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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1da177e4 LT |
2 | /* |
3 | * linux/fs/attr.c | |
4 | * | |
5 | * Copyright (C) 1991, 1992 Linus Torvalds | |
6 | * changes by Thomas Schoebel-Theuer | |
7 | */ | |
8 | ||
630d9c47 | 9 | #include <linux/export.h> |
1da177e4 LT |
10 | #include <linux/time.h> |
11 | #include <linux/mm.h> | |
12 | #include <linux/string.h> | |
3f07c014 | 13 | #include <linux/sched/signal.h> |
16f7e0fe | 14 | #include <linux/capability.h> |
0eeca283 | 15 | #include <linux/fsnotify.h> |
1da177e4 | 16 | #include <linux/fcntl.h> |
1da177e4 | 17 | #include <linux/security.h> |
975d2943 | 18 | #include <linux/evm.h> |
9957a504 | 19 | #include <linux/ima.h> |
1da177e4 | 20 | |
2f221d6f CB |
21 | /** |
22 | * chown_ok - verify permissions to chown inode | |
23 | * @mnt_userns: user namespace of the mount @inode was found from | |
24 | * @inode: inode to check permissions on | |
25 | * @uid: uid to chown @inode to | |
26 | * | |
27 | * If the inode has been found through an idmapped mount the user namespace of | |
28 | * the vfsmount must be passed through @mnt_userns. This function will then | |
29 | * take care to map the inode according to @mnt_userns before checking | |
30 | * permissions. On non-idmapped mounts or if permission checking is to be | |
31 | * performed on the raw inode simply passs init_user_ns. | |
32 | */ | |
33 | static bool chown_ok(struct user_namespace *mnt_userns, | |
34 | const struct inode *inode, | |
35 | kuid_t uid) | |
0031181c | 36 | { |
2f221d6f | 37 | kuid_t kuid = i_uid_into_mnt(mnt_userns, inode); |
cb70dd7c | 38 | if (uid_eq(current_fsuid(), kuid) && uid_eq(uid, inode->i_uid)) |
0031181c | 39 | return true; |
2f221d6f | 40 | if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN)) |
0031181c | 41 | return true; |
2f221d6f | 42 | if (uid_eq(kuid, INVALID_UID) && |
0031181c EB |
43 | ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) |
44 | return true; | |
45 | return false; | |
46 | } | |
47 | ||
2f221d6f CB |
48 | /** |
49 | * chgrp_ok - verify permissions to chgrp inode | |
50 | * @mnt_userns: user namespace of the mount @inode was found from | |
51 | * @inode: inode to check permissions on | |
52 | * @gid: gid to chown @inode to | |
53 | * | |
54 | * If the inode has been found through an idmapped mount the user namespace of | |
55 | * the vfsmount must be passed through @mnt_userns. This function will then | |
56 | * take care to map the inode according to @mnt_userns before checking | |
57 | * permissions. On non-idmapped mounts or if permission checking is to be | |
58 | * performed on the raw inode simply passs init_user_ns. | |
59 | */ | |
60 | static bool chgrp_ok(struct user_namespace *mnt_userns, | |
61 | const struct inode *inode, kgid_t gid) | |
0031181c | 62 | { |
2f221d6f | 63 | kgid_t kgid = i_gid_into_mnt(mnt_userns, inode); |
a7bef52a CB |
64 | if (uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode))) { |
65 | kgid_t mapped_gid; | |
66 | ||
67 | if (gid_eq(gid, inode->i_gid)) | |
68 | return true; | |
69 | mapped_gid = mapped_kgid_fs(mnt_userns, i_user_ns(inode), gid); | |
70 | if (in_group_p(mapped_gid)) | |
71 | return true; | |
72 | } | |
2f221d6f | 73 | if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN)) |
0031181c | 74 | return true; |
2f221d6f | 75 | if (gid_eq(kgid, INVALID_GID) && |
0031181c EB |
76 | ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) |
77 | return true; | |
78 | return false; | |
79 | } | |
80 | ||
2c27c65e | 81 | /** |
31051c85 | 82 | * setattr_prepare - check if attribute changes to a dentry are allowed |
2f221d6f | 83 | * @mnt_userns: user namespace of the mount the inode was found from |
31051c85 | 84 | * @dentry: dentry to check |
2c27c65e CH |
85 | * @attr: attributes to change |
86 | * | |
