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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 | |
5e13dab9 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 (ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) | |
29 | return true; | |
30 | return false; | |
31 | } | |
32 | ||
33 | static bool chgrp_ok(const struct inode *inode, kgid_t gid) | |
34 | { | |
35 | if (uid_eq(current_fsuid(), inode->i_uid) && | |
36 | (in_group_p(gid) || gid_eq(gid, inode->i_gid))) | |
37 | return true; | |
38 | if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) | |
39 | return true; | |
40 | if (ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) | |
41 | return true; | |
42 | return false; | |
43 | } | |
44 | ||
2c27c65e | 45 | /** |
31051c85 JK |
46 | * setattr_prepare - check if attribute changes to a dentry are allowed |
47 | * @dentry: dentry to check | |
2c27c65e CH |
48 | * @attr: attributes to change |
49 | * | |
50 | * Check if we are allowed to change the attributes contained in @attr | |
31051c85 JK |
51 | * in the given dentry. This includes the normal unix access permission |
52 | * checks, as well as checks for rlimits and others. The function also clears | |
53 | * SGID bit from mode if user is not allowed to set it. Also file capabilities | |
54 | * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set. | |
2c27c65e CH |
55 | * |
56 | * Should be called as the first thing in ->setattr implementations, | |
57 | * possibly after taking additional locks. | |
58 | */ | |
31051c85 | 59 | int setattr_prepare(struct dentry *dentry, struct iattr *attr) |
1da177e4 | 60 | { |
31051c85 | 61 | struct inode *inode = d_inode(dentry); |
1da177e4 LT |
62 | unsigned int ia_valid = attr->ia_valid; |
63 | ||
2c27c65e CH |
64 | /* |
65 | * First check size constraints. These can't be overriden using | |
66 | * ATTR_FORCE. | |
67 | */ | |
68 | if (ia_valid & ATTR_SIZE) { | |
69 | int error = inode_newsize_ok(inode, attr->ia_size); | |
70 | if (error) | |
71 | return error; | |
72 | } | |
73 | ||
1da177e4 LT |
74 | /* If force is set do it anyway. */ |
75 | if (ia_valid & ATTR_FORCE) | |
030b533c | 76 | goto kill_priv; |
1da177e4 LT |
77 | |
78 | /* Make sure a caller can chown. */ | |
5e13dab9 | 79 | if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid)) |
2c27c65e | 80 | return -EPERM; |
1da177e4 LT |
81 | |
82 | /* Make sure caller can chgrp. */ | |
5e13dab9 | 83 | if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid)) |
2c27c65e | 84 | return -EPERM; |
1da177e4 LT |
85 | |
86 | /* Make sure a caller can chmod. */ | |
87 | if (ia_valid & ATTR_MODE) { | |
2e149670 | 88 | if (!inode_owner_or_capable(inode)) |
2c27c65e | 89 | return -EPERM; |
1da177e4 LT |
90 | /* Also check the setgid bit! */ |
91 | if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : | |
7fa294c8 | 92 | inode->i_gid) && |
23adbe12 | 93 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
1da177e4 LT |
94 | attr->ia_mode &= ~S_ISGID; |
95 | } | |
96 | ||
97 | /* Check for setting the inode time. */ | |
9767d749 | 98 | if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { |
2e149670 | 99 | if (!inode_owner_or_capable(inode)) |
2c27c65e | 100 | return -EPERM; |
1da177e4 | 101 | } |
2c27c65e | 102 | |
030b533c JK |
103 | kill_priv: |
104 | /* User has permission for the change */ | |
105 | if (ia_valid & ATTR_KILL_PRIV) { | |
106 | int error; | |
107 | ||
108 | error = security_inode_killpriv(dentry); | |
109 | if (error) | |
110 | return error; | |
111 | } | |
112 | ||
2c27c65e | 113 | return 0; |
1da177e4 | 114 | } |
31051c85 | 115 | EXPORT_SYMBOL(setattr_prepare); |
1da177e4 | 116 | |
25d9e2d1 | 117 | /** |
118 | * inode_newsize_ok - may this inode be truncated to a given size | |
119 | * @inode: the inode to be truncated | |
120 | * @offset: the new size to assign to the inode | |
