4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
8 #include <linux/export.h>
9 #include <linux/time.h>
11 #include <linux/string.h>
12 #include <linux/capability.h>
13 #include <linux/fsnotify.h>
14 #include <linux/fcntl.h>
15 #include <linux/security.h>
16 #include <linux/evm.h>
17 #include <linux/ima.h>
20 * setattr_prepare - check if attribute changes to a dentry are allowed
21 * @dentry: dentry to check
22 * @attr: attributes to change
24 * Check if we are allowed to change the attributes contained in @attr
25 * in the given dentry. This includes the normal unix access permission
26 * checks, as well as checks for rlimits and others. The function also clears
27 * SGID bit from mode if user is not allowed to set it. Also file capabilities
28 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
30 * Should be called as the first thing in ->setattr implementations,
31 * possibly after taking additional locks.
33 int setattr_prepare(struct dentry *dentry, struct iattr *attr)
35 struct inode *inode = d_inode(dentry);
36 unsigned int ia_valid = attr->ia_valid;
39 * First check size constraints. These can't be overriden using
42 if (ia_valid & ATTR_SIZE) {
43 int error = inode_newsize_ok(inode, attr->ia_size);
48 /* If force is set do it anyway. */
49 if (ia_valid & ATTR_FORCE)
52 /* Make sure a caller can chown. */
53 if ((ia_valid & ATTR_UID) &&
54 (!uid_eq(current_fsuid(), inode->i_uid) ||
55 !uid_eq(attr->ia_uid, inode->i_uid)) &&
56 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
59 /* Make sure caller can chgrp. */
60 if ((ia_valid & ATTR_GID) &&
61 (!uid_eq(current_fsuid(), inode->i_uid) ||
62 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
63 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
66 /* Make sure a caller can chmod. */
67 if (ia_valid & ATTR_MODE) {
68 if (!inode_owner_or_capable(inode))
70 /* Also check the setgid bit! */
71 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
73 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
74 attr->ia_mode &= ~S_ISGID;
77 /* Check for setting the inode time. */
78 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
79 if (!inode_owner_or_capable(inode))
85 EXPORT_SYMBOL(setattr_prepare);
88 * inode_newsize_ok - may this inode be truncated to a given size
89 * @inode: the inode to be truncated
90 * @offset: the new size to assign to the inode
91 * @Returns: 0 on success, -ve errno on failure
93 * inode_newsize_ok must be called with i_mutex held.
95 * inode_newsize_ok will check filesystem limits and ulimits to check that the
96 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
97 * when necessary. Caller must not proceed with inode size change if failure is
98 * returned. @inode must be a file (not directory), with appropriate
99 * permissions to allow truncate (inode_newsize_ok does NOT check these
102 int inode_newsize_ok(const struct inode *inode, loff_t offset)
104 if (inode->i_size < offset) {
107 limit = rlimit(RLIMIT_FSIZE);
108 if (limit != RLIM_INFINITY && offset > limit)
110 if (offset > inode->i_sb->s_maxbytes)
114 * truncation of in-use swapfiles is disallowed - it would
115 * cause subsequent swapout to scribble on the now-freed
118 if (IS_SWAPFILE(inode))
124 send_sig(SIGXFSZ, current, 0);
128 EXPORT_SYMBOL(inode_newsize_ok);
131 * setattr_copy - copy simple metadata updates into the generic inode
132 * @inode: the inode to be updated
133 * @attr: the new attributes
135 * setattr_copy must be called with i_mutex held.
137 * setattr_copy updates the inode's metadata with that specified
138 * in attr. Noticeably missing is inode size update, which is more complex
139 * as it requires pagecache updates.
141 * The inode is not marked as dirty after this operation. The rationale is
142 * that for "simple" filesystems, the struct inode is the inode storage.
143 * The caller is free to mark the inode dirty afterwards if needed.
