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Linux/fs/kernfs/inode.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * fs/kernfs/inode.c - kernfs inode implementation
  4  *
  5  * Copyright (c) 2001-3 Patrick Mochel
  6  * Copyright (c) 2007 SUSE Linux Products GmbH
  7  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
  8  */
  9 
 10 #include <linux/pagemap.h>
 11 #include <linux/backing-dev.h>
 12 #include <linux/capability.h>
 13 #include <linux/errno.h>
 14 #include <linux/slab.h>
 15 #include <linux/xattr.h>
 16 #include <linux/security.h>
 17 
 18 #include "kernfs-internal.h"
 19 
 20 static const struct address_space_operations kernfs_aops = {
 21         .readpage       = simple_readpage,
 22         .write_begin    = simple_write_begin,
 23         .write_end      = simple_write_end,
 24 };
 25 
 26 static const struct inode_operations kernfs_iops = {
 27         .permission     = kernfs_iop_permission,
 28         .setattr        = kernfs_iop_setattr,
 29         .getattr        = kernfs_iop_getattr,
 30         .listxattr      = kernfs_iop_listxattr,
 31 };
 32 
 33 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
 34 {
 35         static DEFINE_MUTEX(iattr_mutex);
 36         struct kernfs_iattrs *ret;
 37 
 38         mutex_lock(&iattr_mutex);
 39 
 40         if (kn->iattr || !alloc)
 41                 goto out_unlock;
 42 
 43         kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
 44         if (!kn->iattr)
 45                 goto out_unlock;
 46 
 47         /* assign default attributes */
 48         kn->iattr->ia_uid = GLOBAL_ROOT_UID;
 49         kn->iattr->ia_gid = GLOBAL_ROOT_GID;
 50 
 51         ktime_get_real_ts64(&kn->iattr->ia_atime);
 52         kn->iattr->ia_mtime = kn->iattr->ia_atime;
 53         kn->iattr->ia_ctime = kn->iattr->ia_atime;
 54 
 55         simple_xattrs_init(&kn->iattr->xattrs);
 56 out_unlock:
 57         ret = kn->iattr;
 58         mutex_unlock(&iattr_mutex);
 59         return ret;
 60 }
 61 
 62 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
 63 {
 64         return __kernfs_iattrs(kn, 1);
 65 }
 66 
 67 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
 68 {
 69         return __kernfs_iattrs(kn, 0);
 70 }
 71 
 72 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 73 {
 74         struct kernfs_iattrs *attrs;
 75         unsigned int ia_valid = iattr->ia_valid;
 76 
 77         attrs = kernfs_iattrs(kn);
 78         if (!attrs)
 79                 return -ENOMEM;
 80 
 81         if (ia_valid & ATTR_UID)
 82                 attrs->ia_uid = iattr->ia_uid;
 83         if (ia_valid & ATTR_GID)
 84                 attrs->ia_gid = iattr->ia_gid;
 85         if (ia_valid & ATTR_ATIME)
 86                 attrs->ia_atime = iattr->ia_atime;
 87         if (ia_valid & ATTR_MTIME)
 88                 attrs->ia_mtime = iattr->ia_mtime;
 89         if (ia_valid & ATTR_CTIME)
 90                 attrs->ia_ctime = iattr->ia_ctime;
 91         if (ia_valid & ATTR_MODE)
 92                 kn->mode = iattr->ia_mode;
 93         return 0;
 94 }
 95 
 96 /**
 97  * kernfs_setattr - set iattr on a node
 98  * @kn: target node
 99  * @iattr: iattr to set
100  *
101  * Returns 0 on success, -errno on failure.
102  */
103 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
104 {
105         int ret;
106 
107         mutex_lock(&kernfs_mutex);
108         ret = __kernfs_setattr(kn, iattr);
109         mutex_unlock(&kernfs_mutex);
110         return ret;
111 }
112 
113 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
114 {
115         struct inode *inode = d_inode(dentry);
116         struct kernfs_node *kn = inode->i_private;
117         int error;
118 
119         if (!kn)
120                 return -EINVAL;
121 
122         mutex_lock(&kernfs_mutex);
123         error = setattr_prepare(dentry, iattr);
124         if (error)
125                 goto out;
126 
127         error = __kernfs_setattr(kn, iattr);
128         if (error)
129                 goto out;
130 
131         /* this ignores size changes */
132         setattr_copy(inode, iattr);
133 
134 out:
135         mutex_unlock(&kernfs_mutex);
136         return error;
137 }
138 
139 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
140 {
141         struct kernfs_node *kn = kernfs_dentry_node(dentry);
142         struct kernfs_iattrs *attrs;
143 
144         attrs = kernfs_iattrs(kn);
145         if (!attrs)
146                 return -ENOMEM;
147 
148         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
149 }
150 
151 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
152 {
153         inode->i_mode = mode;
154         inode->i_atime = inode->i_mtime =
155                 inode->i_ctime = current_time(inode);
156 }
157 
158 static inline void set_inode_attr(struct inode *inode,
159                                   struct kernfs_iattrs *attrs)
160 {
161         struct super_block *sb = inode->i_sb;
162         inode->i_uid = attrs->ia_uid;
163         inode->i_gid = attrs->ia_gid;
164         inode->i_atime = timespec64_trunc(attrs->ia_atime, sb->s_time_gran);
165         inode->i_mtime = timespec64_trunc(attrs->ia_mtime, sb->s_time_gran);
166         inode->i_ctime = timespec64_trunc(attrs->ia_ctime, sb->s_time_gran);
167 }
168 
169 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
170 {
171         struct kernfs_iattrs *attrs = kn->iattr;
172 
173         inode->i_mode = kn->mode;
174         if (attrs)
175                 /*
176                  * kernfs_node has non-default attributes get them from
177                  * persistent copy in kernfs_node.