87 | * Check if we are allowed to change the attributes contained in @attr | |
31051c85 JK |
88 | * in the given dentry. This includes the normal unix access permission |
89 | * checks, as well as checks for rlimits and others. The function also clears | |
90 | * SGID bit from mode if user is not allowed to set it. Also file capabilities | |
91 | * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set. | |
2c27c65e | 92 | * |
2f221d6f CB |
93 | * If the inode has been found through an idmapped mount the user namespace of |
94 | * the vfsmount must be passed through @mnt_userns. This function will then | |
95 | * take care to map the inode according to @mnt_userns before checking | |
96 | * permissions. On non-idmapped mounts or if permission checking is to be | |
97 | * performed on the raw inode simply passs init_user_ns. | |
98 | * | |
2c27c65e CH |
99 | * Should be called as the first thing in ->setattr implementations, |
100 | * possibly after taking additional locks. | |
101 | */ | |
2f221d6f CB |
102 | int setattr_prepare(struct user_namespace *mnt_userns, struct dentry *dentry, |
103 | struct iattr *attr) | |
1da177e4 | 104 | { |
31051c85 | 105 | struct inode *inode = d_inode(dentry); |
1da177e4 LT |
106 | unsigned int ia_valid = attr->ia_valid; |
107 | ||
2c27c65e CH |
108 | /* |
109 | * First check size constraints. These can't be overriden using | |
110 | * ATTR_FORCE. | |
111 | */ | |
112 | if (ia_valid & ATTR_SIZE) { | |
113 | int error = inode_newsize_ok(inode, attr->ia_size); | |
114 | if (error) | |
115 | return error; | |
116 | } | |
117 | ||
1da177e4 LT |
118 | /* If force is set do it anyway. */ |
119 | if (ia_valid & ATTR_FORCE) | |
030b533c | 120 | goto kill_priv; |
1da177e4 LT |
121 | |
122 | /* Make sure a caller can chown. */ | |
2f221d6f | 123 | if ((ia_valid & ATTR_UID) && !chown_ok(mnt_userns, inode, attr->ia_uid)) |
2c27c65e | 124 | return -EPERM; |
1da177e4 LT |
125 | |
126 | /* Make sure caller can chgrp. */ | |
2f221d6f | 127 | if ((ia_valid & ATTR_GID) && !chgrp_ok(mnt_userns, inode, attr->ia_gid)) |
2c27c65e | 128 | return -EPERM; |
1da177e4 LT |
129 | |
130 | /* Make sure a caller can chmod. */ | |
131 | if (ia_valid & ATTR_MODE) { | |
a7bef52a CB |
132 | kgid_t mapped_gid; |
133 | ||
2f221d6f | 134 | if (!inode_owner_or_capable(mnt_userns, inode)) |
2c27c65e | 135 | return -EPERM; |
a7bef52a CB |
136 | |
137 | if (ia_valid & ATTR_GID) | |
138 | mapped_gid = mapped_kgid_fs(mnt_userns, | |
139 | i_user_ns(inode), attr->ia_gid); | |
140 | else | |
141 | mapped_gid = i_gid_into_mnt(mnt_userns, inode); | |
142 | ||
1da177e4 | 143 | /* Also check the setgid bit! */ |
a7bef52a CB |
144 | if (!in_group_p(mapped_gid) && |
145 | !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) | |
1da177e4 LT |
146 | attr->ia_mode &= ~S_ISGID; |
147 | } | |
148 | ||
149 | /* Check for setting the inode time. */ | |
9767d749 | 150 | if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { |
2f221d6f | 151 | if (!inode_owner_or_capable(mnt_userns, inode)) |
2c27c65e | 152 | return -EPERM; |
1da177e4 | 153 | } |
2c27c65e | 154 | |
030b533c JK |
155 | kill_priv: |
156 | /* User has permission for the change */ | |
157 | if (ia_valid & ATTR_KILL_PRIV) { | |
158 | int error; | |
159 | ||
71bc356f | 160 | error = security_inode_killpriv(mnt_userns, dentry); |
030b533c JK |
161 | if (error) |
162 | return error; | |
163 | } | |
164 | ||
2c27c65e | 165 | return 0; |
1da177e4 | 166 | } |
31051c85 | 167 | EXPORT_SYMBOL(setattr_prepare); |
1da177e4 | 168 | |
25d9e2d1 NP |
169 | /** |
170 | * inode_newsize_ok - may this inode be truncated to a given size | |
171 | * @inode: the inode to be truncated | |
172 | * @offset: the new size to assign to the inode | |
25d9e2d1 | 173 | * |
7bb46a67 NP |
174 | * inode_newsize_ok must be called with i_mutex held. |
175 | * | |
