Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 246 insertions, 0 deletions

diff --git a/kernel/ucount.c b/kernel/ucount.c
new file mode 100644
index 000000000..f48d1b637
--- /dev/null
+++ b/kernel/ucount.c
@@ -0,0 +1,246 @@
+/*
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2 of the
+ *  License.
+ */
+
+#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 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 int zero = 0;
+static int int_max = INT_MAX;
+#define UCOUNT_ENTRY(name)				\
+	{						\
+		.procname	= name,			\
+		.maxlen		= sizeof(int),		\
+		.mode		= 0644,			\
+		.proc_handler	= proc_dointvec_minmax,	\
+		.extra1		= &zero,		\
+		.extra2		= &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);