[thirdparty/linux.git] / fs / filesystems.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/filesystems.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  table of configured filesystems
 */

#include <linux/syscalls.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kmod.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fs_parser.h>

/*
 * Handling of filesystem drivers list.
 * Rules:
 *	Inclusion to/removals from/scanning of list are protected by spinlock.
 *	During the unload module must call unregister_filesystem().
 *	We can access the fields of list element if:
 *		1) spinlock is held or
 *		2) we hold the reference to the module.
 *	The latter can be guaranteed by call of try_module_get(); if it
 *	returned 0 we must skip the element, otherwise we got the reference.
 *	Once the reference is obtained we can drop the spinlock.
 */

static struct file_system_type *file_systems;
static DEFINE_RWLOCK(file_systems_lock);

/* WARNING: This can be used only if we _already_ own a reference */
struct file_system_type *get_filesystem(struct file_system_type *fs)
{
	__module_get(fs->owner);
	return fs;
}

void put_filesystem(struct file_system_type *fs)
{
	module_put(fs->owner);
}

static struct file_system_type **find_filesystem(const char *name, unsigned len)
{
	struct file_system_type **p;
	for (p = &file_systems; *p; p = &(*p)->next)
		if (strncmp((*p)->name, name, len) == 0 &&
		    !(*p)->name[len])
			break;
	return p;
}

/**
 *	register_filesystem - register a new filesystem
 *	@fs: the file system structure
 *
 *	Adds the file system passed to the list of file systems the kernel
 *	is aware of for mount and other syscalls. Returns 0 on success,
 *	or a negative errno code on an error.
 *
 *	The &struct file_system_type that is passed is linked into the kernel 
 *	structures and must not be freed until the file system has been
 *	unregistered.
 */
 
int register_filesystem(struct file_system_type * fs)
{
	int res = 0;
	struct file_system_type ** p;

	if (fs->parameters &&
	    !fs_validate_description(fs->name, fs->parameters))
		return -EINVAL;

	BUG_ON(strchr(fs->name, '.'));
	if (fs->next)
		return -EBUSY;
	write_lock(&file_systems_lock);
	p = find_filesystem(fs->name, strlen(fs->name));
	if (*p)
		res = -EBUSY;
	else
		*p = fs;
	write_unlock(&file_systems_lock);
	return res;
}

EXPORT_SYMBOL(register_filesystem);

/**
 *	unregister_filesystem - unregister a file system
 *	@fs: filesystem to unregister
 *
 *	Remove a file system that was previously successfully registered
 *	with the kernel. An error is returned if the file system is not found.
 *	Zero is returned on a success.
 *	
 *	Once this function has returned the &struct file_system_type structure
 *	may be freed or reused.
 */
 
int unregister_filesystem(struct file_system_type * fs)
{
	struct file_system_type ** tmp;

	write_lock(&file_systems_lock);
	tmp = &file_systems;
	while (*tmp) {
		if (fs == *tmp) {
			*tmp = fs->next;
			fs->next = NULL;
			write_unlock(&file_systems_lock);
			synchronize_rcu();
			return 0;
		}
		tmp = &(*tmp)->next;
	}
	write_unlock(&file_systems_lock);

	return -EINVAL;
}

EXPORT_SYMBOL(unregister_filesystem);

#ifdef CONFIG_SYSFS_SYSCALL
static int fs_index(const char __user * __name)
{
	struct file_system_type * tmp;
	struct filename *name;
	int err, index;

	name = getname(__name);
	err = PTR_ERR(name);
	if (IS_ERR(name))
		return err;

	err = -EINVAL;
	read_lock(&file_systems_lock);
	for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
		if (strcmp(tmp->name, name->name) == 0) {
			err = index;
			break;
		}
	}
	read_unlock(&file_systems_lock);
	putname(name);
	return err;
}

static int fs_name(unsigned int index, char __user * buf)
{
	struct file_system_type * tmp;
	int len, res;

	read_lock(&file_systems_lock);
	for (tmp = file_systems; tmp; tmp = tmp->next, index--)
		if (index <= 0 && try_module_get(tmp->owner))
			break;
	read_unlock(&file_systems_lock);
	if (!tmp)
		return -EINVAL;

	/* OK, we got the reference, so we can safely block */
	len = strlen(tmp->name) + 1;
	res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
	put_filesystem(tmp);
	return res;
}

static int fs_maxindex(void)
{
	struct file_system_type * tmp;
	int index;

	read_lock(&file_systems_lock);
	for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
		;
	read_unlock(&file_systems_lock);
	return index;
}

/*
 * Whee.. Weird sysv syscall. 
 */
SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
{
	int retval = -EINVAL;

	switch (option) {
		case 1:
			retval = fs_index((const char __user *) arg1);
			break;

		case 2:
			retval = fs_name(arg1, (char __user *) arg2);
			break;

		case 3:
			retval = fs_maxindex();
			break;
	}
	return retval;
}
#endif

int __init get_filesystem_list(char *buf)
{
	int len = 0;
	struct file_system_type * tmp;

	read_lock(&file_systems_lock);
	tmp = file_systems;
	while (tmp && len < PAGE_SIZE - 80) {
		len += sprintf(buf+len, "%s\t%s\n",
			(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
			tmp->name);
		tmp = tmp->next;
	}
	read_unlock(&file_systems_lock);
	return len;
}