145 void setattr_copy(struct inode *inode, const struct iattr *attr)
147 unsigned int ia_valid = attr->ia_valid;
149 if (ia_valid & ATTR_UID)
150 inode->i_uid = attr->ia_uid;
151 if (ia_valid & ATTR_GID)
152 inode->i_gid = attr->ia_gid;
153 if (ia_valid & ATTR_ATIME)
154 inode->i_atime = timespec_trunc(attr->ia_atime,
155 inode->i_sb->s_time_gran);
156 if (ia_valid & ATTR_MTIME)
157 inode->i_mtime = timespec_trunc(attr->ia_mtime,
158 inode->i_sb->s_time_gran);
159 if (ia_valid & ATTR_CTIME)
160 inode->i_ctime = timespec_trunc(attr->ia_ctime,
161 inode->i_sb->s_time_gran);
162 if (ia_valid & ATTR_MODE) {
163 umode_t mode = attr->ia_mode;
165 if (!in_group_p(inode->i_gid) &&
166 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
168 inode->i_mode = mode;
171 EXPORT_SYMBOL(setattr_copy);
174 * notify_change - modify attributes of a filesytem object
175 * @dentry: object affected
176 * @iattr: new attributes
177 * @delegated_inode: returns inode, if the inode is delegated
179 * The caller must hold the i_mutex on the affected object.
181 * If notify_change discovers a delegation in need of breaking,
182 * it will return -EWOULDBLOCK and return a reference to the inode in
183 * delegated_inode. The caller should then break the delegation and
184 * retry. Because breaking a delegation may take a long time, the
185 * caller should drop the i_mutex before doing so.
187 * Alternatively, a caller may pass NULL for delegated_inode. This may
188 * be appropriate for callers that expect the underlying filesystem not
189 * to be NFS exported. Also, passing NULL is fine for callers holding
190 * the file open for write, as there can be no conflicting delegation in
193 int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
195 struct inode *inode = dentry->d_inode;
196 umode_t mode = inode->i_mode;
199 unsigned int ia_valid = attr->ia_valid;
201 WARN_ON_ONCE(!inode_is_locked(inode));
203 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
204 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
208 if ((ia_valid & ATTR_MODE)) {
209 umode_t amode = attr->ia_mode;
210 /* Flag setting protected by i_mutex */
212 inode->i_flags &= ~S_NOSEC;
215 now = current_fs_time(inode->i_sb);
217 attr->ia_ctime = now;
218 if (!(ia_valid & ATTR_ATIME_SET))
219 attr->ia_atime = now;
220 if (!(ia_valid & ATTR_MTIME_SET))
221 attr->ia_mtime = now;
222 if (ia_valid & ATTR_KILL_PRIV) {
223 attr->ia_valid &= ~ATTR_KILL_PRIV;
224 ia_valid &= ~ATTR_KILL_PRIV;
225 error = security_inode_need_killpriv(dentry);
227 error = security_inode_killpriv(dentry);
233 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
234 * that the function has the ability to reinterpret a mode change
235 * that's due to these bits. This adds an implicit restriction that
236 * no function will ever call notify_change with both ATTR_MODE and
237 * ATTR_KILL_S*ID set.
239 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
240 (ia_valid & ATTR_MODE))
243 if (ia_valid & ATTR_KILL_SUID) {
244 if (mode & S_ISUID) {
245 ia_valid = attr->ia_valid |= ATTR_MODE;
246 attr->ia_mode = (inode->i_mode & ~S_ISUID);
249 if (ia_valid & ATTR_KILL_SGID) {
250 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
251 if (!(ia_valid & ATTR_MODE)) {
252 ia_valid = attr->ia_valid |= ATTR_MODE;
253 attr->ia_mode = inode->i_mode;
255 attr->ia_mode &= ~S_ISGID;
258 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
262 * Verify that uid/gid changes are valid in the target
263 * namespace of the superblock.
265 if (ia_valid & ATTR_UID &&
266 !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
268 if (ia_valid & ATTR_GID &&
269 !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
272 /* Don't allow modifications of files with invalid uids or
273 * gids unless those uids & gids are being made valid.
275 if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
277 if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
280 error = security_inode_setattr(dentry, attr);
283 error = try_break_deleg(inode, delegated_inode);
287 if (inode->i_op->setattr)
288 error = inode->i_op->setattr(dentry, attr);
290 error = simple_setattr(dentry, attr);
293 fsnotify_change(dentry, ia_valid);
294 ima_inode_post_setattr(dentry);
295 evm_inode_post_setattr(dentry, ia_valid);
300 EXPORT_SYMBOL(notify_change);