// SPDX-License-Identifier: GPL-2.0/* *  linux/fs/proc/root.c * *  Copyright (C) 1991, 1992 Linus Torvalds * *  proc root directory handling functions */#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;	enum proc_hidepid	hidepid;	int			gid;	enum proc_pidonly	pidonly;}; enum proc_param {	Opt_gid,	Opt_hidepid,	Opt_subset,	Opt_pidns,}; static const struct fs_parameter_spec proc_fs_parameters[] = {	fsparam_u32("gid",		Opt_gid),	fsparam_string("hidepid",	Opt_hidepid),	fsparam_string("subset",	Opt_subset),	fsparam_file_or_string("pidns",	Opt_pidns),	{}}; static inline int valid_hidepid(unsigned int value){	return (value == HIDEPID_OFF ||		value == HIDEPID_NO_ACCESS ||		value == HIDEPID_INVISIBLE ||		value == HIDEPID_NOT_PTRACEABLE);} static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param){	struct proc_fs_context *ctx = fc->fs_private;	struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);	struct fs_parse_result result;	int base = (unsigned long)hidepid_u32_spec.data; 	if (param->type != fs_value_is_string)		return invalf(fc, "proc: unexpected type of hidepid value\n"); 	if (!kstrtouint(param->string, base, &result.uint_32)) {		if (!valid_hidepid(result.uint_32))			return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);		ctx->hidepid = result.uint_32;		return 0;	} 	if (!strcmp(param->string, "off"))		ctx->hidepid = HIDEPID_OFF;	else if (!strcmp(param->string, "noaccess"))		ctx->hidepid = HIDEPID_NO_ACCESS;	else if (!strcmp(param->string, "invisible"))		ctx->hidepid = HIDEPID_INVISIBLE;	else if (!strcmp(param->string, "ptraceable"))		ctx->hidepid = HIDEPID_NOT_PTRACEABLE;	else		return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); 	return 0;} static int proc_parse_subset_param(struct fs_context *fc, char *value){	struct proc_fs_context *ctx = fc->fs_private; 	while (value) {		char *ptr = strchr(value, ','); 		if (ptr != NULL)			*ptr++ = '\0'; 		if (*value != '\0') {			if (!strcmp(value, "pid")) {				ctx->pidonly = PROC_PIDONLY_ON;			} else {				return invalf(fc, "proc: unsupported subset option - %s\n", value);			}		}		value = ptr;	} 	return 0;} #ifdef CONFIG_PID_NSstatic int proc_parse_pidns_param(struct fs_context *fc,				  struct fs_parameter *param,				  struct fs_parse_result *result){	struct proc_fs_context *ctx = fc->fs_private;	struct pid_namespace *target, *active = task_active_pid_ns(current);	struct ns_common *ns;	struct file *ns_filp __free(fput) = NULL; 	switch (param->type) {	case fs_value_is_file:		/* came through fsconfig, steal the file reference */		ns_filp = no_free_ptr(param->file);		break;	case fs_value_is_string:		ns_filp = filp_open(param->string, O_RDONLY, 0);		break;	default:		WARN_ON_ONCE(true);		break;	}	if (!ns_filp)		ns_filp = ERR_PTR(-EBADF);	if (IS_ERR(ns_filp)) {		errorfc(fc, "could not get file from pidns argument");		return PTR_ERR(ns_filp);	} 	if (!proc_ns_file(ns_filp))		return invalfc(fc, "pidns argument is not an nsfs file");	ns = get_proc_ns(file_inode(ns_filp));	if (ns->ns_type != CLONE_NEWPID)		return invalfc(fc, "pidns argument is not a pidns file");	target = container_of(ns, struct pid_namespace, ns); 	/*	 * pidns= is shorthand for joining the pidns to get a fsopen fd, so the	 * permission model should be the same as pidns_install().	 */	if (!ns_capable(target->user_ns, CAP_SYS_ADMIN)) {		errorfc(fc, "insufficient permissions to set pidns");		return -EPERM;	}	if (!pidns_is_ancestor(target, active))		return invalfc(fc, "cannot set pidns to non-descendant pidns"); 	put_pid_ns(ctx->pid_ns);	ctx->pid_ns = get_pid_ns(target);	put_user_ns(fc->user_ns);	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);	return 0;}#endif /* CONFIG_PID_NS */ 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, err; 	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:		err = proc_parse_hidepid_param(fc, param);		if (err)			return err;		break; 	case Opt_subset:		err = proc_parse_subset_param(fc, param->string);		if (err)			return err;		break; 	case Opt_pidns:#ifdef CONFIG_PID_NS		/*		 * We would have to RCU-protect every proc_pid_ns() or		 * proc_sb_info() access if we allowed this to be reconfigured		 * for an existing procfs instance. Luckily, procfs instances		 * are cheap to create, and mount-beneath would let you		 * atomically replace an instance even with overmounts.		 */		if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {			errorfc(fc, "cannot reconfigure pidns for existing procfs");			return -EBUSY;		}		err = proc_parse_pidns_param(fc, param, &result);		if (err)			return err;		break;#else		errorfc(fc, "pidns mount flag not supported on this system");		return -EOPNOTSUPP;#endif 	default:		return -EINVAL;	} 	ctx->mask |= 1 << opt;	return 0;} static int proc_apply_options(struct proc_fs_info *fs_info,			       struct fs_context *fc,			       struct user_namespace *user_ns){	struct proc_fs_context *ctx = fc->fs_private; 	if ((ctx->mask & (1 << Opt_subset)) &&	    fc->purpose == FS_CONTEXT_FOR_RECONFIGURE &&	    ctx->pidonly != fs_info->pidonly)		return invalf(fc, "proc: subset=pid cannot be changed\n"); 	if (ctx->mask & (1 << Opt_gid))		fs_info->pid_gid = make_kgid(user_ns, ctx->gid);	if (ctx->mask & (1 << Opt_hidepid))		fs_info->hide_pid = ctx->hidepid;	if (ctx->mask & (1 << Opt_subset))		fs_info->pidonly = ctx->pidonly;	if (ctx->mask & (1 << Opt_pidns) &&	    !WARN_ON_ONCE(fc->purpose == FS_CONTEXT_FOR_RECONFIGURE)) {		put_pid_ns(fs_info->pid_ns);		fs_info->pid_ns = get_pid_ns(ctx->pid_ns);	}	return 0;} static int proc_fill_super(struct super_block *s, struct fs_context *fc){	struct proc_fs_context *ctx = fc->fs_private;	struct inode *root_inode;	struct proc_fs_info *fs_info;	int ret; 	fs_info = kzalloc_obj(*fs_info);	if (!fs_info)		return -ENOMEM; 	fs_info->pid_ns = get_pid_ns(ctx->pid_ns);	fs_info->mounter_cred = get_cred(fc->cred);	ret = proc_apply_options(fs_info, fc, current_user_ns());	if (ret)		return ret; 	/* User space would break if executables or devices appear on proc */	s->s_iflags |= 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;	s->s_fs_info = fs_info; 	if (fs_info->pidonly == PROC_PIDONLY_ON)		s->s_iflags |= SB_I_RESTRICTED_VARIANT; 	/*	 * 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 proc_fs_info *fs_info = proc_sb_info(sb); 	sync_filesystem(sb); 	return proc_apply_options(fs_info, fc, current_user_ns());} static int proc_get_tree(struct fs_context *fc){	return get_tree_nodev(fc, proc_fill_super);} static void proc_fs_context_free(struct fs_context *fc){	struct proc_fs_context *ctx = fc->fs_private; 	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_obj(struct proc_fs_context);	if (!ctx)		return -ENOMEM; 	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));	put_user_ns(fc->user_ns);	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);	fc->fs_private = ctx;	fc->ops = &proc_fs_context_ops;	return 0;} static void proc_kill_sb(struct super_block *sb){	struct proc_fs_info *fs_info = proc_sb_info(sb); 	kill_anon_super(sb);	if (fs_info) {		put_pid_ns(fs_info->pid_ns);		put_cred(fs_info->mounter_cred);		kfree_rcu(fs_info, rcu);	}} 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 | FS_USERNS_MOUNT_RESTRICTED | FS_DISALLOW_NOTIFY_PERM,}; 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(); 	/*	 * Last things last. It is not like userspace processes eager	 * to open /proc files exist at this point but register last	 * anyway.	 */	register_filesystem(&proc_fs_type);} static int proc_root_getattr(struct mnt_idmap *idmap,			     const struct path *path, struct kstat *stat,			     u32 request_mask, unsigned int query_flags){	generic_fillattr(&nop_mnt_idmap, request_mask, 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	= PROCFS_ROOT_INO,	.namelen	= 5,	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,	.nlink		= 2,	.refcnt		= REFCOUNT_INIT(1),	.proc_iops	= &proc_root_inode_operations,	.proc_dir_ops	= &proc_root_operations,	.parent		= &proc_root,	.subdir		= RB_ROOT,	.name		= "/proc",};