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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
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 = 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}
201EXPORT_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 */
223int 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}
348EXPORT_SYMBOL(notify_change);
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/export.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#include <linux/evm.h>
17
18/**
19 * inode_change_ok - check if attribute changes to an inode are allowed
20 * @inode: inode to check
21 * @attr: attributes to change
22 *
23 * Check if we are allowed to change the attributes contained in @attr
24 * in the given inode. This includes the normal unix access permission
25 * checks, as well as checks for rlimits and others.
26 *
27 * Should be called as the first thing in ->setattr implementations,
28 * possibly after taking additional locks.
29 */
30int inode_change_ok(const struct inode *inode, struct iattr *attr)
31{
32 unsigned int ia_valid = attr->ia_valid;
33
34 /*
35 * First check size constraints. These can't be overriden using
36 * ATTR_FORCE.
37 */
38 if (ia_valid & ATTR_SIZE) {
39 int error = inode_newsize_ok(inode, attr->ia_size);
40 if (error)
41 return error;
42 }
43
44 /* If force is set do it anyway. */
45 if (ia_valid & ATTR_FORCE)
46 return 0;
47
48 /* Make sure a caller can chown. */
49 if ((ia_valid & ATTR_UID) &&
50 (!uid_eq(current_fsuid(), inode->i_uid) ||
51 !uid_eq(attr->ia_uid, inode->i_uid)) && !capable(CAP_CHOWN))
52 return -EPERM;
53
54 /* Make sure caller can chgrp. */
55 if ((ia_valid & ATTR_GID) &&
56 (!uid_eq(current_fsuid(), inode->i_uid) ||
57 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
58 !capable(CAP_CHOWN))
59 return -EPERM;
60
61 /* Make sure a caller can chmod. */
62 if (ia_valid & ATTR_MODE) {
63 if (!inode_owner_or_capable(inode))
64 return -EPERM;
65 /* Also check the setgid bit! */
66 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
67 inode->i_gid) && !capable(CAP_FSETID))
68 attr->ia_mode &= ~S_ISGID;
69 }
70
71 /* Check for setting the inode time. */
72 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
73 if (!inode_owner_or_capable(inode))
74 return -EPERM;
75 }
76
77 return 0;
78}
79EXPORT_SYMBOL(inode_change_ok);
80
81/**
82 * inode_newsize_ok - may this inode be truncated to a given size
83 * @inode: the inode to be truncated
84 * @offset: the new size to assign to the inode
85 * @Returns: 0 on success, -ve errno on failure
86 *
87 * inode_newsize_ok must be called with i_mutex held.
88 *
89 * inode_newsize_ok will check filesystem limits and ulimits to check that the
90 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
91 * when necessary. Caller must not proceed with inode size change if failure is
92 * returned. @inode must be a file (not directory), with appropriate
93 * permissions to allow truncate (inode_newsize_ok does NOT check these
94 * conditions).
95 */
96int inode_newsize_ok(const struct inode *inode, loff_t offset)
97{
98 if (inode->i_size < offset) {
99 unsigned long limit;
100
101 limit = rlimit(RLIMIT_FSIZE);
102 if (limit != RLIM_INFINITY && offset > limit)
103 goto out_sig;
104 if (offset > inode->i_sb->s_maxbytes)
105 goto out_big;
106 } else {
107 /*
108 * truncation of in-use swapfiles is disallowed - it would
109 * cause subsequent swapout to scribble on the now-freed
110 * blocks.
111 */
112 if (IS_SWAPFILE(inode))
113 return -ETXTBSY;
114 }
115
116 return 0;
117out_sig:
118 send_sig(SIGXFSZ, current, 0);
119out_big:
120 return -EFBIG;
121}
122EXPORT_SYMBOL(inode_newsize_ok);
123
124/**
125 * setattr_copy - copy simple metadata updates into the generic inode
126 * @inode: the inode to be updated
127 * @attr: the new attributes
128 *
129 * setattr_copy must be called with i_mutex held.
130 *
131 * setattr_copy updates the inode's metadata with that specified
132 * in attr. Noticeably missing is inode size update, which is more complex
133 * as it requires pagecache updates.
