Greg Kroah-Hartman | b244131 | 2017-11-01 15:07:57 +0100 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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> |
Alexey Dobriyan | 6827400 | 2008-10-04 14:08:37 +0400 | [diff] [blame] | 12 | #include <linux/proc_fs.h> |
| 13 | #include <linux/seq_file.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 14 | #include <linux/kmod.h> |
| 15 | #include <linux/init.h> |
| 16 | #include <linux/module.h> |
Tejun Heo | 5a0e3ad | 2010-03-24 17:04:11 +0900 | [diff] [blame] | 17 | #include <linux/slab.h> |
Linus Torvalds | 7c0f6ba | 2016-12-24 11:46:01 -0800 | [diff] [blame] | 18 | #include <linux/uaccess.h> |
David Howells | 3e1aeb0 | 2018-11-01 23:07:25 +0000 | [diff] [blame] | 19 | #include <linux/fs_parser.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 20 | |
| 21 | /* |
| 22 | * Handling of filesystem drivers list. |
| 23 | * Rules: |
| 24 | * Inclusion to/removals from/scanning of list are protected by spinlock. |
| 25 | * During the unload module must call unregister_filesystem(). |
| 26 | * We can access the fields of list element if: |
| 27 | * 1) spinlock is held or |
| 28 | * 2) we hold the reference to the module. |
| 29 | * The latter can be guaranteed by call of try_module_get(); if it |
| 30 | * returned 0 we must skip the element, otherwise we got the reference. |
| 31 | * Once the reference is obtained we can drop the spinlock. |
| 32 | */ |
| 33 | |
| 34 | static struct file_system_type *file_systems; |
| 35 | static DEFINE_RWLOCK(file_systems_lock); |
| 36 | |
| 37 | /* WARNING: This can be used only if we _already_ own a reference */ |
David Howells | ee416bc | 2017-07-04 17:25:16 +0100 | [diff] [blame] | 38 | struct file_system_type *get_filesystem(struct file_system_type *fs) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 39 | { |
| 40 | __module_get(fs->owner); |
David Howells | ee416bc | 2017-07-04 17:25:16 +0100 | [diff] [blame] | 41 | return fs; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 42 | } |
| 43 | |
| 44 | void put_filesystem(struct file_system_type *fs) |
| 45 | { |
| 46 | module_put(fs->owner); |
| 47 | } |
| 48 | |
Miklos Szeredi | 79c0b2d | 2007-05-08 00:25:43 -0700 | [diff] [blame] | 49 | static struct file_system_type **find_filesystem(const char *name, unsigned len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 50 | { |
| 51 | struct file_system_type **p; |
Al Viro | 558041d | 2016-01-19 11:40:44 -0500 | [diff] [blame] | 52 | for (p = &file_systems; *p; p = &(*p)->next) |
| 53 | if (strncmp((*p)->name, name, len) == 0 && |
| 54 | !(*p)->name[len]) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | break; |
| 56 | return p; |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * register_filesystem - register a new filesystem |
| 61 | * @fs: the file system structure |
| 62 | * |
| 63 | * Adds the file system passed to the list of file systems the kernel |
| 64 | * is aware of for mount and other syscalls. Returns 0 on success, |
| 65 | * or a negative errno code on an error. |
| 66 | * |
| 67 | * The &struct file_system_type that is passed is linked into the kernel |
| 68 | * structures and must not be freed until the file system has been |
| 69 | * unregistered. |
| 70 | */ |
| 71 | |
| 72 | int register_filesystem(struct file_system_type * fs) |
| 73 | { |
| 74 | int res = 0; |
| 75 | struct file_system_type ** p; |
| 76 | |
Eric Sandeen | 96cafb9 | 2019-12-06 10:45:01 -0600 | [diff] [blame] | 77 | if (fs->parameters && |
| 78 | !fs_validate_description(fs->name, fs->parameters)) |
David Howells | 3e1aeb0 | 2018-11-01 23:07:25 +0000 | [diff] [blame] | 79 | return -EINVAL; |
| 80 | |
Miklos Szeredi | 79c0b2d | 2007-05-08 00:25:43 -0700 | [diff] [blame] | 81 | BUG_ON(strchr(fs->name, '.')); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 82 | if (fs->next) |
| 83 | return -EBUSY; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 84 | write_lock(&file_systems_lock); |
