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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 | |
0031181c EB |
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 | ||
2c27c65e | 47 | /** |
31051c85 JK |
48 | * setattr_prepare - check if attribute changes to a dentry are allowed |
49 | * @dentry: dentry to check | |
2c27c65e CH |
50 | * @attr: attributes to change |
51 | * | |
52 | * Check if we are allowed to change the attributes contained in @attr | |
31051c85 JK |
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. | |
2c27c65e CH |
57 | * |
58 | * Should be called as the first thing in ->setattr implementations, | |
59 | * possibly after taking additional locks. | |
60 | */ | |
31051c85 | 61 | int setattr_prepare(struct dentry *dentry, struct iattr *attr) |
1da177e4 | 62 | { |
31051c85 | 63 | struct inode *inode = d_inode(dentry); |
1da177e4 LT |
64 | unsigned int ia_valid = attr->ia_valid; |
65 | ||
2c27c65e CH |
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 | ||
1da177e4 LT |
76 | /* If force is set do it anyway. */ |
77 | if (ia_valid & ATTR_FORCE) | |
030b533c | 78 | goto kill_priv; |
1da177e4 LT |
79 | |
80 | /* Make sure a caller can chown. */ | |
0031181c | 81 | if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid)) |
2c27c65e | 82 | return -EPERM; |
1da177e4 LT |
83 | |
84 | /* Make sure caller can chgrp. */ | |
0031181c | 85 | if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid)) |
2c27c65e | 86 | return -EPERM; |
1da177e4 LT |
87 | |
88 | /* Make sure a caller can chmod. */ | |
89 | if (ia_valid & ATTR_MODE) { | |
2e149670 | 90 | if (!inode_owner_or_capable(inode)) |
2c27c65e | 91 | return -EPERM; |
1da177e4 LT |
92 | /* Also check the setgid bit! */ |
93 | if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : | |
7fa294c8 | 94 | inode->i_gid) && |
23adbe12 | 95 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
1da177e4 LT |
96 | attr->ia_mode &= ~S_ISGID; |
97 | } | |
98 | ||
99 | /* Check for setting the inode time. */ | |
9767d749 | 100 | if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { |
2e149670 | 101 | if (!inode_owner_or_capable(inode)) |
2c27c65e | 102 | return -EPERM; |
1da177e4 | 103 | } |
2c27c65e | 104 | |
030b533c JK |
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 | ||
2c27c65e | 115 | return 0; |
1da177e4 | 116 | } |
31051c85 | 117 | EXPORT_SYMBOL(setattr_prepare); |
1da177e4 | 118 | |
25d9e2d1 | 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 | * @Returns: 0 on success, -ve errno on failure | |
124 | * | |
7bb46a67 | 125 | * inode_newsize_ok must be called with i_mutex held. |
126 | * | |
25d9e2d1 | 127 | * inode_newsize_ok will check filesystem limits and ulimits to check that the |
128 | * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ | |
129 | * when necessary. Caller must not proceed with inode size change if failure is | |
130 | * returned. @inode must be a file (not directory), with appropriate | |
131 | * permissions to allow truncate (inode_newsize_ok does NOT check these | |
132 | * conditions). | |
25d9e2d1 | 133 | */ |
134 | int inode_newsize_ok(const struct inode *inode, loff_t offset) | |
135 | { | |
136 | if (inode->i_size < offset) { | |
137 | unsigned long limit; | |
138 | ||
d554ed89 | 139 | limit = rlimit(RLIMIT_FSIZE); |
25d9e2d1 | 140 | if (limit != RLIM_INFINITY && offset > limit) |
141 | goto out_sig; | |
142 | if (offset > inode->i_sb->s_maxbytes) | |
143 | goto out_big; | |
144 | } else { | |
145 | /* | |
146 | * truncation of in-use swapfiles is disallowed - it would | |
147 | * cause subsequent swapout to scribble on the now-freed | |
148 | * blocks. | |
149 | */ | |
150 | if (IS_SWAPFILE(inode)) | |
151 | return -ETXTBSY; | |
152 | } | |
153 | ||
154 | return 0; | |
155 | out_sig: | |
156 | send_sig(SIGXFSZ, current, 0); | |
157 | out_big: | |
