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328970de | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
7063fbf2 JB |
2 | /* -*- mode: c; c-basic-offset: 8; -*- |
3 | * vim: noexpandtab sw=8 ts=8 sts=0: | |
4 | * | |
5 | * symlink.c - operations for configfs symlinks. | |
6 | * | |
7063fbf2 JB |
7 | * Based on sysfs: |
8 | * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel | |
9 | * | |
10 | * configfs Copyright (C) 2005 Oracle. All rights reserved. | |
11 | */ | |
12 | ||
13 | #include <linux/fs.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/namei.h> | |
5a0e3ad6 | 16 | #include <linux/slab.h> |
7063fbf2 JB |
17 | |
18 | #include <linux/configfs.h> | |
19 | #include "configfs_internal.h" | |
20 | ||
9a73d78c LR |
21 | /* Protects attachments of new symlinks */ |
22 | DEFINE_MUTEX(configfs_symlink_mutex); | |
23 | ||
7063fbf2 JB |
24 | static int item_depth(struct config_item * item) |
25 | { | |
26 | struct config_item * p = item; | |
27 | int depth = 0; | |
28 | do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p)); | |
29 | return depth; | |
30 | } | |
31 | ||
32 | static int item_path_length(struct config_item * item) | |
33 | { | |
34 | struct config_item * p = item; | |
35 | int length = 1; | |
36 | do { | |
37 | length += strlen(config_item_name(p)) + 1; | |
38 | p = p->ci_parent; | |
39 | } while (p && !configfs_is_root(p)); | |
40 | return length; | |
41 | } | |
42 | ||
43 | static void fill_item_path(struct config_item * item, char * buffer, int length) | |
44 | { | |
45 | struct config_item * p; | |
46 | ||
47 | --length; | |
48 | for (p = item; p && !configfs_is_root(p); p = p->ci_parent) { | |
49 | int cur = strlen(config_item_name(p)); | |
50 | ||
51 | /* back up enough to print this bus id with '/' */ | |
52 | length -= cur; | |
1823342a | 53 | memcpy(buffer + length, config_item_name(p), cur); |
7063fbf2 JB |
54 | *(buffer + --length) = '/'; |
55 | } | |
56 | } | |
57 | ||
58 | static int create_link(struct config_item *parent_item, | |
e7515d06 | 59 | struct config_item *item, |
7063fbf2 JB |
60 | struct dentry *dentry) |
61 | { | |
62 | struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata; | |
63 | struct configfs_symlink *sl; | |
64 | int ret; | |
65 | ||
2a109f2a LR |
66 | ret = -ENOENT; |
67 | if (!configfs_dirent_is_ready(target_sd)) | |
68 | goto out; | |
7063fbf2 JB |
69 | ret = -ENOMEM; |
70 | sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); | |
71 | if (sl) { | |
5301a77d | 72 | spin_lock(&configfs_dirent_lock); |
4768e9b1 LR |
73 | if (target_sd->s_type & CONFIGFS_USET_DROPPING) { |
74 | spin_unlock(&configfs_dirent_lock); | |
4768e9b1 LR |
75 | kfree(sl); |
76 | return -ENOENT; | |
77 | } | |
ba80aa90 | 78 | sl->sl_target = config_item_get(item); |
7063fbf2 | 79 | list_add(&sl->sl_list, &target_sd->s_links); |
5301a77d | 80 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
81 | ret = configfs_create_link(sl, parent_item->ci_dentry, |
82 | dentry); | |
83 | if (ret) { | |
5301a77d | 84 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 85 | list_del_init(&sl->sl_list); |
5301a77d | 86 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
87 | config_item_put(item); |
88 | kfree(sl); | |
89 | } | |
90 | } | |
91 | ||
2a109f2a | 92 | out: |
7063fbf2 JB |
93 | return ret; |
94 | } | |
95 | ||
96 | ||