Miklos Szeredi | 79c0b2d | 2007-05-08 00:25:43 -0700 | [diff] [blame] | 85 | p = find_filesystem(fs->name, strlen(fs->name)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 86 | if (*p) |
| 87 | res = -EBUSY; |
| 88 | else |
| 89 | *p = fs; |
| 90 | write_unlock(&file_systems_lock); |
| 91 | return res; |
| 92 | } |
| 93 | |
| 94 | EXPORT_SYMBOL(register_filesystem); |
| 95 | |
| 96 | /** |
| 97 | * unregister_filesystem - unregister a file system |
| 98 | * @fs: filesystem to unregister |
| 99 | * |
| 100 | * Remove a file system that was previously successfully registered |
| 101 | * with the kernel. An error is returned if the file system is not found. |
| 102 | * Zero is returned on a success. |
| 103 | * |
| 104 | * Once this function has returned the &struct file_system_type structure |
| 105 | * may be freed or reused. |
| 106 | */ |
| 107 | |
| 108 | int unregister_filesystem(struct file_system_type * fs) |
| 109 | { |
| 110 | struct file_system_type ** tmp; |
| 111 | |
| 112 | write_lock(&file_systems_lock); |
| 113 | tmp = &file_systems; |
| 114 | while (*tmp) { |
| 115 | if (fs == *tmp) { |
| 116 | *tmp = fs->next; |
| 117 | fs->next = NULL; |
| 118 | write_unlock(&file_systems_lock); |
Milton Miller | fff3e5a | 2011-04-14 10:30:08 -0500 | [diff] [blame] | 119 | synchronize_rcu(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 120 | return 0; |
| 121 | } |
| 122 | tmp = &(*tmp)->next; |
| 123 | } |
| 124 | write_unlock(&file_systems_lock); |
Nick Piggin | 31e6b01 | 2011-01-07 17:49:52 +1100 | [diff] [blame] | 125 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 126 | return -EINVAL; |
| 127 | } |
| 128 | |
| 129 | EXPORT_SYMBOL(unregister_filesystem); |
| 130 | |
Fabian Frederick | 6af9f7b | 2014-04-03 14:48:25 -0700 | [diff] [blame] | 131 | #ifdef CONFIG_SYSFS_SYSCALL |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 132 | static int fs_index(const char __user * __name) |
| 133 | { |
| 134 | struct file_system_type * tmp; |
Jeff Layton | 91a27b2 | 2012-10-10 15:25:28 -0400 | [diff] [blame] | 135 | struct filename *name; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 136 | int err, index; |
| 137 | |
| 138 | name = getname(__name); |
| 139 | err = PTR_ERR(name); |
| 140 | if (IS_ERR(name)) |
| 141 | return err; |
| 142 | |
| 143 | err = -EINVAL; |
| 144 | read_lock(&file_systems_lock); |
| 145 | for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) { |
Jeff Layton | 91a27b2 | 2012-10-10 15:25:28 -0400 | [diff] [blame] | 146 | if (strcmp(tmp->name, name->name) == 0) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 147 | err = index; |
| 148 | break; |
| 149 | } |
| 150 | } |
| 151 | read_unlock(&file_systems_lock); |
| 152 | putname(name); |
| 153 | return err; |
| 154 | } |
| 155 | |
| 156 | static int fs_name(unsigned int index, char __user * buf) |
| 157 | { |
| 158 | struct file_system_type * tmp; |
| 159 | int len, res; |
| 160 | |
| 161 | read_lock(&file_systems_lock); |
| 162 | for (tmp = file_systems; tmp; tmp = tmp->next, index--) |
| 163 | if (index <= 0 && try_module_get(tmp->owner)) |
| 164 | break; |
| 165 | read_unlock(&file_systems_lock); |
| 166 | if (!tmp) |
| 167 | return -EINVAL; |
| 168 | |
| 169 | /* OK, we got the reference, so we can safely block */ |
| 170 | len = strlen(tmp->name) + 1; |
| 171 | res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0; |
| 172 | put_filesystem(tmp); |
| 173 | return res; |
| 174 | } |
| 175 | |
| 176 | static int fs_maxindex(void) |
| 177 | { |
| 178 | struct file_system_type * tmp; |
| 179 | int index; |
| 180 | |
| 181 | read_lock(&file_systems_lock); |
| 182 | for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++) |
| 183 | ; |
| 184 | read_unlock(&file_systems_lock); |
| 185 | return index; |
| 186 | } |
| 187 | |
| 188 | /* |
| 189 | * Whee.. Weird sysv syscall. |
| 190 | */ |
Heiko Carstens | 1e7bfb2 | 2009-01-14 14:14:29 +0100 | [diff] [blame] | 191 | SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 192 | { |
| 193 | int retval = -EINVAL; |