158 | return -EFBIG; | |
159 | } | |
160 | EXPORT_SYMBOL(inode_newsize_ok); | |
161 | ||
7bb46a67 | 162 | /** |
6a1a90ad | 163 | * setattr_copy - copy simple metadata updates into the generic inode |
7bb46a67 | 164 | * @inode: the inode to be updated |
165 | * @attr: the new attributes | |
166 | * | |
6a1a90ad | 167 | * setattr_copy must be called with i_mutex held. |
7bb46a67 | 168 | * |
6a1a90ad | 169 | * setattr_copy updates the inode's metadata with that specified |
25985edc | 170 | * in attr. Noticeably missing is inode size update, which is more complex |
2c27c65e | 171 | * as it requires pagecache updates. |
7bb46a67 | 172 | * |
173 | * The inode is not marked as dirty after this operation. The rationale is | |
174 | * that for "simple" filesystems, the struct inode is the inode storage. | |
175 | * The caller is free to mark the inode dirty afterwards if needed. | |
176 | */ | |
6a1a90ad | 177 | void setattr_copy(struct inode *inode, const struct iattr *attr) |
1da177e4 LT |
178 | { |
179 | unsigned int ia_valid = attr->ia_valid; | |
4a30131e | 180 | |
1da177e4 LT |
181 | if (ia_valid & ATTR_UID) |
182 | inode->i_uid = attr->ia_uid; | |
183 | if (ia_valid & ATTR_GID) | |
184 | inode->i_gid = attr->ia_gid; | |
185 | if (ia_valid & ATTR_ATIME) | |
186 | inode->i_atime = timespec_trunc(attr->ia_atime, | |
187 | inode->i_sb->s_time_gran); | |
188 | if (ia_valid & ATTR_MTIME) | |
189 | inode->i_mtime = timespec_trunc(attr->ia_mtime, | |
190 | inode->i_sb->s_time_gran); | |
191 | if (ia_valid & ATTR_CTIME) | |
192 | inode->i_ctime = timespec_trunc(attr->ia_ctime, | |
193 | inode->i_sb->s_time_gran); | |
194 | if (ia_valid & ATTR_MODE) { | |
195 | umode_t mode = attr->ia_mode; | |
196 | ||
7fa294c8 | 197 | if (!in_group_p(inode->i_gid) && |
23adbe12 | 198 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
1da177e4 LT |
199 | mode &= ~S_ISGID; |
200 | inode->i_mode = mode; | |
201 | } | |
7bb46a67 | 202 | } |
6a1a90ad | 203 | EXPORT_SYMBOL(setattr_copy); |
7bb46a67 | 204 | |
27ac0ffe BF |
205 | /** |
206 | * notify_change - modify attributes of a filesytem object | |
207 | * @dentry: object affected | |
208 | * @iattr: new attributes | |
209 | * @delegated_inode: returns inode, if the inode is delegated | |
210 | * | |
211 | * The caller must hold the i_mutex on the affected object. | |
212 | * | |
213 | * If notify_change discovers a delegation in need of breaking, | |
214 | * it will return -EWOULDBLOCK and return a reference to the inode in | |
215 | * delegated_inode. The caller should then break the delegation and | |
216 | * retry. Because breaking a delegation may take a long time, the | |
217 | * caller should drop the i_mutex before doing so. | |
218 | * | |
219 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
220 | * be appropriate for callers that expect the underlying filesystem not | |
221 | * to be NFS exported. Also, passing NULL is fine for callers holding | |
222 | * the file open for write, as there can be no conflicting delegation in | |
223 | * that case. | |
224 | */ | |
225 | int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode) | |
1da177e4 LT |
226 | { |
227 | struct inode *inode = dentry->d_inode; | |
8d334acd | 228 | umode_t mode = inode->i_mode; |
1da177e4 LT |
229 | int error; |
230 | struct timespec now; | |
231 | unsigned int ia_valid = attr->ia_valid; | |
232 | ||
5955102c | 233 | WARN_ON_ONCE(!inode_is_locked(inode)); |
c4107b30 | 234 | |
beb29e05 MS |
235 | if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { |
236 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) | |
237 | return -EPERM; | |
238 | } | |
239 | ||
f2b20f6e MS |
240 | /* |
241 | * If utimes(2) and friends are called with times == NULL (or both | |
242 | * times are UTIME_NOW), then we need to check for write permission | |
243 | */ | |
