// SPDX-License-Identifier: GPL-2.0/*  FUSE: Filesystem in Userspace  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>*/ #include "fuse_i.h"#include "dev.h" #include <linux/init.h>#include <linux/module.h>#include <linux/fs_context.h>#include <linux/namei.h> #define FUSE_CTL_SUPER_MAGIC 0x65735543 /* * This is non-NULL when the single instance of the control filesystem * exists.  Protected by fuse_mutex */static struct super_block *fuse_control_sb; static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file){	struct fuse_conn *fc;	mutex_lock(&fuse_mutex);	fc = file_inode(file)->i_private;	if (fc)		fc = fuse_conn_get(fc);	mutex_unlock(&fuse_mutex);	return fc;} static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,				     size_t count, loff_t *ppos){	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);	if (fc) {		fuse_chan_abort(fc->chan, fc->abort_err);		fuse_conn_put(fc);	}	return count;} static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,				      size_t len, loff_t *ppos){	char tmp[32];	size_t size; 	if (!*ppos) {		long value;		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);		if (!fc)			return 0; 		value = fuse_chan_num_waiting(fc->chan);		file->private_data = (void *)value;		fuse_conn_put(fc);	}	size = sprintf(tmp, "%ld\n", (long)file->private_data);	return simple_read_from_buffer(buf, len, ppos, tmp, size);} static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,				    size_t len, loff_t *ppos, unsigned val){	char tmp[32];	size_t size = sprintf(tmp, "%u\n", val); 	return simple_read_from_buffer(buf, len, ppos, tmp, size);} static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,				     size_t count, loff_t *ppos, unsigned *val,				     unsigned global_limit){	unsigned long t;	unsigned limit = (1 << 16) - 1;	int err; 	if (*ppos)		return -EINVAL; 	err = kstrtoul_from_user(buf, count, 0, &t);	if (err)		return err; 	if (!capable(CAP_SYS_ADMIN))		limit = min(limit, global_limit); 	if (t > limit)		return -EINVAL; 	*val = t; 	return count;} static ssize_t fuse_conn_max_background_read(struct file *file,					     char __user *buf, size_t len,					     loff_t *ppos){	struct fuse_conn *fc;	unsigned val; 	fc = fuse_ctl_file_conn_get(file);	if (!fc)		return 0; 	val = fuse_chan_max_background(fc->chan);	fuse_conn_put(fc); 	return fuse_conn_limit_read(file, buf, len, ppos, val);} static ssize_t fuse_conn_max_background_write(struct file *file,					      const char __user *buf,					      size_t count, loff_t *ppos){	unsigned int val = 0;	ssize_t ret; 	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,				    max_user_bgreq);	if (ret > 0) {		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);		if (fc) {			fuse_chan_max_background_set(fc->chan, val);			fuse_conn_put(fc);		}	} 	return ret;} static ssize_t fuse_conn_congestion_threshold_read(struct file *file,						   char __user *buf, size_t len,						   loff_t *ppos){	struct fuse_conn *fc;	unsigned val; 	fc = fuse_ctl_file_conn_get(file);	if (!fc)		return 0; 	val = READ_ONCE(fc->congestion_threshold);	fuse_conn_put(fc); 	return fuse_conn_limit_read(file, buf, len, ppos, val);} static ssize_t fuse_conn_congestion_threshold_write(struct file *file,						    const char __user *buf,						    size_t count, loff_t *ppos){	unsigned int val = 0;	struct fuse_conn *fc;	ssize_t ret; 	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,				    max_user_congthresh);	if (ret <= 0)		goto out;	fc = fuse_ctl_file_conn_get(file);	if (!fc)		goto out; 	WRITE_ONCE(fc->congestion_threshold, val);	fuse_conn_put(fc);out:	return ret;} static const struct file_operations fuse_ctl_abort_ops = {	.open = nonseekable_open,	.write = fuse_conn_abort_write,}; static const struct file_operations fuse_ctl_waiting_ops = {	.open = nonseekable_open,	.read = fuse_conn_waiting_read,}; static const struct file_operations fuse_conn_max_background_ops = {	.open = nonseekable_open,	.read = fuse_conn_max_background_read,	.write = fuse_conn_max_background_write,}; static const struct file_operations fuse_conn_congestion_threshold_ops = {	.open = nonseekable_open,	.read = fuse_conn_congestion_threshold_read,	.write = fuse_conn_congestion_threshold_write,}; static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,					  struct fuse_conn *fc,					  const char *name, int mode,					  const struct inode_operations *iop,					  const struct file_operations *fop){	struct dentry *dentry;	struct inode *inode; 	dentry = d_alloc_name(parent, name);	if (!dentry)		return NULL; 	inode = new_inode(fuse_control_sb);	if (!inode) {		dput(dentry);		return NULL;	} 	inode->i_ino = get_next_ino();	inode->i_mode = mode;	inode->i_uid = fc->user_id;	inode->i_gid = fc->group_id;	simple_inode_init_ts(inode);	/* setting ->i_op to NULL is not allowed */	if (iop)		inode->i_op = iop;	inode->i_fop = fop;	if (S_ISDIR(mode)) {		inc_nlink(d_inode(parent));		inc_nlink(inode);	}	inode->i_private = fc;	d_make_persistent(dentry, inode);	dput(dentry); 	/*	 * We are returning a borrowed reference here - it's only good while	 * fuse_mutex is held.  Actually it's d_make_persistent() return	 * value...	 */	return dentry;} /* * Add a connection to the control filesystem (if it exists).  Caller * must hold fuse_mutex */int fuse_ctl_add_conn(struct fuse_conn *fc){	struct dentry *parent;	char name[32]; 	if (!fuse_control_sb || fc->no_control)		return 0; 	parent = fuse_control_sb->s_root;	sprintf(name, "%u", fc->dev);	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500,				     &simple_dir_inode_operations,				     &simple_dir_operations);	if (!parent)		goto err; 	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400,				 NULL, &fuse_ctl_waiting_ops) ||	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200,				 NULL, &fuse_ctl_abort_ops) ||	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,				 NULL, &fuse_conn_max_background_ops) ||	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",				 S_IFREG | 0600, NULL,				 &fuse_conn_congestion_threshold_ops))		goto err; 	return 0;  err:	fuse_ctl_remove_conn(fc);	return -ENOMEM;} static void remove_one(struct dentry *dentry){	d_inode(dentry)->i_private = NULL;} /* * Remove a connection from the control filesystem (if it exists). * Caller must hold fuse_mutex */void fuse_ctl_remove_conn(struct fuse_conn *fc){	char name[32]; 	if (!fuse_control_sb || fc->no_control)		return; 	sprintf(name, "%u", fc->dev);	simple_remove_by_name(fuse_control_sb->s_root, name, remove_one);} static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc){	static const struct tree_descr empty_descr = {""};	struct fuse_conn *fc;	int err; 	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);	if (err)		return err; 	mutex_lock(&fuse_mutex);	BUG_ON(fuse_control_sb);	fuse_control_sb = sb;	list_for_each_entry(fc, &fuse_conn_list, entry) {		err = fuse_ctl_add_conn(fc);		if (err) {			fuse_control_sb = NULL;			mutex_unlock(&fuse_mutex);			return err;		}	}	mutex_unlock(&fuse_mutex); 	return 0;} static int fuse_ctl_get_tree(struct fs_context *fsc){	return get_tree_single(fsc, fuse_ctl_fill_super);} static const struct fs_context_operations fuse_ctl_context_ops = {	.get_tree	= fuse_ctl_get_tree,}; static int fuse_ctl_init_fs_context(struct fs_context *fsc){	fsc->ops = &fuse_ctl_context_ops;	return 0;} static void fuse_ctl_kill_sb(struct super_block *sb){	mutex_lock(&fuse_mutex);	fuse_control_sb = NULL;	mutex_unlock(&fuse_mutex); 	kill_anon_super(sb);} static struct file_system_type fuse_ctl_fs_type = {	.owner		= THIS_MODULE,	.name		= "fusectl",	.init_fs_context = fuse_ctl_init_fs_context,	.kill_sb	= fuse_ctl_kill_sb,};MODULE_ALIAS_FS("fusectl"); int __init fuse_ctl_init(void){	return register_filesystem(&fuse_ctl_fs_type);} void __exit fuse_ctl_cleanup(void){	unregister_filesystem(&fuse_ctl_fs_type);}