1 // SPDX-License-Identifier: GPL-2.0 1 // SPDX-License-Identifier: GPL-2.0
2 /* 2 /*
3 * linux/fs/filesystems.c 3 * linux/fs/filesystems.c
4 * 4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds 5 * Copyright (C) 1991, 1992 Linus Torvalds
6 * 6 *
7 * table of configured filesystems 7 * table of configured filesystems
8 */ 8 */
9 9
10 #include <linux/syscalls.h> 10 #include <linux/syscalls.h>
11 #include <linux/fs.h> 11 #include <linux/fs.h>
12 #include <linux/proc_fs.h> 12 #include <linux/proc_fs.h>
13 #include <linux/seq_file.h> 13 #include <linux/seq_file.h>
14 #include <linux/kmod.h> 14 #include <linux/kmod.h>
15 #include <linux/init.h> 15 #include <linux/init.h>
16 #include <linux/module.h> 16 #include <linux/module.h>
17 #include <linux/slab.h> 17 #include <linux/slab.h>
18 #include <linux/uaccess.h> 18 #include <linux/uaccess.h>
19 #include <linux/fs_parser.h> 19 #include <linux/fs_parser.h>
20 20
21 /* 21 /*
22 * Handling of filesystem drivers list. 22 * Handling of filesystem drivers list.
23 * Rules: 23 * Rules:
24 * Inclusion to/removals from/scanning of 24 * Inclusion to/removals from/scanning of list are protected by spinlock.
25 * During the unload module must call unr 25 * During the unload module must call unregister_filesystem().
26 * We can access the fields of list eleme 26 * We can access the fields of list element if:
27 * 1) spinlock is held or 27 * 1) spinlock is held or
28 * 2) we hold the reference to th 28 * 2) we hold the reference to the module.
29 * The latter can be guaranteed by call o 29 * The latter can be guaranteed by call of try_module_get(); if it
30 * returned 0 we must skip the element, o 30 * returned 0 we must skip the element, otherwise we got the reference.
31 * Once the reference is obtained we can 31 * Once the reference is obtained we can drop the spinlock.
32 */ 32 */
33 33
34 static struct file_system_type *file_systems; 34 static struct file_system_type *file_systems;
35 static DEFINE_RWLOCK(file_systems_lock); 35 static DEFINE_RWLOCK(file_systems_lock);
36 36
37 /* WARNING: This can be used only if we _alrea 37 /* WARNING: This can be used only if we _already_ own a reference */
38 struct file_system_type *get_filesystem(struct 38 struct file_system_type *get_filesystem(struct file_system_type *fs)
39 { 39 {
40 __module_get(fs->owner); 40 __module_get(fs->owner);
41 return fs; 41 return fs;
42 } 42 }
43 43
44 void put_filesystem(struct file_system_type *f 44 void put_filesystem(struct file_system_type *fs)
45 { 45 {
46 module_put(fs->owner); 46 module_put(fs->owner);
47 } 47 }
48 48
49 static struct file_system_type **find_filesyst 49 static struct file_system_type **find_filesystem(const char *name, unsigned len)
50 { 50 {
51 struct file_system_type **p; 51 struct file_system_type **p;
52 for (p = &file_systems; *p; p = &(*p)- 52 for (p = &file_systems; *p; p = &(*p)->next)
53 if (strncmp((*p)->name, name, 53 if (strncmp((*p)->name, name, len) == 0 &&
54 !(*p)->name[len]) 54 !(*p)->name[len])
55 break; 55 break;
56 return p; 56 return p;
57 } 57 }
58 58
59 /** 59 /**
60 * register_filesystem - register a new f 60 * register_filesystem - register a new filesystem
61 * @fs: the file system structure 61 * @fs: the file system structure
62 * 62 *
63 * Adds the file system passed to the lis 63 * Adds the file system passed to the list of file systems the kernel
64 * is aware of for mount and other syscal 64 * is aware of for mount and other syscalls. Returns 0 on success,
65 * or a negative errno code on an error. 65 * or a negative errno code on an error.
