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cgroupns: Add a limit on the number of cgroup namespaces

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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-08-08 14:25:30 -05:00
parent aba3566163
commit d08311dd6f
4 changed files with 21 additions and 0 deletions
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1
include/linux/cgroup.h
View file

@ -621,6 +621,7 @@ struct cgroup_namespace {
atomic_t count;
struct ns_common ns;
struct user_namespace *user_ns;
struct ucounts *ucounts;
struct css_set *root_cset;
};

1
include/linux/user_namespace.h
View file

@ -29,6 +29,7 @@ enum ucount_type {
UCOUNT_PID_NAMESPACES,
UCOUNT_UTS_NAMESPACES,
UCOUNT_IPC_NAMESPACES,
UCOUNT_CGROUP_NAMESPACES,
UCOUNT_COUNTS,
};

18
kernel/cgroup.c
View file

@ -6295,6 +6295,16 @@ void cgroup_sk_free(struct sock_cgroup_data *skcd)
/* cgroup namespaces */
static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES);
}
static void dec_cgroup_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES);
}
static struct cgroup_namespace *alloc_cgroup_ns(void)
{
struct cgroup_namespace *new_ns;
@ -6316,6 +6326,7 @@ static struct cgroup_namespace *alloc_cgroup_ns(void)
void free_cgroup_ns(struct cgroup_namespace *ns)
{
put_css_set(ns->root_cset);
dec_cgroup_namespaces(ns->ucounts);
put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns);
kfree(ns);
@ -6327,6 +6338,7 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
struct cgroup_namespace *old_ns)
{
struct cgroup_namespace *new_ns;
struct ucounts *ucounts;
struct css_set *cset;
BUG_ON(!old_ns);
@ -6340,6 +6352,10 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
if (!ns_capable(user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
ucounts = inc_cgroup_namespaces(user_ns);
if (!ucounts)
return ERR_PTR(-ENFILE);
/* It is not safe to take cgroup_mutex here */
spin_lock_irq(&css_set_lock);
cset = task_css_set(current);
@ -6349,10 +6365,12 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
new_ns = alloc_cgroup_ns();
if (IS_ERR(new_ns)) {
put_css_set(cset);
dec_cgroup_namespaces(ucounts);
return new_ns;
}
new_ns->user_ns = get_user_ns(user_ns);
new_ns->ucounts = ucounts;
new_ns->root_cset = cset;
return new_ns;

1
kernel/ucount.c
View file

@ -71,6 +71,7 @@ static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_pid_namespaces"),
UCOUNT_ENTRY("max_uts_namespaces"),
UCOUNT_ENTRY("max_ipc_namespaces"),
UCOUNT_ENTRY("max_cgroup_namespaces"),
{ }
};
#endif /* CONFIG_SYSCTL */