25d9e2d1 NP |
176 | * inode_newsize_ok will check filesystem limits and ulimits to check that the |
177 | * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ | |
178 | * when necessary. Caller must not proceed with inode size change if failure is | |
179 | * returned. @inode must be a file (not directory), with appropriate | |
180 | * permissions to allow truncate (inode_newsize_ok does NOT check these | |
181 | * conditions). | |
3fae1746 MW |
182 | * |
183 | * Return: 0 on success, -ve errno on failure | |
25d9e2d1 NP |
184 | */ |
185 | int inode_newsize_ok(const struct inode *inode, loff_t offset) | |
186 | { | |
19abb9e7 DH |
187 | if (offset < 0) |
188 | return -EINVAL; | |
25d9e2d1 NP |
189 | if (inode->i_size < offset) { |
190 | unsigned long limit; | |
191 | ||
d554ed89 | 192 | limit = rlimit(RLIMIT_FSIZE); |
25d9e2d1 NP |
193 | if (limit != RLIM_INFINITY && offset > limit) |
194 | goto out_sig; | |
195 | if (offset > inode->i_sb->s_maxbytes) | |
196 | goto out_big; | |
197 | } else { | |
198 | /* | |
199 | * truncation of in-use swapfiles is disallowed - it would | |
200 | * cause subsequent swapout to scribble on the now-freed | |
201 | * blocks. | |
202 | */ | |
203 | if (IS_SWAPFILE(inode)) | |
204 | return -ETXTBSY; | |
205 | } | |
206 | ||
207 | return 0; | |
208 | out_sig: | |
209 | send_sig(SIGXFSZ, current, 0); | |
210 | out_big: | |
211 | return -EFBIG; | |
212 | } | |
213 | EXPORT_SYMBOL(inode_newsize_ok); | |
214 | ||
7bb46a67 | 215 | /** |
6a1a90ad | 216 | * setattr_copy - copy simple metadata updates into the generic inode |
2f221d6f | 217 | * @mnt_userns: user namespace of the mount the inode was found from |
7bb46a67 NP |
218 | * @inode: the inode to be updated |
219 | * @attr: the new attributes | |
220 | * | |
6a1a90ad | 221 | * setattr_copy must be called with i_mutex held. |
7bb46a67 | 222 | * |
6a1a90ad | 223 | * setattr_copy updates the inode's metadata with that specified |
2f221d6f CB |
224 | * in attr on idmapped mounts. If file ownership is changed setattr_copy |
225 | * doesn't map ia_uid and ia_gid. It will asssume the caller has already | |
226 | * provided the intended values. Necessary permission checks to determine | |
227 | * whether or not the S_ISGID property needs to be removed are performed with | |
228 | * the correct idmapped mount permission helpers. | |
229 | * Noticeably missing is inode size update, which is more complex | |
2c27c65e | 230 | * as it requires pagecache updates. |
7bb46a67 | 231 | * |
2f221d6f CB |
232 | * If the inode has been found through an idmapped mount the user namespace of |
233 | * the vfsmount must be passed through @mnt_userns. This function will then | |
234 | * take care to map the inode according to @mnt_userns before checking | |
235 | * permissions. On non-idmapped mounts or if permission checking is to be | |
236 | * performed on the raw inode simply passs init_user_ns. | |
237 | * | |
7bb46a67 NP |
238 | * The inode is not marked as dirty after this operation. The rationale is |
239 | * that for "simple" filesystems, the struct inode is the inode storage. | |
240 | * The caller is free to mark the inode dirty afterwards if needed. | |
241 | */ | |
2f221d6f CB |
242 | void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode, |
243 | const struct iattr *attr) | |
1da177e4 LT |
244 | { |
245 | unsigned int ia_valid = attr->ia_valid; | |
4a30131e | 246 | |
1da177e4 LT |
247 | if (ia_valid & ATTR_UID) |
248 | inode->i_uid = attr->ia_uid; | |
249 | if (ia_valid & ATTR_GID) | |
250 | inode->i_gid = attr->ia_gid; | |
eb31e2f6 AG |
251 | if (ia_valid & ATTR_ATIME) |
252 | inode->i_atime = attr->ia_atime; | |
253 | if (ia_valid & ATTR_MTIME) | |
254 | inode->i_mtime = attr->ia_mtime; | |
255 | if (ia_valid & ATTR_CTIME) | |
256 | inode->i_ctime = attr->ia_ctime; | |
1da177e4 LT |