121 | * @Returns: 0 on success, -ve errno on failure | |
122 | * | |
7bb46a67 | 123 | * inode_newsize_ok must be called with i_mutex held. |
124 | * | |
25d9e2d1 | 125 | * inode_newsize_ok will check filesystem limits and ulimits to check that the |
126 | * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ | |
127 | * when necessary. Caller must not proceed with inode size change if failure is | |
128 | * returned. @inode must be a file (not directory), with appropriate | |
129 | * permissions to allow truncate (inode_newsize_ok does NOT check these | |
130 | * conditions). | |
25d9e2d1 | 131 | */ |
132 | int inode_newsize_ok(const struct inode *inode, loff_t offset) | |
133 | { | |
134 | if (inode->i_size < offset) { | |
135 | unsigned long limit; | |
136 | ||
d554ed89 | 137 | limit = rlimit(RLIMIT_FSIZE); |
25d9e2d1 | 138 | if (limit != RLIM_INFINITY && offset > limit) |
139 | goto out_sig; | |
140 | if (offset > inode->i_sb->s_maxbytes) | |
141 | goto out_big; | |
142 | } else { | |
143 | /* | |
144 | * truncation of in-use swapfiles is disallowed - it would | |
145 | * cause subsequent swapout to scribble on the now-freed | |
146 | * blocks. | |
147 | */ | |
148 | if (IS_SWAPFILE(inode)) | |
149 | return -ETXTBSY; | |
150 | } | |
151 | ||
152 | return 0; | |
153 | out_sig: | |
154 | send_sig(SIGXFSZ, current, 0); | |
155 | out_big: | |
156 | return -EFBIG; | |
157 | } | |
158 | EXPORT_SYMBOL(inode_newsize_ok); | |
159 | ||
7bb46a67 | 160 | /** |
6a1a90ad | 161 | * setattr_copy - copy simple metadata updates into the generic inode |
7bb46a67 | 162 | * @inode: the inode to be updated |
163 | * @attr: the new attributes | |
164 | * | |
6a1a90ad | 165 | * setattr_copy must be called with i_mutex held. |
7bb46a67 | 166 | * |
6a1a90ad | 167 | * setattr_copy updates the inode's metadata with that specified |
25985edc | 168 | * in attr. Noticeably missing is inode size update, which is more complex |
2c27c65e | 169 | * as it requires pagecache updates. |
7bb46a67 | 170 | * |
171 | * The inode is not marked as dirty after this operation. The rationale is | |
172 | * that for "simple" filesystems, the struct inode is the inode storage. | |
173 | * The caller is free to mark the inode dirty afterwards if needed. | |
174 | */ | |
6a1a90ad | 175 | void setattr_copy(struct inode *inode, const struct iattr *attr) |
1da177e4 LT |
176 | { |
177 | unsigned int ia_valid = attr->ia_valid; | |
4a30131e | 178 | |
1da177e4 LT |
179 | if (ia_valid & ATTR_UID) |
180 | inode->i_uid = attr->ia_uid; | |
181 | if (ia_valid & ATTR_GID) | |
182 | inode->i_gid = attr->ia_gid; | |
183 | if (ia_valid & ATTR_ATIME) | |
184 | inode->i_atime = timespec_trunc(attr->ia_atime, | |
185 | inode->i_sb->s_time_gran); | |
186 | if (ia_valid & ATTR_MTIME) | |
187 | inode->i_mtime = timespec_trunc(attr->ia_mtime, | |
188 | inode->i_sb->s_time_gran); | |
189 | if (ia_valid & ATTR_CTIME) | |
190 | inode->i_ctime = timespec_trunc(attr->ia_ctime, | |
191 | inode->i_sb->s_time_gran); | |
192 | if (ia_valid & ATTR_MODE) { | |
193 | umode_t mode = attr->ia_mode; | |
194 | ||
7fa294c8 | 195 | if (!in_group_p(inode->i_gid) && |
23adbe12 | 196 | !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
1da177e4 LT |
197 | mode &= ~S_ISGID; |
198 | inode->i_mode = mode; | |
199 | } | |
7bb46a67 | 200 | } |
6a1a90ad | 201 | EXPORT_SYMBOL(setattr_copy); |
7bb46a67 | 202 | |
27ac0ffe BF |
203 | /** |
204 | * notify_change - modify attributes of a filesytem object | |
205 | * @dentry: object affected | |
206 | * @iattr: 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) | |
1da177e4 LT |
224 | { |
225 | struct inode *inode = dentry->d_inode; | |
8d334acd | 226 | umode_t mode = inode->i_mode; |
1da177e4 LT |
227 | int error; |
228 | struct timespec now; | |
229 | unsigned int ia_valid = attr->ia_valid; | |
