inode is not marked as dirty after this operation. The rationale is
172 * that for "simple" filesystems, the struct inode is the inode storage.
173 * The caller is free to mark the inode dirty afterwards if needed.
175 void setattr_copy(struct inode
*inode
, const struct iattr
*attr
)
177 unsigned int ia_valid
= attr
->ia_valid
;
179 if (ia_valid
& ATTR_UID
)
180 inode
->i_uid
= attr
->ia_uid
;
181 if (ia_valid
& ATTR_GID
)
182 inode
->i_gid
= attr
->ia_gid
;
183 if (ia_valid
& ATTR_ATIME
)
184 inode
->i_atime
= timespec_trunc(attr
->ia_atime
,
185 inode
->i_sb
->s_time_gran
);
186 if (ia_valid
& ATTR_MTIME
)
187 inode
->i_mtime
= timespec_trunc(attr
->ia_mtime
,
188 inode
->i_sb
->s_time_gran
);
189 if (ia_valid
& ATTR_CTIME
)
190 inode
->i_ctime
= timespec_trunc(attr
->ia_ctime
,
191 inode
->i_sb
->s_time_gran
);
192 if (ia_valid
& ATTR_MODE
) {
193 umode_t mode
= attr
->ia_mode
;
195 if (!in_group_p(inode
->i_gid
) &&
196 !capable_wrt_inode_uidgid(inode
, CAP_FSETID
))
198 inode
->i_mode
= mode
;
201 EXPORT_SYMBOL(setattr_copy
);
204 * notify_change - modify attributes of a filesytem object
205 * @dentry: object affected
206 * @iattr: new attributes
207 * @delegated_inode: returns inode, if the inode is delegated
209 * The caller must hold the i_mutex on the affected object.
211 * If notify_change discovers a delegation in need of breaking,
212 * it will return -EWOULDBLOCK and return a reference to the inode in
213 * delegated_inode. The caller should then break the delegation and
214 * retry. Because breaking a delegation may take a long time, the
215 * caller should drop the i_mutex before doing so.
217 * Alternatively, a caller may pass NULL for delegated_inode. This may
218 * be appropriate for callers that expect the underlying filesystem not
219 * to be NFS exported. Also, passing NULL is fine for callers holding
220 * the file open for write, as there can be no conflicting delegation in
223 int notify_change(struct dentry
* dentry
, struct iattr
* attr
, struct inode
**delegated_inode
)
225 struct inode
*inode
= dentry
->d_inode
;
226 umode_t mode
= inode
->i_mode
;
229 unsigned int ia_valid
= attr
->ia_valid
;
231 WARN_ON_ONCE(!inode_is_locked(inode
));
233 if (ia_valid
& (ATTR_MODE
| ATTR_UID
| ATTR_GID
| ATTR_TIMES_SET
)) {
234 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
239 * If utimes(2) and friends are called with times == NULL (or both
240 * times are UTIME_NOW), then we need to check for write permission
242 if (ia_valid
& ATTR_TOUCH
) {
243 if (IS_IMMUTABLE(inode
))
246 if (!inode_owner_or_capable(inode
)) {
247 error
= inode_permission(inode
, MAY_WRITE
);
253 if ((ia_valid
& ATTR_MODE
)) {
254 umode_t amode
= attr
->ia_mode
;
255 /* Flag setting protected by i_mutex */
257 inode
->i_flags
&= ~S_NOSEC
;
260 now
= current_time(inode
);
262 attr
->ia_ctime
= now
;
263 if (!(ia_valid
& ATTR_ATIME_SET
))
264 attr
->ia_atime
= now
;
265 if (!(ia_valid
& ATTR_MTIME_SET
))
266 attr
->ia_mtime
= now
;
267 if (ia_valid
& ATTR_KILL_PRIV
) {
268 error
= security_inode_need_killpriv(dentry
);
272 ia_valid
= attr
->ia_valid
&= ~ATTR_KILL_PRIV
;
276 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
277 * that the function has the ability to reinterpret a mode change
278 * that's due to these bits. This adds an implicit restriction that
279 * no function will ever call notify_change with both ATTR_MODE and
280 * ATTR_KILL_S*ID set.
282 if ((ia_valid
& (ATTR_KILL_SUID
|ATTR_KILL_SGID
)) &&
283 (ia_valid
& ATTR_MODE
))
286 if (ia_valid
& ATTR_KILL_SUID
) {
287 if (mode
& S_ISUID
) {
288 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
289 attr
->ia_mode
= (inode
->i_mode
& ~S_ISUID
);
292 if (ia_valid
& ATTR_KILL_SGID
) {
293 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
)) {
294 if (!(ia_valid
& ATTR_MODE
)) {
295 ia_valid
= attr
->ia_valid
|= ATTR_MODE
;
296 attr
->ia_mode
= inode
->i_mode
;
298 attr
->ia_mode
&= ~S_ISGID
;
301 if (!(attr
->ia_valid
& ~(ATTR_KILL_SUID
| ATTR_KILL_SGID
)))
305 * Verify that uid/gid changes are valid in the target
306 * namespace of the superblock.
308 if (ia_valid
& ATTR_UID
&&
309 !kuid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_uid
))
311 if (ia_valid
& ATTR_GID
&&
312 !kgid_has_mapping(inode
->i_sb
->s_user_ns
, attr
->ia_gid
))
315 /* Don't allow modifications of files with invalid uids or
316 * gids unless those uids & gids are being made valid.
318 if (!(ia_valid
& ATTR_UID
) && !uid_valid(inode
->i_uid
))
320 if (!(ia_valid
& ATTR_GID
) && !gid_valid(inode
->i_gid
))
323 error
= security_inode_setattr(dentry
, attr
);
326 error
= try_break_deleg(inode
, delegated_inode
);
330 if (inode
->i_op
->setattr
)
331 error
= inode
->i_op
->setattr(dentry
, attr
);
333 error
= simple_setattr(dentry
, attr
);
336 fsnotify_change(dentry
, ia_valid
);
337 ima_inode_post_setattr(dentry
);
338 evm_inode_post_setattr(dentry
, ia_valid
);
343 EXPORT_SYMBOL(notify_change
);