// 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/export.h>#include <linux/hash.h>#include <linux/kmemleak.h>#include <linux/user_namespace.h> struct ucounts init_ucounts = {	.ns    = &init_user_ns,	.uid   = GLOBAL_ROOT_UID,	.count = RCUREF_INIT(1),}; #define UCOUNTS_HASHTABLE_BITS 10#define UCOUNTS_HASHTABLE_ENTRIES (1 << UCOUNTS_HASHTABLE_BITS)static struct hlist_nulls_head ucounts_hashtable[UCOUNTS_HASHTABLE_ENTRIES] = {	[0 ... UCOUNTS_HASHTABLE_ENTRIES - 1] = HLIST_NULLS_HEAD_INIT(0)};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,			   const 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_noaudit(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,}; static long ue_zero = 0;static long ue_int_max = INT_MAX; #define UCOUNT_ENTRY(name)					\	{							\		.procname	= name,				\		.maxlen		= sizeof(long),			\		.mode		= 0644,				\		.proc_handler	= proc_doulongvec_minmax,	\		.extra1		= &ue_zero,			\		.extra2		= &ue_int_max,			\	}static const 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"),	UCOUNT_ENTRY("max_time_namespaces"),#ifdef CONFIG_INOTIFY_USER	UCOUNT_ENTRY("max_inotify_instances"),	UCOUNT_ENTRY("max_inotify_watches"),#endif#ifdef CONFIG_FANOTIFY	UCOUNT_ENTRY("max_fanotify_groups"),	UCOUNT_ENTRY("max_fanotify_marks"),#endif#if IS_ENABLED(CONFIG_BINFMT_MISC)	UCOUNT_ENTRY("max_binfmt_misc_interpreters"),#endif};#endif /* CONFIG_SYSCTL */ bool setup_userns_sysctls(struct user_namespace *ns){#ifdef CONFIG_SYSCTL	struct ctl_table *tbl; 	BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS);	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,						      ARRAY_SIZE(user_table));	}	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	const 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_nulls_head *hashent){	struct ucounts *ucounts;	struct hlist_nulls_node *pos; 	guard(rcu)();	hlist_nulls_for_each_entry_rcu(ucounts, pos, hashent, node) {		if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) {			if (rcuref_get(&ucounts->count))				return ucounts;		}	}	return NULL;} static void hlist_add_ucounts(struct ucounts *ucounts){	struct hlist_nulls_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); 	spin_lock_irq(&ucounts_lock);	hlist_nulls_add_head_rcu(&ucounts->node, hashent);	spin_unlock_irq(&ucounts_lock);} struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid){	struct hlist_nulls_head *hashent = ucounts_hashentry(ns, uid);	struct ucounts *ucounts, *new; 	ucounts = find_ucounts(ns, uid, hashent);	if (ucounts)		return ucounts; 	new = kzalloc_obj(*new);	if (!new)		return NULL; 	new->ns = ns;	new->uid = uid;	rcuref_init(&new->count, 1); 	spin_lock_irq(&ucounts_lock);	ucounts = find_ucounts(ns, uid, hashent);	if (ucounts) {		spin_unlock_irq(&ucounts_lock);		kfree(new);		return ucounts;	} 	hlist_nulls_add_head_rcu(&new->node, hashent);	get_user_ns(new->ns);	spin_unlock_irq(&ucounts_lock);	return new;} void put_ucounts(struct ucounts *ucounts){	unsigned long flags; 	if (rcuref_put(&ucounts->count)) {		spin_lock_irqsave(&ucounts_lock, flags);		hlist_nulls_del_rcu(&ucounts->node);		spin_unlock_irqrestore(&ucounts_lock, flags); 		put_user_ns(ucounts->ns);		kfree_rcu(ucounts, rcu);	}} static inline bool atomic_long_inc_below(atomic_long_t *v, long u){	long c = atomic_long_read(v); 	do {		if (unlikely(c >= u))			return false;	} while (!atomic_long_try_cmpxchg(v, &c, c+1)); 	return true;} 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 = alloc_ucounts(ns, uid);	for (iter = ucounts; iter; iter = tns->ucounts) {		long max;		tns = iter->ns;		max = READ_ONCE(tns->ucount_max[type]);		if (!atomic_long_inc_below(&iter->ucount[type], max))			goto fail;	}	return ucounts;fail:	bad = iter;	for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)		atomic_long_dec(&iter->ucount[type]); 	put_ucounts(ucounts);	return NULL;}EXPORT_SYMBOL_FOR_MODULES(inc_ucount, "binfmt_misc"); void dec_ucount(struct ucounts *ucounts, enum ucount_type type){	struct ucounts *iter;	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		long dec = atomic_long_dec_if_positive(&iter->ucount[type]);		WARN_ON_ONCE(dec < 0);	}	put_ucounts(ucounts);}EXPORT_SYMBOL_FOR_MODULES(dec_ucount, "binfmt_misc"); long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v){	struct ucounts *iter;	long max = LONG_MAX;	long ret = 0; 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		long new = atomic_long_add_return(v, &iter->rlimit[type]);		if (new < 0 || new > max)			ret = LONG_MAX;		else if (iter == ucounts)			ret = new;		max = get_userns_rlimit_max(iter->ns, type);	}	return ret;} bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v){	struct ucounts *iter;	long new = -1; /* Silence compiler warning */	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		long dec = atomic_long_sub_return(v, &iter->rlimit[type]);		WARN_ON_ONCE(dec < 0);		if (iter == ucounts)			new = dec;	}	return (new == 0);} static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,				struct ucounts *last, enum rlimit_type type){	struct ucounts *iter, *next;	for (iter = ucounts; iter != last; iter = next) {		long dec = atomic_long_sub_return(1, &iter->rlimit[type]);		WARN_ON_ONCE(dec < 0);		next = iter->ns->ucounts;		if (dec == 0)			put_ucounts(iter);	}} void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type){	do_dec_rlimit_put_ucounts(ucounts, NULL, type);} long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type,			    bool override_rlimit){	/* Caller must hold a reference to ucounts */	struct ucounts *iter;	long max = LONG_MAX;	long dec, ret = 0; 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		long new = atomic_long_add_return(1, &iter->rlimit[type]);		if (new < 0 || new > max)			goto dec_unwind;		if (iter == ucounts)			ret = new;		if (!override_rlimit)			max = get_userns_rlimit_max(iter->ns, type);		/*		 * Grab an extra ucount reference for the caller when		 * the rlimit count was previously 0.		 */		if (new != 1)			continue;		if (!get_ucounts(iter))			goto dec_unwind;	}	return ret;dec_unwind:	dec = atomic_long_sub_return(1, &iter->rlimit[type]);	WARN_ON_ONCE(dec < 0);	do_dec_rlimit_put_ucounts(ucounts, iter, type);	return 0;} bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long rlimit){	struct ucounts *iter;	long max = rlimit;	if (rlimit > LONG_MAX)		max = LONG_MAX;	for (iter = ucounts; iter; iter = iter->ns->ucounts) {		long val = get_rlimit_value(iter, type);		if (val < 0 || val > max)			return true;		max = get_userns_rlimit_max(iter->ns, type);	}	return false;} 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_sz("user", empty, 0);	kmemleak_ignore(user_header);	BUG_ON(!user_header);	BUG_ON(!setup_userns_sysctls(&init_user_ns));#endif	hlist_add_ucounts(&init_ucounts);	inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1);	return 0;}subsys_initcall(user_namespace_sysctl_init);