230 | ||
5955102c | 231 | WARN_ON_ONCE(!inode_is_locked(inode)); |
c4107b30 | 232 | |
beb29e05 MS |
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 | ||
f2b20f6e MS |
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 | ||
69b45732 | 253 | if ((ia_valid & ATTR_MODE)) { |
8d334acd | 254 | umode_t amode = attr->ia_mode; |
69b45732 AK |
255 | /* Flag setting protected by i_mutex */ |
256 | if (is_sxid(amode)) | |
257 | inode->i_flags &= ~S_NOSEC; | |
258 | } | |
259 | ||
c2050a45 | 260 | now = current_time(inode); |
1da177e4 LT |
261 | |
262 | attr->ia_ctime = now; | |
263 | if (!(ia_valid & ATTR_ATIME_SET)) | |
264 | attr->ia_atime = now; | |
265 | if (!(ia_valid & ATTR_MTIME_SET)) | |
266 | attr->ia_mtime = now; | |
b5376771 | 267 | if (ia_valid & ATTR_KILL_PRIV) { |
b5376771 | 268 | error = security_inode_need_killpriv(dentry); |
030b533c | 269 | if (error < 0) |
b5376771 | 270 | return error; |
030b533c JK |
271 | if (error == 0) |
272 | ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; | |
b5376771 | 273 | } |
6de0ec00 JL |
274 | |
275 | /* | |
276 | * We now pass ATTR_KILL_S*ID to the lower level setattr function so | |
277 | * that the function has the ability to reinterpret a mode change | |
278 | * that's due to these bits. This adds an implicit restriction that | |
279 | * no function will ever call notify_change with both ATTR_MODE and | |
280 | * ATTR_KILL_S*ID set. | |
281 | */ | |
282 | if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) && | |
283 | (ia_valid & ATTR_MODE)) | |
284 | BUG(); | |
285 | ||
1da177e4 | 286 | if (ia_valid & ATTR_KILL_SUID) { |
1da177e4 | 287 | if (mode & S_ISUID) { |
6de0ec00 JL |
288 | ia_valid = attr->ia_valid |= ATTR_MODE; |
289 | attr->ia_mode = (inode->i_mode & ~S_ISUID); | |
1da177e4 LT |
290 | } |
291 | } | |
292 | if (ia_valid & ATTR_KILL_SGID) { | |
1da177e4 LT |
293 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { |
294 | if (!(ia_valid & ATTR_MODE)) { | |
295 | ia_valid = attr->ia_valid |= ATTR_MODE; | |
296 | attr->ia_mode = inode->i_mode; | |
297 | } | |
298 | attr->ia_mode &= ~S_ISGID; | |
299 | } | |
300 | } | |
6de0ec00 | 301 | if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) |
1da177e4 LT |
302 | return 0; |
303 | ||
a475acf0 SF |
304 | /* |
305 | * Verify that uid/gid changes are valid in the target | |
306 | * namespace of the superblock. | |
307 | */ | |
308 | if (ia_valid & ATTR_UID && | |
309 | !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) | |
310 | return -EOVERFLOW; | |
311 | if (ia_valid & ATTR_GID && | |
312 | !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) | |
313 | return -EOVERFLOW; | |
314 | ||
0bd23d09 EB |
315 | /* Don't allow modifications of files with invalid uids or |
316 | * gids unless those uids & gids are being made valid. | |
317 | */ | |
318 | if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid)) | |
319 | return -EOVERFLOW; | |
320 | if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid)) | |
321 | return -EOVERFLOW; | |
322 | ||
a77b72da | 323 | error = security_inode_setattr(dentry, attr); |
27ac0ffe BF |
324 | if (error) |
325 | return error; | |
326 | error = try_break_deleg(inode, delegated_inode); | |
a77b72da MS |
327 | if (error) |
328 | return error; | |
329 | ||
eef2380c | 330 | if (inode->i_op->setattr) |
a77b72da | 331 | error = inode->i_op->setattr(dentry, attr); |
eef2380c CH |
332 | else |
333 | error = simple_setattr(dentry, attr); | |
1da177e4 | 334 | |
975d2943 | 335 | if (!error) { |
0eeca283 | 336 | fsnotify_change(dentry, ia_valid); |
9957a504 | 337 | ima_inode_post_setattr(dentry); |
975d2943 MZ |
338 | evm_inode_post_setattr(dentry, ia_valid); |
339 | } | |
0eeca283 | 340 | |
1da177e4 LT |
341 | return error; |
342 | } | |
1da177e4 | 343 | EXPORT_SYMBOL(notify_change); |