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))
82 EXPORT_SYMBOL(setattr_prepare);
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) && !capable(CAP_FSETID))
164 inode->i_mode = mode;
167 EXPORT_SYMBOL(setattr_copy);
169 int notify_change(struct dentry * dentry, struct iattr * attr)
171 struct inode *inode = dentry->d_inode;
172 mode_t mode = inode->i_mode;
175 unsigned int ia_valid = attr->ia_valid;
177 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
178 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
182 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
183 if (attr->ia_size != inode->i_size)
184 inode_inc_iversion(inode);
187 if ((ia_valid & ATTR_MODE)) {
188 mode_t amode = attr->ia_mode;
189 /* Flag setting protected by i_mutex */
191 inode->i_flags &= ~S_NOSEC;
194 now = current_fs_time(inode->i_sb);
196 attr->ia_ctime = now;
197 if (!(ia_valid & ATTR_ATIME_SET))
198 attr->ia_atime = now;
199 if (!(ia_valid & ATTR_MTIME_SET))
200 attr->ia_mtime = now;
201 if (ia_valid & ATTR_KILL_PRIV) {
202 attr->ia_valid &= ~ATTR_KILL_PRIV;
203 ia_valid &= ~ATTR_KILL_PRIV;
204 error = security_inode_need_killpriv(dentry);
206 error = security_inode_killpriv(dentry);
212 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
213 * that the function has the ability to reinterpret a mode change
214 * that's due to these bits. This adds an implicit restriction that
215 * no function will ever call notify_change with both ATTR_MODE and
216 * ATTR_KILL_S*ID set.
218 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
219 (ia_valid & ATTR_MODE))
222 if (ia_valid & ATTR_KILL_SUID) {
223 if (mode & S_ISUID) {
224 ia_valid = attr->ia_valid |= ATTR_MODE;
225 attr->ia_mode = (inode->i_mode & ~S_ISUID);
228 if (ia_valid & ATTR_KILL_SGID) {
229 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
230 if (!(ia_valid & ATTR_MODE)) {
231 ia_valid = attr->ia_valid |= ATTR_MODE;
232 attr->ia_mode = inode->i_mode;
234 attr->ia_mode &= ~S_ISGID;
237 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
240 error = security_inode_setattr(dentry, attr);
244 if (inode->i_op->setattr)
245 error = inode->i_op->setattr(dentry, attr);
247 error = simple_setattr(dentry, attr);
250 fsnotify_change(dentry, ia_valid);
251 evm_inode_post_setattr(dentry, ia_valid);
257 EXPORT_SYMBOL(notify_change);