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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/attr.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
6 */
7
Paul Gortmaker630d9c42011-11-16 23:57:37 -05008#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07009#include <linux/time.h>
10#include <linux/mm.h>
11#include <linux/string.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080012#include <linux/capability.h>
Robert Love0eeca282005-07-12 17:06:03 -040013#include <linux/fsnotify.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/fcntl.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <linux/security.h>
Mimi Zohar975d2942011-03-09 14:39:57 -050016#include <linux/evm.h>
Mimi Zohar9957a502011-03-09 22:57:53 -050017#include <linux/ima.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Christoph Hellwig2c27c652010-06-04 11:30:04 +020019/**
Jan Kara31051c82016-05-26 16:55:18 +020020 * setattr_prepare - check if attribute changes to a dentry are allowed
21 * @dentry: dentry to check
Christoph Hellwig2c27c652010-06-04 11:30:04 +020022 * @attr: attributes to change
23 *
24 * Check if we are allowed to change the attributes contained in @attr
Jan Kara31051c82016-05-26 16:55:18 +020025 * in the given dentry. This includes the normal unix access permission
26 * checks, as well as checks for rlimits and others. The function also clears
27 * SGID bit from mode if user is not allowed to set it. Also file capabilities
28 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
Christoph Hellwig2c27c652010-06-04 11:30:04 +020029 *
30 * Should be called as the first thing in ->setattr implementations,
31 * possibly after taking additional locks.
32 */
Jan Kara31051c82016-05-26 16:55:18 +020033int setattr_prepare(struct dentry *dentry, struct iattr *attr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070034{
Jan Kara31051c82016-05-26 16:55:18 +020035 struct inode *inode = d_inode(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -070036 unsigned int ia_valid = attr->ia_valid;
37
Christoph Hellwig2c27c652010-06-04 11:30:04 +020038 /*
39 * First check size constraints. These can't be overriden using
40 * ATTR_FORCE.
41 */
42 if (ia_valid & ATTR_SIZE) {
43 int error = inode_newsize_ok(inode, attr->ia_size);
44 if (error)
45 return error;
46 }
47
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 /* If force is set do it anyway. */
49 if (ia_valid & ATTR_FORCE)
Jan Kara030b5332016-05-26 17:21:32 +020050 goto kill_priv;
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
52 /* Make sure a caller can chown. */
53 if ((ia_valid & ATTR_UID) &&
Eric W. Biederman8e96e3b2012-03-03 21:17:15 -080054 (!uid_eq(current_fsuid(), inode->i_uid) ||
Eric W. Biederman7fa294c2012-09-02 19:12:51 -070055 !uid_eq(attr->ia_uid, inode->i_uid)) &&
Andy Lutomirski23adbe12014-06-10 12:45:42 -070056 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020057 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
59 /* Make sure caller can chgrp. */
60 if ((ia_valid & ATTR_GID) &&
Eric W. Biederman8e96e3b2012-03-03 21:17:15 -080061 (!uid_eq(current_fsuid(), inode->i_uid) ||
62 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
Andy Lutomirski23adbe12014-06-10 12:45:42 -070063 !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020064 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
66 /* Make sure a caller can chmod. */
67 if (ia_valid & ATTR_MODE) {
Serge E. Hallyn2e149672011-03-23 16:43:26 -070068 if (!inode_owner_or_capable(inode))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020069 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 /* Also check the setgid bit! */
71 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
Eric W. Biederman7fa294c2012-09-02 19:12:51 -070072 inode->i_gid) &&
Andy Lutomirski23adbe12014-06-10 12:45:42 -070073 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 attr->ia_mode &= ~S_ISGID;
75 }
76
77 /* Check for setting the inode time. */
Miklos Szeredi9767d742008-07-01 15:01:26 +020078 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
Serge E. Hallyn2e149672011-03-23 16:43:26 -070079 if (!inode_owner_or_capable(inode))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020080 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 }
Christoph Hellwig2c27c652010-06-04 11:30:04 +020082
Jan Kara030b5332016-05-26 17:21:32 +020083kill_priv:
84 /* User has permission for the change */
85 if (ia_valid & ATTR_KILL_PRIV) {
86 int error;
87
88 error = security_inode_killpriv(dentry);
89 if (error)
90 return error;
91 }
92
Christoph Hellwig2c27c652010-06-04 11:30:04 +020093 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070094}
Jan Kara31051c82016-05-26 16:55:18 +020095EXPORT_SYMBOL(setattr_prepare);
Linus Torvalds1da177e2005-04-16 15:20:36 -070096
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +100097/**
98 * inode_newsize_ok - may this inode be truncated to a given size
99 * @inode: the inode to be truncated
100 * @offset: the new size to assign to the inode
101 * @Returns: 0 on success, -ve errno on failure
102 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000103 * inode_newsize_ok must be called with i_mutex held.
