summaryrefslogtreecommitdiff
path: root/kernel/ucount.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/ucount.c')
-rw-r--r--kernel/ucount.c235
1 files changed, 235 insertions, 0 deletions
diff --git a/kernel/ucount.c b/kernel/ucount.c
new file mode 100644
index 000000000000..9d20d5dd298a
--- /dev/null
+++ b/kernel/ucount.c
@@ -0,0 +1,235 @@
+/*
+ * 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/hash.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"),
+ { }
+};
+#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(&ucounts_lock);
+ ucounts = find_ucounts(ns, uid, hashent);
+ if (!ucounts) {
+ spin_unlock(&ucounts_lock);
+
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return NULL;
+
+ new->ns = ns;
+ new->uid = uid;
+ atomic_set(&new->count, 0);
+
+ spin_lock(&ucounts_lock);
+ ucounts = find_ucounts(ns, uid, hashent);
+ if (ucounts) {
+ kfree(new);
+ } else {
+ hlist_add_head(&new->node, hashent);
+ ucounts = new;
+ }
+ }
+ if (!atomic_add_unless(&ucounts->count, 1, INT_MAX))
+ ucounts = NULL;
+ spin_unlock(&ucounts_lock);
+ return ucounts;
+}
+
+static void put_ucounts(struct ucounts *ucounts)
+{
+ if (atomic_dec_and_test(&ucounts->count)) {
+ spin_lock(&ucounts_lock);
+ hlist_del_init(&ucounts->node);
+ spin_unlock(&ucounts_lock);
+
+ 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);
+ BUG_ON(!user_header);
+ BUG_ON(!setup_userns_sysctls(&init_user_ns));
+#endif
+ return 0;
+}
+subsys_initcall(user_namespace_sysctl_init);
+
+