66 * 66 *
67 * The &struct file_system_type that is p 67 * The &struct file_system_type that is passed is linked into the kernel
68 * structures and must not be freed until 68 * structures and must not be freed until the file system has been
69 * unregistered. 69 * unregistered.
70 */ 70 */
71 71
72 int register_filesystem(struct file_system_typ 72 int register_filesystem(struct file_system_type * fs)
73 { 73 {
74 int res = 0; 74 int res = 0;
75 struct file_system_type ** p; 75 struct file_system_type ** p;
76 76
77 if (fs->parameters && 77 if (fs->parameters &&
78 !fs_validate_description(fs->name, 78 !fs_validate_description(fs->name, fs->parameters))
79 return -EINVAL; 79 return -EINVAL;
80 80
81 BUG_ON(strchr(fs->name, '.')); 81 BUG_ON(strchr(fs->name, '.'));
82 if (fs->next) 82 if (fs->next)
83 return -EBUSY; 83 return -EBUSY;
84 write_lock(&file_systems_lock); 84 write_lock(&file_systems_lock);
85 p = find_filesystem(fs->name, strlen(f 85 p = find_filesystem(fs->name, strlen(fs->name));
86 if (*p) 86 if (*p)
87 res = -EBUSY; 87 res = -EBUSY;
88 else 88 else
89 *p = fs; 89 *p = fs;
90 write_unlock(&file_systems_lock); 90 write_unlock(&file_systems_lock);
91 return res; 91 return res;
92 } 92 }
93 93
94 EXPORT_SYMBOL(register_filesystem); 94 EXPORT_SYMBOL(register_filesystem);
95 95
96 /** 96 /**
97 * unregister_filesystem - unregister a f 97 * unregister_filesystem - unregister a file system
98 * @fs: filesystem to unregister 98 * @fs: filesystem to unregister
99 * 99 *
100 * Remove a file system that was previous 100 * Remove a file system that was previously successfully registered
101 * with the kernel. An error is returned 101 * with the kernel. An error is returned if the file system is not found.
102 * Zero is returned on a success. 102 * Zero is returned on a success.
103 * 103 *
104 * Once this function has returned the &s 104 * Once this function has returned the &struct file_system_type structure
105 * may be freed or reused. 105 * may be freed or reused.
106 */ 106 */
107 107
108 int unregister_filesystem(struct file_system_t 108 int unregister_filesystem(struct file_system_type * fs)
109 { 109 {
110 struct file_system_type ** tmp; 110 struct file_system_type ** tmp;
111 111
112 write_lock(&file_systems_lock); 112 write_lock(&file_systems_lock);
113 tmp = &file_systems; 113 tmp = &file_systems;
114 while (*tmp) { 114 while (*tmp) {
115 if (fs == *tmp) { 115 if (fs == *tmp) {
116 *tmp = fs->next; 116 *tmp = fs->next;
117 fs->next = NULL; 117 fs->next = NULL;
118 write_unlock(&file_sys 118 write_unlock(&file_systems_lock);
119 synchronize_rcu(); 119 synchronize_rcu();
120 return 0; 120 return 0;
121 } 121 }
122 tmp = &(*tmp)->next; 122 tmp = &(*tmp)->next;
123 } 123 }
124 write_unlock(&file_systems_lock); 124 write_unlock(&file_systems_lock);
125 125
126 return -EINVAL; 126 return -EINVAL;
127 } 127 }
128 128
129 EXPORT_SYMBOL(unregister_filesystem); 129 EXPORT_SYMBOL(unregister_filesystem);
130 130
131 #ifdef CONFIG_SYSFS_SYSCALL 131 #ifdef CONFIG_SYSFS_SYSCALL
132 static int fs_index(const char __user * __name 132 static int fs_index(const char __user * __name)
133 { 133 {
134 struct file_system_type * tmp; 134 struct file_system_type * tmp;
135 struct filename *name; 135 struct filename *name;
136 int err, index; 136 int err, index;
137 137
138 name = getname(__name); 138 name = getname(__name);
139 err = PTR_ERR(name); 139 err = PTR_ERR(name);
