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1/*
2 * linux/fs/filesystems.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * table of configured filesystems
7 */
8
9#include <linux/syscalls.h>
10#include <linux/fs.h>
11#include <linux/proc_fs.h>
12#include <linux/seq_file.h>
13#include <linux/kmod.h>
14#include <linux/init.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17#include <linux/uaccess.h>
18
19/*
20 * Handling of filesystem drivers list.
21 * Rules:
22 * Inclusion to/removals from/scanning of list are protected by spinlock.
23 * During the unload module must call unregister_filesystem().
24 * We can access the fields of list element if:
25 * 1) spinlock is held or
26 * 2) we hold the reference to the module.
27 * The latter can be guaranteed by call of try_module_get(); if it
28 * returned 0 we must skip the element, otherwise we got the reference.
29 * Once the reference is obtained we can drop the spinlock.
30 */
31
32static struct file_system_type *file_systems;
33static DEFINE_RWLOCK(file_systems_lock);
34
35/* WARNING: This can be used only if we _already_ own a reference */
36void get_filesystem(struct file_system_type *fs)
37{
38 __module_get(fs->owner);
39}
40
41void put_filesystem(struct file_system_type *fs)
42{
43 module_put(fs->owner);
44}
45
46static struct file_system_type **find_filesystem(const char *name, unsigned len)
47{
48 struct file_system_type **p;
49 for (p = &file_systems; *p; p = &(*p)->next)
50 if (strncmp((*p)->name, name, len) == 0 &&
51 !(*p)->name[len])
52 break;
53 return p;
54}
55
56/**
57 * register_filesystem - register a new filesystem
58 * @fs: the file system structure
59 *
60 * Adds the file system passed to the list of file systems the kernel
61 * is aware of for mount and other syscalls. Returns 0 on success,
62 * or a negative errno code on an error.
63 *
64 * The &struct file_system_type that is passed is linked into the kernel
65 * structures and must not be freed until the file system has been
66 * unregistered.
67 */
68
69int register_filesystem(struct file_system_type * fs)
70{
71 int res = 0;
72 struct file_system_type ** p;
73
74 BUG_ON(strchr(fs->name, '.'));
75 if (fs->next)
76 return -EBUSY;
77 write_lock(&file_systems_lock);
78 p = find_filesystem(fs->name, strlen(fs->name));
79 if (*p)
80 res = -EBUSY;
81 else
82 *p = fs;
83 write_unlock(&file_systems_lock);
84 return res;
85}
86
87EXPORT_SYMBOL(register_filesystem);
88
89/**
90 * unregister_filesystem - unregister a file system
91 * @fs: filesystem to unregister
92 *
93 * Remove a file system that was previously successfully registered
94 * with the kernel. An error is returned if the file system is not found.
95 * Zero is returned on a success.
96 *
97 * Once this function has returned the &struct file_system_type structure
98 * may be freed or reused.