257 | if (ia_valid & ATTR_MODE) { |
258 | umode_t mode = attr->ia_mode; | |
2f221d6f CB |
259 | kgid_t kgid = i_gid_into_mnt(mnt_userns, inode); |
260 | if (!in_group_p(kgid) && | |
261 | !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) | |
1da177e4 LT |
262 | mode &= ~S_ISGID; |
263 | inode->i_mode = mode; | |
264 | } | |
7bb46a67 | 265 | } |
6a1a90ad | 266 | EXPORT_SYMBOL(setattr_copy); |
7bb46a67 | 267 | |
7bb698f0 AG |
268 | int may_setattr(struct user_namespace *mnt_userns, struct inode *inode, |
269 | unsigned int ia_valid) | |
270 | { | |
271 | int error; | |
272 | ||
273 | if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { | |
274 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) | |
275 | return -EPERM; | |
276 | } | |
277 | ||
278 | /* | |
279 | * If utimes(2) and friends are called with times == NULL (or both | |
280 | * times are UTIME_NOW), then we need to check for write permission | |
281 | */ | |
282 | if (ia_valid & ATTR_TOUCH) { | |
283 | if (IS_IMMUTABLE(inode)) | |
284 | return -EPERM; | |
285 | ||
286 | if (!inode_owner_or_capable(mnt_userns, inode)) { | |
287 | error = inode_permission(mnt_userns, inode, MAY_WRITE); | |
288 | if (error) | |
289 | return error; | |
290 | } | |
291 | } | |
292 | return 0; | |
293 | } | |
294 | EXPORT_SYMBOL(may_setattr); | |
295 | ||
27ac0ffe BF |
296 | /** |
297 | * notify_change - modify attributes of a filesytem object | |
2f221d6f | 298 | * @mnt_userns: user namespace of the mount the inode was found from |
27ac0ffe | 299 | * @dentry: object affected |
3fae1746 | 300 | * @attr: new attributes |
27ac0ffe BF |
301 | * @delegated_inode: returns inode, if the inode is delegated |
302 | * | |
303 | * The caller must hold the i_mutex on the affected object. | |
304 | * | |
305 | * If notify_change discovers a delegation in need of breaking, | |
306 | * it will return -EWOULDBLOCK and return a reference to the inode in | |
307 | * delegated_inode. The caller should then break the delegation and | |
308 | * retry. Because breaking a delegation may take a long time, the | |
309 | * caller should drop the i_mutex before doing so. | |
310 | * | |
2f221d6f CB |
311 | * If file ownership is changed notify_change() doesn't map ia_uid and |
312 | * ia_gid. It will asssume the caller has already provided the intended values. | |
313 | * | |
27ac0ffe BF |
314 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
315 | * be appropriate for callers that expect the underlying filesystem not | |
316 | * to be NFS exported. Also, passing NULL is fine for callers holding | |
317 | * the file open for write, as there can be no conflicting delegation in | |
318 | * that case. | |
2f221d6f CB |
319 | * |
320 | * If the inode has been found through an idmapped mount the user namespace of | |
321 | * the vfsmount must be passed through @mnt_userns. This function will then | |
322 | * take care to map the inode according to @mnt_userns before checking | |
323 | * permissions. On non-idmapped mounts or if permission checking is to be | |
324 | * performed on the raw inode simply passs init_user_ns. | |
27ac0ffe | 325 | */ |
2f221d6f CB |
326 | int notify_change(struct user_namespace *mnt_userns, struct dentry *dentry, |
327 | struct iattr *attr, struct inode **delegated_inode) | |
1da177e4 LT |
328 | { |
329 | struct inode *inode = dentry->d_inode; | |
8d334acd | 330 | umode_t mode = inode->i_mode; |
1da177e4 | 331 | int error; |
95582b00 | 332 | struct timespec64 now; |
1da177e4 LT |
333 | unsigned int ia_valid = attr->ia_valid; |
334 | ||
5955102c | 335 | WARN_ON_ONCE(!inode_is_locked(inode)); |
c4107b30 | 336 | |
7bb698f0 AG |
337 | error = may_setattr(mnt_userns, inode, ia_valid); |
338 | if (error) | |
339 | return error; | |
f2b20f6e | 340 | |
69b45732 | 341 | if ((ia_valid & ATTR_MODE)) { |
8d334acd | 342 | umode_t amode = attr->ia_mode; |
