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 * inode_change_ok - check if attribute changes to an inode are allowed
21 * @inode: inode to check
22 * @attr: attributes to change
24 * Check if we are allowed to change the attributes contained in @attr
25 * in the given inode. This includes the normal unix access permission
26 * checks, as well as checks for rlimits and others.
28 * Should be called as the first thing in ->setattr implementations,
29 * possibly after taking additional locks.
31 int inode_change_ok(const struct inode *inode, struct iattr *attr)
33 unsigned int ia_valid = attr->ia_valid;
36 * First check size constraints. These can't be overriden using
39 if (ia_valid & ATTR_SIZE) {
40 int error = inode_newsize_ok(inode, attr->ia_size);
45 /* If force is set do it anyway. */
46 if (ia_valid & ATTR_FORCE)
49 /* Make sure a caller can chown. */
50 if ((ia_valid & ATTR_UID) &&
51 (!uid_eq(current_fsuid(), inode->i_uid) ||
52 !uid_eq(attr->ia_uid, inode->i_uid)) &&
53 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
56 /* Make sure caller can chgrp. */
57 if ((ia_valid & ATTR_GID) &&
58 (!uid_eq(current_fsuid(), inode->i_uid) ||
59 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
60 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
63 /* Make sure a caller can chmod. */
64 if (ia_valid & ATTR_MODE) {
65 if (!inode_owner_or_capable(inode))
67 /* Also check the setgid bit! */
68 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
70 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
71 attr->ia_mode &= ~S_ISGID;
74 /* Check for setting the inode time. */
75 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
76 if (!inode_owner_or_capable(inode))
82 EXPORT_SYMBOL(inode_change_ok);
85 * inode_newsize_ok - may this inode be truncated to a given size
86 * @inode: the inode to be truncated
87 * @offset: the new size to assign to the inode
88 * @Returns: 0 on success, -ve errno on failure
90 * inode_newsize_ok must be called with i_mutex held.
92 * inode_newsize_ok will check filesystem limits and ulimits to check that the
93 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
94 * when necessary. Caller must not proceed with inode size change if failure is
95 * returned. @inode must be a file (not directory), with appropriate
96 * permissions to allow truncate (inode_newsize_ok does NOT check these
99 int inode_newsize_ok(const struct inode *inode, loff_t offset)
101 if (inode->i_size < offset) {
104 limit = rlimit(RLIMIT_FSIZE);
105 if (limit != RLIM_INFINITY && offset > limit)
107 if (offset > inode->i_sb->s_maxbytes)
111 * truncation of in-use swapfiles is disallowed - it would
112 * cause subsequent swapout to scribble on the now-freed
115 if (IS_SWAPFILE(inode))
121 send_sig(SIGXFSZ, current, 0);
125 EXPORT_SYMBOL(inode_newsize_ok);
128 * setattr_copy - copy simple metadata updates into the generic inode
129 * @inode: the inode to be updated
130 * @attr: the new attributes
132 * setattr_copy must be called with i_mutex held.
134 * setattr_copy updates the inode's metadata with that specified
135 * in attr. Noticeably missing is inode size update, which is more complex
136 * as it requires pagecache updates.
138 * The inode is not marked as dirty after this operation. The rationale is
139 * that for "simple" filesystems, the struct inode is the inode storage.
140 * The caller is free to mark the inode dirty afterwards if needed.
142 void setattr_copy(struct inode *inode, const struct iattr *attr)
144 unsigned int ia_valid = attr->ia_valid;
146 if (ia_valid & ATTR_UID)
147 inode->i_uid = attr->ia_uid;
148 if (ia_valid & ATTR_GID)
149 inode->i_gid = attr->ia_gid;
150 if (ia_valid & ATTR_ATIME)
151 inode->i_atime = timespec_trunc(attr->ia_atime,
152 inode->i_sb->s_time_gran);
153 if (ia_valid & ATTR_MTIME)
154 inode->i_mtime = timespec_trunc(attr->ia_mtime,
155 inode->i_sb->s_time_gran);
156 if (ia_valid & ATTR_CTIME)
157 inode->i_ctime = timespec_trunc(attr->ia_ctime,
158 inode->i_sb->s_time_gran);
159 if (ia_valid & ATTR_MODE) {
160 umode_t mode = attr->ia_mode;
162 if (!in_group_p(inode->i_gid) &&
163 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
165 inode->i_mode = mode;
168 EXPORT_SYMBOL(setattr_copy);
171 * notify_change - modify attributes of a filesytem object
172 * @dentry: object affected
173 * @iattr: new attributes
174 * @delegated_inode: returns inode, if the inode is delegated
176 * The caller must hold the i_mutex on the affected object.
178 * If notify_change discovers a delegation in need of breaking,
179 * it will return -EWOULDBLOCK and return a reference to the inode in
180 * delegated_inode. The caller should then break the delegation and
181 * retry. Because breaking a delegation may take a long time, the
182 * caller should drop the i_mutex before doing so.
184 * Alternatively, a caller may pass NULL for delegated_inode. This may
185 * be appropriate for callers that expect the underlying filesystem not
186 * to be NFS exported. Also, passing NULL is fine for callers holding
187 * the file open for write, as there can be no conflicting delegation in
190 int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
192 struct inode *inode = dentry->d_inode;
193 umode_t mode = inode->i_mode;
196 unsigned int ia_valid = attr->ia_valid;
198 WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
200 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
201 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
205 if ((ia_valid & ATTR_MODE)) {
206 umode_t amode = attr->ia_mode;
207 /* Flag setting protected by i_mutex */
209 inode->i_flags &= ~S_NOSEC;
212 now = current_fs_time(inode->i_sb);
214 attr->ia_ctime = now;
215 if (!(ia_valid & ATTR_ATIME_SET))
216 attr->ia_atime = now;
217 if (!(ia_valid & ATTR_MTIME_SET))
218 attr->ia_mtime = now;
219 if (ia_valid & ATTR_KILL_PRIV) {
220 attr->ia_valid &= ~ATTR_KILL_PRIV;
221 ia_valid &= ~ATTR_KILL_PRIV;
222 error = security_inode_need_killpriv(dentry);
224 error = security_inode_killpriv(dentry);
230 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
231 * that the function has the ability to reinterpret a mode change
232 * that's due to these bits. This adds an implicit restriction that
233 * no function will ever call notify_change with both ATTR_MODE and
234 * ATTR_KILL_S*ID set.
236 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
237 (ia_valid & ATTR_MODE))
240 if (ia_valid & ATTR_KILL_SUID) {
241 if (mode & S_ISUID) {
242 ia_valid = attr->ia_valid |= ATTR_MODE;
243 attr->ia_mode = (inode->i_mode & ~S_ISUID);
246 if (ia_valid & ATTR_KILL_SGID) {
247 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
248 if (!(ia_valid & ATTR_MODE)) {
249 ia_valid = attr->ia_valid |= ATTR_MODE;
250 attr->ia_mode = inode->i_mode;
252 attr->ia_mode &= ~S_ISGID;
255 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
258 error = security_inode_setattr(dentry, attr);
261 error = try_break_deleg(inode, delegated_inode);
265 if (inode->i_op->setattr)
266 error = inode->i_op->setattr(dentry, attr);
268 error = simple_setattr(dentry, attr);
271 fsnotify_change(dentry, ia_valid);
272 ima_inode_post_setattr(dentry);
273 evm_inode_post_setattr(dentry, ia_valid);
278 EXPORT_SYMBOL(notify_change);