99 */
100
101int unregister_filesystem(struct file_system_type * fs)
102{
103 struct file_system_type ** tmp;
104
105 write_lock(&file_systems_lock);
106 tmp = &file_systems;
107 while (*tmp) {
108 if (fs == *tmp) {
109 *tmp = fs->next;
110 fs->next = NULL;
111 write_unlock(&file_systems_lock);
112 synchronize_rcu();
113 return 0;
114 }
115 tmp = &(*tmp)->next;
116 }
117 write_unlock(&file_systems_lock);
118
119 return -EINVAL;
120}
121
122EXPORT_SYMBOL(unregister_filesystem);
123
124#ifdef CONFIG_SYSFS_SYSCALL
125static int fs_index(const char __user * __name)
126{
127 struct file_system_type * tmp;
128 struct filename *name;
129 int err, index;
130
131 name = getname(__name);
132 err = PTR_ERR(name);
133 if (IS_ERR(name))
134 return err;
135
136 err = -EINVAL;
137 read_lock(&file_systems_lock);
138 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
139 if (strcmp(tmp->name, name->name) == 0) {
140 err = index;
141 break;
142 }
143 }
144 read_unlock(&file_systems_lock);
145 putname(name);
146 return err;
147}
148
149static int fs_name(unsigned int index, char __user * buf)
150{
151 struct file_system_type * tmp;
152 int len, res;
153
154 read_lock(&file_systems_lock);
155 for (tmp = file_systems; tmp; tmp = tmp->next, index--)
156 if (index <= 0 && try_module_get(tmp->owner))
157 break;
158 read_unlock(&file_systems_lock);
159 if (!tmp)
160 return -EINVAL;
161
162 /* OK, we got the reference, so we can safely block */
163 len = strlen(tmp->name) + 1;
164 res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
165 put_filesystem(tmp);
166 return res;
167}
168
169static int fs_maxindex(void)
170{
171 struct file_system_type * tmp;
172 int index;
173
174 read_lock(&file_systems_lock);
175 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
176 ;
177 read_unlock(&file_systems_lock);
178 return index;
179}
180
181/*
182 * Whee.. Weird sysv syscall.
183 */
184SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
185{
186 int retval = -EINVAL;
187
188 switch (option) {
189 case 1:
190 retval = fs_index((const char __user *) arg1);
191 break;
192
193 case 2:
194 retval = fs_name(arg1, (char __user *) arg2);
195 break;
196
197 case 3:
198 retval = fs_maxindex();
199 break;
200 }
201 return retval;
202}
203#endif
204
205int __init get_filesystem_list(char *buf)
206{
207 int len = 0;
208 struct file_system_type * tmp;
209
210 read_lock(&file_systems_lock);
211 tmp = file_systems;
212 while (tmp && len < PAGE_SIZE - 80) {
213 len += sprintf(buf+len, "%s\t%s\n",
214 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
215 tmp->name);
216 tmp = tmp->next;
217 }
218 read_unlock(&file_systems_lock);
219 return len;
220}
221
222#ifdef CONFIG_PROC_FS
223static int filesystems_proc_show(struct seq_file *m, void *v)
224{
225 struct file_system_type * tmp;
226
227 read_lock(&file_systems_lock);
228 tmp = file_systems;
229 while (tmp) {
230 seq_printf(m, "%s\t%s\n",
231 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
232 tmp->name);
233 tmp = tmp->next;
234 }
235 read_unlock(&file_systems_lock);
236 return 0;
237}
238
239static int filesystems_proc_open(struct inode *inode, struct file *file)
240{
241 return single_open(file, filesystems_proc_show, NULL);
242}
243
244static const struct file_operations filesystems_proc_fops = {
245 .open = filesystems_proc_open,
246 .read = seq_read,
247 .llseek = seq_lseek,
248 .release = single_release,
249};
250
251static int __init proc_filesystems_init(void)
252{
253 proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
254 return 0;
255}
256module_init(proc_filesystems_init);
257#endif
258
259static struct file_system_type *__get_fs_type(const char *name, int len)
260{
261 struct file_system_type *fs;
262
263 read_lock(&file_systems_lock);
264 fs = *(find_filesystem(name, len));
265 if (fs && !try_module_get(fs->owner))
266 fs = NULL;
267 read_unlock(&file_systems_lock);
268 return fs;
269}
270
271struct file_system_type *get_fs_type(const char *name)
272{
273 struct file_system_type *fs;
274 const char *dot = strchr(name, '.');
275 int len = dot ? dot - name : strlen(name);
276
277 fs = __get_fs_type(name, len);
278 if (!fs && (request_module("fs-%.*s", len, name) == 0))
279 fs = __get_fs_type(name, len);
280
281 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
282 put_filesystem(fs);
283 fs = NULL;
284 }
285 return fs;
286}
287
288EXPORT_SYMBOL(get_fs_type);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/filesystems.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * table of configured filesystems
8 */
9
10#include <linux/syscalls.h>
11#include <linux/fs.h>
12#include <linux/proc_fs.h>
13#include <linux/seq_file.h>
14#include <linux/kmod.h>
15#include <linux/init.h>
16#include <linux/module.h>
17#include <linux/slab.h>
18#include <linux/uaccess.h>
19
20/*
21 * Handling of filesystem drivers list.
