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pidns: Add a limit on the number of pid 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 14:08:36 -05:00
parent 25f9c0817c
commit f333c700c6
4 changed files with 24 additions and 4 deletions
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1
include/linux/pid_namespace.h
View file

@ -40,6 +40,7 @@ struct pid_namespace {
struct fs_pin *bacct; struct fs_pin *bacct;
#endif #endif
struct user_namespace *user_ns; struct user_namespace *user_ns;
struct ucounts *ucounts;
struct work_struct proc_work; struct work_struct proc_work;
kgid_t pid_gid; kgid_t pid_gid;
int hide_pid; int hide_pid;

1
include/linux/user_namespace.h
View file

@ -26,6 +26,7 @@ struct ucounts;
enum ucount_type { enum ucount_type {
UCOUNT_USER_NAMESPACES, UCOUNT_USER_NAMESPACES,
UCOUNT_PID_NAMESPACES,
UCOUNT_COUNTS, UCOUNT_COUNTS,
}; };

23
kernel/pid_namespace.c
View file

@ -79,23 +79,36 @@ static void proc_cleanup_work(struct work_struct *work)
/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
#define MAX_PID_NS_LEVEL 32 #define MAX_PID_NS_LEVEL 32
static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
}
static void dec_pid_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
}
static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns, static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
struct pid_namespace *parent_pid_ns) struct pid_namespace *parent_pid_ns)
{ {
struct pid_namespace *ns; struct pid_namespace *ns;
unsigned int level = parent_pid_ns->level + 1; unsigned int level = parent_pid_ns->level + 1;
struct ucounts *ucounts;
int i; int i;
int err; int err;
if (level > MAX_PID_NS_LEVEL) {
err = -EINVAL; err = -EINVAL;
if (level > MAX_PID_NS_LEVEL)
goto out;
ucounts = inc_pid_namespaces(user_ns);
if (!ucounts)
goto out; goto out;
}
err = -ENOMEM; err = -ENOMEM;
ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
if (ns == NULL) if (ns == NULL)
goto out; goto out_dec;
ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!ns->pidmap[0].page) if (!ns->pidmap[0].page)
@ -114,6 +127,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
ns->level = level; ns->level = level;
ns->parent = get_pid_ns(parent_pid_ns); ns->parent = get_pid_ns(parent_pid_ns);
ns->user_ns = get_user_ns(user_ns); ns->user_ns = get_user_ns(user_ns);
ns->ucounts = ucounts;
ns->nr_hashed = PIDNS_HASH_ADDING; ns->nr_hashed = PIDNS_HASH_ADDING;
INIT_WORK(&ns->proc_work, proc_cleanup_work); INIT_WORK(&ns->proc_work, proc_cleanup_work);
@ -129,6 +143,8 @@ out_free_map:
kfree(ns->pidmap[0].page); kfree(ns->pidmap[0].page);
out_free: out_free:
kmem_cache_free(pid_ns_cachep, ns); kmem_cache_free(pid_ns_cachep, ns);
out_dec:
dec_pid_namespaces(ucounts);
out: out:
return ERR_PTR(err); return ERR_PTR(err);
} }
@ -146,6 +162,7 @@ static void destroy_pid_namespace(struct pid_namespace *ns)
ns_free_inum(&ns->ns); ns_free_inum(&ns->ns);
for (i = 0; i < PIDMAP_ENTRIES; i++) for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page); kfree(ns->pidmap[i].page);
dec_pid_namespaces(ns->ucounts);
put_user_ns(ns->user_ns); put_user_ns(ns->user_ns);
call_rcu(&ns->rcu, delayed_free_pidns); call_rcu(&ns->rcu, delayed_free_pidns);
} }

1
kernel/ucount.c
View file

@ -68,6 +68,7 @@ static int int_max = INT_MAX;
} }
static struct ctl_table user_table[] = { static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_user_namespaces"), UCOUNT_ENTRY("max_user_namespaces"),
UCOUNT_ENTRY("max_pid_namespaces"),
{ } { }
}; };
#endif /* CONFIG_SYSCTL */ #endif /* CONFIG_SYSCTL */