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