421748ec | 97 | static int get_target(const char *symname, struct path *path, |
b7c177fc | 98 | struct config_item **target, struct super_block *sb) |
7063fbf2 JB |
99 | { |
100 | int ret; | |
101 | ||
421748ec | 102 | ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path); |
7063fbf2 | 103 | if (!ret) { |
b7c177fc | 104 | if (path->dentry->d_sb == sb) { |
421748ec | 105 | *target = configfs_get_config_item(path->dentry); |
7063fbf2 JB |
106 | if (!*target) { |
107 | ret = -ENOENT; | |
421748ec | 108 | path_put(path); |
7063fbf2 | 109 | } |
9b6e3102 | 110 | } else { |
7063fbf2 | 111 | ret = -EPERM; |
9b6e3102 AV |
112 | path_put(path); |
113 | } | |
7063fbf2 JB |
114 | } |
115 | ||
116 | return ret; | |
117 | } | |
118 | ||
119 | ||
120 | int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) | |
121 | { | |
122 | int ret; | |
421748ec | 123 | struct path path; |
2a109f2a | 124 | struct configfs_dirent *sd; |
7063fbf2 | 125 | struct config_item *parent_item; |
3c48f23a | 126 | struct config_item *target_item = NULL; |
aa293583 | 127 | const struct config_item_type *type; |
7063fbf2 | 128 | |
2a109f2a LR |
129 | sd = dentry->d_parent->d_fsdata; |
130 | /* | |
131 | * Fake invisibility if dir belongs to a group/default groups hierarchy | |
132 | * being attached | |
133 | */ | |
134 | ret = -ENOENT; | |
135 | if (!configfs_dirent_is_ready(sd)) | |
136 | goto out; | |
137 | ||
7063fbf2 JB |
138 | parent_item = configfs_get_config_item(dentry->d_parent); |
139 | type = parent_item->ci_type; | |
140 | ||
2a109f2a | 141 | ret = -EPERM; |
7063fbf2 JB |
142 | if (!type || !type->ct_item_ops || |
143 | !type->ct_item_ops->allow_link) | |
144 | goto out_put; | |
145 | ||
b7c177fc | 146 | ret = get_target(symname, &path, &target_item, dentry->d_sb); |
7063fbf2 JB |
147 | if (ret) |
148 | goto out_put; | |
149 | ||
150 | ret = type->ct_item_ops->allow_link(parent_item, target_item); | |
e7520651 | 151 | if (!ret) { |
9a73d78c | 152 | mutex_lock(&configfs_symlink_mutex); |
7063fbf2 | 153 | ret = create_link(parent_item, target_item, dentry); |
9a73d78c | 154 | mutex_unlock(&configfs_symlink_mutex); |
e7520651 LR |
155 | if (ret && type->ct_item_ops->drop_link) |
156 | type->ct_item_ops->drop_link(parent_item, | |
157 | target_item); | |
158 | } | |
7063fbf2 JB |
159 | |
160 | config_item_put(target_item); | |
421748ec | 161 | path_put(&path); |
7063fbf2 JB |
162 | |
163 | out_put: | |
164 | config_item_put(parent_item); | |
165 | ||
166 | out: | |
167 | return ret; | |
168 | } | |
169 | ||
170 | int configfs_unlink(struct inode *dir, struct dentry *dentry) | |
171 | { | |
172 | struct configfs_dirent *sd = dentry->d_fsdata; | |
173 | struct configfs_symlink *sl; | |
174 | struct config_item *parent_item; | |
aa293583 | 175 | const struct config_item_type *type; |
7063fbf2 JB |
176 | int ret; |
177 | ||
178 | ret = -EPERM; /* What lack-of-symlink returns */ | |
179 | if (!(sd->s_type & CONFIGFS_ITEM_LINK)) | |
180 | goto out; | |
181 | ||
7063fbf2 JB |
182 | sl = sd->s_element; |
183 | ||
184 | parent_item = configfs_get_config_item(dentry->d_parent); | |
185 | type = parent_item->ci_type; | |
186 | ||
6f610764 | 187 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 188 | list_del_init(&sd->s_sibling); |
6f610764 | 189 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
190 | configfs_drop_dentry(sd, dentry->d_parent); |
