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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/module.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
17/**
18 * inode_change_ok - check if attribute changes to an inode are allowed
19 * @inode: inode to check
20 * @attr: attributes to change
21 *
22 * Check if we are allowed to change the attributes contained in @attr
23 * in the given inode. This includes the normal unix access permission
24 * checks, as well as checks for rlimits and others.
25 *
26 * Should be called as the first thing in ->setattr implementations,
27 * possibly after taking additional locks.
28 */
29int inode_change_ok(const struct inode *inode, struct iattr *attr)
30{
31 unsigned int ia_valid = attr->ia_valid;
32
33 /*
34 * First check size constraints. These can't be overriden using
35 * ATTR_FORCE.
36 */
37 if (ia_valid & ATTR_SIZE) {
38 int error = inode_newsize_ok(inode, attr->ia_size);
39 if (error)
40 return error;
41 }
42
43 /* If force is set do it anyway. */
44 if (ia_valid & ATTR_FORCE)
45 return 0;
46
47 /* Make sure a caller can chown. */
48 if ((ia_valid & ATTR_UID) &&
49 (current_fsuid() != inode->i_uid ||
50 attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
51 return -EPERM;
52
53 /* Make sure caller can chgrp. */
54 if ((ia_valid & ATTR_GID) &&
55 (current_fsuid() != inode->i_uid ||
56 (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
57 !capable(CAP_CHOWN))
58 return -EPERM;
59
60 /* Make sure a caller can chmod. */
61 if (ia_valid & ATTR_MODE) {
62 if (!inode_owner_or_capable(inode))
63 return -EPERM;
64 /* Also check the setgid bit! */
65 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
66 inode->i_gid) && !capable(CAP_FSETID))
67 attr->ia_mode &= ~S_ISGID;
68 }
69
70 /* Check for setting the inode time. */
71 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
72 if (!inode_owner_or_capable(inode))
73 return -EPERM;
74 }
75
76 return 0;
77}
78EXPORT_SYMBOL(inode_change_ok);
79
80/**
81 * inode_newsize_ok - may this inode be truncated to a given size
82 * @inode: the inode to be truncated
83 * @offset: the new size to assign to the inode
84 * @Returns: 0 on success, -ve errno on failure
85 *
86 * inode_newsize_ok must be called with i_mutex held.
87 *
88 * inode_newsize_ok will check filesystem limits and ulimits to check that the
89 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
90 * when necessary. Caller must not proceed with inode size change if failure is
91 * returned. @inode must be a file (not directory), with appropriate
92 * permissions to allow truncate (inode_newsize_ok does NOT check these
93 * conditions).
94 */
95int inode_newsize_ok(const struct inode *inode, loff_t offset)
96{
97 if (inode->i_size < offset) {
98 unsigned long limit;
99
100 limit = rlimit(RLIMIT_FSIZE);
101 if (limit != RLIM_INFINITY && offset > limit)
102 goto out_sig;
103 if (offset > inode->i_sb->s_maxbytes)
104 goto out_big;
105 } else {
106 /*
107 * truncation of in-use swapfiles is disallowed - it would
108 * cause subsequent swapout to scribble on the now-freed
109 * blocks.
110 */
111 if (IS_SWAPFILE(inode))
112 return -ETXTBSY;
113 }
114
115 return 0;
116out_sig:
117 send_sig(SIGXFSZ, current, 0);
118out_big:
119 return -EFBIG;
120}
121EXPORT_SYMBOL(inode_newsize_ok);
122
123/**
124 * setattr_copy - copy simple metadata updates into the generic inode
125 * @inode: the inode to be updated
126 * @attr: the new attributes
127 *
128 * setattr_copy must be called with i_mutex held.
129 *
130 * setattr_copy updates the inode's metadata with that specified
131 * in attr. Noticeably missing is inode size update, which is more complex
132 * as it requires pagecache updates.
133 *
134 * The inode is not marked as dirty after this operation. The rationale is
135 * that for "simple" filesystems, the struct inode is the inode storage.
136 * The caller is free to mark the inode dirty afterwards if needed.