140 if (IS_ERR(name)) 140 if (IS_ERR(name))
141 return err; 141 return err;
142 142
143 err = -EINVAL; 143 err = -EINVAL;
144 read_lock(&file_systems_lock); 144 read_lock(&file_systems_lock);
145 for (tmp=file_systems, index=0 ; tmp ; 145 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
146 if (strcmp(tmp->name, name->na 146 if (strcmp(tmp->name, name->name) == 0) {
147 err = index; 147 err = index;
148 break; 148 break;
149 } 149 }
150 } 150 }
151 read_unlock(&file_systems_lock); 151 read_unlock(&file_systems_lock);
152 putname(name); 152 putname(name);
153 return err; 153 return err;
154 } 154 }
155 155
156 static int fs_name(unsigned int index, char __ 156 static int fs_name(unsigned int index, char __user * buf)
157 { 157 {
158 struct file_system_type * tmp; 158 struct file_system_type * tmp;
159 int len, res; 159 int len, res;
160 160
161 read_lock(&file_systems_lock); 161 read_lock(&file_systems_lock);
162 for (tmp = file_systems; tmp; tmp = tm 162 for (tmp = file_systems; tmp; tmp = tmp->next, index--)
163 if (index <= 0 && try_module_g 163 if (index <= 0 && try_module_get(tmp->owner))
164 break; 164 break;
165 read_unlock(&file_systems_lock); 165 read_unlock(&file_systems_lock);
166 if (!tmp) 166 if (!tmp)
167 return -EINVAL; 167 return -EINVAL;
168 168
169 /* OK, we got the reference, so we can 169 /* OK, we got the reference, so we can safely block */
170 len = strlen(tmp->name) + 1; 170 len = strlen(tmp->name) + 1;
171 res = copy_to_user(buf, tmp->name, len 171 res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
172 put_filesystem(tmp); 172 put_filesystem(tmp);
173 return res; 173 return res;
174 } 174 }
175 175
176 static int fs_maxindex(void) 176 static int fs_maxindex(void)
177 { 177 {
178 struct file_system_type * tmp; 178 struct file_system_type * tmp;
179 int index; 179 int index;
180 180
181 read_lock(&file_systems_lock); 181 read_lock(&file_systems_lock);
182 for (tmp = file_systems, index = 0 ; t 182 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
183 ; 183 ;
184 read_unlock(&file_systems_lock); 184 read_unlock(&file_systems_lock);
185 return index; 185 return index;
186 } 186 }
187 187
188 /* 188 /*
189 * Whee.. Weird sysv syscall. 189 * Whee.. Weird sysv syscall.
190 */ 190 */
191 SYSCALL_DEFINE3(sysfs, int, option, unsigned l 191 SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
192 { 192 {
193 int retval = -EINVAL; 193 int retval = -EINVAL;
194 194
195 switch (option) { 195 switch (option) {
196 case 1: 196 case 1:
197 retval = fs_index((con 197 retval = fs_index((const char __user *) arg1);
198 break; 198 break;
199 199
200 case 2: 200 case 2:
201 retval = fs_name(arg1, 201 retval = fs_name(arg1, (char __user *) arg2);
202 break; 202 break;
203 203
204 case 3: 204 case 3:
205 retval = fs_maxindex() 205 retval = fs_maxindex();
206 break; 206 break;
207 } 207 }
208 return retval; 208 return retval;
209 } 209 }
210 #endif 210 #endif
211 211
212 int __init list_bdev_fs_names(char *buf, size_ 212 int __init list_bdev_fs_names(char *buf, size_t size)
213 { 213 {
214 struct file_system_type *p; 214 struct file_system_type *p;
215 size_t len; 215 size_t len;
216 int count = 0; 216 int count = 0;
217 217
218 read_lock(&file_systems_lock); 218 read_lock(&file_systems_lock);
219 for (p = file_systems; p; p = p->next) 219 for (p = file_systems; p; p = p->next) {
220 if (!(p->fs_flags & FS_REQUIRE 220 if (!(p->fs_flags & FS_REQUIRES_DEV))
