1 files changed, 377 insertions, 0 deletions
diff --git a/kernel/ucount.c b/kernel/ucount.c
new file mode 100644
index 0000000000..4aa6166cb8
--- /dev/null
+++ b/kernel/ucount.c
@@ -0,0 +1,377 @@
+// 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>
+
+struct ucounts init_ucounts = {
+	.ns    = &init_user_ns,
+	.uid   = GLOBAL_ROOT_UID,
+	.count = ATOMIC_INIT(1),
+};
+
+#define UCOUNTS_HASHTABLE_BITS 10
+static 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_SYSCTL
+static 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,
+};
+
+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 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
+	{ }
+};
+#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 + 1);
+	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
+	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 void hlist_add_ucounts(struct ucounts *ucounts)
+{
+	struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid);
+	spin_lock_irq(&ucounts_lock);
+	hlist_add_head(&ucounts->node, hashent);
+	spin_unlock_irq(&ucounts_lock);
+}
+
+static inline bool get_ucounts_or_wrap(struct ucounts *ucounts)
+{
+	/* Returns true on a successful get, false if the count wraps. */
+	return !atomic_add_negative(1, &ucounts->count);
+}
+
+struct ucounts *get_ucounts(struct ucounts *ucounts)
+{
+	if (!get_ucounts_or_wrap(ucounts)) {
+		put_ucounts(ucounts);
+		ucounts = NULL;
+	}
+	return ucounts;
+}
+
+struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
+{
+	struct hlist_head *hashent = ucounts_hashentry(ns, uid);
+	struct ucounts *ucounts, *new;
+	bool wrapped;
+
+	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;
+		atomic_set(&new->count, 1);
+
+		spin_lock_irq(&ucounts_lock);
+		ucounts = find_ucounts(ns, uid, hashent);
+		if (ucounts) {
+			kfree(new);
+		} else {
+			hlist_add_head(&new->node, hashent);
+			get_user_ns(new->ns);
+			spin_unlock_irq(&ucounts_lock);
+			return new;
+		}
+	}
+	wrapped = !get_ucounts_or_wrap(ucounts);
+	spin_unlock_irq(&ucounts_lock);
+	if (wrapped) {
+		put_ucounts(ucounts);
+		return NULL;
+	}
+	return ucounts;
+}
+
+void put_ucounts(struct ucounts *ucounts)
+{
+	unsigned long flags;
+
+	if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) {
+		hlist_del_init(&ucounts->node);
+		spin_unlock_irqrestore(&ucounts_lock, flags);
+		put_user_ns(ucounts->ns);
+		kfree(ucounts);
+	}
+}
+
+static inline bool atomic_long_inc_below(atomic_long_t *v, int u)
+{
+	long c, old;
+	c = atomic_long_read(v);
+	for (;;) {
+		if (unlikely(c >= u))
+			return false;
+		old = atomic_long_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 = 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;
+}
+
+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);
+}
+
+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)
+{
+	/* 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 unwind;
+		if (iter == ucounts)
+			ret = new;
+		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);
+unwind:
+	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);