244 | if (ia_valid & ATTR_TOUCH) { | |
245 | if (IS_IMMUTABLE(inode)) | |
246 | return -EPERM; | |
247 | ||
248 | if (!inode_owner_or_capable(inode)) { | |
249 | error = inode_permission(inode, MAY_WRITE); | |
250 | if (error) | |
251 | return error; | |
252 | } | |
253 | } | |
254 | ||
69b45732 | 255 | if ((ia_valid & ATTR_MODE)) { |
8d334acd | 256 | umode_t amode = attr->ia_mode; |
69b45732 AK |
257 | /* Flag setting protected by i_mutex */ |
258 | if (is_sxid(amode)) | |
259 | inode->i_flags &= ~S_NOSEC; | |
260 | } | |
261 | ||
c2050a45 | 262 | now = current_time(inode); |
1da177e4 LT |
263 | |
264 | attr->ia_ctime = now; | |
265 | if (!(ia_valid & ATTR_ATIME_SET)) | |
266 | attr->ia_atime = now; | |
267 | if (!(ia_valid & ATTR_MTIME_SET)) | |
268 | attr->ia_mtime = now; | |
b5376771 | 269 | if (ia_valid & ATTR_KILL_PRIV) { |
b5376771 | 270 | error = security_inode_need_killpriv(dentry); |
030b533c | 271 | if (error < 0) |
b5376771 | 272 | return error; |
030b533c JK |
273 | if (error == 0) |
274 | ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; | |
b5376771 | 275 | } |
6de0ec00 JL |
276 | |
277 | /* | |
278 | * We now pass ATTR_KILL_S*ID to the lower level setattr function so | |
279 | * that the function has the ability to reinterpret a mode change | |
280 | * that's due to these bits. This adds an implicit restriction that | |
281 | * no function will ever call notify_change with both ATTR_MODE and | |
282 | * ATTR_KILL_S*ID set. | |
283 | */ | |
284 | if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && | |
285 | (ia_valid & ATTR_MODE)) | |
286 | BUG(); | |
287 | ||
1da177e4 | 288 | if (ia_valid & ATTR_KILL_SUID) { |
1da177e4 | 289 | if (mode & S_ISUID) { |
6de0ec00 JL |
290 | ia_valid = attr->ia_valid |= ATTR_MODE; |
291 | attr->ia_mode = (inode->i_mode & ~S_ISUID); | |
1da177e4 LT |
292 | } |
293 | } | |
294 | if (ia_valid & ATTR_KILL_SGID) { | |
1da177e4 LT |
295 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { |
296 | if (!(ia_valid & ATTR_MODE)) { | |
297 | ia_valid = attr->ia_valid |= ATTR_MODE; | |
298 | attr->ia_mode = inode->i_mode; | |
299 | } | |
300 | attr->ia_mode &= ~S_ISGID; | |
301 | } | |
302 | } | |
6de0ec00 | 303 | if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) |
1da177e4 LT |
304 | return 0; |
305 | ||
a475acf0 SF |
306 | /* |
307 | * Verify that uid/gid changes are valid in the target | |
308 | * namespace of the superblock. | |
309 | */ | |
310 | if (ia_valid & ATTR_UID && | |
311 | !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) | |
312 | return -EOVERFLOW; | |
313 | if (ia_valid & ATTR_GID && | |
314 | !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) | |
315 | return -EOVERFLOW; | |
316 | ||
0bd23d09 EB |
317 | /* Don't allow modifications of files with invalid uids or |
318 | * gids unless those uids & gids are being made valid. | |
319 | */ | |
320 | if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid)) | |
321 | return -EOVERFLOW; | |
322 | if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid)) | |
323 | return -EOVERFLOW; | |
324 | ||
a77b72da | 325 | error = security_inode_setattr(dentry, attr); |
27ac0ffe BF |
326 | if (error) |
327 | return error; | |
328 | error = try_break_deleg(inode, delegated_inode); | |
a77b72da MS |
329 | if (error) |
330 | return error; | |
331 | ||
eef2380c | 332 | if (inode->i_op->setattr) |
a77b72da | 333 | error = inode->i_op->setattr(dentry, attr); |
eef2380c CH |
334 | else |
335 | error = simple_setattr(dentry, attr); | |
1da177e4 | 336 | |
975d2943 | 337 | if (!error) { |
0eeca283 | 338 | fsnotify_change(dentry, ia_valid); |
9957a504 | 339 | ima_inode_post_setattr(dentry); |
975d2943 MZ |
340 | evm_inode_post_setattr(dentry, ia_valid); |
341 | } | |
0eeca283 | 342 | |
1da177e4 LT |
343 | return error; |
344 | } | |
1da177e4 | 345 | EXPORT_SYMBOL(notify_change); |