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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | /* | |
3 | * linux/fs/attr.c | |
4 | * | |
5 | * Copyright (C) 1991, 1992 Linus Torvalds | |
6 | * changes by Thomas Schoebel-Theuer | |
7 | */ | |
8 | ||
9 | #include <linux/export.h> | |
10 | #include <linux/time.h> | |
11 | #include <linux/mm.h> | |
12 | #include <linux/string.h> | |
13 | #include <linux/sched/signal.h> | |
14 | #include <linux/capability.h> | |
15 | #include <linux/fsnotify.h> | |
16 | #include <linux/fcntl.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/evm.h> | |
19 | #include <linux/ima.h> | |
20 | ||
21 | static bool chown_ok(const struct inode *inode, kuid_t uid) | |
22 | { | |
23 | if (uid_eq(current_fsuid(), inode->i_uid) && | |
24 | uid_eq(uid, inode->i_uid)) | |
25 | return true; | |
26 | if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) | |
27 | return true; | |
28 | if (uid_eq(inode->i_uid, INVALID_UID) && | |
29 | ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) | |
30 | return true; | |
31 | return false; | |
32 | } | |
33 | ||
34 | static bool chgrp_ok(const struct inode *inode, kgid_t gid) | |
35 | { | |
36 | if (uid_eq(current_fsuid(), inode->i_uid) && | |
37 | (in_group_p(gid) || gid_eq(gid, inode->i_gid))) | |
38 | return true; | |
39 | if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) | |
40 | return true; | |
41 | if (gid_eq(inode->i_gid, INVALID_GID) && | |
42 | ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) | |
43 | return true; | |
44 | return false; | |
45 | } | |
46 | ||
47 | /** | |
48 | * setattr_prepare - check if attribute changes to a dentry are allowed | |
49 | * @dentry: dentry to check | |
50 | * @attr: attributes to change | |
51 | * | |
52 | * Check if we are allowed to change the attributes contained in @attr | |
53 | * in the given dentry. This includes the normal unix access permission | |
54 | * checks, as well as checks for rlimits and others. The function also clears | |
55 | * SGID bit from mode if user is not allowed to set it. Also file capabilities | |
56 | * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set. | |
57 | * | |
58 | * Should be called as the first thing in ->setattr implementations, | |
59 | * possibly after taking additional locks. | |
60 | */ | |
61 | int setattr_prepare(struct dentry *dentry, struct iattr *attr) | |
62 | { | |
63 | struct inode *inode = d_inode(dentry); | |
64 | unsigned int ia_valid = attr->ia_valid; | |
65 | ||
66 | /* | |
67 | * First check size constraints. These can't be overriden using | |
68 | * ATTR_FORCE. | |
69 | */ | |
70 | if (ia_valid & ATTR_SIZE) { | |
71 | int error = inode_newsize_ok(inode, attr->ia_size); | |
72 | if (error) | |
73 | return error; | |
74 | } | |
75 | ||
76 | /* If force is set do it anyway. */ | |
77 | if (ia_valid & ATTR_FORCE) | |
78 | goto kill_priv; | |
79 | ||
80 | /* Make sure a caller can chown. */ | |
81 | if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid)) | |
82 | return -EPERM; | |
83 | ||
84 | /* Make sure caller can chgrp. */ | |
85 | if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid)) | |
86 | return -EPERM; | |
87 | ||
88 | /* Make sure a caller can chmod. */ | |
89 | if (ia_valid & ATTR_MODE) { | |
90 | if (!inode_owner_or_capable(inode)) | |
91 | return -EPERM; | |
92 | /* Also check the setgid bit! */ | |
93 | if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : | |
94 | inode->i_gid) && | |
95 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) | |
96 | attr->ia_mode &= ~S_ISGID; | |
97 | } | |
98 | ||
99 | /* Check for setting the inode time. */ | |
100 | if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { | |
101 | if (!inode_owner_or_capable(inode)) | |
102 | return -EPERM; | |
103 | } | |
104 | ||
105 | kill_priv: | |
106 | /* User has permission for the change */ | |
107 | if (ia_valid & ATTR_KILL_PRIV) { | |
108 | int error; | |
109 | ||
110 | error = security_inode_killpriv(dentry); | |
111 | if (error) | |
112 | return error; | |
113 | } | |
114 | ||
115 | return 0; | |
116 | } | |
117 | EXPORT_SYMBOL(setattr_prepare); | |
118 | ||
119 | /** | |
120 | * inode_newsize_ok - may this inode be truncated to a given size | |
