4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
8 #include <linux/module.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>
19 * setattr_prepare - check if attribute changes to a dentry are allowed
20 * @dentry: dentry to check
21 * @attr: attributes to change
23 * Check if we are allowed to change the attributes contained in @attr
24 * in the given dentry. This includes the normal unix access permission
25 * checks, as well as checks for rlimits and others. The function also clears
26 * SGID bit from mode if user is not allowed to set it. Also file capabilities
27 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
29 * Should be called as the first thing in ->setattr implementations,
30 * possibly after taking additional locks.
32 int setattr_prepare(struct dentry *dentry, struct iattr *attr)
34 struct inode *inode = dentry->d_inode;
35 unsigned int ia_valid = attr->ia_valid;
38 * First check size constraints. These can't be overriden using
41 if (ia_valid & ATTR_SIZE) {
42 int error = inode_newsize_ok(inode, attr->ia_size);
47 /* If force is set do it anyway. */
48 if (ia_valid & ATTR_FORCE)
51 /* Make sure a caller can chown. */
52 if ((ia_valid & ATTR_UID) &&
53 (current_fsuid() != inode->i_uid ||
54 attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
57 /* Make sure caller can chgrp. */
58 if ((ia_valid & ATTR_GID) &&
59 (current_fsuid() != inode->i_uid ||
60 (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
64 /* Make sure a caller can chmod. */
65 if (ia_valid & ATTR_MODE) {
66 if (!inode_owner_or_capable(inode))
68 /* Also check the setgid bit! */
69 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
70 inode->i_gid) && !capable(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))
81 /* User has permission for the change */
82 if (ia_valid & ATTR_KILL_PRIV) {
85 error = security_inode_killpriv(dentry);
92 EXPORT_SYMBOL(setattr_prepare);
95 * inode_newsize_ok - may this inode be truncated to a given size
96 * @inode: the inode to be truncated
97 * @offset: the new size to assign to the inode
98 * @Returns: 0 on success, -ve errno on failure
100 * inode_newsize_ok must be called with i_mutex held.
102 * inode_newsize_ok will check filesystem limits and ulimits to check that the
103 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
104 * when necessary. Caller must not proceed with inode size change if failure is
105 * returned. @inode must be a file (not directory), with appropriate
106 * permissions to allow truncate (inode_newsize_ok does NOT check these
109 int inode_newsize_ok(const struct inode *inode, loff_t offset)
111 if (inode->i_size < offset) {
114 limit = rlimit(RLIMIT_FSIZE);
115 if (limit != RLIM_INFINITY && offset > limit)
117 if (offset > inode->i_sb->s_maxbytes)
121 * truncation of in-use swapfiles is disallowed - it would
122 * cause subsequent swapout to scribble on the now-freed
125 if (IS_SWAPFILE(inode))
131 send_sig(SIGXFSZ, current, 0);
135 EXPORT_SYMBOL(inode_newsize_ok);
138 * setattr_copy - copy simple metadata updates into the generic inode
139 * @inode: the inode to be updated
140 * @attr: the new attributes
142 * setattr_copy must be called with i_mutex held.
144 * setattr_copy updates the inode's metadata with that specified
145 * in attr. Noticeably missing is inode size update, which is more complex
146 * as it requires pagecache updates.
148 * The inode is not marked as dirty after this operation. The rationale is
149 * that for "simple" filesystems, the struct inode is the inode storage.
150 * The caller is free to mark the inode dirty afterwards if needed.
152 void setattr_copy(struct inode *inode, const struct iattr *attr)
154 unsigned int ia_valid = attr->ia_valid;
156 if (ia_valid & ATTR_UID)
157 inode->i_uid = attr->ia_uid;
158 if (ia_valid & ATTR_GID)
159 inode->i_gid = attr->ia_gid;
160 if (ia_valid & ATTR_ATIME)
161 inode->i_atime = timespec_trunc(attr->ia_atime,
162 inode->i_sb->s_time_gran);
163 if (ia_valid & ATTR_MTIME)
164 inode->i_mtime = timespec_trunc(attr->ia_mtime,
165 inode->i_sb->s_time_gran);
166 if (ia_valid & ATTR_CTIME)
167 inode->i_ctime = timespec_trunc(attr->ia_ctime,
168 inode->i_sb->s_time_gran);
169 if (ia_valid & ATTR_MODE) {
170 umode_t mode = attr->ia_mode;
172 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
174 inode->i_mode = mode;
177 EXPORT_SYMBOL(setattr_copy);
179 int notify_change(struct dentry * dentry, struct iattr * attr)
181 struct inode *inode = dentry->d_inode;
182 mode_t mode = inode->i_mode;
185 unsigned int ia_valid = attr->ia_valid;
187 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
188 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
192 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
193 if (attr->ia_size != inode->i_size)
194 inode_inc_iversion(inode);
197 if ((ia_valid & ATTR_MODE)) {
198 mode_t amode = attr->ia_mode;
199 /* Flag setting protected by i_mutex */
201 inode->i_flags &= ~S_NOSEC;
204 now = current_fs_time(inode->i_sb);
206 attr->ia_ctime = now;
207 if (!(ia_valid & ATTR_ATIME_SET))
208 attr->ia_atime = now;
209 if (!(ia_valid & ATTR_MTIME_SET))
210 attr->ia_mtime = now;
211 if (ia_valid & ATTR_KILL_PRIV) {
212 error = security_inode_need_killpriv(dentry);
216 ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
220 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
221 * that the function has the ability to reinterpret a mode change
222 * that's due to these bits. This adds an implicit restriction that
223 * no function will ever call notify_change with both ATTR_MODE and
224 * ATTR_KILL_S*ID set.
226 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
227 (ia_valid & ATTR_MODE))
230 if (ia_valid & ATTR_KILL_SUID) {
231 if (mode & S_ISUID) {
232 ia_valid = attr->ia_valid |= ATTR_MODE;
233 attr->ia_mode = (inode->i_mode & ~S_ISUID);
236 if (ia_valid & ATTR_KILL_SGID) {
237 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
238 if (!(ia_valid & ATTR_MODE)) {
239 ia_valid = attr->ia_valid |= ATTR_MODE;
240 attr->ia_mode = inode->i_mode;
242 attr->ia_mode &= ~S_ISGID;
245 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
248 error = security_inode_setattr(dentry, attr);
252 if (inode->i_op->setattr)
253 error = inode->i_op->setattr(dentry, attr);
255 error = simple_setattr(dentry, attr);
258 fsnotify_change(dentry, ia_valid);
259 evm_inode_post_setattr(dentry, ia_valid);
265 EXPORT_SYMBOL(notify_change);