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);