1 /*
2 * linux/fs/attr.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
6 */
7
8 #include <linux/module.h>
9 #include <linux/time.h>
10 #include <linux/mm.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
17 /**
18 * inode_change_ok - check if attribute changes to an inode are allowed
19 * @inode: inode to check
20 * @attr: attributes to change
21 *
22 * Check if we are allowed to change the attributes contained in @attr
23 * in the given inode. This includes the normal unix access permission
24 * checks, as well as checks for rlimits and others.
25 *
26 * Should be called as the first thing in ->setattr implementations,
27 * possibly after taking additional locks.
28 */
inode_change_ok(const struct inode * inode,struct iattr * attr)29 int inode_change_ok(const struct inode *inode, struct iattr *attr)
30 {
31 unsigned int ia_valid = attr->ia_valid;
32
33 /*
34 * First check size constraints. These can't be overriden using
35 * ATTR_FORCE.
36 */
37 if (ia_valid & ATTR_SIZE) {
38 int error = inode_newsize_ok(inode, attr->ia_size);
39 if (error)
40 return error;
41 }
42
43 /* If force is set do it anyway. */
44 if (ia_valid & ATTR_FORCE)
45 return 0;
46
47 /* Make sure a caller can chown. */
48 if ((ia_valid & ATTR_UID) &&
49 (current_fsuid() != inode->i_uid ||
50 attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
51 return -EPERM;
52
53 /* Make sure caller can chgrp. */
54 if ((ia_valid & ATTR_GID) &&
55 (current_fsuid() != inode->i_uid ||
56 (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
57 !capable(CAP_CHOWN))
58 return -EPERM;
59
60 /* Make sure a caller can chmod. */
61 if (ia_valid & ATTR_MODE) {
62 if (!inode_owner_or_capable(inode))
63 return -EPERM;
64 /* Also check the setgid bit! */
65 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
66 inode->i_gid) && !capable(CAP_FSETID))
67 attr->ia_mode &= ~S_ISGID;
68 }
69
70 /* Check for setting the inode time. */
71 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
72 if (!inode_owner_or_capable(inode))
73 return -EPERM;
74 }
75
76 return 0;
77 }
78 EXPORT_SYMBOL(inode_change_ok);
79
80 /**
81 * inode_newsize_ok - may this inode be truncated to a given size
82 * @inode: the inode to be truncated
83 * @offset: the new size to assign to the inode
84 * @Returns: 0 on success, -ve errno on failure
85 *
86 * inode_newsize_ok must be called with i_mutex held.
87 *
88 * inode_newsize_ok will check filesystem limits and ulimits to check that the
89 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
90 * when necessary. Caller must not proceed with inode size change if failure is
91 * returned. @inode must be a file (not directory), with appropriate
92 * permissions to allow truncate (inode_newsize_ok does NOT check these
93 * conditions).
94 */
inode_newsize_ok(const struct inode * inode,loff_t offset)95 int inode_newsize_ok(const struct inode *inode, loff_t offset)
96 {
97 if (inode->i_size < offset) {
98 unsigned long limit;
99
100 limit = rlimit(RLIMIT_FSIZE);
101 if (limit != RLIM_INFINITY && offset > limit)
102 goto out_sig;
103 if (offset > inode->i_sb->s_maxbytes)
104 goto out_big;
105 } else {
106 /*
107 * truncation of in-use swapfiles is disallowed - it would
108 * cause subsequent swapout to scribble on the now-freed
109 * blocks.
110 */
111 if (IS_SWAPFILE(inode))
112 return -ETXTBSY;
113 }
114
115 return 0;
116 out_sig:
117 send_sig(SIGXFSZ, current, 0);
118 out_big:
119 return -EFBIG;
120 }
121 EXPORT_SYMBOL(inode_newsize_ok);
122
123 /**
124 * setattr_copy - copy simple metadata updates into the generic inode
125 * @inode: the inode to be updated
126 * @attr: the new attributes
127 *
128 * setattr_copy must be called with i_mutex held.
129 *
130 * setattr_copy updates the inode's metadata with that specified
131 * in attr. Noticeably missing is inode size update, which is more complex
132 * as it requires pagecache updates.
