// SPDX-License-Identifier: GPL-2.0/* *  linux/fs/proc/root.c * *  Copyright (C) 1991, 1992 Linus Torvalds * *  proc root directory handling functions */ #include <linux/uaccess.h> #include <linux/errno.h>#include <linux/time.h>#include <linux/proc_fs.h>#include <linux/stat.h>#include <linux/init.h>#include <linux/sched.h>#include <linux/sched/stat.h>#include <linux/module.h>#include <linux/bitops.h>#include <linux/user_namespace.h>#include <linux/fs_context.h>#include <linux/mount.h>#include <linux/pid_namespace.h>#include <linux/fs_parser.h>#include <linux/cred.h>#include <linux/magic.h>#include <linux/slab.h> #include "internal.h" struct proc_fs_context {	struct pid_namespace	*pid_ns;	unsigned int		mask;	int			hidepid;	int			gid;}; enum proc_param {	Opt_gid,	Opt_hidepid,}; static const struct fs_parameter_spec proc_param_specs[] = {	fsparam_u32("gid",	Opt_gid),	fsparam_u32("hidepid",	Opt_hidepid),	{}}; static const struct fs_parameter_description proc_fs_parameters = {	.name		= "proc",	.specs		= proc_param_specs,}; static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param){	struct proc_fs_context *ctx = fc->fs_private;	struct fs_parse_result result;	int opt; 	opt = fs_parse(fc, &proc_fs_parameters, param, &result);	if (opt < 0)		return opt; 	switch (opt) {	case Opt_gid:		ctx->gid = result.uint_32;		break; 	case Opt_hidepid:		ctx->hidepid = result.uint_32;		if (ctx->hidepid < HIDEPID_OFF ||		    ctx->hidepid > HIDEPID_INVISIBLE)			return invalf(fc, "proc: hidepid value must be between 0 and 2.\n");		break; 	default:		return -EINVAL;	} 	ctx->mask |= 1 << opt;	return 0;} static void proc_apply_options(struct super_block *s,			       struct fs_context *fc,			       struct pid_namespace *pid_ns,			       struct user_namespace *user_ns){	struct proc_fs_context *ctx = fc->fs_private; 	if (ctx->mask & (1 << Opt_gid))		pid_ns->pid_gid = make_kgid(user_ns, ctx->gid);	if (ctx->mask & (1 << Opt_hidepid))		pid_ns->hide_pid = ctx->hidepid;} static int proc_fill_super(struct super_block *s, struct fs_context *fc){	struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info);	struct inode *root_inode;	int ret; 	proc_apply_options(s, fc, pid_ns, current_user_ns()); 	/* User space would break if executables or devices appear on proc */	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;	s->s_blocksize = 1024;	s->s_blocksize_bits = 10;	s->s_magic = PROC_SUPER_MAGIC;	s->s_op = &proc_sops;	s->s_time_gran = 1; 	/*	 * procfs isn't actually a stacking filesystem; however, there is	 * too much magic going on inside it to permit stacking things on	 * top of it	 */	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;		/* procfs dentries and inodes don't require IO to create */	s->s_shrink.seeks = 0; 	pde_get(&proc_root);	root_inode = proc_get_inode(s, &proc_root);	if (!root_inode) {		pr_err("proc_fill_super: get root inode failed\n");		return -ENOMEM;	} 	s->s_root = d_make_root(root_inode);	if (!s->s_root) {		pr_err("proc_fill_super: allocate dentry failed\n");		return -ENOMEM;	} 	ret = proc_setup_self(s);	if (ret) {		return ret;	}	return proc_setup_thread_self(s);} static int proc_reconfigure(struct fs_context *fc){	struct super_block *sb = fc->root->d_sb;	struct pid_namespace *pid = sb->s_fs_info; 	sync_filesystem(sb); 	proc_apply_options(sb, fc, pid, current_user_ns());	return 0;} static int proc_get_tree(struct fs_context *fc){	struct proc_fs_context *ctx = fc->fs_private; 	put_user_ns(fc->user_ns);	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);	fc->s_fs_info = ctx->pid_ns;	return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);} static void proc_fs_context_free(struct