178                  */
179                 set_inode_attr(inode, attrs);
180 
181         if (kernfs_type(kn) == KERNFS_DIR)
182                 set_nlink(inode, kn->dir.subdirs + 2);
183 }
184 
185 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
186                        u32 request_mask, unsigned int query_flags)
187 {
188         struct inode *inode = d_inode(path->dentry);
189         struct kernfs_node *kn = inode->i_private;
190 
191         mutex_lock(&kernfs_mutex);
192         kernfs_refresh_inode(kn, inode);
193         mutex_unlock(&kernfs_mutex);
194 
195         generic_fillattr(inode, stat);
196         return 0;
197 }
198 
199 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
200 {
201         kernfs_get(kn);
202         inode->i_private = kn;
203         inode->i_mapping->a_ops = &kernfs_aops;
204         inode->i_op = &kernfs_iops;
205         inode->i_generation = kn->id.generation;
206 
207         set_default_inode_attr(inode, kn->mode);
208         kernfs_refresh_inode(kn, inode);
209 
210         /* initialize inode according to type */
211         switch (kernfs_type(kn)) {
212         case KERNFS_DIR:
213                 inode->i_op = &kernfs_dir_iops;
214                 inode->i_fop = &kernfs_dir_fops;
215                 if (kn->flags & KERNFS_EMPTY_DIR)
216                         make_empty_dir_inode(inode);
217                 break;
218         case KERNFS_FILE:
219                 inode->i_size = kn->attr.size;
220                 inode->i_fop = &kernfs_file_fops;
221                 break;
222         case KERNFS_LINK:
223                 inode->i_op = &kernfs_symlink_iops;
224                 break;
225         default:
226                 BUG();
227         }
228 
229         unlock_new_inode(inode);
230 }
231 
232 /**
233  *      kernfs_get_inode - get inode for kernfs_node
234  *      @sb: super block
235  *      @kn: kernfs_node to allocate inode for
236  *
237  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
238  *      allocated and basics are initialized.  New inode is returned
239  *      locked.
240  *
241  *      LOCKING:
242  *      Kernel thread context (may sleep).
243  *
244  *      RETURNS:
245  *      Pointer to allocated inode on success, NULL on failure.
246  */
247 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
248 {
249         struct inode *inode;
250 
251         inode = iget_locked(sb, kn->id.ino);
252         if (inode && (inode->i_state & I_NEW))
253                 kernfs_init_inode(kn, inode);
254 
255         return inode;
256 }
257 
258 /*
259  * The kernfs_node serves as both an inode and a directory entry for
260  * kernfs.  To prevent the kernfs inode numbers from being freed
261  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
262  * super_operations.evict_inode() implementation is needed to drop that
263  * reference upon inode destruction.
264  */
265 void kernfs_evict_inode(struct inode *inode)
266 {
267         struct kernfs_node *kn = inode->i_private;
268 
269         truncate_inode_pages_final(&inode->i_data);
270         clear_inode(inode);
271         kernfs_put(kn);
272 }
273 
274 int kernfs_iop_permission(struct inode *inode, int mask)
275 {
276         struct kernfs_node *kn;
277 
278         if (mask & MAY_NOT_BLOCK)
279                 return -ECHILD;
280 
281         kn = inode->i_private;
282 
283         mutex_lock(&kernfs_mutex);
284         kernfs_refresh_inode(kn, inode);
285         mutex_unlock(&kernfs_mutex);
286 
287         return generic_permission(inode, mask);
288 }
289 
290 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
291                      void *value, size_t size)
292 {
293         struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
294         if (!attrs)
295                 return -ENODATA;
296 
297         return simple_xattr_get(&attrs->xattrs, name, value, size);
298 }
299 
300 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
301                      const void *value, size_t size, int flags)
302 {
303         struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
304         if (!attrs)
305                 return -ENOMEM;
306 
307         return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
308 }
309 
310 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
311                                 struct dentry *unused, struct inode *inode,
312                                 const char *suffix, void *value, size_t size)
313 {
314         const char *name = xattr_full_name(handler, suffix);
315         struct kernfs_node *kn = inode->i_private;
316 
317         return kernfs_xattr_get(kn, name, value, size);
318 }
319 
320 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
321                                 struct dentry *unused, struct inode *inode,
322                                 const char *suffix, const void *value,
323                                 size_t size, int flags)
324 {
325         const char *name = xattr_full_name(handler, suffix);
326         struct kernfs_node *kn = inode->i_private;
327 
328         return kernfs_xattr_set(kn, name, value, size, flags);
329 }
330 
331 static const struct xattr_handler kernfs_trusted_xattr_handler = {
332         .prefix = XATTR_TRUSTED_PREFIX,
333         .get = kernfs_vfs_xattr_get,
334         .set = kernfs_vfs_xattr_set,
335 };
336 
337 static const struct xattr_handler kernfs_security_xattr_handler = {
338         .prefix = XATTR_SECURITY_PREFIX,
339         .get = kernfs_vfs_xattr_get,
340         .set = kernfs_vfs_xattr_set,
341 };
342 
343 const struct xattr_handler *kernfs_xattr_handlers[] = {
344         &kernfs_trusted_xattr_handler,
345         &kernfs_security_xattr_handler,
346         NULL
347 };
348 

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