1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* CacheFiles extended attribute management
3 *
4 * Copyright (C) 2021 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 #define CACHEFILES_COOKIE_TYPE_DATA 1
19
20 struct cachefiles_xattr {
21 __be64 object_size; /* Actual size of the object */
22 __be64 zero_point; /* Size after which server has no data not written by us */
23 __u8 type; /* Type of object */
24 __u8 content; /* Content presence (enum cachefiles_content) */
25 __u8 data[]; /* netfs coherency data */
26 } __packed;
27
28 static const char cachefiles_xattr_cache[] =
29 XATTR_USER_PREFIX "CacheFiles.cache";
30
31 struct cachefiles_vol_xattr {
32 __be32 reserved; /* Reserved, should be 0 */
33 __u8 data[]; /* netfs volume coherency data */
34 } __packed;
35
36 /*
37 * set the state xattr on a cache file
38 */
cachefiles_set_object_xattr(struct cachefiles_object * object)39 int cachefiles_set_object_xattr(struct cachefiles_object *object)
40 {
41 struct cachefiles_xattr *buf;
42 struct dentry *dentry;
43 struct file *file = object->file;
44 unsigned int len = object->cookie->aux_len;
45 int ret;
46
47 if (!file)
48 return -ESTALE;
49 dentry = file->f_path.dentry;
50
51 _enter("%x,#%d", object->debug_id, len);
52
53 buf = kmalloc(sizeof(struct cachefiles_xattr) + len, GFP_KERNEL);
54 if (!buf)
55 return -ENOMEM;
56
57 buf->object_size = cpu_to_be64(object->cookie->object_size);
58 buf->zero_point = 0;
59 buf->type = CACHEFILES_COOKIE_TYPE_DATA;
60 buf->content = object->content_info;
61 if (test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
62 buf->content = CACHEFILES_CONTENT_DIRTY;
63 if (len > 0)
64 memcpy(buf->data, fscache_get_aux(object->cookie), len);
65
66 ret = cachefiles_inject_write_error();
67 if (ret == 0)
68 ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
69 buf, sizeof(struct cachefiles_xattr) + len, 0);
70 if (ret < 0) {
71 trace_cachefiles_vfs_error(object, file_inode(file), ret,
72 cachefiles_trace_setxattr_error);
73 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
74 buf->content,
75 cachefiles_coherency_set_fail);
76 if (ret != -ENOMEM)
77 cachefiles_io_error_obj(
78 object,
79 "Failed to set xattr with error %d", ret);
80 } else {
81 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
82 buf->content,
83 cachefiles_coherency_set_ok);
84 }
85
86 kfree(buf);
87 _leave(" = %d", ret);
88 return ret;
89 }
90
91 /*
92 * check the consistency between the backing cache and the FS-Cache cookie
93 */
cachefiles_check_auxdata(struct cachefiles_object * object,struct file * file)94 int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file)
95 {
96 struct cachefiles_xattr *buf;
97 struct dentry *dentry = file->f_path.dentry;
98 unsigned int len = object->cookie->aux_len, tlen;
99 const void *p = fscache_get_aux(object->cookie);
100 enum cachefiles_coherency_trace why;
101 ssize_t xlen;
102 int ret = -ESTALE;
103
104 tlen = sizeof(struct cachefiles_xattr) + len;
105 buf = kmalloc(tlen, GFP_KERNEL);
106 if (!buf)
107 return -ENOMEM;
108
109 xlen = cachefiles_inject_read_error();
110 if (xlen == 0)
111 xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, tlen);
112 if (xlen != tlen) {
113 if (xlen < 0)
114 trace_cachefiles_vfs_error(object, file_inode(file), xlen,
115 cachefiles_trace_getxattr_error);
116 if (xlen == -EIO)
117 cachefiles_io_error_obj(
118 object,
119 "Failed to read aux with error %zd", xlen);
120 why = cachefiles_coherency_check_xattr;
121 } else if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
122 why = cachefiles_coherency_check_type;
123 } else if (memcmp(buf->data, p, len) != 0) {
124 why = cachefiles_coherency_check_aux;
125 } else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) {
126 why = cachefiles_coherency_check_objsize;
127 } else if (buf->content == CACHEFILES_CONTENT_DIRTY) {
128 // TODO: Begin conflict resolution
129 pr_warn("Dirty object in cache\n");
130 why = cachefiles_coherency_check_dirty;
131 } else {
132 why = cachefiles_coherency_check_ok;
133 ret = 0;
134 }
135
136 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
137 buf->content, why);
138 kfree(buf);
139 return ret;
140 }
141
142 /*
143 * remove the object's xattr to mark it stale
144 */
cachefiles_remove_object_xattr(struct cachefiles_cache * cache,struct cachefiles_object * object,struct dentry * dentry)145 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
146 struct cachefiles_object *object,
147 struct dentry *dentry)
148 {
149 int ret;
150
151 ret = cachefiles_inject_remove_error();
152 if (ret == 0)
153 ret = vfs_removexattr(&init_user_ns, dentry, cachefiles_xattr_cache);
154 if (ret < 0) {
155 trace_cachefiles_vfs_error(object, d_inode(dentry), ret,
156 cachefiles_trace_remxattr_error);
157 if (ret == -ENOENT || ret == -ENODATA)
158 ret = 0;
159 else if (ret != -ENOMEM)
160 cachefiles_io_error(cache,
161 "Can't remove xattr from %lu"
162 " (error %d)",
163 d_backing_inode(dentry)->i_ino, -ret);
164 }
165
166 _leave(" = %d", ret);
167 return ret;
168 }
169
170 /*
171 * Stick a marker on the cache object to indicate that it's dirty.