22 * Rules:
23 * Inclusion to/removals from/scanning of list are protected by spinlock.
24 * During the unload module must call unregister_filesystem().
25 * We can access the fields of list element if:
26 * 1) spinlock is held or
27 * 2) we hold the reference to the module.
28 * The latter can be guaranteed by call of try_module_get(); if it
29 * returned 0 we must skip the element, otherwise we got the reference.
30 * Once the reference is obtained we can drop the spinlock.
31 */
32
33static struct file_system_type *file_systems;
34static DEFINE_RWLOCK(file_systems_lock);
35
36/* WARNING: This can be used only if we _already_ own a reference */
37struct file_system_type *get_filesystem(struct file_system_type *fs)
38{
39 __module_get(fs->owner);
40 return fs;
41}
42
43void put_filesystem(struct file_system_type *fs)
44{
45 module_put(fs->owner);
46}
47
48static struct file_system_type **find_filesystem(const char *name, unsigned len)
49{
50 struct file_system_type **p;
51 for (p = &file_systems; *p; p = &(*p)->next)
52 if (strncmp((*p)->name, name, len) == 0 &&
53 !(*p)->name[len])
54 break;
55 return p;
56}
57
58/**
59 * register_filesystem - register a new filesystem
60 * @fs: the file system structure
61 *
62 * Adds the file system passed to the list of file systems the kernel
63 * is aware of for mount and other syscalls. Returns 0 on success,
64 * or a negative errno code on an error.
65 *
66 * The &struct file_system_type that is passed is linked into the kernel
67 * structures and must not be freed until the file system has been
68 * unregistered.
69 */
70
71int register_filesystem(struct file_system_type * fs)
72{
73 int res = 0;
74 struct file_system_type ** p;
75
76 BUG_ON(strchr(fs->name, '.'));
77 if (fs->next)
78 return -EBUSY;
79 write_lock(&file_systems_lock);
80 p = find_filesystem(fs->name, strlen(fs->name));
81 if (*p)
82 res = -EBUSY;
83 else
84 *p = fs;
85 write_unlock(&file_systems_lock);
86 return res;
87}
88
89EXPORT_SYMBOL(register_filesystem);
90
91/**
92 * unregister_filesystem - unregister a file system
93 * @fs: filesystem to unregister
94 *
95 * Remove a file system that was previously successfully registered
96 * with the kernel. An error is returned if the file system is not found.
97 * Zero is returned on a success.
98 *
99 * Once this function has returned the &struct file_system_type structure
100 * may be freed or reused.
