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