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Linux/fs/cachefiles/xattr.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* CacheFiles extended attribute management
  3  *
  4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
  5  * Written by David Howells (dhowells@redhat.com)
  6  */
  7 
  8 #include <linux/module.h>
  9 #include <linux/sched.h>
 10 #include <linux/file.h>
 11 #include <linux/fs.h>
 12 #include <linux/fsnotify.h>
 13 #include <linux/quotaops.h>
 14 #include <linux/xattr.h>
 15 #include <linux/slab.h>
 16 #include "internal.h"
 17 
 18 static const char cachefiles_xattr_cache[] =
 19         XATTR_USER_PREFIX "CacheFiles.cache";
 20 
 21 /*
 22  * check the type label on an object
 23  * - done using xattrs
 24  */
 25 int cachefiles_check_object_type(struct cachefiles_object *object)
 26 {
 27         struct dentry *dentry = object->dentry;
 28         char type[3], xtype[3];
 29         int ret;
 30 
 31         ASSERT(dentry);
 32         ASSERT(d_backing_inode(dentry));
 33 
 34         if (!object->fscache.cookie)
 35                 strcpy(type, "C3");
 36         else
 37                 snprintf(type, 3, "%02x", object->fscache.cookie->def->type);
 38 
 39         _enter("%p{%s}", object, type);
 40 
 41         /* attempt to install a type label directly */
 42         ret = vfs_setxattr(dentry, cachefiles_xattr_cache, type, 2,
 43                            XATTR_CREATE);
 44         if (ret == 0) {
 45                 _debug("SET"); /* we succeeded */
 46                 goto error;
 47         }
 48 
 49         if (ret != -EEXIST) {
 50                 pr_err("Can't set xattr on %pd [%lu] (err %d)\n",
 51                        dentry, d_backing_inode(dentry)->i_ino,
 52                        -ret);
 53                 goto error;
 54         }
 55 
 56         /* read the current type label */
 57         ret = vfs_getxattr(dentry, cachefiles_xattr_cache, xtype, 3);
 58         if (ret < 0) {
 59                 if (ret == -ERANGE)
 60                         goto bad_type_length;
 61 
 62                 pr_err("Can't read xattr on %pd [%lu] (err %d)\n",
 63                        dentry, d_backing_inode(dentry)->i_ino,
 64                        -ret);
 65                 goto error;
 66         }
 67 
 68         /* check the type is what we're expecting */
 69         if (ret != 2)
 70                 goto bad_type_length;
 71 
 72         if (xtype[0] != type[0] || xtype[1] != type[1])
 73                 goto bad_type;
 74 
 75         ret = 0;
 76 
 77 error:
 78         _leave(" = %d", ret);
 79         return ret;
 80 
 81 bad_type_length:
 82         pr_err("Cache object %lu type xattr length incorrect\n",
 83                d_backing_inode(dentry)->i_ino);
 84         ret = -EIO;
 85         goto error;
 86 
 87 bad_type:
 88         xtype[2] = 0;
 89         pr_err("Cache object %pd [%lu] type %s not %s\n",
 90                dentry, d_backing_inode(dentry)->i_ino,
 91                xtype, type);
 92         ret = -EIO;
 93         goto error;
 94 }
 95 
 96 /*
 97  * set the state xattr on a cache file
 98  */
 99 int cachefiles_set_object_xattr(struct cachefiles_object *object,
100                                 struct cachefiles_xattr *auxdata)
101 {
102         struct dentry *dentry = object->dentry;
103         int ret;
104 
105         ASSERT(dentry);
106 
107         _enter("%p,#%d", object, auxdata->len);
108 
109         /* attempt to install the cache metadata directly */
110         _debug("SET #%u", auxdata->len);
111 
112         clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
113         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
114                            &auxdata->type, auxdata->len,
115                            XATTR_CREATE);
116         if (ret < 0 && ret != -ENOMEM)
117                 cachefiles_io_error_obj(
118                         object,
119                         "Failed to set xattr with error %d", ret);
120 
121         _leave(" = %d", ret);
122         return ret;
123 }
124 
125 /*
126  * update the state xattr on a cache file
127  */
128 int cachefiles_update_object_xattr(struct cachefiles_object *object,
129                                    struct cachefiles_xattr *auxdata)
130 {
131         struct dentry *dentry = object->dentry;
132         int ret;
133 
134         if (!dentry)
135                 return -ESTALE;
136 
137         _enter("%p,#%d", object, auxdata->len);
138 
139         /* attempt to install the cache metadata directly */
140         _debug("SET #%u", auxdata->len);
141 
142         clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
143         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
144                            &auxdata->type, auxdata->len,
145                            XATTR_REPLACE);
146         if (ret < 0 && ret != -ENOMEM)
147                 cachefiles_io_error_obj(
148                         object,
149                         "Failed to update xattr with error %d", ret);
150 
151         _leave(" = %d", ret);
152         return ret;
153 }
154 
155 /*
156  * check the consistency between the backing cache and the FS-Cache cookie
157  */
158 int cachefiles_check_auxdata(struct cachefiles_object *object)
159 {
160         struct cachefiles_xattr *auxbuf;
161         enum fscache_checkaux validity;
162         struct dentry *dentry = object->dentry;
163         ssize_t xlen;
164         int ret;
165 
166         ASSERT(dentry);
167         ASSERT(d_backing_inode(dentry));
168         ASSERT(object->fscache.cookie->def->check_aux);
