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Linux/fs/kernfs/inode.c

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  1 /*
  2  * fs/kernfs/inode.c - kernfs inode implementation
  3  *
  4  * Copyright (c) 2001-3 Patrick Mochel
  5  * Copyright (c) 2007 SUSE Linux Products GmbH
  6  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
  7  *
  8  * This file is released under the GPLv2.
  9  */
 10 
 11 #include <linux/pagemap.h>
 12 #include <linux/backing-dev.h>
 13 #include <linux/capability.h>
 14 #include <linux/errno.h>
 15 #include <linux/slab.h>
 16 #include <linux/xattr.h>
 17 #include <linux/security.h>
 18 
 19 #include "kernfs-internal.h"
 20 
 21 static const struct address_space_operations kernfs_aops = {
 22         .readpage       = simple_readpage,
 23         .write_begin    = simple_write_begin,
 24         .write_end      = simple_write_end,
 25 };
 26 
 27 static const struct inode_operations kernfs_iops = {
 28         .permission     = kernfs_iop_permission,
 29         .setattr        = kernfs_iop_setattr,
 30         .getattr        = kernfs_iop_getattr,
 31         .setxattr       = kernfs_iop_setxattr,
 32         .removexattr    = kernfs_iop_removexattr,
 33         .getxattr       = kernfs_iop_getxattr,
 34         .listxattr      = kernfs_iop_listxattr,
 35 };
 36 
 37 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
 38 {
 39         static DEFINE_MUTEX(iattr_mutex);
 40         struct kernfs_iattrs *ret;
 41         struct iattr *iattrs;
 42 
 43         mutex_lock(&iattr_mutex);
 44 
 45         if (kn->iattr)
 46                 goto out_unlock;
 47 
 48         kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
 49         if (!kn->iattr)
 50                 goto out_unlock;
 51         iattrs = &kn->iattr->ia_iattr;
 52 
 53         /* assign default attributes */
 54         iattrs->ia_mode = kn->mode;
 55         iattrs->ia_uid = GLOBAL_ROOT_UID;
 56         iattrs->ia_gid = GLOBAL_ROOT_GID;
 57 
 58         ktime_get_real_ts(&iattrs->ia_atime);
 59         iattrs->ia_mtime = iattrs->ia_atime;
 60         iattrs->ia_ctime = iattrs->ia_atime;
 61 
 62         simple_xattrs_init(&kn->iattr->xattrs);
 63 out_unlock:
 64         ret = kn->iattr;
 65         mutex_unlock(&iattr_mutex);
 66         return ret;
 67 }
 68 
 69 static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 70 {
 71         struct kernfs_iattrs *attrs;
 72         struct iattr *iattrs;
 73         unsigned int ia_valid = iattr->ia_valid;
 74 
 75         attrs = kernfs_iattrs(kn);
 76         if (!attrs)
 77                 return -ENOMEM;
 78 
 79         iattrs = &attrs->ia_iattr;
 80 
 81         if (ia_valid & ATTR_UID)
 82                 iattrs->ia_uid = iattr->ia_uid;
 83         if (ia_valid & ATTR_GID)
 84                 iattrs->ia_gid = iattr->ia_gid;
 85         if (ia_valid & ATTR_ATIME)
 86                 iattrs->ia_atime = iattr->ia_atime;
 87         if (ia_valid & ATTR_MTIME)
 88                 iattrs->ia_mtime = iattr->ia_mtime;
 89         if (ia_valid & ATTR_CTIME)
 90                 iattrs->ia_ctime = iattr->ia_ctime;
 91         if (ia_valid & ATTR_MODE) {
 92                 umode_t mode = iattr->ia_mode;
 93                 iattrs->ia_mode = kn->mode = mode;
 94         }
 95         return 0;
 96 }
 97 
 98 /**
 99  * kernfs_setattr - set iattr on a node
100  * @kn: target node
101  * @iattr: iattr to set
102  *
103  * Returns 0 on success, -errno on failure.