191 | dput(dentry); | |
192 | configfs_put(sd); | |
193 | ||
194 | /* | |
195 | * drop_link() must be called before | |
196 | * list_del_init(&sl->sl_list), so that the order of | |
197 | * drop_link(this, target) and drop_item(target) is preserved. | |
198 | */ | |
199 | if (type && type->ct_item_ops && | |
200 | type->ct_item_ops->drop_link) | |
201 | type->ct_item_ops->drop_link(parent_item, | |
202 | sl->sl_target); | |
203 | ||
5301a77d | 204 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 205 | list_del_init(&sl->sl_list); |
5301a77d | 206 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
207 | |
208 | /* Put reference from create_link() */ | |
209 | config_item_put(sl->sl_target); | |
210 | kfree(sl); | |
211 | ||
212 | config_item_put(parent_item); | |
213 | ||
214 | ret = 0; | |
215 | ||
216 | out: | |
217 | return ret; | |
218 | } | |
219 | ||
220 | static int configfs_get_target_path(struct config_item * item, struct config_item * target, | |
221 | char *path) | |
222 | { | |
223 | char * s; | |
224 | int depth, size; | |
225 | ||
226 | depth = item_depth(item); | |
227 | size = item_path_length(target) + depth * 3 - 1; | |
228 | if (size > PATH_MAX) | |
229 | return -ENAMETOOLONG; | |
230 | ||
8e24eea7 | 231 | pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size); |
7063fbf2 JB |
232 | |
233 | for (s = path; depth--; s += 3) | |
234 | strcpy(s,"../"); | |
235 | ||
236 | fill_item_path(target, path, size); | |
8e24eea7 | 237 | pr_debug("%s: path = '%s'\n", __func__, path); |
7063fbf2 JB |
238 | |
239 | return 0; | |
240 | } | |
241 | ||
242 | static int configfs_getlink(struct dentry *dentry, char * path) | |
243 | { | |
244 | struct config_item *item, *target_item; | |
245 | int error = 0; | |
246 | ||
247 | item = configfs_get_config_item(dentry->d_parent); | |
248 | if (!item) | |
249 | return -EINVAL; | |
250 | ||
251 | target_item = configfs_get_config_item(dentry); | |
252 | if (!target_item) { | |
253 | config_item_put(item); | |
254 | return -EINVAL; | |
255 | } | |
256 | ||
257 | down_read(&configfs_rename_sem); | |
258 | error = configfs_get_target_path(item, target_item, path); | |
259 | up_read(&configfs_rename_sem); | |
260 | ||
261 | config_item_put(item); | |
262 | config_item_put(target_item); | |
263 | return error; | |
264 | ||
265 | } | |
266 | ||
6b255391 | 267 | static const char *configfs_get_link(struct dentry *dentry, |
fceef393 AV |
268 | struct inode *inode, |
269 | struct delayed_call *done) | |
7063fbf2 | 270 | { |
fceef393 | 271 | char *body; |
680baacb | 272 | int error; |
7063fbf2 | 273 | |
6b255391 AV |
274 | if (!dentry) |
275 | return ERR_PTR(-ECHILD); | |
276 | ||
fceef393 AV |
277 | body = kzalloc(PAGE_SIZE, GFP_KERNEL); |
278 | if (!body) | |
680baacb AV |
279 | return ERR_PTR(-ENOMEM); |
280 | ||
fceef393 | 281 | error = configfs_getlink(dentry, body); |
680baacb | 282 | if (!error) { |
fceef393 AV |
283 | set_delayed_call(done, kfree_link, body); |
284 | return body; | |
7063fbf2 JB |
285 | } |
286 | ||
fceef393 | 287 | kfree(body); |
680baacb | 288 | return ERR_PTR(error); |
7063fbf2 JB |
289 | } |
290 | ||
754661f1 | 291 | const struct inode_operations configfs_symlink_inode_operations = { |
6b255391 | 292 | .get_link = configfs_get_link, |
3d0f89bb | 293 | .setattr = configfs_setattr, |
7063fbf2 JB |
294 | }; |
295 |