169 
170         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
171         if (!auxbuf)
172                 return -ENOMEM;
173 
174         xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
175                             &auxbuf->type, 512 + 1);
176         ret = -ESTALE;
177         if (xlen < 1 ||
178             auxbuf->type != object->fscache.cookie->def->type)
179                 goto error;
180 
181         xlen--;
182         validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen,
183                                      i_size_read(d_backing_inode(dentry)));
184         if (validity != FSCACHE_CHECKAUX_OKAY)
185                 goto error;
186 
187         ret = 0;
188 error:
189         kfree(auxbuf);
190         return ret;
191 }
192 
193 /*
194  * check the state xattr on a cache file
195  * - return -ESTALE if the object should be deleted
196  */
197 int cachefiles_check_object_xattr(struct cachefiles_object *object,
198                                   struct cachefiles_xattr *auxdata)
199 {
200         struct cachefiles_xattr *auxbuf;
201         struct dentry *dentry = object->dentry;
202         int ret;
203 
204         _enter("%p,#%d", object, auxdata->len);
205 
206         ASSERT(dentry);
207         ASSERT(d_backing_inode(dentry));
208 
209         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
210         if (!auxbuf) {
211                 _leave(" = -ENOMEM");
212                 return -ENOMEM;
213         }
214 
215         /* read the current type label */
216         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
217                            &auxbuf->type, 512 + 1);
218         if (ret < 0) {
219                 if (ret == -ENODATA)
220                         goto stale; /* no attribute - power went off
221                                      * mid-cull? */
222 
223                 if (ret == -ERANGE)
224                         goto bad_type_length;
225 
226                 cachefiles_io_error_obj(object,
227                                         "Can't read xattr on %lu (err %d)",
228                                         d_backing_inode(dentry)->i_ino, -ret);
229                 goto error;
230         }
231 
232         /* check the on-disk object */
233         if (ret < 1)
234                 goto bad_type_length;
235 
236         if (auxbuf->type != auxdata->type)
237                 goto stale;
238 
239         auxbuf->len = ret;
240 
241         /* consult the netfs */
242         if (object->fscache.cookie->def->check_aux) {
243                 enum fscache_checkaux result;
244                 unsigned int dlen;
245 
246                 dlen = auxbuf->len - 1;
247 
248                 _debug("checkaux %s #%u",
249                        object->fscache.cookie->def->name, dlen);
250 
251                 result = fscache_check_aux(&object->fscache,
252                                            &auxbuf->data, dlen,
253                                            i_size_read(d_backing_inode(dentry)));
254 
255                 switch (result) {
256                         /* entry okay as is */
257                 case FSCACHE_CHECKAUX_OKAY:
258                         goto okay;
259 
260                         /* entry requires update */
261                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
262                         break;
263 
264                         /* entry requires deletion */
265                 case FSCACHE_CHECKAUX_OBSOLETE:
266                         goto stale;
267 
268                 default:
269                         BUG();
270                 }
271 
272                 /* update the current label */
273                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
274                                    &auxdata->type, auxdata->len,
275                                    XATTR_REPLACE);
276                 if (ret < 0) {
277                         cachefiles_io_error_obj(object,
278                                                 "Can't update xattr on %lu"
279                                                 " (error %d)",
280                                                 d_backing_inode(dentry)->i_ino, -ret);
281                         goto error;
282                 }
283         }
284 
285 okay:
286         ret = 0;
287 
288 error:
289         kfree(auxbuf);
290         _leave(" = %d", ret);
291         return ret;
292 
293 bad_type_length:
294         pr_err("Cache object %lu xattr length incorrect\n",
295                d_backing_inode(dentry)->i_ino);
296         ret = -EIO;
297         goto error;
298 
299 stale:
300         ret = -ESTALE;
301         goto error;
302 }
303 
304 /*
305  * remove the object's xattr to mark it stale
306  */
307 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
308                                    struct dentry *dentry)
309 {
310         int ret;
311 
312         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
313         if (ret < 0) {
314                 if (ret == -ENOENT || ret == -ENODATA)
315                         ret = 0;
316                 else if (ret != -ENOMEM)
317                         cachefiles_io_error(cache,
318                                             "Can't remove xattr from %lu"
319                                             " (error %d)",
320                                             d_backing_inode(dentry)->i_ino, -ret);
321         }
322 
323         _leave(" = %d", ret);
324         return ret;
325 }
326 

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