104  */
105 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
106 {
107         int ret;
108 
109         mutex_lock(&kernfs_mutex);
110         ret = __kernfs_setattr(kn, iattr);
111         mutex_unlock(&kernfs_mutex);
112         return ret;
113 }
114 
115 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
116 {
117         struct inode *inode = d_inode(dentry);
118         struct kernfs_node *kn = dentry->d_fsdata;
119         int error;
120 
121         if (!kn)
122                 return -EINVAL;
123 
124         mutex_lock(&kernfs_mutex);
125         error = inode_change_ok(inode, iattr);
126         if (error)
127                 goto out;
128 
129         error = __kernfs_setattr(kn, iattr);
130         if (error)
131                 goto out;
132 
133         /* this ignores size changes */
134         setattr_copy(inode, iattr);
135 
136 out:
137         mutex_unlock(&kernfs_mutex);
138         return error;
139 }
140 
141 static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
142                                   u32 *secdata_len)
143 {
144         struct kernfs_iattrs *attrs;
145         void *old_secdata;
146         size_t old_secdata_len;
147 
148         attrs = kernfs_iattrs(kn);
149         if (!attrs)
150                 return -ENOMEM;
151 
152         old_secdata = attrs->ia_secdata;
153         old_secdata_len = attrs->ia_secdata_len;
154 
155         attrs->ia_secdata = *secdata;
156         attrs->ia_secdata_len = *secdata_len;
157 
158         *secdata = old_secdata;
159         *secdata_len = old_secdata_len;
160         return 0;
161 }
162 
163 int kernfs_iop_setxattr(struct dentry *unused, struct inode *inode,
164                         const char *name, const void *value,
165                         size_t size, int flags)
166 {
167         struct kernfs_node *kn = inode->i_private;
168         struct kernfs_iattrs *attrs;
169         void *secdata;
170         int error;
171         u32 secdata_len = 0;
172 
173         attrs = kernfs_iattrs(kn);
174         if (!attrs)
175                 return -ENOMEM;
176 
177         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
178                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
179                 error = security_inode_setsecurity(inode, suffix,
180                                                 value, size, flags);
181                 if (error)
182                         return error;
183                 error = security_inode_getsecctx(inode,
184                                                 &secdata, &secdata_len);
185                 if (error)
186                         return error;
187 
188                 mutex_lock(&kernfs_mutex);
189                 error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
190                 mutex_unlock(&kernfs_mutex);
191 
192                 if (secdata)
193                         security_release_secctx(secdata, secdata_len);
194                 return error;
195         } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
196                 return simple_xattr_set(&attrs->xattrs, name, value, size,
197                                         flags);
198         }
199 
200         return -EINVAL;
201 }
202 
203 int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
204 {
205         struct kernfs_node *kn = dentry->d_fsdata;
206         struct kernfs_iattrs *attrs;
207 
208         attrs = kernfs_iattrs(kn);
209         if (!attrs)
210                 return -ENOMEM;
211 
212         return simple_xattr_set(&attrs->xattrs, name, NULL, 0, XATTR_REPLACE);
213 }
214 
215 ssize_t kernfs_iop_getxattr(struct dentry *unused, struct inode *inode,
216                             const char *name, void *buf, size_t size)
217 {
218         struct kernfs_node *kn = inode->i_private;
219         struct kernfs_iattrs *attrs;
220 
221         attrs = kernfs_iattrs(kn);
222         if (!attrs)
223                 return -ENOMEM;
224 
225         return simple_xattr_get(&attrs->xattrs, name, buf, size);
226 }
227 
228 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
229 {
230         struct kernfs_node *kn = dentry->d_fsdata;
231         struct kernfs_iattrs *attrs;
232 
233         attrs = kernfs_iattrs(kn);
234         if (!attrs)
235                 return -ENOMEM;
236 
237         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
238 }
239 
240 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
241 {
242         inode->i_mode = mode;
243         inode->i_atime = inode->i_mtime =
244                 inode->i_ctime = current_fs_time(inode->i_sb);
245 }
246 
247 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
248 {
249         struct super_block *sb = inode->i_sb;
250         inode->i_uid = iattr->ia_uid;
251         inode->i_gid = iattr->ia_gid;
252         inode->i_atime = timespec_trunc(iattr->ia_atime, sb->s_time_gran);
253         inode->i_mtime = timespec_trunc(iattr->ia_mtime, sb->s_time_gran);
254         inode->i_ctime = timespec_trunc(iattr->ia_ctime, sb->s_time_gran);
255 }
256 
257 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
258 {
259         struct kernfs_iattrs *attrs = kn->iattr;
260 
261         inode->i_mode = kn->mode;
262         if (attrs) {
263                 /*
264                  * kernfs_node has non-default attributes get them from
265                  * persistent copy in kernfs_node.