221 continue; 221 continue;
222 len = strlen(p->name) + 1; 222 len = strlen(p->name) + 1;
223 if (len > size) { 223 if (len > size) {
224 pr_warn("%s: truncatin 224 pr_warn("%s: truncating file system list\n", __func__);
225 break; 225 break;
226 } 226 }
227 memcpy(buf, p->name, len); 227 memcpy(buf, p->name, len);
228 buf += len; 228 buf += len;
229 size -= len; 229 size -= len;
230 count++; 230 count++;
231 } 231 }
232 read_unlock(&file_systems_lock); 232 read_unlock(&file_systems_lock);
233 return count; 233 return count;
234 } 234 }
235 235
236 #ifdef CONFIG_PROC_FS 236 #ifdef CONFIG_PROC_FS
237 static int filesystems_proc_show(struct seq_fi 237 static int filesystems_proc_show(struct seq_file *m, void *v)
238 { 238 {
239 struct file_system_type * tmp; 239 struct file_system_type * tmp;
240 240
241 read_lock(&file_systems_lock); 241 read_lock(&file_systems_lock);
242 tmp = file_systems; 242 tmp = file_systems;
243 while (tmp) { 243 while (tmp) {
244 seq_printf(m, "%s\t%s\n", 244 seq_printf(m, "%s\t%s\n",
245 (tmp->fs_flags & FS_RE 245 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
246 tmp->name); 246 tmp->name);
247 tmp = tmp->next; 247 tmp = tmp->next;
248 } 248 }
249 read_unlock(&file_systems_lock); 249 read_unlock(&file_systems_lock);
250 return 0; 250 return 0;
251 } 251 }
252 252
253 static int __init proc_filesystems_init(void) 253 static int __init proc_filesystems_init(void)
254 { 254 {
255 proc_create_single("filesystems", 0, N 255 proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
256 return 0; 256 return 0;
257 } 257 }
258 module_init(proc_filesystems_init); 258 module_init(proc_filesystems_init);
259 #endif 259 #endif
260 260
261 static struct file_system_type *__get_fs_type( 261 static struct file_system_type *__get_fs_type(const char *name, int len)
262 { 262 {
263 struct file_system_type *fs; 263 struct file_system_type *fs;
264 264
265 read_lock(&file_systems_lock); 265 read_lock(&file_systems_lock);
266 fs = *(find_filesystem(name, len)); 266 fs = *(find_filesystem(name, len));
267 if (fs && !try_module_get(fs->owner)) 267 if (fs && !try_module_get(fs->owner))
268 fs = NULL; 268 fs = NULL;
269 read_unlock(&file_systems_lock); 269 read_unlock(&file_systems_lock);
270 return fs; 270 return fs;
271 } 271 }
272 272
273 struct file_system_type *get_fs_type(const cha 273 struct file_system_type *get_fs_type(const char *name)
274 { 274 {
275 struct file_system_type *fs; 275 struct file_system_type *fs;
276 const char *dot = strchr(name, '.'); 276 const char *dot = strchr(name, '.');
277 int len = dot ? dot - name : strlen(na 277 int len = dot ? dot - name : strlen(name);
278 278
279 fs = __get_fs_type(name, len); 279 fs = __get_fs_type(name, len);
280 if (!fs && (request_module("fs-%.*s", 280 if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
281 fs = __get_fs_type(name, len); 281 fs = __get_fs_type(name, len);
282 if (!fs) 282 if (!fs)
283 pr_warn_once("request_ 283 pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n",
284 len, name 284 len, name);
285 } 285 }
286 286
287 if (dot && fs && !(fs->fs_flags & FS_H 287 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
288 put_filesystem(fs); 288 put_filesystem(fs);
289 fs = NULL; 289 fs = NULL;
290 } 290 }
291 return fs; 291 return fs;
292 } 292 }
293 293
294 EXPORT_SYMBOL(get_fs_type); 294 EXPORT_SYMBOL(get_fs_type);
295 295
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