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)
139 if (inode->i_size < offset) {
142 limit = rlimit(RLIMIT_FSIZE);
143 if (limit != RLIM_INFINITY && offset > limit)
145 if (offset > inode->i_sb->s_maxbytes)
149 * truncation of in-use swapfiles is disallowed - it would
150 * cause subsequent swapout to scribble on the now-freed
153 if (IS_SWAPFILE(inode))
159 send_sig(SIGXFSZ, current, 0);
163 EXPORT_SYMBOL(inode_newsize_ok);
166 * setattr_copy - copy simple metadata updates into the generic inode
167 * @inode: the inode to be updated
168 * @attr: the new attributes
170 * setattr_copy must be called with i_mutex held.
172 * setattr_copy updates the inode's metadata with that specified
173 * in attr. Noticeably missing is inode size update, which is more complex
174 * as it requires pagecache updates.
176 * The inode is not marked as dirty after this operation. The rationale is
177 * that for "simple" filesystems, the struct inode is the inode storage.
178 * The caller is free to mark the inode dirty afterwards if needed.
180 void setattr_copy(struct inode *inode, const struct iattr *attr)
182 unsigned int ia_valid = attr->ia_valid;
184 if (ia_valid & ATTR_UID)
185 inode->i_uid = attr->ia_uid;
186 if (ia_valid & ATTR_GID)
187 inode->i_gid = attr->ia_gid;
188 if (ia_valid & ATTR_ATIME)
189 inode->i_atime = attr->ia_atime;
190 if (ia_valid & ATTR_MTIME)
191 inode->i_mtime = attr->ia_mtime;
192 if (ia_valid & ATTR_CTIME)
193 inode->i_ctime = attr->ia_ctime;
194 if (ia_valid & ATTR_MODE) {
195 umode_t mode = attr->ia_mode;
197 if (!in_group_p(inode->i_gid) &&
198 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
200 inode->i_mode = mode;
203 EXPORT_SYMBOL(setattr_copy);
206 * notify_change - modify attributes of a filesytem object
207 * @dentry: object affected
208 * @attr: new attributes
209 * @delegated_inode: returns inode, if the inode is delegated
211 * The caller must hold the i_mutex on the affected object.
213 * If notify_change discovers a delegation in need of breaking,
214 * it will return -EWOULDBLOCK and return a reference to the inode in
215 * delegated_inode. The caller should then break the delegation and
216 * retry. Because breaking a delegation may take a long time, the
217 * caller should drop the i_mutex before doing so.
219 * Alternatively, a caller may pass NULL for delegated_inode. This may
220 * be appropriate for callers that expect the underlying filesystem not
221 * to be NFS exported. Also, passing NULL is fine for callers holding
222 * the file open for write, as there can be no conflicting delegation in
225 int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
227 struct inode *inode = dentry->d_inode;
228 umode_t mode = inode->i_mode;
230 struct timespec64 now;
231 unsigned int ia_valid = attr->ia_valid;
233 WARN_ON_ONCE(!inode_is_locked(inode));
235 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
236 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
241 * If utimes(2) and friends are called with times == NULL (or both
242 * times are UTIME_NOW), then we need to check for write permission
244 if (ia_valid & ATTR_TOUCH) {
245 if (IS_IMMUTABLE(inode))
248 if (!inode_owner_or_capable(inode)) {
249 error = inode_permission(inode, MAY_WRITE);
255 if ((ia_valid & ATTR_MODE)) {
257 * Don't allow changing the mode of symlinks:
259 * (1) The vfs doesn't take the mode of symlinks into account
260 * during permission checking.
261 * (2) This has never worked correctly. Most major filesystems
262 * did return EOPNOTSUPP due to interactions with POSIX ACLs
263 * but did still updated the mode of the symlink.
264 * This inconsistency led system call wrapper providers such
265 * as libc to block changing the mode of symlinks with
266 * EOPNOTSUPP already.
267 * (3) To even do this in the first place one would have to use
268 * specific file descriptors and quite some effort.
270 if (S_ISLNK(inode->i_mode))
273 /* Flag setting protected by i_mutex */
274 if (is_sxid(attr->ia_mode))
275 inode->i_flags &= ~S_NOSEC;
278 now = current_time(inode);
280 attr->ia_ctime = now;
281 if (!(ia_valid & ATTR_ATIME_SET))
282 attr->ia_atime = now;
284 attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
285 if (!(ia_valid & ATTR_MTIME_SET))
286 attr->ia_mtime = now;
288 attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);
290 if (ia_valid & ATTR_KILL_PRIV) {
291 error = security_inode_need_killpriv(dentry);
295 ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
299 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
300 * that the function has the ability to reinterpret a mode change
301 * that's due to these bits. This adds an implicit restriction that
302 * no function will ever call notify_change with both ATTR_MODE and
303 * ATTR_KILL_S*ID set.
305 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
306 (ia_valid & ATTR_MODE))
309 if (ia_valid & ATTR_KILL_SUID) {
310 if (mode & S_ISUID) {
311 ia_valid = attr->ia_valid |= ATTR_MODE;
312 attr->ia_mode = (inode->i_mode & ~S_ISUID);
315 if (ia_valid & ATTR_KILL_SGID) {
316 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
317 if (!(ia_valid & ATTR_MODE)) {
318 ia_valid = attr->ia_valid |= ATTR_MODE;
319 attr->ia_mode = inode->i_mode;
321 attr->ia_mode &= ~S_ISGID;
324 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
328 * Verify that uid/gid changes are valid in the target
329 * namespace of the superblock.
331 if (ia_valid & ATTR_UID &&
332 !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
334 if (ia_valid & ATTR_GID &&
335 !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
338 /* Don't allow modifications of files with invalid uids or
339 * gids unless those uids & gids are being made valid.
341 if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
343 if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
346 error = security_inode_setattr(dentry, attr);
349 error = try_break_deleg(inode, delegated_inode);
353 if (inode->i_op->setattr)
354 error = inode->i_op->setattr(dentry, attr);
356 error = simple_setattr(dentry, attr);
359 fsnotify_change(dentry, ia_valid);
360 ima_inode_post_setattr(dentry);
361 evm_inode_post_setattr(dentry, ia_valid);
366 EXPORT_SYMBOL(notify_change);