121 | * @inode: the inode to be truncated | |
122 | * @offset: the new size to assign to the inode | |
123 | * | |
124 | * inode_newsize_ok must be called with i_mutex held. | |
125 | * | |
126 | * inode_newsize_ok will check filesystem limits and ulimits to check that the | |
127 | * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ | |
128 | * when necessary. Caller must not proceed with inode size change if failure is | |
129 | * returned. @inode must be a file (not directory), with appropriate | |
130 | * permissions to allow truncate (inode_newsize_ok does NOT check these | |
131 | * conditions). | |
132 | * | |
133 | * Return: 0 on success, -ve errno on failure | |
134 | */ | |
135 | int inode_newsize_ok(const struct inode *inode, loff_t offset) | |
136 | { | |
137 | if (inode->i_size < offset) { | |
138 | unsigned long limit; | |
139 | ||
140 | limit = rlimit(RLIMIT_FSIZE); | |
141 | if (limit != RLIM_INFINITY && offset > limit) | |
142 | goto out_sig; | |
143 | if (offset > inode->i_sb->s_maxbytes) | |
144 | goto out_big; | |
145 | } else { | |
146 | /* | |
147 | * truncation of in-use swapfiles is disallowed - it would | |
148 | * cause subsequent swapout to scribble on the now-freed | |
149 | * blocks. | |
150 | */ | |
151 | if (IS_SWAPFILE(inode)) | |
152 | return -ETXTBSY; | |
153 | } | |
154 | ||
155 | return 0; | |
156 | out_sig: | |
157 | send_sig(SIGXFSZ, current, 0); | |
158 | out_big: | |
159 | return -EFBIG; | |
160 | } | |
161 | EXPORT_SYMBOL(inode_newsize_ok); | |
162 | ||
163 | /** | |
164 | * setattr_copy - copy simple metadata updates into the generic inode | |
165 | * @inode: the inode to be updated | |
166 | * @attr: the new attributes | |
167 | * | |
168 | * setattr_copy must be called with i_mutex held. | |
169 | * | |
170 | * setattr_copy updates the inode's metadata with that specified | |
171 | * in attr. Noticeably missing is inode size update, which is more complex | |
172 | * as it requires pagecache updates. | |
173 | * | |
174 | * The inode is not marked as dirty after this operation. The rationale is | |
175 | * that for "simple" filesystems, the struct inode is the inode storage. | |
176 | * The caller is free to mark the inode dirty afterwards if needed. | |
177 | */ | |
178 | void setattr_copy(struct inode *inode, const struct iattr *attr) | |
179 | { | |
180 | unsigned int ia_valid = attr->ia_valid; | |
181 | ||
182 | if (ia_valid & ATTR_UID) | |
183 | inode->i_uid = attr->ia_uid; | |
184 | if (ia_valid & ATTR_GID) | |
185 | inode->i_gid = attr->ia_gid; | |
186 | if (ia_valid & ATTR_ATIME) | |
187 | inode->i_atime = attr->ia_atime; | |
188 | if (ia_valid & ATTR_MTIME) | |
189 | inode->i_mtime = attr->ia_mtime; | |
190 | if (ia_valid & ATTR_CTIME) | |
191 | inode->i_ctime = attr->ia_ctime; | |
192 | if (ia_valid & ATTR_MODE) { | |
193 | umode_t mode = attr->ia_mode; | |
194 | ||
195 | if (!in_group_p(inode->i_gid) && | |
196 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) | |
197 | mode &= ~S_ISGID; | |
198 | inode->i_mode = mode; | |
199 | } | |
200 | } | |
201 | EXPORT_SYMBOL(setattr_copy); | |
202 | ||
203 | /** | |
204 | * notify_change - modify attributes of a filesytem object | |
205 | * @dentry: object affected | |
206 | * @attr: new attributes | |
207 | * @delegated_inode: returns inode, if the inode is delegated | |
208 | * | |
209 | * The caller must hold the i_mutex on the affected object. | |
210 | * | |
211 | * If notify_change discovers a delegation in need of breaking, | |
212 | * it will return -EWOULDBLOCK and return a reference to the inode in | |
213 | * delegated_inode. The caller should then break the delegation and | |
214 | * retry. Because breaking a delegation may take a long time, the | |
215 | * caller should drop the i_mutex before doing so. | |
216 | * | |
217 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
218 | * be appropriate for callers that expect the underlying filesystem not | |
219 | * to be NFS exported. Also, passing NULL is fine for callers holding | |
220 | * the file open for write, as there can be no conflicting delegation in | |
221 | * that case. | |
222 | */ | |
223 | int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode) | |
224 | { | |
225 | struct inode *inode = dentry->d_inode; | |