#ifdef CONFIG_PROC_FS
static int filesystems_proc_show(struct seq_file *m, void *v)
{
	struct file_system_type * tmp;

	read_lock(&file_systems_lock);
	tmp = file_systems;
	while (tmp) {
		seq_printf(m, "%s\t%s\n",
			(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
			tmp->name);
		tmp = tmp->next;
	}
	read_unlock(&file_systems_lock);
	return 0;
}

static int __init proc_filesystems_init(void)
{
	proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
	return 0;
}
module_init(proc_filesystems_init);
#endif

static struct file_system_type *__get_fs_type(const char *name, int len)
{
	struct file_system_type *fs;

	read_lock(&file_systems_lock);
	fs = *(find_filesystem(name, len));
	if (fs && !try_module_get(fs->owner))
		fs = NULL;
	read_unlock(&file_systems_lock);
	return fs;
}

struct file_system_type *get_fs_type(const char *name)
{
	struct file_system_type *fs;
	const char *dot = strchr(name, '.');
	int len = dot ? dot - name : strlen(name);

	fs = __get_fs_type(name, len);
	if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
		fs = __get_fs_type(name, len);
		if (!fs)
			pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n",
				     len, name);
	}

	if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
		put_filesystem(fs);
		fs = NULL;
	}
	return fs;
}

EXPORT_SYMBOL(get_fs_type);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	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>
68274007 AD	12	#include <linux/proc_fs.h>
68274007 AD	13	#include <linux/seq_file.h>
1da177e4 LT	14	#include <linux/kmod.h>
	15	#include <linux/init.h>
	16	#include <linux/module.h>
5a0e3ad6	17	#include <linux/slab.h>
7c0f6ba6	18	#include <linux/uaccess.h>
3e1aeb00	19	#include <linux/fs_parser.h>
1da177e4 LT	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 */
ee416bcd	38	struct file_system_type get_filesystem(struct file_system_type fs)
1da177e4 LT	39	{
1da177e4 LT	40	__module_get(fs->owner);
ee416bcd	41	return fs;
1da177e4 LT	42	}
	43
	44	void put_filesystem(struct file_system_type *fs)
	45	{
	46	module_put(fs->owner);
	47	}
	48
79c0b2df	49	static struct file_system_type *find_filesystem(const char name, unsigned len)
1da177e4 LT	50	{
1da177e4 LT	51	struct file_system_type **p;
558041d8 AV	52	for (p = &file_systems; p; p = &(p)->next)
	53	if (strncmp((*p)->name, name, len) == 0 &&
	54	!(*p)->name[len])
1da177e4 LT	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
96cafb9c ES	77	if (fs->parameters &&
96cafb9c ES	78	!fs_validate_description(fs->name, fs->parameters))
3e1aeb00 DH	79	return -EINVAL;
3e1aeb00 DH	80
79c0b2df	81	BUG_ON(strchr(fs->name, '.'));
1da177e4 LT	82	if (fs->next)
1da177e4 LT	83	return -EBUSY;
1da177e4	84	write_lock(&file_systems_lock);
79c0b2df	85	p = find_filesystem(fs->name, strlen(fs->name));
1da177e4 LT	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);
fff3e5ad	119	synchronize_rcu();
1da177e4 LT	120	return 0;
	121	}
	122	tmp = &(*tmp)->next;
	123	}
	124	write_unlock(&file_systems_lock);
31e6b01f	125
1da177e4 LT	126	return -EINVAL;
	127	}
	128
	129	EXPORT_SYMBOL(unregister_filesystem);
	130
6af9f7bf	131	#ifdef CONFIG_SYSFS_SYSCALL
1da177e4 LT	132	static int fs_index(const char __user * __name)
	133	{
	134	struct file_system_type * tmp;
91a27b2a	135	struct filename *name;
1da177e4 LT	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++) {
91a27b2a	146	if (strcmp(tmp->name, name->name) == 0) {
1da177e4 LT	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	*/
1e7bfb21	191	SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
1da177e4 LT	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	}
6af9f7bf	210	#endif
1da177e4	211
38e23c95	212	int __init get_filesystem_list(char *buf)
1da177e4 LT	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
68274007 AD	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
68274007 AD	246	static int __init proc_filesystems_init(void)
68274007 AD	247	{
3f3942ac	248	proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
68274007 AD	249	return 0;
	250	}
	251	module_init(proc_filesystems_init);
	252	#endif
	253
d8e9650d	254	static struct file_system_type __get_fs_type(const char name, int len)
1da177e4 LT	255	{
	256	struct file_system_type *fs;
	257
	258	read_lock(&file_systems_lock);
79c0b2df	259	fs = *(find_filesystem(name, len));
1da177e4 LT	260	if (fs && !try_module_get(fs->owner))
	261	fs = NULL;
	262	read_unlock(&file_systems_lock);
d8e9650d LZ	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);
41124db8	273	if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
d8e9650d	274	fs = __get_fs_type(name, len);
26c5d78c EB	275	if (!fs)
	276	pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n",
	277	len, name);
41124db8	278	}
79c0b2df MS	279
	280	if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
	281	put_filesystem(fs);
	282	fs = NULL;
	283	}
1da177e4 LT	284	return fs;
	285	}
	286
	287	EXPORT_SYMBOL(get_fs_type);