fs_context *fc){	struct proc_fs_context *ctx = fc->fs_private; 	if (ctx->pid_ns)		put_pid_ns(ctx->pid_ns);	kfree(ctx);} static const struct fs_context_operations proc_fs_context_ops = {	.free		= proc_fs_context_free,	.parse_param	= proc_parse_param,	.get_tree	= proc_get_tree,	.reconfigure	= proc_reconfigure,}; static int proc_init_fs_context(struct fs_context *fc){	struct proc_fs_context *ctx; 	ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);	if (!ctx)		return -ENOMEM; 	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));	fc->fs_private = ctx;	fc->ops = &proc_fs_context_ops;	return 0;} static void proc_kill_sb(struct super_block *sb){	struct pid_namespace *ns; 	ns = (struct pid_namespace *)sb->s_fs_info;	if (ns->proc_self)		dput(ns->proc_self);	if (ns->proc_thread_self)		dput(ns->proc_thread_self);	kill_anon_super(sb);	put_pid_ns(ns);} static struct file_system_type proc_fs_type = {	.name			= "proc",	.init_fs_context	= proc_init_fs_context,	.parameters		= &proc_fs_parameters,	.kill_sb		= proc_kill_sb,	.fs_flags		= FS_USERNS_MOUNT,}; void __init proc_root_init(void){	proc_init_kmemcache();	set_proc_pid_nlink();	proc_self_init();	proc_thread_self_init();	proc_symlink("mounts", NULL, "self/mounts"); 	proc_net_init();	proc_mkdir("fs", NULL);	proc_mkdir("driver", NULL);	proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)	/* just give it a mountpoint */	proc_create_mount_point("openprom");#endif	proc_tty_init();	proc_mkdir("bus", NULL);	proc_sys_init(); 	register_filesystem(&proc_fs_type);} static int proc_root_getattr(const struct path *path, struct kstat *stat,			     u32 request_mask, unsigned int query_flags){	generic_fillattr(d_inode(path->dentry), stat);	stat->nlink = proc_root.nlink + nr_processes();	return 0;} static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags){	if (!proc_pid_lookup(dentry, flags))		return NULL; 	return proc_lookup(dir, dentry, flags);} static int proc_root_readdir(struct file *file, struct dir_context *ctx){	if (ctx->pos < FIRST_PROCESS_ENTRY) {		int error = proc_readdir(file, ctx);		if (unlikely(error <= 0))			return error;		ctx->pos = FIRST_PROCESS_ENTRY;	} 	return proc_pid_readdir(file, ctx);} /* * The root /proc directory is special, as it has the * <pid> directories. Thus we don't use the generic * directory handling functions for that.. */static const struct file_operations proc_root_operations = {	.read		 = generic_read_dir,	.iterate_shared	 = proc_root_readdir,	.llseek		= generic_file_llseek,}; /* * proc root can do almost nothing.. */static const struct inode_operations proc_root_inode_operations = {	.lookup		= proc_root_lookup,	.getattr	= proc_root_getattr,}; /* * This is the root "inode" in the /proc tree.. */struct proc_dir_entry proc_root = {	.low_ino	= PROC_ROOT_INO, 	.namelen	= 5, 	.mode		= S_IFDIR | S_IRUGO | S_IXUGO, 	.nlink		= 2, 	.refcnt		= REFCOUNT_INIT(1),	.proc_iops	= &proc_root_inode_operations, 	.proc_fops	= &proc_root_operations,	.parent		= &proc_root,	.subdir		= RB_ROOT,	.name		= "/proc",}; int pid_ns_prepare_proc(struct pid_namespace *ns){	struct proc_fs_context *ctx;	struct fs_context *fc;	struct vfsmount *mnt; 	fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT);	if (IS_ERR(fc))		return PTR_ERR(fc); 	if (fc->user_ns != ns->user_ns) {		put_user_ns(fc->user_ns);		fc->user_ns = get_user_ns(ns->user_ns);	} 	ctx = fc->fs_private;	if (ctx->pid_ns != ns) {		put_pid_ns(ctx->pid_ns);		get_pid_ns(ns);		ctx->pid_ns = ns;	} 	mnt = fc_mount(fc);	put_fs_context(fc);	if (IS_ERR(mnt))		return PTR_ERR(mnt); 	ns->proc_mnt = mnt;	return 0;} void pid_ns_release_proc(struct pid_namespace *ns){	kern_unmount(ns->proc_mnt);}