226 | umode_t mode = inode->i_mode; | |
227 | int error; | |
228 | struct timespec64 now; | |
229 | unsigned int ia_valid = attr->ia_valid; | |
230 | ||
231 | WARN_ON_ONCE(!inode_is_locked(inode)); | |
232 | ||
233 | if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { | |
234 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) | |
235 | return -EPERM; | |
236 | } | |
237 | ||
238 | /* | |
239 | * If utimes(2) and friends are called with times == NULL (or both | |
240 | * times are UTIME_NOW), then we need to check for write permission | |
241 | */ | |
242 | if (ia_valid & ATTR_TOUCH) { | |
243 | if (IS_IMMUTABLE(inode)) | |
244 | return -EPERM; | |
245 | ||
246 | if (!inode_owner_or_capable(inode)) { | |
247 | error = inode_permission(inode, MAY_WRITE); | |
248 | if (error) | |
249 | return error; | |
250 | } | |
251 | } | |
252 | ||
253 | if ((ia_valid & ATTR_MODE)) { | |
254 | umode_t amode = attr->ia_mode; | |
255 | /* Flag setting protected by i_mutex */ | |
256 | if (is_sxid(amode)) | |
257 | inode->i_flags &= ~S_NOSEC; | |
258 | } | |
259 | ||
260 | now = current_time(inode); | |
261 | ||
262 | attr->ia_ctime = now; | |
263 | if (!(ia_valid & ATTR_ATIME_SET)) | |
264 | attr->ia_atime = now; | |
265 | else | |
266 | attr->ia_atime = timestamp_truncate(attr->ia_atime, inode); | |
267 | if (!(ia_valid & ATTR_MTIME_SET)) | |
268 | attr->ia_mtime = now; | |
269 | else | |
270 | attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode); | |
271 | ||
272 | if (ia_valid & ATTR_KILL_PRIV) { | |
273 | error = security_inode_need_killpriv(dentry); | |
274 | if (error < 0) | |
275 | return error; | |
276 | if (error == 0) | |
277 | ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; | |
278 | } | |
279 | ||
280 | /* | |
281 | * We now pass ATTR_KILL_S*ID to the lower level setattr function so | |
282 | * that the function has the ability to reinterpret a mode change | |
283 | * that's due to these bits. This adds an implicit restriction that | |
284 | * no function will ever call notify_change with both ATTR_MODE and | |
285 | * ATTR_KILL_S*ID set. | |
286 | */ | |
287 | if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && | |
288 | (ia_valid & ATTR_MODE)) | |
289 | BUG(); | |
290 | ||
291 | if (ia_valid & ATTR_KILL_SUID) { | |
292 | if (mode & S_ISUID) { | |
293 | ia_valid = attr->ia_valid |= ATTR_MODE; | |
294 | attr->ia_mode = (inode->i_mode & ~S_ISUID); | |
295 | } | |
296 | } | |
297 | if (ia_valid & ATTR_KILL_SGID) { | |
298 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { | |
299 | if (!(ia_valid & ATTR_MODE)) { | |
300 | ia_valid = attr->ia_valid |= ATTR_MODE; | |
301 | attr->ia_mode = inode->i_mode; | |
302 | } | |
303 | attr->ia_mode &= ~S_ISGID; | |
304 | } | |
305 | } | |
306 | if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) | |
307 | return 0; | |
308 | ||
309 | /* | |
310 | * Verify that uid/gid changes are valid in the target | |
311 | * namespace of the superblock. | |
312 | */ | |
313 | if (ia_valid & ATTR_UID && | |
314 | !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) | |
315 | return -EOVERFLOW; | |
316 | if (ia_valid & ATTR_GID && | |
317 | !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) | |
318 | return -EOVERFLOW; | |
319 | ||
320 | /* Don't allow modifications of files with invalid uids or | |
321 | * gids unless those uids & gids are being made valid. | |
322 | */ | |
323 | if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid)) | |
324 | return -EOVERFLOW; | |
325 | if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid)) | |
326 | return -EOVERFLOW; | |
327 | ||
328 | error = security_inode_setattr(dentry, attr); | |
329 | if (error) | |
330 | return error; | |
331 | error = try_break_deleg(inode, delegated_inode); | |
332 | if (error) | |
333 | return error; | |
334 | ||
335 | if (inode->i_op->setattr) | |
336 | error = inode->i_op->setattr(dentry, attr); | |
337 | else | |
338 | error = simple_setattr(dentry, attr); | |
339 | ||
340 | if (!error) { | |
341 | fsnotify_change(dentry, ia_valid); | |
342 | ima_inode_post_setattr(dentry); | |
343 | evm_inode_post_setattr(dentry, ia_valid); | |
344 | } | |
345 | ||
346 | return error; | |
347 | } | |
348 | EXPORT_SYMBOL(notify_change); |