104 *
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +1000105 * inode_newsize_ok will check filesystem limits and ulimits to check that the
106 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
107 * when necessary. Caller must not proceed with inode size change if failure is
108 * returned. @inode must be a file (not directory), with appropriate
109 * permissions to allow truncate (inode_newsize_ok does NOT check these
110 * conditions).
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +1000111 */
112int inode_newsize_ok(const struct inode *inode, loff_t offset)
113{
114 if (inode->i_size < offset) {
115 unsigned long limit;
116
Jiri Slabyd554ed892010-03-05 13:42:42 -0800117 limit = rlimit(RLIMIT_FSIZE);
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +1000118 if (limit != RLIM_INFINITY && offset > limit)
119 goto out_sig;
120 if (offset > inode->i_sb->s_maxbytes)
121 goto out_big;
122 } else {
123 /*
124 * truncation of in-use swapfiles is disallowed - it would
125 * cause subsequent swapout to scribble on the now-freed
126 * blocks.
127 */
128 if (IS_SWAPFILE(inode))
129 return -ETXTBSY;
130 }
131
132 return 0;
133out_sig:
134 send_sig(SIGXFSZ, current, 0);
135out_big:
136 return -EFBIG;
137}
138EXPORT_SYMBOL(inode_newsize_ok);
139
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000140/**
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200141 * setattr_copy - copy simple metadata updates into the generic inode
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000142 * @inode: the inode to be updated
143 * @attr: the new attributes
144 *
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200145 * setattr_copy must be called with i_mutex held.
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000146 *
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200147 * setattr_copy updates the inode's metadata with that specified
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300148 * in attr. Noticeably missing is inode size update, which is more complex
Christoph Hellwig2c27c652010-06-04 11:30:04 +0200149 * as it requires pagecache updates.
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000150 *
151 * The inode is not marked as dirty after this operation. The rationale is
152 * that for "simple" filesystems, the struct inode is the inode storage.
153 * The caller is free to mark the inode dirty afterwards if needed.
154 */
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200155void setattr_copy(struct inode *inode, const struct iattr *attr)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156{
157 unsigned int ia_valid = attr->ia_valid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 if (ia_valid & ATTR_UID)
160 inode->i_uid = attr->ia_uid;
161 if (ia_valid & ATTR_GID)
162 inode->i_gid = attr->ia_gid;
163 if (ia_valid & ATTR_ATIME)
164 inode->i_atime = timespec_trunc(attr->ia_atime,
165 inode->i_sb->s_time_gran);
166 if (ia_valid & ATTR_MTIME)
167 inode->i_mtime = timespec_trunc(attr->ia_mtime,
168 inode->i_sb->s_time_gran);
169 if (ia_valid & ATTR_CTIME)
170 inode->i_ctime = timespec_trunc(attr->ia_ctime,
171 inode->i_sb->s_time_gran);
172 if (ia_valid & ATTR_MODE) {
173 umode_t mode = attr->ia_mode;
174
Eric W. Biederman7fa294c2012-09-02 19:12:51 -0700175 if (!in_group_p(inode->i_gid) &&
Andy Lutomirski23adbe12014-06-10 12:45:42 -0700176 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177 mode &= ~S_ISGID;
178 inode->i_mode = mode;
179 }
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000180}
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200181EXPORT_SYMBOL(setattr_copy);
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000182
J. Bruce Fields27ac0ff2011-09-20 17:19:26 -0400183/**
184 * notify_change - modify attributes of a filesytem object
185 * @dentry: object affected
186 * @iattr: new attributes
187 * @delegated_inode: returns inode, if the inode is delegated
188 *
189 * The caller must hold the i_mutex on the affected object.
190 *
191 * If notify_change discovers a delegation in need of breaking,
192 * it will return -EWOULDBLOCK and return a reference to the inode in
193 * delegated_inode. The caller should then break the delegation and
194 * retry. Because breaking a delegation may take a long time, the
195 * caller should drop the i_mutex before doing so.
196 *
197 * Alternatively, a caller may pass NULL for delegated_inode. This may
198 * be appropriate for callers that expect the underlying filesystem not
199 * to be NFS exported. Also, passing NULL is fine for callers holding
200 * the file open for write, as there can be no conflicting delegation in
201 * that case.