133 *
134 * The inode is not marked as dirty after this operation. The rationale is
135 * that for "simple" filesystems, the struct inode is the inode storage.
136 * The caller is free to mark the inode dirty afterwards if needed.
137 */
setattr_copy(struct inode * inode,const struct iattr * attr)138 void setattr_copy(struct inode *inode, const struct iattr *attr)
139 {
140 unsigned int ia_valid = attr->ia_valid;
141
142 if (ia_valid & ATTR_UID)
143 inode->i_uid = attr->ia_uid;
144 if (ia_valid & ATTR_GID)
145 inode->i_gid = attr->ia_gid;
146 if (ia_valid & ATTR_ATIME)
147 inode->i_atime = timespec_trunc(attr->ia_atime,
148 inode->i_sb->s_time_gran);
149 if (ia_valid & ATTR_MTIME)
150 inode->i_mtime = timespec_trunc(attr->ia_mtime,
151 inode->i_sb->s_time_gran);
152 if (ia_valid & ATTR_CTIME)
153 inode->i_ctime = timespec_trunc(attr->ia_ctime,
154 inode->i_sb->s_time_gran);
155 if (ia_valid & ATTR_MODE) {
156 umode_t mode = attr->ia_mode;
157
158 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
159 mode &= ~S_ISGID;
160 inode->i_mode = mode;
161 }
162 }
163 EXPORT_SYMBOL(setattr_copy);
164
notify_change(struct dentry * dentry,struct iattr * attr)165 int notify_change(struct dentry * dentry, struct iattr * attr)
166 {
167 struct inode *inode = dentry->d_inode;
168 mode_t mode = inode->i_mode;
169 int error;
170 struct timespec now;
171 unsigned int ia_valid = attr->ia_valid;
172
173 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
174 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
175 return -EPERM;
176 }
177
178 now = current_fs_time(inode->i_sb);
179
180 attr->ia_ctime = now;
181 if (!(ia_valid & ATTR_ATIME_SET))
182 attr->ia_atime = now;
183 if (!(ia_valid & ATTR_MTIME_SET))
184 attr->ia_mtime = now;
185 if (ia_valid & ATTR_KILL_PRIV) {
186 attr->ia_valid &= ~ATTR_KILL_PRIV;
187 ia_valid &= ~ATTR_KILL_PRIV;
188 error = security_inode_need_killpriv(dentry);
189 if (error > 0)
190 error = security_inode_killpriv(dentry);
191 if (error)
192 return error;
193 }
194
195 /*
196 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
197 * that the function has the ability to reinterpret a mode change
198 * that's due to these bits. This adds an implicit restriction that
199 * no function will ever call notify_change with both ATTR_MODE and
200 * ATTR_KILL_S*ID set.
201 */
202 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
203 (ia_valid & ATTR_MODE))
204 BUG();
205
206 if (ia_valid & ATTR_KILL_SUID) {
207 if (mode & S_ISUID) {
208 ia_valid = attr->ia_valid |= ATTR_MODE;
209 attr->ia_mode = (inode->i_mode & ~S_ISUID);
210 }
211 }
212 if (ia_valid & ATTR_KILL_SGID) {
213 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
214 if (!(ia_valid & ATTR_MODE)) {
215 ia_valid = attr->ia_valid |= ATTR_MODE;
216 attr->ia_mode = inode->i_mode;
217 }
218 attr->ia_mode &= ~S_ISGID;
219 }
220 }
221 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
222 return 0;
223
224 error = security_inode_setattr(dentry, attr);
225 if (error)
226 return error;
227
228 if (ia_valid & ATTR_SIZE)
229 down_write(&dentry->d_inode->i_alloc_sem);
230
231 if (inode->i_op->setattr)
232 error = inode->i_op->setattr(dentry, attr);
233 else
234 error = simple_setattr(dentry, attr);
235
236 if (ia_valid & ATTR_SIZE)
237 up_write(&dentry->d_inode->i_alloc_sem);
238
239 if (!error)
240 fsnotify_change(dentry, ia_valid);
241
242 return error;
243 }
244
245 EXPORT_SYMBOL(notify_change);
246