| 194 | |
| 195 | switch (option) { |
| 196 | case 1: |
| 197 | retval = fs_index((const char __user *) arg1); |
| 198 | break; |
| 199 | |
| 200 | case 2: |
| 201 | retval = fs_name(arg1, (char __user *) arg2); |
| 202 | break; |
| 203 | |
| 204 | case 3: |
| 205 | retval = fs_maxindex(); |
| 206 | break; |
| 207 | } |
| 208 | return retval; |
| 209 | } |
Fabian Frederick | 6af9f7b | 2014-04-03 14:48:25 -0700 | [diff] [blame] | 210 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 211 | |
Tetsuo Handa | 38e23c9 | 2009-04-09 20:17:52 +0900 | [diff] [blame] | 212 | int __init get_filesystem_list(char *buf) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 213 | { |
| 214 | int len = 0; |
| 215 | struct file_system_type * tmp; |
| 216 | |
| 217 | read_lock(&file_systems_lock); |
| 218 | tmp = file_systems; |
| 219 | while (tmp && len < PAGE_SIZE - 80) { |
| 220 | len += sprintf(buf+len, "%s\t%s\n", |
| 221 | (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev", |
| 222 | tmp->name); |
| 223 | tmp = tmp->next; |
| 224 | } |
| 225 | read_unlock(&file_systems_lock); |
| 226 | return len; |
| 227 | } |
| 228 | |
Alexey Dobriyan | 6827400 | 2008-10-04 14:08:37 +0400 | [diff] [blame] | 229 | #ifdef CONFIG_PROC_FS |
| 230 | static int filesystems_proc_show(struct seq_file *m, void *v) |
| 231 | { |
| 232 | struct file_system_type * tmp; |
| 233 | |
| 234 | read_lock(&file_systems_lock); |
| 235 | tmp = file_systems; |
| 236 | while (tmp) { |
| 237 | seq_printf(m, "%s\t%s\n", |
| 238 | (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev", |
| 239 | tmp->name); |
| 240 | tmp = tmp->next; |
| 241 | } |
| 242 | read_unlock(&file_systems_lock); |
| 243 | return 0; |
| 244 | } |
| 245 | |
Alexey Dobriyan | 6827400 | 2008-10-04 14:08:37 +0400 | [diff] [blame] | 246 | static int __init proc_filesystems_init(void) |
| 247 | { |
Christoph Hellwig | 3f3942a | 2018-05-15 15:57:23 +0200 | [diff] [blame] | 248 | proc_create_single("filesystems", 0, NULL, filesystems_proc_show); |
Alexey Dobriyan | 6827400 | 2008-10-04 14:08:37 +0400 | [diff] [blame] | 249 | return 0; |
| 250 | } |
| 251 | module_init(proc_filesystems_init); |
| 252 | #endif |
| 253 | |
Li Zefan | d8e9650d | 2008-12-25 13:32:15 +0800 | [diff] [blame] | 254 | static struct file_system_type *__get_fs_type(const char *name, int len) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 255 | { |
| 256 | struct file_system_type *fs; |
| 257 | |
| 258 | read_lock(&file_systems_lock); |
Miklos Szeredi | 79c0b2d | 2007-05-08 00:25:43 -0700 | [diff] [blame] | 259 | fs = *(find_filesystem(name, len)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 260 | if (fs && !try_module_get(fs->owner)) |
| 261 | fs = NULL; |
| 262 | read_unlock(&file_systems_lock); |
Li Zefan | d8e9650d | 2008-12-25 13:32:15 +0800 | [diff] [blame] | 263 | return fs; |
| 264 | } |
| 265 | |
| 266 | struct file_system_type *get_fs_type(const char *name) |
| 267 | { |
| 268 | struct file_system_type *fs; |
| 269 | const char *dot = strchr(name, '.'); |
| 270 | int len = dot ? dot - name : strlen(name); |
| 271 | |
| 272 | fs = __get_fs_type(name, len); |
Luis R. Rodriguez | 41124db | 2017-06-01 11:08:01 -0700 | [diff] [blame] | 273 | if (!fs && (request_module("fs-%.*s", len, name) == 0)) { |
Li Zefan | d8e9650d | 2008-12-25 13:32:15 +0800 | [diff] [blame] | 274 | fs = __get_fs_type(name, len); |
Eric Biggers | 26c5d78 | 2020-04-10 14:33:47 -0700 | [diff] [blame] | 275 | if (!fs) |
| 276 | pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n", |
| 277 | len, name); |
Luis R. Rodriguez | 41124db | 2017-06-01 11:08:01 -0700 | [diff] [blame] | 278 | } |
Miklos Szeredi | 79c0b2d | 2007-05-08 00:25:43 -0700 | [diff] [blame] | 279 | |
| 280 | if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) { |
| 281 | put_filesystem(fs); |
| 282 | fs = NULL; |
| 283 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 284 | return fs; |
| 285 | } |
| 286 | |
| 287 | EXPORT_SYMBOL(get_fs_type); |