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 (!is_owner_or_cap(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 (!is_owner_or_cap(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. Noticably 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	now = current_fs_time(inode->i_sb);
179
180	attr->ia_ctime = now;
181	if (!(ia_valid & ATTR_ATIME_SET))
182		attr->ia_atime = now;
183	if (!(ia_valid & ATTR_MTIME_SET))
184		attr->ia_mtime = now;
185	if (ia_valid & ATTR_KILL_PRIV) {
186		attr->ia_valid &= ~ATTR_KILL_PRIV;
187		ia_valid &= ~ATTR_KILL_PRIV;
188		error = security_inode_need_killpriv(dentry);
189		if (error > 0)
190			error = security_inode_killpriv(dentry);
191		if (error)
192			return error;
193	}
194
195	/*
196	 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
197	 * that the function has the ability to reinterpret a mode change
198	 * that's due to these bits. This adds an implicit restriction that
199	 * no function will ever call notify_change with both ATTR_MODE and
200	 * ATTR_KILL_S*ID set.
201	 */
202	if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
203	    (ia_valid & ATTR_MODE))
204		BUG();
205
206	if (ia_valid & ATTR_KILL_SUID) {
207		if (mode & S_ISUID) {
208			ia_valid = attr->ia_valid |= ATTR_MODE;
209			attr->ia_mode = (inode->i_mode & ~S_ISUID);
210		}
211	}
212	if (ia_valid & ATTR_KILL_SGID) {
213		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
214			if (!(ia_valid & ATTR_MODE)) {
215				ia_valid = attr->ia_valid |= ATTR_MODE;
216				attr->ia_mode = inode->i_mode;
217			}
218			attr->ia_mode &= ~S_ISGID;
219		}
220	}
221	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
222		return 0;
223
224	error = security_inode_setattr(dentry, attr);
225	if (error)
226		return error;
227
228	if (ia_valid & ATTR_SIZE)
229		down_write(&dentry->d_inode->i_alloc_sem);
230
231	if (inode->i_op->setattr)
232		error = inode->i_op->setattr(dentry, attr);
233	else
234		error = simple_setattr(dentry, attr);
235
236	if (ia_valid & ATTR_SIZE)
237		up_write(&dentry->d_inode->i_alloc_sem);
238
239	if (!error)
240		fsnotify_change(dentry, ia_valid);
241
242	return error;
243}
244
245EXPORT_SYMBOL(notify_change);
246