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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/**
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 */
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +100031int inode_change_ok(const struct inode *inode, struct iattr *attr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070032{
Linus Torvalds1da177e2005-04-16 15:20:36 -070033 unsigned int ia_valid = attr->ia_valid;
34
Christoph Hellwig2c27c652010-06-04 11:30:04 +020035 /*
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
Linus Torvalds1da177e2005-04-16 15:20:36 -070045 /* If force is set do it anyway. */
46 if (ia_valid & ATTR_FORCE)
Christoph Hellwig2c27c652010-06-04 11:30:04 +020047 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070048
49 /* Make sure a caller can chown. */
50 if ((ia_valid & ATTR_UID) &&
Eric W. Biederman8e96e3b2012-03-03 21:17:15 -080051 (!uid_eq(current_fsuid(), inode->i_uid) ||
Eric W. Biederman7fa294c2012-09-02 19:12:51 -070052 !uid_eq(attr->ia_uid, inode->i_uid)) &&
53 !inode_capable(inode, CAP_CHOWN))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020054 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070055
56 /* Make sure caller can chgrp. */
57 if ((ia_valid & ATTR_GID) &&
Eric W. Biederman8e96e3b2012-03-03 21:17:15 -080058 (!uid_eq(current_fsuid(), inode->i_uid) ||
59 (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
Eric W. Biederman7fa294c2012-09-02 19:12:51 -070060 !inode_capable(inode, CAP_CHOWN))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020061 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070062
63 /* Make sure a caller can chmod. */
64 if (ia_valid & ATTR_MODE) {
Serge E. Hallyn2e149672011-03-23 16:43:26 -070065 if (!inode_owner_or_capable(inode))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020066 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070067 /* Also check the setgid bit! */
68 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
Eric W. Biederman7fa294c2012-09-02 19:12:51 -070069 inode->i_gid) &&
70 !inode_capable(inode, CAP_FSETID))
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 attr->ia_mode &= ~S_ISGID;
72 }
73
74 /* Check for setting the inode time. */
Miklos Szeredi9767d742008-07-01 15:01:26 +020075 if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
Serge E. Hallyn2e149672011-03-23 16:43:26 -070076 if (!inode_owner_or_capable(inode))
Christoph Hellwig2c27c652010-06-04 11:30:04 +020077 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 }
Christoph Hellwig2c27c652010-06-04 11:30:04 +020079
80 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070081}
Linus Torvalds1da177e2005-04-16 15:20:36 -070082EXPORT_SYMBOL(inode_change_ok);
83
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +100084/**
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 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +100090 * inode_newsize_ok must be called with i_mutex held.
91 *
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +100092 * 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).
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +100098 */
99int inode_newsize_ok(const struct inode *inode, loff_t offset)
100{
101 if (inode->i_size < offset) {
102 unsigned long limit;
103
Jiri Slabyd554ed892010-03-05 13:42:42 -0800104 limit = rlimit(RLIMIT_FSIZE);
npiggin@suse.de25d9e2d2009-08-21 02:35:05 +1000105 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
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000127/**
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200128 * setattr_copy - copy simple metadata updates into the generic inode
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000129 * @inode: the inode to be updated
130 * @attr: the new attributes
131 *
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200132 * setattr_copy must be called with i_mutex held.
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000133 *
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200134 * setattr_copy updates the inode's metadata with that specified
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300135 * in attr. Noticeably missing is inode size update, which is more complex
Christoph Hellwig2c27c652010-06-04 11:30:04 +0200136 * as it requires pagecache updates.
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000137 *
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 */
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200142void setattr_copy(struct inode *inode, const struct iattr *attr)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143{
144 unsigned int ia_valid = attr->ia_valid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 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
Eric W. Biederman7fa294c2012-09-02 19:12:51 -0700162 if (!in_group_p(inode->i_gid) &&
163 !inode_capable(inode, CAP_FSETID))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164 mode &= ~S_ISGID;
165 inode->i_mode = mode;
166 }
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000167}
Christoph Hellwig6a1a90a2010-06-04 11:30:00 +0200168EXPORT_SYMBOL(setattr_copy);
npiggin@suse.de7bb46a62010-05-27 01:05:33 +1000169
J. Bruce Fields27ac0ff2011-09-20 17:19:26 -0400170/**
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)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191{
192 struct inode *inode = dentry->d_inode;
Al Viro8d334ac2011-07-24 23:21:59 -0400193 umode_t mode = inode->i_mode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 int error;
195 struct timespec now;
196 unsigned int ia_valid = attr->ia_valid;
197
Andrew Mortonc4107b32012-06-20 09:55:58 +1000198 WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
199
Miklos Szeredibeb29e02008-07-01 15:01:29 +0200200 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
Andi Kleen69b45732011-05-28 08:25:51 -0700205 if ((ia_valid & ATTR_MODE)) {
Al Viro8d334ac2011-07-24 23:21:59 -0400206 umode_t amode = attr->ia_mode;
Andi Kleen69b45732011-05-28 08:25:51 -0700207 /* Flag setting protected by i_mutex */
208 if (is_sxid(amode))
209 inode->i_flags &= ~S_NOSEC;
210 }
211
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 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;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700219 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 }
Jeff Layton6de0ec02007-10-18 03:05:20 -0700228
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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 if (ia_valid & ATTR_KILL_SUID) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241 if (mode & S_ISUID) {
Jeff Layton6de0ec02007-10-18 03:05:20 -0700242 ia_valid = attr->ia_valid |= ATTR_MODE;
243 attr->ia_mode = (inode->i_mode & ~S_ISUID);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244 }
245 }
246 if (ia_valid & ATTR_KILL_SGID) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247 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 }
Jeff Layton6de0ec02007-10-18 03:05:20 -0700255 if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 return 0;
257
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200258 error = security_inode_setattr(dentry, attr);
259 if (error)
260 return error;
J. Bruce Fields27ac0ff2011-09-20 17:19:26 -0400261 error = try_break_deleg(inode, delegated_inode);
262 if (error)
263 return error;
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200264
Christoph Hellwigeef23802010-06-04 11:30:01 +0200265 if (inode->i_op->setattr)
Miklos Szeredia77b72d2008-07-30 14:06:22 +0200266 error = inode->i_op->setattr(dentry, attr);
Christoph Hellwigeef23802010-06-04 11:30:01 +0200267 else
268 error = simple_setattr(dentry, attr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269
Mimi Zohar975d2942011-03-09 14:39:57 -0500270 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -0400271 fsnotify_change(dentry, ia_valid);
Mimi Zohar9957a502011-03-09 22:57:53 -0500272 ima_inode_post_setattr(dentry);
Mimi Zohar975d2942011-03-09 14:39:57 -0500273 evm_inode_post_setattr(dentry, ia_valid);
274 }
Robert Love0eeca282005-07-12 17:06:03 -0400275
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 return error;
277}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700278EXPORT_SYMBOL(notify_change);