137 */
138void setattr_copy(struct inode *inode, const struct iattr *attr)
139{
140 unsigned int ia_valid = attr->ia_valid;
141
142 if (ia_valid & ATTR_UID)
143 inode->i_uid = attr->ia_uid;
144 if (ia_valid & ATTR_GID)
145 inode->i_gid = attr->ia_gid;
146 if (ia_valid & ATTR_ATIME)
147 inode->i_atime = timespec_trunc(attr->ia_atime,
148 inode->i_sb->s_time_gran);
149 if (ia_valid & ATTR_MTIME)
150 inode->i_mtime = timespec_trunc(attr->ia_mtime,
151 inode->i_sb->s_time_gran);
152 if (ia_valid & ATTR_CTIME)
153 inode->i_ctime = timespec_trunc(attr->ia_ctime,
154 inode->i_sb->s_time_gran);
155 if (ia_valid & ATTR_MODE) {
156 umode_t mode = attr->ia_mode;
157
158 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
159 mode &= ~S_ISGID;
160 inode->i_mode = mode;
161 }
162}
163EXPORT_SYMBOL(setattr_copy);
164
165int notify_change(struct dentry * dentry, struct iattr * attr)
166{
167 struct inode *inode = dentry->d_inode;
168 mode_t mode = inode->i_mode;
169 int error;
170 struct timespec now;
171 unsigned int ia_valid = attr->ia_valid;
172
173 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
174 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
175 return -EPERM;
176 }
177
178 if ((ia_valid & ATTR_MODE)) {
179 mode_t amode = attr->ia_mode;
180 /* Flag setting protected by i_mutex */
181 if (is_sxid(amode))
182 inode->i_flags &= ~S_NOSEC;
183 }
184
185 now = current_fs_time(inode->i_sb);
186
187 attr->ia_ctime = now;
188 if (!(ia_valid & ATTR_ATIME_SET))
189 attr->ia_atime = now;
190 if (!(ia_valid & ATTR_MTIME_SET))
191 attr->ia_mtime = now;
192 if (ia_valid & ATTR_KILL_PRIV) {
193 attr->ia_valid &= ~ATTR_KILL_PRIV;
194 ia_valid &= ~ATTR_KILL_PRIV;
195 error = security_inode_need_killpriv(dentry);
196 if (error > 0)
197 error = security_inode_killpriv(dentry);
198 if (error)
199 return error;
200 }
201
202 /*
203 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
204 * that the function has the ability to reinterpret a mode change
205 * that's due to these bits. This adds an implicit restriction that
206 * no function will ever call notify_change with both ATTR_MODE and
207 * ATTR_KILL_S*ID set.
208 */
209 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
210 (ia_valid & ATTR_MODE))
211 BUG();
212
213 if (ia_valid & ATTR_KILL_SUID) {
214 if (mode & S_ISUID) {
215 ia_valid = attr->ia_valid |= ATTR_MODE;
216 attr->ia_mode = (inode->i_mode & ~S_ISUID);
217 }
218 }
219 if (ia_valid & ATTR_KILL_SGID) {
220 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
221 if (!(ia_valid & ATTR_MODE)) {
222 ia_valid = attr->ia_valid |= ATTR_MODE;
223 attr->ia_mode = inode->i_mode;
224 }
225 attr->ia_mode &= ~S_ISGID;
226 }
227 }
228 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
229 return 0;
230
231 error = security_inode_setattr(dentry, attr);
232 if (error)
233 return error;
234
235 if (inode->i_op->setattr)
236 error = inode->i_op->setattr(dentry, attr);
237 else
238 error = simple_setattr(dentry, attr);
239
240 if (!error)
241 fsnotify_change(dentry, ia_valid);
242
243 return error;
244}
245
246EXPORT_SYMBOL(notify_change);
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
21static 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
34static 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 */
61int 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
105kill_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}
117EXPORT_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 */
135int 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;
156out_sig:
157 send_sig(SIGXFSZ, current, 0);
158out_big:
159 return -EFBIG;
160}
161EXPORT_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 */
178void 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 = timestamp_truncate(attr->ia_atime,
188 inode);
189 }
190 if (ia_valid & ATTR_MTIME) {
191 inode->i_mtime = timestamp_truncate(attr->ia_mtime,
192 inode);
193 }
194 if (ia_valid & ATTR_CTIME) {
195 inode->i_ctime = timestamp_truncate(attr->ia_ctime,
196 inode);
197 }
198 if (ia_valid & ATTR_MODE) {
199 umode_t mode = attr->ia_mode;
200
201 if (!in_group_p(inode->i_gid) &&
202 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
203 mode &= ~S_ISGID;
204 inode->i_mode = mode;
205 }
206}
207EXPORT_SYMBOL(setattr_copy);
208
209/**
210 * notify_change - modify attributes of a filesytem object
211 * @dentry: object affected
212 * @attr: new attributes
213 * @delegated_inode: returns inode, if the inode is delegated
214 *
215 * The caller must hold the i_mutex on the affected object.
