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 * setattr_prepare - check if attribute changes to a dentry are allowed
23 * @dentry: dentry to check
24 * @attr: attributes to change
26 * Check if we are allowed to change the attributes contained in @attr
27 * in the given dentry. This includes the normal unix access permission
28 * checks, as well as checks for rlimits and others. The function also clears
29 * SGID bit from mode if user is not allowed to set it. Also file capabilities
30 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
32 * Should be called as the first thing in ->setattr implementations,
33 * possibly after taking additional locks.
35 int setattr_prepare(struct dentry *dentry, struct iattr *attr)
37 struct inode *inode = d_inode(dentry);
38 unsigned int ia_valid = attr->ia_valid;
41 * First check size constraints. These can't be overriden using
44 if (ia_valid & ATTR_SIZE) {
45 int error = inode_newsize_ok(inode, attr->ia_size);
50 /* If force is set do it anyway. */
51 if (ia_valid & ATTR_FORCE)
54 /* Make sure a caller can chown. */
55 if ((ia_valid & ATTR_UID) &&
56 (!uid_eq(current_fsuid(), inode->i_uid) ||
57 !uid_eq(attr->ia_uid, inode->i_uid)) &&
58 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
61 /* Make sure caller can chgrp. */
62 if ((ia_valid & ATTR_GID) &&
63 (!uid_eq(current_fsuid(), inode->i_uid) ||
64 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
65 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
68 /* Make sure a caller can chmod. */
69 if (ia_valid & ATTR_MODE) {
70 if (!inode_owner_or_capable(inode))
72 /* Also check the setgid bit! */
73 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
75 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
76 attr->ia_mode &= ~S_ISGID;
79 /* Check for setting the inode time. */
80 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
81 if (!inode_owner_or_capable(inode))
86 /* User has permission for the change */
87 if (ia_valid & ATTR_KILL_PRIV) {
90 error = security_inode_killpriv(dentry);
97 EXPORT_SYMBOL(setattr_prepare);
100 * inode_newsize_ok - may this inode be truncated to a given size
101 * @inode: the inode to be truncated
102 * @offset: the new size to assign to the inode
103 * @Returns: 0 on success, -ve errno on failure
105 * inode_newsize_ok must be called with i_mutex held.
107 * inode_newsize_ok will check filesystem limits and ulimits to check that the
108 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
109 * when necessary. Caller must not proceed with inode size change if failure is
110 * returned. @inode must be a file (not directory), with appropriate
111 * permissions to allow truncate (inode_newsize_ok does NOT check these
114 int inode_newsize_ok(const struct inode *inode, loff_t offset)
118 if (inode->i_size < offset) {
121 limit = rlimit(RLIMIT_FSIZE);
122 if (limit != RLIM_INFINITY && offset > limit)
124 if (offset > inode->i_sb->s_maxbytes)
128 * truncation of in-use swapfiles is disallowed - it would
129 * cause subsequent swapout to scribble on the now-freed
132 if (IS_SWAPFILE(inode))
138 send_sig(SIGXFSZ, current, 0);
142 EXPORT_SYMBOL(inode_newsize_ok);
145 * setattr_copy - copy simple metadata updates into the generic inode
146 * @inode: the inode to be updated
147 * @attr: the new attributes
149 * setattr_copy must be called with i_mutex held.
151 * setattr_copy updates the inode's metadata with that specified
152 * in attr. Noticeably missing is inode size update, which is more complex
153 * as it requires pagecache updates.
155 * The inode is not marked as dirty after this operation. The rationale is
156 * that for "simple" filesystems, the struct inode is the inode storage.
157 * The caller is free to mark the inode dirty afterwards if needed.
159 void setattr_copy(struct inode *inode, const struct iattr *attr)
161 unsigned int ia_valid = attr->ia_valid;
163 if (ia_valid & ATTR_UID)
164 inode->i_uid = attr->ia_uid;
165 if (ia_valid & ATTR_GID)
166 inode->i_gid = attr->ia_gid;
167 if (ia_valid & ATTR_ATIME)
168 inode->i_atime = timespec_trunc(attr->ia_atime,
169 inode->i_sb->s_time_gran);
170 if (ia_valid & ATTR_MTIME)
171 inode->i_mtime = timespec_trunc(attr->ia_mtime,
172 inode->i_sb->s_time_gran);
173 if (ia_valid & ATTR_CTIME)
174 inode->i_ctime = timespec_trunc(attr->ia_ctime,
175 inode->i_sb->s_time_gran);
176 if (ia_valid & ATTR_MODE) {
177 umode_t mode = attr->ia_mode;
179 if (!in_group_p(inode->i_gid) &&
180 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
182 inode->i_mode = mode;
185 EXPORT_SYMBOL(setattr_copy);
188 * notify_change - modify attributes of a filesytem object
189 * @dentry: object affected
190 * @iattr: new attributes
191 * @delegated_inode: returns inode, if the inode is delegated
193 * The caller must hold the i_mutex on the affected object.
195 * If notify_change discovers a delegation in need of breaking,
196 * it will return -EWOULDBLOCK and return a reference to the inode in
197 * delegated_inode. The caller should then break the delegation and
198 * retry. Because breaking a delegation may take a long time, the
199 * caller should drop the i_mutex before doing so.
201 * Alternatively, a caller may pass NULL for delegated_inode. This may
202 * be appropriate for callers that expect the underlying filesystem not
203 * to be NFS exported. Also, passing NULL is fine for callers holding
204 * the file open for write, as there can be no conflicting delegation in
207 int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
209 struct inode *inode = dentry->d_inode;
210 umode_t mode = inode->i_mode;
213 unsigned int ia_valid = attr->ia_valid;
215 WARN_ON_ONCE(!inode_is_locked(inode));
217 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
218 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
223 * If utimes(2) and friends are called with times == NULL (or both
224 * times are UTIME_NOW), then we need to check for write permission
226 if (ia_valid & ATTR_TOUCH) {
227 if (IS_IMMUTABLE(inode))
230 if (!inode_owner_or_capable(inode)) {
231 error = inode_permission(inode, MAY_WRITE);
237 if ((ia_valid & ATTR_MODE)) {
239 * Don't allow changing the mode of symlinks:
241 * (1) The vfs doesn't take the mode of symlinks into account
242 * during permission checking.
243 * (2) This has never worked correctly. Most major filesystems
244 * did return EOPNOTSUPP due to interactions with POSIX ACLs
245 * but did still updated the mode of the symlink.
246 * This inconsistency led system call wrapper providers such
247 * as libc to block changing the mode of symlinks with
248 * EOPNOTSUPP already.
249 * (3) To even do this in the first place one would have to use
250 * specific file descriptors and quite some effort.
252 if (S_ISLNK(inode->i_mode))
255 /* Flag setting protected by i_mutex */
256 if (is_sxid(attr->ia_mode))
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);