// SPDX-License-Identifier: GPL-2.0-only #include <linux/stat.h>#include <linux/sysctl.h>#include <linux/slab.h>#include <linux/cred.h>#include <linux/hash.h>#include <linux/kmemleak.h>#include <linux/user_namespace.h> #define UCOUNTS_HASHTABLE_BITS 10static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];static DEFINE_SPINLOCK(ucounts_lock); #define ucounts_hashfn(ns, uid)						\	hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \		  UCOUNTS_HASHTABLE_BITS)#define ucounts_hashentry(ns, uid)	\	(ucounts_hashtable + ucounts_hashfn(ns, uid))  #ifdef CONFIG_SYSCTLstatic struct ctl_table_set *set_lookup(struct ctl_table_root *root){	return &current_user_ns()->set;} static int set_is_seen(struct ctl_table_set *set){	return &current_user_ns()->set == set;} static int set_permissions(struct ctl_table_header *head,				  struct ctl_table *table){	struct user_namespace *user_ns =		container_of(head->set, struct user_namespace, set);	int mode; 	/* Allow users with CAP_SYS_RESOURCE unrestrained access */	if (ns_capable(user_ns, CAP_SYS_RESOURCE))		mode = (table->mode & S_IRWXU) >> 6;	else	/* Allow all others at most read-only access */		mode = table->mode & S_IROTH;	return (mode << 6) | (mode << 3) | mode;} static struct ctl_table_root set_root = {	.lookup = set_lookup,	.permissions = set_permissions,}; #define UCOUNT_ENTRY(name)				\	{						\		.procname	= name,			\		.maxlen		= sizeof(int),		\		.mode		= 0644,			\		.proc_handler	= proc_dointvec_minmax,	\		.extra1		= SYSCTL_ZERO,		\		.extra2		= SYSCTL_INT_MAX,	\	}static struct ctl_table user_table[] = {	UCOUNT_ENTRY("max_user_namespaces"),	UCOUNT_ENTRY("max_pid_namespaces"),	UCOUNT_ENTRY("max_uts_namespaces"),	UCOUNT_ENTRY("max_ipc_namespaces"),	UCOUNT_ENTRY("max_net_namespaces"),	UCOUNT_ENTRY("max_mnt_namespaces"),	UCOUNT_ENTRY("max_cgroup_namespaces"),#ifdef CONFIG_INOTIFY_USER	UCOUNT_ENTRY("max_inotify_instances"),	UCOUNT_ENTRY("max_inotify_watches"),#endif	{ }};#endif /* CONFIG_SYSCTL */ bool setup_userns_sysctls(struct user_namespace *ns){#ifdef CONFIG_SYSCTL	struct ctl_table *tbl;	setup_sysctl_set(&ns->set, &set_root, set_is_seen);	tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);	if (tbl) {		int i;		for (i = 0; i < UCOUNT_COUNTS; i++) {			tbl[i].data = &ns->ucount_max[i];		}		ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);	}	if (!ns->sysctls) {		kfree(tbl);		retire_sysctl_set(&ns->set);		return false;	}#endif	return true;} void retire_userns_sysctls(struct user_namespace *ns){#ifdef CONFIG_SYSCTL	struct ctl_table *tbl; 	tbl = ns->sysctls->ctl_table_arg;	unregister_sysctl_table(ns->sysctls);	retire_sysctl_set(&ns->set);	kfree(tbl);#endif} static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent){	struct ucounts *ucounts; 	hlist_for_each_entry(ucounts, hashent, node) {		if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns))			return ucounts;	}	return NULL;} static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid){	struct hlist_head *hashent = ucounts_hashentry(ns, uid);	struct ucounts *ucounts, *new; 	spin_lock_irq(&ucounts_lock);	ucounts = find_ucounts(ns, uid, hashent);	if (!ucounts) {		spin_unlock_irq(&ucounts_lock); 		new = kzalloc(sizeof(*new), GFP_KERNEL);		if (!new)			return NULL; 		new->ns = ns;		new->uid = uid;		new->count = 0; 		spin_lock_irq(&ucounts_lock);		ucounts = find_ucounts(ns, uid, hashent);		if (ucounts) {			kfree(new);		} else {			hlist_add_head(&new->node, hashent);			ucounts = new;		}	}	if (ucounts->count == INT_MAX)		ucounts = NULL;	else		ucounts->count += 1;	spin_unlock_irq(&ucounts_lock);	return ucounts;} static void put_ucounts(struct ucounts *ucounts){	unsigned long flags; 	spin_lock_irqsave(&ucounts_lock, flags);	ucounts->count -= 1;	if (!ucounts->count)		hlist_del_init(&ucounts->node);	else		ucounts = NULL;	spin_unlock_irqrestore(&ucounts_lock, flags); 	kfree(ucounts);} static inline bool atomic_inc_below(atomic_t *v, int u){	int c, old;	c = atomic_read(v);	for (;;) {		if (unlikely(c >= u))			return false;		old = atomic_cmpxchg(v, c, c+1);		if (likely(old == c))			return true;		c = old;	}} struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,			   enum ucount_type type){	struct ucounts *ucounts, *iter, *bad;	struct user_namespace *tns;	ucounts = get_ucounts(ns, uid);	for (iter = ucounts; iter; iter = tns->ucounts) {		int max;		tns = iter->ns;		max = READ_ONCE(tns->ucount_max[type]);		if (!atomic_inc_below(&iter->ucount[type], max))			goto fail;	}	return ucounts;fail:	bad = iter;	for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)		atomic_dec(&iter->ucount[type]); 	put_ucounts(ucounts);	return NULL;} void dec_ucount(struct ucounts *ucounts, enum ucount_type type){	struct ucounts *iter;	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		int dec = atomic_dec_if_positive(&iter->ucount[type]);		WARN_ON_ONCE(dec < 0);	}	put_ucounts(ucounts);} static __init int user_namespace_sysctl_init(void){#ifdef CONFIG_SYSCTL	static struct ctl_table_header *user_header;	static struct ctl_table empty[1];	/*	 * It is necessary to register the user directory in the	 * default set so that registrations in the child sets work	 * properly.	 */	user_header = register_sysctl("user", empty);	kmemleak_ignore(user_header);	BUG_ON(!user_header);	BUG_ON(!setup_userns_sysctls(&init_user_ns));#endif	return 0;}subsys_initcall(user_namespace_sysctl_init);