69b45732 AK |
343 | /* Flag setting protected by i_mutex */ |
344 | if (is_sxid(amode)) | |
345 | inode->i_flags &= ~S_NOSEC; | |
346 | } | |
347 | ||
c2050a45 | 348 | now = current_time(inode); |
1da177e4 LT |
349 | |
350 | attr->ia_ctime = now; | |
351 | if (!(ia_valid & ATTR_ATIME_SET)) | |
352 | attr->ia_atime = now; | |
eb31e2f6 AG |
353 | else |
354 | attr->ia_atime = timestamp_truncate(attr->ia_atime, inode); | |
1da177e4 LT |
355 | if (!(ia_valid & ATTR_MTIME_SET)) |
356 | attr->ia_mtime = now; | |
eb31e2f6 AG |
357 | else |
358 | attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode); | |
359 | ||
b5376771 | 360 | if (ia_valid & ATTR_KILL_PRIV) { |
b5376771 | 361 | error = security_inode_need_killpriv(dentry); |
030b533c | 362 | if (error < 0) |
b5376771 | 363 | return error; |
030b533c JK |
364 | if (error == 0) |
365 | ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; | |
b5376771 | 366 | } |
6de0ec00 JL |
367 | |
368 | /* | |
369 | * We now pass ATTR_KILL_S*ID to the lower level setattr function so | |
370 | * that the function has the ability to reinterpret a mode change | |
371 | * that's due to these bits. This adds an implicit restriction that | |
372 | * no function will ever call notify_change with both ATTR_MODE and | |
373 | * ATTR_KILL_S*ID set. | |
374 | */ | |
375 | if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && | |
376 | (ia_valid & ATTR_MODE)) | |
377 | BUG(); | |
378 | ||
1da177e4 | 379 | if (ia_valid & ATTR_KILL_SUID) { |
1da177e4 | 380 | if (mode & S_ISUID) { |
6de0ec00 JL |
381 | ia_valid = attr->ia_valid |= ATTR_MODE; |
382 | attr->ia_mode = (inode->i_mode & ~S_ISUID); | |
1da177e4 LT |
383 | } |
384 | } | |
385 | if (ia_valid & ATTR_KILL_SGID) { | |
1da177e4 LT |
386 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { |
387 | if (!(ia_valid & ATTR_MODE)) { | |
388 | ia_valid = attr->ia_valid |= ATTR_MODE; | |
389 | attr->ia_mode = inode->i_mode; | |
390 | } | |
391 | attr->ia_mode &= ~S_ISGID; | |
392 | } | |
393 | } | |
6de0ec00 | 394 | if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) |
1da177e4 LT |
395 | return 0; |
396 | ||
a475acf0 SF |
397 | /* |
398 | * Verify that uid/gid changes are valid in the target | |
399 | * namespace of the superblock. | |
400 | */ | |
401 | if (ia_valid & ATTR_UID && | |
402 | !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) | |
403 | return -EOVERFLOW; | |
404 | if (ia_valid & ATTR_GID && | |
405 | !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) | |
406 | return -EOVERFLOW; | |
407 | ||
0bd23d09 EB |
408 | /* Don't allow modifications of files with invalid uids or |
409 | * gids unless those uids & gids are being made valid. | |
410 | */ | |
2f221d6f CB |
411 | if (!(ia_valid & ATTR_UID) && |
412 | !uid_valid(i_uid_into_mnt(mnt_userns, inode))) | |
0bd23d09 | 413 | return -EOVERFLOW; |
2f221d6f CB |
414 | if (!(ia_valid & ATTR_GID) && |
415 | !gid_valid(i_gid_into_mnt(mnt_userns, inode))) | |
0bd23d09 EB |
416 | return -EOVERFLOW; |
417 | ||
a77b72da | 418 | error = security_inode_setattr(dentry, attr); |
27ac0ffe BF |
419 | if (error) |
420 | return error; | |
421 | error = try_break_deleg(inode, delegated_inode); | |
a77b72da MS |
422 | if (error) |
423 | return error; | |
424 | ||
eef2380c | 425 | if (inode->i_op->setattr) |
549c7297 | 426 | error = inode->i_op->setattr(mnt_userns, dentry, attr); |
eef2380c | 427 | else |
549c7297 | 428 | error = simple_setattr(mnt_userns, dentry, attr); |
1da177e4 | 429 | |
975d2943 | 430 | if (!error) { |
0eeca283 | 431 | fsnotify_change(dentry, ia_valid); |
a2d2329e | 432 | ima_inode_post_setattr(mnt_userns, dentry); |
975d2943 MZ |
433 | evm_inode_post_setattr(dentry, ia_valid); |
434 | } | |
0eeca283 | 435 | |
1da177e4 LT |
436 | return error; |
437 | } | |
1da177e4 | 438 | EXPORT_SYMBOL(notify_change); |