userns: Generalize the user namespace count into ucount
The same kind of recursive sane default limit and policy
countrol that has been implemented for the user namespace
is desirable for the other namespaces, so generalize
the user namespace refernce count into a ucount.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 826de7a1..9b676ea 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -23,6 +23,12 @@
#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
struct ucounts;
+
+enum ucount_type {
+ UCOUNT_USER_NAMESPACES,
+ UCOUNT_COUNTS,
+};
+
struct user_namespace {
struct uid_gid_map uid_map;
struct uid_gid_map gid_map;
@@ -46,7 +52,7 @@
struct ctl_table_header *sysctls;
#endif
struct ucounts *ucounts;
- int max_user_namespaces;
+ int ucount_max[UCOUNT_COUNTS];
};
struct ucounts {
@@ -54,15 +60,15 @@
struct user_namespace *ns;
kuid_t uid;
atomic_t count;
- atomic_t user_namespaces;
+ atomic_t ucount[UCOUNT_COUNTS];
};
extern struct user_namespace init_user_ns;
bool setup_userns_sysctls(struct user_namespace *ns);
void retire_userns_sysctls(struct user_namespace *ns);
-struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid);
-void dec_user_namespaces(struct ucounts *ucounts);
+struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
+void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
#ifdef CONFIG_USER_NS
diff --git a/kernel/fork.c b/kernel/fork.c
index d8cde53..3cb4853 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -302,6 +302,7 @@
void __init fork_init(void)
{
+ int i;
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
@@ -322,7 +323,9 @@
init_task.signal->rlim[RLIMIT_SIGPENDING] =
init_task.signal->rlim[RLIMIT_NPROC];
- init_user_ns.max_user_namespaces = max_threads/2;
+ for (i = 0; i < UCOUNT_COUNTS; i++) {
+ init_user_ns.ucount_max[i] = max_threads/2;
+ }
}
int __weak arch_dup_task_struct(struct task_struct *dst,
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 33c4187..0f9ab3b 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -57,16 +57,17 @@
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[] = {
- {
- .procname = "max_user_namespaces",
- .data = &init_user_ns.max_user_namespaces,
- .maxlen = sizeof(init_user_ns.max_user_namespaces),
- .mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = &zero,
- .extra2 = &int_max,
- },
+ UCOUNT_ENTRY("max_user_namespaces"),
{ }
};
#endif /* CONFIG_SYSCTL */
@@ -78,8 +79,10 @@
setup_sysctl_set(&ns->set, &set_root, set_is_seen);
tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
if (tbl) {
- tbl[0].data = &ns->max_user_namespaces;
-
+ 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) {
@@ -172,7 +175,8 @@
}
}
-struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
+struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
+ enum ucount_type type)
{
struct ucounts *ucounts, *iter, *bad;
struct user_namespace *tns;
@@ -180,31 +184,30 @@
for (iter = ucounts; iter; iter = tns->ucounts) {
int max;
tns = iter->ns;
- max = READ_ONCE(tns->max_user_namespaces);
- if (!atomic_inc_below(&iter->user_namespaces, max))
+ 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->user_namespaces);
+ atomic_dec(&iter->ucount[type]);
put_ucounts(ucounts);
return NULL;
}
-void dec_user_namespaces(struct ucounts *ucounts)
+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->user_namespaces);
+ 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
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 58c67e5..0edafe3 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -31,6 +31,16 @@
struct uid_gid_map *map);
static void free_user_ns(struct work_struct *work);
+static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
+{
+ return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
+}
+
+static void dec_user_namespaces(struct ucounts *ucounts)
+{
+ return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
+}
+
static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
{
/* Start with the same capabilities as init but useless for doing
@@ -64,7 +74,7 @@
kuid_t owner = new->euid;
kgid_t group = new->egid;
struct ucounts *ucounts;
- int ret;
+ int ret, i;
ret = -EUSERS;
if (parent_ns->level > 32)
@@ -110,7 +120,9 @@
ns->owner = owner;
ns->group = group;
INIT_WORK(&ns->work, free_user_ns);
- ns->max_user_namespaces = INT_MAX;
+ for (i = 0; i < UCOUNT_COUNTS; i++) {
+ ns->ucount_max[i] = INT_MAX;
+ }
ns->ucounts = ucounts;
/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */