Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * inode.c - part of tracefs, a pseudo file system for activating tracing
4 : *
5 : * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
6 : *
7 : * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
8 : *
9 : * tracefs is the file system that is used by the tracing infrastructure.
10 : */
11 :
12 : #include <linux/module.h>
13 : #include <linux/fs.h>
14 : #include <linux/mount.h>
15 : #include <linux/kobject.h>
16 : #include <linux/namei.h>
17 : #include <linux/tracefs.h>
18 : #include <linux/fsnotify.h>
19 : #include <linux/security.h>
20 : #include <linux/seq_file.h>
21 : #include <linux/parser.h>
22 : #include <linux/magic.h>
23 : #include <linux/slab.h>
24 :
25 : #define TRACEFS_DEFAULT_MODE 0700
26 :
27 : static struct vfsmount *tracefs_mount;
28 : static int tracefs_mount_count;
29 : static bool tracefs_registered;
30 :
31 0 : static ssize_t default_read_file(struct file *file, char __user *buf,
32 : size_t count, loff_t *ppos)
33 : {
34 0 : return 0;
35 : }
36 :
37 0 : static ssize_t default_write_file(struct file *file, const char __user *buf,
38 : size_t count, loff_t *ppos)
39 : {
40 0 : return count;
41 : }
42 :
43 : static const struct file_operations tracefs_file_operations = {
44 : .read = default_read_file,
45 : .write = default_write_file,
46 : .open = simple_open,
47 : .llseek = noop_llseek,
48 : };
49 :
50 : static struct tracefs_dir_ops {
51 : int (*mkdir)(const char *name);
52 : int (*rmdir)(const char *name);
53 : } tracefs_ops __ro_after_init;
54 :
55 0 : static char *get_dname(struct dentry *dentry)
56 : {
57 0 : const char *dname;
58 0 : char *name;
59 0 : int len = dentry->d_name.len;
60 :
61 0 : dname = dentry->d_name.name;
62 0 : name = kmalloc(len + 1, GFP_KERNEL);
63 0 : if (!name)
64 : return NULL;
65 0 : memcpy(name, dname, len);
66 0 : name[len] = 0;
67 0 : return name;
68 : }
69 :
70 0 : static int tracefs_syscall_mkdir(struct user_namespace *mnt_userns,
71 : struct inode *inode, struct dentry *dentry,
72 : umode_t mode)
73 : {
74 0 : char *name;
75 0 : int ret;
76 :
77 0 : name = get_dname(dentry);
78 0 : if (!name)
79 : return -ENOMEM;
80 :
81 : /*
82 : * The mkdir call can call the generic functions that create
83 : * the files within the tracefs system. It is up to the individual
84 : * mkdir routine to handle races.
85 : */
86 0 : inode_unlock(inode);
87 0 : ret = tracefs_ops.mkdir(name);
88 0 : inode_lock(inode);
89 :
90 0 : kfree(name);
91 :
92 0 : return ret;
93 : }
94 :
95 0 : static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
96 : {
97 0 : char *name;
98 0 : int ret;
99 :
100 0 : name = get_dname(dentry);
101 0 : if (!name)
102 : return -ENOMEM;
103 :
104 : /*
105 : * The rmdir call can call the generic functions that create
106 : * the files within the tracefs system. It is up to the individual
107 : * rmdir routine to handle races.
108 : * This time we need to unlock not only the parent (inode) but
109 : * also the directory that is being deleted.
110 : */
111 0 : inode_unlock(inode);
112 0 : inode_unlock(dentry->d_inode);
113 :
114 0 : ret = tracefs_ops.rmdir(name);
115 :
116 0 : inode_lock_nested(inode, I_MUTEX_PARENT);
117 0 : inode_lock(dentry->d_inode);
118 :
119 0 : kfree(name);
120 :
121 0 : return ret;
122 : }
123 :
124 : static const struct inode_operations tracefs_dir_inode_operations = {
125 : .lookup = simple_lookup,
126 : .mkdir = tracefs_syscall_mkdir,
127 : .rmdir = tracefs_syscall_rmdir,
128 : };
129 :
130 3450 : static struct inode *tracefs_get_inode(struct super_block *sb)
131 : {
132 3450 : struct inode *inode = new_inode(sb);
133 3450 : if (inode) {
134 3450 : inode->i_ino = get_next_ino();
135 3450 : inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
136 : }
137 3450 : return inode;
138 : }
139 :
140 : struct tracefs_mount_opts {
141 : kuid_t uid;
142 : kgid_t gid;
143 : umode_t mode;
144 : };
145 :
146 : enum {
147 : Opt_uid,
148 : Opt_gid,
149 : Opt_mode,
150 : Opt_err
151 : };
152 :
153 : static const match_table_t tokens = {
154 : {Opt_uid, "uid=%u"},
155 : {Opt_gid, "gid=%u"},
156 : {Opt_mode, "mode=%o"},
157 : {Opt_err, NULL}
158 : };
159 :
160 : struct tracefs_fs_info {
161 : struct tracefs_mount_opts mount_opts;
162 : };
163 :
164 1 : static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
165 : {
166 1 : substring_t args[MAX_OPT_ARGS];
167 1 : int option;
168 1 : int token;
169 1 : kuid_t uid;
170 1 : kgid_t gid;
171 1 : char *p;
172 :
173 1 : opts->mode = TRACEFS_DEFAULT_MODE;
174 :
175 1 : while ((p = strsep(&data, ",")) != NULL) {
176 0 : if (!*p)
177 0 : continue;
178 :
179 0 : token = match_token(p, tokens, args);
180 0 : switch (token) {
181 0 : case Opt_uid:
182 0 : if (match_int(&args[0], &option))
183 : return -EINVAL;
184 0 : uid = make_kuid(current_user_ns(), option);
185 0 : if (!uid_valid(uid))
186 : return -EINVAL;
187 0 : opts->uid = uid;
188 0 : break;
189 0 : case Opt_gid:
190 0 : if (match_int(&args[0], &option))
191 : return -EINVAL;
192 0 : gid = make_kgid(current_user_ns(), option);
193 0 : if (!gid_valid(gid))
194 : return -EINVAL;
195 0 : opts->gid = gid;
196 0 : break;
197 0 : case Opt_mode:
198 0 : if (match_octal(&args[0], &option))
199 : return -EINVAL;
200 0 : opts->mode = option & S_IALLUGO;
201 0 : break;
202 : /*
203 : * We might like to report bad mount options here;
204 : * but traditionally tracefs has ignored all mount options
205 : */
206 : }
207 : }
208 :
209 : return 0;
210 : }
211 :
212 1 : static int tracefs_apply_options(struct super_block *sb)
213 : {
214 1 : struct tracefs_fs_info *fsi = sb->s_fs_info;
215 1 : struct inode *inode = sb->s_root->d_inode;
216 1 : struct tracefs_mount_opts *opts = &fsi->mount_opts;
217 :
218 1 : inode->i_mode &= ~S_IALLUGO;
219 1 : inode->i_mode |= opts->mode;
220 :
221 1 : inode->i_uid = opts->uid;
222 1 : inode->i_gid = opts->gid;
223 :
224 1 : return 0;
225 : }
226 :
227 0 : static int tracefs_remount(struct super_block *sb, int *flags, char *data)
228 : {
229 0 : int err;
230 0 : struct tracefs_fs_info *fsi = sb->s_fs_info;
231 :
232 0 : sync_filesystem(sb);
233 0 : err = tracefs_parse_options(data, &fsi->mount_opts);
234 0 : if (err)
235 0 : goto fail;
236 :
237 0 : tracefs_apply_options(sb);
238 :
239 0 : fail:
240 0 : return err;
241 : }
242 :
243 0 : static int tracefs_show_options(struct seq_file *m, struct dentry *root)
244 : {
245 0 : struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
246 0 : struct tracefs_mount_opts *opts = &fsi->mount_opts;
247 :
248 0 : if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
249 0 : seq_printf(m, ",uid=%u",
250 : from_kuid_munged(&init_user_ns, opts->uid));
251 0 : if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
252 0 : seq_printf(m, ",gid=%u",
253 : from_kgid_munged(&init_user_ns, opts->gid));
254 0 : if (opts->mode != TRACEFS_DEFAULT_MODE)
255 0 : seq_printf(m, ",mode=%o", opts->mode);
256 :
257 0 : return 0;
258 : }
259 :
260 : static const struct super_operations tracefs_super_operations = {
261 : .statfs = simple_statfs,
262 : .remount_fs = tracefs_remount,
263 : .show_options = tracefs_show_options,
264 : };
265 :
266 1 : static int trace_fill_super(struct super_block *sb, void *data, int silent)
267 : {
268 1 : static const struct tree_descr trace_files[] = {{""}};
269 1 : struct tracefs_fs_info *fsi;
270 1 : int err;
271 :
272 1 : fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
273 1 : sb->s_fs_info = fsi;
274 1 : if (!fsi) {
275 0 : err = -ENOMEM;
276 0 : goto fail;
277 : }
278 :
279 1 : err = tracefs_parse_options(data, &fsi->mount_opts);
280 1 : if (err)
281 0 : goto fail;
282 :
283 1 : err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
284 1 : if (err)
285 0 : goto fail;
286 :
287 1 : sb->s_op = &tracefs_super_operations;
288 :
289 1 : tracefs_apply_options(sb);
290 :
291 1 : return 0;
292 :
293 0 : fail:
294 0 : kfree(fsi);
295 0 : sb->s_fs_info = NULL;
296 0 : return err;
297 : }
298 :
299 1 : static struct dentry *trace_mount(struct file_system_type *fs_type,
300 : int flags, const char *dev_name,
301 : void *data)
302 : {
303 1 : return mount_single(fs_type, flags, data, trace_fill_super);
304 : }
305 :
306 : static struct file_system_type trace_fs_type = {
307 : .owner = THIS_MODULE,
308 : .name = "tracefs",
309 : .mount = trace_mount,
310 : .kill_sb = kill_litter_super,
311 : };
312 : MODULE_ALIAS_FS("tracefs");
313 :
314 3450 : static struct dentry *start_creating(const char *name, struct dentry *parent)
315 : {
316 3450 : struct dentry *dentry;
317 3450 : int error;
318 :
319 3450 : pr_debug("tracefs: creating file '%s'\n",name);
320 :
321 3450 : error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
322 : &tracefs_mount_count);
323 3450 : if (error)
324 0 : return ERR_PTR(error);
325 :
326 : /* If the parent is not specified, we create it in the root.
327 : * We need the root dentry to do this, which is in the super
328 : * block. A pointer to that is in the struct vfsmount that we
329 : * have around.
330 : */
331 3450 : if (!parent)
332 30 : parent = tracefs_mount->mnt_root;
333 :
334 3450 : inode_lock(parent->d_inode);
335 3450 : if (unlikely(IS_DEADDIR(parent->d_inode)))
336 3450 : dentry = ERR_PTR(-ENOENT);
337 : else
338 3450 : dentry = lookup_one_len(name, parent, strlen(name));
339 3450 : if (!IS_ERR(dentry) && dentry->d_inode) {
340 0 : dput(dentry);
341 0 : dentry = ERR_PTR(-EEXIST);
342 : }
343 :
344 3450 : if (IS_ERR(dentry)) {
345 0 : inode_unlock(parent->d_inode);
346 0 : simple_release_fs(&tracefs_mount, &tracefs_mount_count);
347 : }
348 :
349 : return dentry;
350 : }
351 :
352 0 : static struct dentry *failed_creating(struct dentry *dentry)
353 : {
354 0 : inode_unlock(dentry->d_parent->d_inode);
355 0 : dput(dentry);
356 0 : simple_release_fs(&tracefs_mount, &tracefs_mount_count);
357 0 : return NULL;
358 : }
359 :
360 3450 : static struct dentry *end_creating(struct dentry *dentry)
361 : {
362 3450 : inode_unlock(dentry->d_parent->d_inode);
363 3450 : return dentry;
364 : }
365 :
366 : /**
367 : * tracefs_create_file - create a file in the tracefs filesystem
368 : * @name: a pointer to a string containing the name of the file to create.
369 : * @mode: the permission that the file should have.
370 : * @parent: a pointer to the parent dentry for this file. This should be a
371 : * directory dentry if set. If this parameter is NULL, then the
372 : * file will be created in the root of the tracefs filesystem.
373 : * @data: a pointer to something that the caller will want to get to later
374 : * on. The inode.i_private pointer will point to this value on
375 : * the open() call.
376 : * @fops: a pointer to a struct file_operations that should be used for
377 : * this file.
378 : *
379 : * This is the basic "create a file" function for tracefs. It allows for a
380 : * wide range of flexibility in creating a file, or a directory (if you want
381 : * to create a directory, the tracefs_create_dir() function is
382 : * recommended to be used instead.)
383 : *
384 : * This function will return a pointer to a dentry if it succeeds. This
385 : * pointer must be passed to the tracefs_remove() function when the file is
386 : * to be removed (no automatic cleanup happens if your module is unloaded,
387 : * you are responsible here.) If an error occurs, %NULL will be returned.
388 : *
389 : * If tracefs is not enabled in the kernel, the value -%ENODEV will be
390 : * returned.
391 : */
392 2842 : struct dentry *tracefs_create_file(const char *name, umode_t mode,
393 : struct dentry *parent, void *data,
394 : const struct file_operations *fops)
395 : {
396 2842 : struct dentry *dentry;
397 2842 : struct inode *inode;
398 :
399 2842 : if (security_locked_down(LOCKDOWN_TRACEFS))
400 : return NULL;
401 :
402 2842 : if (!(mode & S_IFMT))
403 2842 : mode |= S_IFREG;
404 2842 : BUG_ON(!S_ISREG(mode));
405 2842 : dentry = start_creating(name, parent);
406 :
407 2842 : if (IS_ERR(dentry))
408 : return NULL;
409 :
410 2842 : inode = tracefs_get_inode(dentry->d_sb);
411 2842 : if (unlikely(!inode))
412 0 : return failed_creating(dentry);
413 :
414 2842 : inode->i_mode = mode;
415 2842 : inode->i_fop = fops ? fops : &tracefs_file_operations;
416 2842 : inode->i_private = data;
417 2842 : d_instantiate(dentry, inode);
418 2842 : fsnotify_create(dentry->d_parent->d_inode, dentry);
419 2842 : return end_creating(dentry);
420 : }
421 :
422 608 : static struct dentry *__create_dir(const char *name, struct dentry *parent,
423 : const struct inode_operations *ops)
424 : {
425 608 : struct dentry *dentry = start_creating(name, parent);
426 608 : struct inode *inode;
427 :
428 608 : if (IS_ERR(dentry))
429 : return NULL;
430 :
431 608 : inode = tracefs_get_inode(dentry->d_sb);
432 608 : if (unlikely(!inode))
433 0 : return failed_creating(dentry);
434 :
435 608 : inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
436 608 : inode->i_op = ops;
437 608 : inode->i_fop = &simple_dir_operations;
438 :
439 : /* directory inodes start off with i_nlink == 2 (for "." entry) */
440 608 : inc_nlink(inode);
441 608 : d_instantiate(dentry, inode);
442 608 : inc_nlink(dentry->d_parent->d_inode);
443 608 : fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
444 608 : return end_creating(dentry);
445 : }
446 :
447 : /**
448 : * tracefs_create_dir - create a directory in the tracefs filesystem
449 : * @name: a pointer to a string containing the name of the directory to
450 : * create.
451 : * @parent: a pointer to the parent dentry for this file. This should be a
452 : * directory dentry if set. If this parameter is NULL, then the
453 : * directory will be created in the root of the tracefs filesystem.
454 : *
455 : * This function creates a directory in tracefs with the given name.
456 : *
457 : * This function will return a pointer to a dentry if it succeeds. This
458 : * pointer must be passed to the tracefs_remove() function when the file is
459 : * to be removed. If an error occurs, %NULL will be returned.
460 : *
461 : * If tracing is not enabled in the kernel, the value -%ENODEV will be
462 : * returned.
463 : */
464 607 : struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
465 : {
466 607 : return __create_dir(name, parent, &simple_dir_inode_operations);
467 : }
468 :
469 : /**
470 : * tracefs_create_instance_dir - create the tracing instances directory
471 : * @name: The name of the instances directory to create
472 : * @parent: The parent directory that the instances directory will exist
473 : * @mkdir: The function to call when a mkdir is performed.
474 : * @rmdir: The function to call when a rmdir is performed.
475 : *
476 : * Only one instances directory is allowed.
477 : *
478 : * The instances directory is special as it allows for mkdir and rmdir to
479 : * to be done by userspace. When a mkdir or rmdir is performed, the inode
480 : * locks are released and the methhods passed in (@mkdir and @rmdir) are
481 : * called without locks and with the name of the directory being created
482 : * within the instances directory.
483 : *
484 : * Returns the dentry of the instances directory.
485 : */
486 1 : __init struct dentry *tracefs_create_instance_dir(const char *name,
487 : struct dentry *parent,
488 : int (*mkdir)(const char *name),
489 : int (*rmdir)(const char *name))
490 : {
491 1 : struct dentry *dentry;
492 :
493 : /* Only allow one instance of the instances directory. */
494 2 : if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
495 : return NULL;
496 :
497 1 : dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
498 1 : if (!dentry)
499 : return NULL;
500 :
501 1 : tracefs_ops.mkdir = mkdir;
502 1 : tracefs_ops.rmdir = rmdir;
503 :
504 1 : return dentry;
505 : }
506 :
507 0 : static void remove_one(struct dentry *victim)
508 : {
509 0 : simple_release_fs(&tracefs_mount, &tracefs_mount_count);
510 0 : }
511 :
512 : /**
513 : * tracefs_remove - recursively removes a directory
514 : * @dentry: a pointer to a the dentry of the directory to be removed.
515 : *
516 : * This function recursively removes a directory tree in tracefs that
517 : * was previously created with a call to another tracefs function
518 : * (like tracefs_create_file() or variants thereof.)
519 : */
520 0 : void tracefs_remove(struct dentry *dentry)
521 : {
522 0 : if (IS_ERR_OR_NULL(dentry))
523 : return;
524 :
525 0 : simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
526 0 : simple_recursive_removal(dentry, remove_one);
527 0 : simple_release_fs(&tracefs_mount, &tracefs_mount_count);
528 : }
529 :
530 : /**
531 : * tracefs_initialized - Tells whether tracefs has been registered
532 : */
533 1 : bool tracefs_initialized(void)
534 : {
535 1 : return tracefs_registered;
536 : }
537 :
538 1 : static int __init tracefs_init(void)
539 : {
540 1 : int retval;
541 :
542 1 : retval = sysfs_create_mount_point(kernel_kobj, "tracing");
543 1 : if (retval)
544 : return -EINVAL;
545 :
546 1 : retval = register_filesystem(&trace_fs_type);
547 1 : if (!retval)
548 1 : tracefs_registered = true;
549 :
550 : return retval;
551 : }
552 : core_initcall(tracefs_init);
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