134 *
135 * The inode is not marked as dirty after this operation. The rationale is
136 * that for "simple" filesystems, the struct inode is the inode storage.
137 * The caller is free to mark the inode dirty afterwards if needed.
138 */
139void setattr_copy(struct inode *inode, const struct iattr *attr)
140{
141 unsigned int ia_valid = attr->ia_valid;
142
143 if (ia_valid & ATTR_UID)
144 inode->i_uid = attr->ia_uid;
145 if (ia_valid & ATTR_GID)
146 inode->i_gid = attr->ia_gid;
147 if (ia_valid & ATTR_ATIME)
148 inode->i_atime = timespec_trunc(attr->ia_atime,
149 inode->i_sb->s_time_gran);
150 if (ia_valid & ATTR_MTIME)
151 inode->i_mtime = timespec_trunc(attr->ia_mtime,
152 inode->i_sb->s_time_gran);
153 if (ia_valid & ATTR_CTIME)
154 inode->i_ctime = timespec_trunc(attr->ia_ctime,
155 inode->i_sb->s_time_gran);
156 if (ia_valid & ATTR_MODE) {
157 umode_t mode = attr->ia_mode;
158
159 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
160 mode &= ~S_ISGID;
161 inode->i_mode = mode;
162 }
163}
164EXPORT_SYMBOL(setattr_copy);
165
166int notify_change(struct dentry * dentry, struct iattr * attr)
167{
168 struct inode *inode = dentry->d_inode;
169 umode_t mode = inode->i_mode;
170 int error;
171 struct timespec now;
172 unsigned int ia_valid = attr->ia_valid;
173
174 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
175 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
176 return -EPERM;
177 }
178
179 if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
180 if (attr->ia_size != inode->i_size)
181 inode_inc_iversion(inode);
182 }
183
184 if ((ia_valid & ATTR_MODE)) {
185 umode_t amode = attr->ia_mode;
186 /* Flag setting protected by i_mutex */
187 if (is_sxid(amode))
188 inode->i_flags &= ~S_NOSEC;
189 }
190
191 now = current_fs_time(inode->i_sb);
192
193 attr->ia_ctime = now;
194 if (!(ia_valid & ATTR_ATIME_SET))
195 attr->ia_atime = now;
196 if (!(ia_valid & ATTR_MTIME_SET))
197 attr->ia_mtime = now;
198 if (ia_valid & ATTR_KILL_PRIV) {
199 attr->ia_valid &= ~ATTR_KILL_PRIV;
200 ia_valid &= ~ATTR_KILL_PRIV;
201 error = security_inode_need_killpriv(dentry);
202 if (error > 0)
203 error = security_inode_killpriv(dentry);
204 if (error)
205 return error;
206 }
207
208 /*
209 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
210 * that the function has the ability to reinterpret a mode change
211 * that's due to these bits. This adds an implicit restriction that
212 * no function will ever call notify_change with both ATTR_MODE and
213 * ATTR_KILL_S*ID set.
214 */
215 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
216 (ia_valid & ATTR_MODE))
217 BUG();
218
219 if (ia_valid & ATTR_KILL_SUID) {
220 if (mode & S_ISUID) {
221 ia_valid = attr->ia_valid |= ATTR_MODE;
222 attr->ia_mode = (inode->i_mode & ~S_ISUID);
223 }
224 }
225 if (ia_valid & ATTR_KILL_SGID) {
226 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
227 if (!(ia_valid & ATTR_MODE)) {
228 ia_valid = attr->ia_valid |= ATTR_MODE;
229 attr->ia_mode = inode->i_mode;
230 }
231 attr->ia_mode &= ~S_ISGID;
232 }
233 }
234 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
235 return 0;
236
237 error = security_inode_setattr(dentry, attr);
238 if (error)
239 return error;
240
241 if (inode->i_op->setattr)
242 error = inode->i_op->setattr(dentry, attr);
243 else
244 error = simple_setattr(dentry, attr);
245
246 if (!error) {
247 fsnotify_change(dentry, ia_valid);
248 evm_inode_post_setattr(dentry, ia_valid);
249 }
250
251 return error;
252}
253
254EXPORT_SYMBOL(notify_change);