216 *
217 * If notify_change discovers a delegation in need of breaking,
218 * it will return -EWOULDBLOCK and return a reference to the inode in
219 * delegated_inode. The caller should then break the delegation and
220 * retry. Because breaking a delegation may take a long time, the
221 * caller should drop the i_mutex before doing so.
222 *
223 * Alternatively, a caller may pass NULL for delegated_inode. This may
224 * be appropriate for callers that expect the underlying filesystem not
225 * to be NFS exported. Also, passing NULL is fine for callers holding
226 * the file open for write, as there can be no conflicting delegation in
227 * that case.
228 */
229int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
230{
231 struct inode *inode = dentry->d_inode;
232 umode_t mode = inode->i_mode;
233 int error;
234 struct timespec64 now;
235 unsigned int ia_valid = attr->ia_valid;
236
237 WARN_ON_ONCE(!inode_is_locked(inode));
238
239 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
240 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
241 return -EPERM;
242 }
243
244 /*
245 * If utimes(2) and friends are called with times == NULL (or both
246 * times are UTIME_NOW), then we need to check for write permission
247 */
248 if (ia_valid & ATTR_TOUCH) {
249 if (IS_IMMUTABLE(inode))
250 return -EPERM;
251
252 if (!inode_owner_or_capable(inode)) {
253 error = inode_permission(inode, MAY_WRITE);
254 if (error)
255 return error;
256 }
257 }
258
259 if ((ia_valid & ATTR_MODE)) {
260 umode_t amode = attr->ia_mode;
261 /* Flag setting protected by i_mutex */
262 if (is_sxid(amode))
263 inode->i_flags &= ~S_NOSEC;
264 }
265
266 now = current_time(inode);
267
268 attr->ia_ctime = now;
269 if (!(ia_valid & ATTR_ATIME_SET))
270 attr->ia_atime = now;
271 if (!(ia_valid & ATTR_MTIME_SET))
272 attr->ia_mtime = now;
273 if (ia_valid & ATTR_KILL_PRIV) {
274 error = security_inode_need_killpriv(dentry);
275 if (error < 0)
276 return error;
277 if (error == 0)
278 ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
279 }
280
281 /*
282 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
283 * that the function has the ability to reinterpret a mode change
284 * that's due to these bits. This adds an implicit restriction that
285 * no function will ever call notify_change with both ATTR_MODE and
286 * ATTR_KILL_S*ID set.
287 */
288 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
289 (ia_valid & ATTR_MODE))
290 BUG();
291
292 if (ia_valid & ATTR_KILL_SUID) {
293 if (mode & S_ISUID) {
294 ia_valid = attr->ia_valid |= ATTR_MODE;
295 attr->ia_mode = (inode->i_mode & ~S_ISUID);
296 }
297 }
298 if (ia_valid & ATTR_KILL_SGID) {
299 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
300 if (!(ia_valid & ATTR_MODE)) {
301 ia_valid = attr->ia_valid |= ATTR_MODE;
302 attr->ia_mode = inode->i_mode;
303 }
304 attr->ia_mode &= ~S_ISGID;
305 }
306 }
307 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
308 return 0;
309
310 /*
311 * Verify that uid/gid changes are valid in the target
312 * namespace of the superblock.
313 */
314 if (ia_valid & ATTR_UID &&
315 !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
316 return -EOVERFLOW;
317 if (ia_valid & ATTR_GID &&
318 !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
319 return -EOVERFLOW;
320
321 /* Don't allow modifications of files with invalid uids or
322 * gids unless those uids & gids are being made valid.
323 */
324 if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
325 return -EOVERFLOW;
326 if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
327 return -EOVERFLOW;
328
329 error = security_inode_setattr(dentry, attr);
330 if (error)
331 return error;
332 error = try_break_deleg(inode, delegated_inode);
333 if (error)
334 return error;
335
336 if (inode->i_op->setattr)
337 error = inode->i_op->setattr(dentry, attr);
338 else
339 error = simple_setattr(dentry, attr);
340
341 if (!error) {
342 fsnotify_change(dentry, ia_valid);
343 ima_inode_post_setattr(dentry);
344 evm_inode_post_setattr(dentry, ia_valid);
345 }
346
347 return error;
348}
349EXPORT_SYMBOL(notify_change);