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Commit | Line | Data |
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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/export.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 | #include <linux/evm.h> | |
17 | #include <linux/ima.h> | |
18 | ||
19 | /** | |
20 | * inode_change_ok - check if attribute changes to an inode are allowed | |
21 | * @inode: inode to check | |
22 | * @attr: attributes to change | |
23 | * | |
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. | |
27 | * | |
28 | * Should be called as the first thing in ->setattr implementations, | |
29 | * possibly after taking additional locks. | |
30 | */ | |
31 | int inode_change_ok(const struct inode *inode, struct iattr *attr) | |
32 | { | |
33 | unsigned int ia_valid = attr->ia_valid; | |
34 | ||
35 | /* | |
36 | * First check size constraints. These can't be overriden using | |
37 | * ATTR_FORCE. | |
38 | */ | |
39 | if (ia_valid & ATTR_SIZE) { | |
40 | int error = inode_newsize_ok(inode, attr->ia_size); | |
41 | if (error) | |
42 | return error; | |
43 | } | |
44 | ||
45 | /* If force is set do it anyway. */ | |
46 | if (ia_valid & ATTR_FORCE) | |
47 | return 0; | |
48 | ||
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 | !inode_capable(inode, CAP_CHOWN)) | |
54 | return -EPERM; | |
55 | ||
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 | !inode_capable(inode, CAP_CHOWN)) | |
61 | return -EPERM; | |
62 | ||
63 | /* Make sure a caller can chmod. */ | |
64 | if (ia_valid & ATTR_MODE) { | |
65 | if (!inode_owner_or_capable(inode)) | |
66 | return -EPERM; | |
67 | /* Also check the setgid bit! */ | |
68 | if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : | |
69 | inode->i_gid) && | |
70 | !inode_capable(inode, CAP_FSETID)) | |
71 | attr->ia_mode &= ~S_ISGID; | |
72 | } | |
73 | ||
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)) | |
77 | return -EPERM; | |
78 | } | |
79 | ||
80 | return 0; | |
81 | } | |
82 | EXPORT_SYMBOL(inode_change_ok); | |
83 | ||
84 | /** | |
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 | |
89 | * | |
90 | * inode_newsize_ok must be called with i_mutex held. | |
91 | * | |
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 | |
97 | * conditions). | |
98 | */ | |
99 | int inode_newsize_ok(const struct inode *inode, loff_t offset) | |
100 | { | |
101 | if (inode->i_size < offset) { | |
102 | unsigned long limit; | |
103 | ||
104 | limit = rlimit(RLIMIT_FSIZE); | |
105 | if (limit != RLIM_INFINITY && offset > limit) | |
106 | goto out_sig; | |
107 | if (offset > inode->i_sb->s_maxbytes) | |
108 | goto out_big; | |
109 | } else { | |
110 | /* | |
111 | * truncation of in-use swapfiles is disallowed - it would | |
112 | * cause subsequent swapout to scribble on the now-freed | |
113 | * blocks. | |
114 | */ | |
115 | if (IS_SWAPFILE(inode)) | |
116 | return -ETXTBSY; | |
117 | } | |
118 | ||
119 | return 0; | |
120 | out_sig: | |
121 | send_sig(SIGXFSZ, current, 0); | |
122 | out_big: | |
123 | return -EFBIG; | |
124 | } | |
125 | EXPORT_SYMBOL(inode_newsize_ok); | |
126 | ||
127 | /** | |
128 | * setattr_copy - copy simple metadata updates into the generic inode | |
129 | * @inode: the inode to be updated | |
130 | * @attr: the new attributes | |
131 | * | |
132 | * setattr_copy must be called with i_mutex held. | |
133 | * | |
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. | |
137 | * | |
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. | |
141 | */ | |
142 | void setattr_copy(struct inode *inode, const struct iattr *attr) | |
143 | { | |
144 | unsigned int ia_valid = attr->ia_valid; | |
145 | ||
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; | |
161 | ||
162 | if (!in_group_p(inode->i_gid) && | |
163 | !inode_capable(inode, CAP_FSETID)) | |
164 | mode &= ~S_ISGID; | |
165 | inode->i_mode = mode; | |
166 | } | |
167 | } | |
168 | EXPORT_SYMBOL(setattr_copy); | |
169 | ||
170 | /** | |
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 | |
175 | * | |
176 | * The caller must hold the i_mutex on the affected object. | |
177 | * | |
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. | |
183 | * | |
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 | |
188 | * that case. | |
189 | */ | |
190 | int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode) | |
191 | { | |
192 | struct inode *inode = dentry->d_inode; | |
193 | umode_t mode = inode->i_mode; | |
194 | int error; | |
195 | struct timespec now; | |
196 | unsigned int ia_valid = attr->ia_valid; | |
197 | ||
198 | WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); | |
199 | ||
200 | if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { | |
201 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) | |
202 | return -EPERM; | |
203 | } | |
204 | ||
205 | if ((ia_valid & ATTR_MODE)) { | |
206 | umode_t amode = attr->ia_mode; | |
207 | /* Flag setting protected by i_mutex */ | |
208 | if (is_sxid(amode)) | |
209 | inode->i_flags &= ~S_NOSEC; | |
210 | } | |
211 | ||
212 | now = current_fs_time(inode->i_sb); | |
213 | ||
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); | |
223 | if (error > 0) | |
224 | error = security_inode_killpriv(dentry); | |
225 | if (error) | |
226 | return error; | |
227 | } | |
228 | ||
229 | /* | |
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. | |
235 | */ | |
236 | if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && | |
237 | (ia_valid & ATTR_MODE)) | |
238 | BUG(); | |
239 | ||
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); | |
244 | } | |
245 | } | |
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; | |
251 | } | |
252 | attr->ia_mode &= ~S_ISGID; | |
253 | } | |
254 | } | |
255 | if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) | |
256 | return 0; | |
257 | ||
258 | error = security_inode_setattr(dentry, attr); | |
259 | if (error) | |
260 | return error; | |
261 | error = try_break_deleg(inode, delegated_inode); | |
262 | if (error) | |
263 | return error; | |
264 | ||
265 | if (inode->i_op->setattr) | |
266 | error = inode->i_op->setattr(dentry, attr); | |
267 | else | |
268 | error = simple_setattr(dentry, attr); | |
269 | ||
270 | if (!error) { | |
271 | fsnotify_change(dentry, ia_valid); | |
272 | ima_inode_post_setattr(dentry); | |
273 | evm_inode_post_setattr(dentry, ia_valid); | |
274 | } | |
275 | ||
276 | return error; | |
277 | } | |
278 | EXPORT_SYMBOL(notify_change); |