202 */
203int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204{
205 struct inode *inode = dentry->d_inode;
Al Viro8d334ac2011-07-24 23:21:59 -0400206 umode_t mode = inode->i_mode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207 int error;
208 struct timespec now;
209 unsigned int ia_valid = attr->ia_valid;
210
Al Viro59551022016-01-22 15:40:57 -0500211 WARN_ON_ONCE(!inode_is_locked(inode));
Andrew Mortonc4107b32012-06-20 09:55:58 +1000212
Miklos Szeredibeb29e02008-07-01 15:01:29 +0200213 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
214 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
215 return -EPERM;
216 }
217
Andi Kleen69b45732011-05-28 08:25:51 -0700218 if ((ia_valid & ATTR_MODE)) {
Al Viro8d334ac2011-07-24 23:21:59 -0400219 umode_t amode = attr->ia_mode;
Andi Kleen69b45732011-05-28 08:25:51 -0700220 /* Flag setting protected by i_mutex */
221 if (is_sxid(amode))
222 inode->i_flags &= ~S_NOSEC;
223 }
224
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 now = current_fs_time(inode->i_sb);
226
227 attr->ia_ctime = now;
228 if (!(ia_valid & ATTR_ATIME_SET))
229 attr->ia_atime = now;
230 if (!(ia_valid & ATTR_MTIME_SET))
231 attr->ia_mtime = now;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700232 if (ia_valid & ATTR_KILL_PRIV) {
Serge E. Hallynb5376772007-10-16 23:31:36 -0700233 error = security_inode_need_killpriv(dentry);
Jan Kara030b5332016-05-26 17:21:32 +0200234 if (error < 0)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700235 return error;
Jan Kara030b5332016-05-26 17:21:32 +0200236 if (error == 0)
237 ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700238 }
Jeff Layton6de0ec02007-10-18 03:05:20 -0700239
240 /*
241 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
242 * that the function has the ability to reinterpret a mode change
243 * that's due to these bits. This adds an implicit restriction that
244 * no function will ever call notify_change with both ATTR_MODE and
245 * ATTR_KILL_S*ID set.
246 */
247 if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
248 (ia_valid & ATTR_MODE))
249 BUG();
250
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 if (ia_valid & ATTR_KILL_SUID) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 if (mode & S_ISUID) {
Jeff Layton6de0ec02007-10-18 03:05:20 -0700253 ia_valid = attr->ia_valid |= ATTR_MODE;
254 attr->ia_mode = (inode->i_mode & ~S_ISUID);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255 }
256 }
257 if (ia_valid & ATTR_KILL_SGID) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
259 if (!(ia_valid & ATTR_MODE)) {
260 ia_valid = attr->ia_valid |= ATTR_MODE;
261 attr->ia_mode = inode->i_mode;
262 }
263 attr->ia_mode &= ~S_ISGID;
264 }
265 }
Jeff Layton6de0ec02007-10-18 03:05:20 -0700266 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 return 0;
268
Seth Forsheea475acf2016-04-26 14:36:25 -0500269 /*
270 * Verify that uid/gid changes are valid in the target
271 * namespace of the superblock.
272 */
273 if (ia_valid & ATTR_UID &&
274 !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
275 return -EOVERFLOW;
276 if (ia_valid & ATTR_GID &&
277 !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
278 return -EOVERFLOW;
279
Eric W. Biederman0bd23d092016-06-29 14:54:46 -0500280 /* Don't allow modifications of files with invalid uids or
281 * gids unless those uids & gids are being made valid.
282 */
283 if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
284 return -EOVERFLOW;
285 if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
286 return -EOVERFLOW;
287
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200288 error = security_inode_setattr(dentry, attr);
289 if (error)
290 return error;
J. Bruce Fields27ac0ff2011-09-20 17:19:26 -0400291 error = try_break_deleg(inode, delegated_inode);
292 if (error)
293 return error;
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200294
Christoph Hellwigeef23802010-06-04 11:30:01 +0200295 if (inode->i_op->setattr)
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200296 error = inode->i_op->setattr(dentry, attr);
Christoph Hellwigeef23802010-06-04 11:30:01 +0200297 else
298 error = simple_setattr(dentry, attr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299
Mimi Zohar975d2942011-03-09 14:39:57 -0500300 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -0400301 fsnotify_change(dentry, ia_valid);
Mimi Zohar9957a502011-03-09 22:57:53 -0500302 ima_inode_post_setattr(dentry);
Mimi Zohar975d2942011-03-09 14:39:57 -0500303 evm_inode_post_setattr(dentry, ia_valid);
304 }
Robert Love0eeca282005-07-12 17:06:03 -0400305
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 return error;
307}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308EXPORT_SYMBOL(notify_change);