172 */
cachefiles_prepare_to_write(struct fscache_cookie * cookie)173 void cachefiles_prepare_to_write(struct fscache_cookie *cookie)
174 {
175 const struct cred *saved_cred;
176 struct cachefiles_object *object = cookie->cache_priv;
177 struct cachefiles_cache *cache = object->volume->cache;
178
179 _enter("c=%08x", object->cookie->debug_id);
180
181 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
182 cachefiles_begin_secure(cache, &saved_cred);
183 cachefiles_set_object_xattr(object);
184 cachefiles_end_secure(cache, saved_cred);
185 }
186 }
187
188 /*
189 * Set the state xattr on a volume directory.
190 */
cachefiles_set_volume_xattr(struct cachefiles_volume * volume)191 bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
192 {
193 struct cachefiles_vol_xattr *buf;
194 unsigned int len = volume->vcookie->coherency_len;
195 const void *p = volume->vcookie->coherency;
196 struct dentry *dentry = volume->dentry;
197 int ret;
198
199 _enter("%x,#%d", volume->vcookie->debug_id, len);
200
201 len += sizeof(*buf);
202 buf = kmalloc(len, GFP_KERNEL);
203 if (!buf)
204 return false;
205 buf->reserved = cpu_to_be32(0);
206 memcpy(buf->data, p, volume->vcookie->coherency_len);
207
208 ret = cachefiles_inject_write_error();
209 if (ret == 0)
210 ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
211 buf, len, 0);
212 if (ret < 0) {
213 trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,
214 cachefiles_trace_setxattr_error);
215 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
216 cachefiles_coherency_vol_set_fail);
217 if (ret != -ENOMEM)
218 cachefiles_io_error(
219 volume->cache, "Failed to set xattr with error %d", ret);
220 } else {
221 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
222 cachefiles_coherency_vol_set_ok);
223 }
224
225 kfree(buf);
226 _leave(" = %d", ret);
227 return ret == 0;
228 }
229
230 /*
231 * Check the consistency between the backing cache and the volume cookie.
232 */
cachefiles_check_volume_xattr(struct cachefiles_volume * volume)233 int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
234 {
235 struct cachefiles_vol_xattr *buf;
236 struct dentry *dentry = volume->dentry;
237 unsigned int len = volume->vcookie->coherency_len;
238 const void *p = volume->vcookie->coherency;
239 enum cachefiles_coherency_trace why;
240 ssize_t xlen;
241 int ret = -ESTALE;
242
243 _enter("");
244
245 len += sizeof(*buf);
246 buf = kmalloc(len, GFP_KERNEL);
247 if (!buf)
248 return -ENOMEM;
249
250 xlen = cachefiles_inject_read_error();
251 if (xlen == 0)
252 xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, len);
253 if (xlen != len) {
254 if (xlen < 0) {
255 trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,
256 cachefiles_trace_getxattr_error);
257 if (xlen == -EIO)
258 cachefiles_io_error(
259 volume->cache,
260 "Failed to read xattr with error %zd", xlen);
261 }
262 why = cachefiles_coherency_vol_check_xattr;
263 } else if (buf->reserved != cpu_to_be32(0)) {
264 why = cachefiles_coherency_vol_check_resv;
265 } else if (memcmp(buf->data, p, len - sizeof(*buf)) != 0) {
266 why = cachefiles_coherency_vol_check_cmp;
267 } else {
268 why = cachefiles_coherency_vol_check_ok;
269 ret = 0;
270 }
271
272 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino, why);
273 kfree(buf);
274 _leave(" = %d", ret);
275 return ret;
276 }
277