266                  */
267                 set_inode_attr(inode, &attrs->ia_iattr);
268                 security_inode_notifysecctx(inode, attrs->ia_secdata,
269                                             attrs->ia_secdata_len);
270         }
271 
272         if (kernfs_type(kn) == KERNFS_DIR)
273                 set_nlink(inode, kn->dir.subdirs + 2);
274 }
275 
276 int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
277                    struct kstat *stat)
278 {
279         struct kernfs_node *kn = dentry->d_fsdata;
280         struct inode *inode = d_inode(dentry);
281 
282         mutex_lock(&kernfs_mutex);
283         kernfs_refresh_inode(kn, inode);
284         mutex_unlock(&kernfs_mutex);
285 
286         generic_fillattr(inode, stat);
287         return 0;
288 }
289 
290 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
291 {
292         kernfs_get(kn);
293         inode->i_private = kn;
294         inode->i_mapping->a_ops = &kernfs_aops;
295         inode->i_op = &kernfs_iops;
296 
297         set_default_inode_attr(inode, kn->mode);
298         kernfs_refresh_inode(kn, inode);
299 
300         /* initialize inode according to type */
301         switch (kernfs_type(kn)) {
302         case KERNFS_DIR:
303                 inode->i_op = &kernfs_dir_iops;
304                 inode->i_fop = &kernfs_dir_fops;
305                 if (kn->flags & KERNFS_EMPTY_DIR)
306                         make_empty_dir_inode(inode);
307                 break;
308         case KERNFS_FILE:
309                 inode->i_size = kn->attr.size;
310                 inode->i_fop = &kernfs_file_fops;
311                 break;
312         case KERNFS_LINK:
313                 inode->i_op = &kernfs_symlink_iops;
314                 break;
315         default:
316                 BUG();
317         }
318 
319         unlock_new_inode(inode);
320 }
321 
322 /**
323  *      kernfs_get_inode - get inode for kernfs_node
324  *      @sb: super block
325  *      @kn: kernfs_node to allocate inode for
326  *
327  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
328  *      allocated and basics are initialized.  New inode is returned
329  *      locked.
330  *
331  *      LOCKING:
332  *      Kernel thread context (may sleep).
333  *
334  *      RETURNS:
335  *      Pointer to allocated inode on success, NULL on failure.
336  */
337 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
338 {
339         struct inode *inode;
340 
341         inode = iget_locked(sb, kn->ino);
342         if (inode && (inode->i_state & I_NEW))
343                 kernfs_init_inode(kn, inode);
344 
345         return inode;
346 }
347 
348 /*
349  * The kernfs_node serves as both an inode and a directory entry for
350  * kernfs.  To prevent the kernfs inode numbers from being freed
351  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
352  * super_operations.evict_inode() implementation is needed to drop that
353  * reference upon inode destruction.
354  */
355 void kernfs_evict_inode(struct inode *inode)
356 {
357         struct kernfs_node *kn = inode->i_private;
358 
359         truncate_inode_pages_final(&inode->i_data);
360         clear_inode(inode);
361         kernfs_put(kn);
362 }
363 
364 int kernfs_iop_permission(struct inode *inode, int mask)
365 {
366         struct kernfs_node *kn;
367 
368         if (mask & MAY_NOT_BLOCK)
369                 return -ECHILD;
370 
371         kn = inode->i_private;
372 
373         mutex_lock(&kernfs_mutex);
374         kernfs_refresh_inode(kn, inode);
375         mutex_unlock(&kernfs_mutex);
376 
377         return generic_permission(inode, mask);
378 }
379 

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