101 */
102
103int unregister_filesystem(struct file_system_type * fs)
104{
105 struct file_system_type ** tmp;
106
107 write_lock(&file_systems_lock);
108 tmp = &file_systems;
109 while (*tmp) {
110 if (fs == *tmp) {
111 *tmp = fs->next;
112 fs->next = NULL;
113 write_unlock(&file_systems_lock);
114 synchronize_rcu();
115 return 0;
116 }
117 tmp = &(*tmp)->next;
118 }
119 write_unlock(&file_systems_lock);
120
121 return -EINVAL;
122}
123
124EXPORT_SYMBOL(unregister_filesystem);
125
126#ifdef CONFIG_SYSFS_SYSCALL
127static int fs_index(const char __user * __name)
128{
129 struct file_system_type * tmp;
130 struct filename *name;
131 int err, index;
132
133 name = getname(__name);
134 err = PTR_ERR(name);
135 if (IS_ERR(name))
136 return err;
137
138 err = -EINVAL;
139 read_lock(&file_systems_lock);
140 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
141 if (strcmp(tmp->name, name->name) == 0) {
142 err = index;
143 break;
144 }
145 }
146 read_unlock(&file_systems_lock);
147 putname(name);
148 return err;
149}
150
151static int fs_name(unsigned int index, char __user * buf)
152{
153 struct file_system_type * tmp;
154 int len, res;
155
156 read_lock(&file_systems_lock);
157 for (tmp = file_systems; tmp; tmp = tmp->next, index--)
158 if (index <= 0 && try_module_get(tmp->owner))
159 break;
160 read_unlock(&file_systems_lock);
161 if (!tmp)
162 return -EINVAL;
163
164 /* OK, we got the reference, so we can safely block */
165 len = strlen(tmp->name) + 1;
166 res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
167 put_filesystem(tmp);
168 return res;
169}
170
171static int fs_maxindex(void)
172{
173 struct file_system_type * tmp;
174 int index;
175
176 read_lock(&file_systems_lock);
177 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
178 ;
179 read_unlock(&file_systems_lock);
180 return index;
181}
182
183/*
184 * Whee.. Weird sysv syscall.
185 */
186SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
187{
188 int retval = -EINVAL;
189
190 switch (option) {
191 case 1:
192 retval = fs_index((const char __user *) arg1);
193 break;
194
195 case 2:
196 retval = fs_name(arg1, (char __user *) arg2);
197 break;
198
199 case 3:
200 retval = fs_maxindex();
201 break;
202 }
203 return retval;
204}
205#endif
206
207int __init get_filesystem_list(char *buf)
208{
209 int len = 0;
210 struct file_system_type * tmp;
211
212 read_lock(&file_systems_lock);
213 tmp = file_systems;
214 while (tmp && len < PAGE_SIZE - 80) {
215 len += sprintf(buf+len, "%s\t%s\n",
216 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
217 tmp->name);
218 tmp = tmp->next;
219 }
220 read_unlock(&file_systems_lock);
221 return len;
222}
223
224#ifdef CONFIG_PROC_FS
225static int filesystems_proc_show(struct seq_file *m, void *v)
226{
227 struct file_system_type * tmp;
228
229 read_lock(&file_systems_lock);
230 tmp = file_systems;
231 while (tmp) {
232 seq_printf(m, "%s\t%s\n",
233 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
234 tmp->name);
235 tmp = tmp->next;
236 }
237 read_unlock(&file_systems_lock);
238 return 0;
239}
240
241static int filesystems_proc_open(struct inode *inode, struct file *file)
242{
243 return single_open(file, filesystems_proc_show, NULL);
244}
245
246static const struct file_operations filesystems_proc_fops = {
247 .open = filesystems_proc_open,
248 .read = seq_read,
249 .llseek = seq_lseek,
250 .release = single_release,
251};
252
253static int __init proc_filesystems_init(void)
254{
255 proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
256 return 0;
257}
258module_init(proc_filesystems_init);
259#endif
260
261static struct file_system_type *__get_fs_type(const char *name, int len)
262{
263 struct file_system_type *fs;
264
265 read_lock(&file_systems_lock);
266 fs = *(find_filesystem(name, len));
267 if (fs && !try_module_get(fs->owner))
268 fs = NULL;
269 read_unlock(&file_systems_lock);
270 return fs;
271}
272
273struct file_system_type *get_fs_type(const char *name)
274{
275 struct file_system_type *fs;
276 const char *dot = strchr(name, '.');
277 int len = dot ? dot - name : strlen(name);
278
279 fs = __get_fs_type(name, len);
280 if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
281 fs = __get_fs_type(name, len);
282 WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name);
283 }
284
285 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
286 put_filesystem(fs);
287 fs = NULL;
288 }
289 return fs;
290}
291
292EXPORT_SYMBOL(get_fs_type);