// SPDX-License-Identifier: GPL-2.0-only#include <linux/export.h>#include <linux/sched/signal.h>#include <linux/sched/task.h>#include <linux/fs.h>#include <linux/path.h>#include <linux/slab.h>#include <linux/fs_struct.h>#include <linux/init_task.h>#include "internal.h" /* * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. * It can block. */void set_fs_root(struct fs_struct *fs, const struct path *path){	struct path old_root; 	path_get(path);	write_seqlock(&fs->seq);	old_root = fs->root;	fs->root = *path;	write_sequnlock(&fs->seq);	if (old_root.dentry)		path_put(&old_root);} /* * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. * It can block. */void set_fs_pwd(struct fs_struct *fs, const struct path *path){	struct path old_pwd; 	path_get(path);	write_seqlock(&fs->seq);	old_pwd = fs->pwd;	fs->pwd = *path;	write_sequnlock(&fs->seq); 	if (old_pwd.dentry)		path_put(&old_pwd);} static inline int replace_path(struct path *p, const struct path *old, const struct path *new){	if (likely(p->dentry != old->dentry || p->mnt != old->mnt))		return 0;	*p = *new;	return 1;} void chroot_fs_refs(const struct path *old_root, const struct path *new_root){	struct task_struct *g, *p;	struct fs_struct *fs;	int count = 0; 	read_lock(&tasklist_lock);	for_each_process_thread(g, p) {		task_lock(p);		fs = p->fs;		if (fs) {			int hits = 0;			write_seqlock(&fs->seq);			hits += replace_path(&fs->root, old_root, new_root);			hits += replace_path(&fs->pwd, old_root, new_root);			while (hits--) {				count++;				path_get(new_root);			}			write_sequnlock(&fs->seq);		}		task_unlock(p);	}	read_unlock(&tasklist_lock);	while (count--)		path_put(old_root);} void free_fs_struct(struct fs_struct *fs){	path_put(&fs->root);	path_put(&fs->pwd);	kmem_cache_free(fs_cachep, fs);} void exit_fs(struct task_struct *tsk){	struct fs_struct *fs = tsk->fs; 	if (fs) {		int kill;		task_lock(tsk);		read_seqlock_excl(&fs->seq);		tsk->fs = NULL;		kill = !--fs->users;		read_sequnlock_excl(&fs->seq);		task_unlock(tsk);		if (kill)			free_fs_struct(fs);	}} struct fs_struct *copy_fs_struct(struct fs_struct *old){	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);	/* We don't need to lock fs - think why ;-) */	if (fs) {		fs->users = 1;		fs->in_exec = 0;		seqlock_init(&fs->seq);		fs->umask = old->umask; 		read_seqlock_excl(&old->seq);		fs->root = old->root;		path_get(&fs->root);		fs->pwd = old->pwd;		path_get(&fs->pwd);		read_sequnlock_excl(&old->seq);	}	return fs;} int unshare_fs_struct(void){	struct fs_struct *fs = current->fs;	struct fs_struct *new_fs = copy_fs_struct(fs);	int kill; 	if (!new_fs)		return -ENOMEM; 	task_lock(current);	read_seqlock_excl(&fs->seq);	kill = !--fs->users;	current->fs = new_fs;	read_sequnlock_excl(&fs->seq);	task_unlock(current); 	if (kill)		free_fs_struct(fs); 	return 0;}EXPORT_SYMBOL_GPL(unshare_fs_struct); /* to be mentioned only in INIT_TASK */struct fs_struct init_fs = {	.users		= 1,	.seq		= __SEQLOCK_UNLOCKED(init_fs.seq),	.umask		= 0022,};