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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/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 | */ |
29 | int 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 | } |
78 | EXPORT_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 | */ |
95 | int 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; |
116 | out_sig: |
117 | send_sig(SIGXFSZ, current, 0); |
118 | out_big: |
119 | return -EFBIG; |
120 | } |
121 | EXPORT_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 | */ |
138 | void 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 | } |
163 | EXPORT_SYMBOL(setattr_copy); |
164 | |
165 | int 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 (ia_valid & ATTR_SIZE) |
236 | down_write(&dentry->d_inode->i_alloc_sem); |
237 | |
238 | if (inode->i_op->setattr) |
239 | error = inode->i_op->setattr(dentry, attr); |
240 | else |
241 | error = simple_setattr(dentry, attr); |
242 | |
243 | if (ia_valid & ATTR_SIZE) |
244 | up_write(&dentry->d_inode->i_alloc_sem); |
245 | |
246 | if (!error) |
247 | fsnotify_change(dentry, ia_valid); |
248 | |
249 | return error; |
250 | } |
251 | |
252 | EXPORT_SYMBOL(notify_change); |
253 |
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