152 lines
4.5 KiB
Diff
152 lines
4.5 KiB
Diff
From d50977b164e708bf523a35ef53315355528c3ca6 Mon Sep 17 00:00:00 2001
|
|
From: "Jan Alexander Steffens (heftig)" <jan.steffens@gmail.com>
|
|
Date: Mon, 16 Sep 2019 04:53:20 +0200
|
|
Subject: [PATCH] ZEN: Add sysctl and CONFIG to disallow unprivileged
|
|
CLONE_NEWUSER
|
|
|
|
Our default behavior continues to match the vanilla kernel.
|
|
---
|
|
include/linux/user_namespace.h | 4 ++++
|
|
init/Kconfig | 16 ++++++++++++++++
|
|
kernel/fork.c | 14 ++++++++++++++
|
|
kernel/sysctl.c | 12 ++++++++++++
|
|
kernel/user_namespace.c | 7 +++++++
|
|
5 files changed, 53 insertions(+)
|
|
|
|
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
|
|
index 45f09bec02c485..87b20e2ee27445 100644
|
|
--- a/include/linux/user_namespace.h
|
|
+++ b/include/linux/user_namespace.h
|
|
@@ -148,6 +148,8 @@ static inline void set_userns_rlimit_max(struct user_namespace *ns,
|
|
|
|
#ifdef CONFIG_USER_NS
|
|
|
|
+extern int unprivileged_userns_clone;
|
|
+
|
|
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
|
|
{
|
|
if (ns)
|
|
@@ -181,6 +183,8 @@ extern bool current_in_userns(const struct user_namespace *target_ns);
|
|
struct ns_common *ns_get_owner(struct ns_common *ns);
|
|
#else
|
|
|
|
+#define unprivileged_userns_clone 0
|
|
+
|
|
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
|
|
{
|
|
return &init_user_ns;
|
|
diff --git a/init/Kconfig b/init/Kconfig
|
|
index 94125d3b6893c7..9f7139b536f638 100644
|
|
--- a/init/Kconfig
|
|
+++ b/init/Kconfig
|
|
@@ -1247,6 +1247,22 @@ config USER_NS
|
|
|
|
If unsure, say N.
|
|
|
|
+config USER_NS_UNPRIVILEGED
|
|
+ bool "Allow unprivileged users to create namespaces"
|
|
+ default y
|
|
+ depends on USER_NS
|
|
+ help
|
|
+ When disabled, unprivileged users will not be able to create
|
|
+ new namespaces. Allowing users to create their own namespaces
|
|
+ has been part of several recent local privilege escalation
|
|
+ exploits, so if you need user namespaces but are
|
|
+ paranoid^Wsecurity-conscious you want to disable this.
|
|
+
|
|
+ This setting can be overridden at runtime via the
|
|
+ kernel.unprivileged_userns_clone sysctl.
|
|
+
|
|
+ If unsure, say Y.
|
|
+
|
|
config PID_NS
|
|
bool "PID Namespaces"
|
|
default y
|
|
diff --git a/kernel/fork.c b/kernel/fork.c
|
|
index 08969f5aa38d59..ff601cb7a1fae0 100644
|
|
--- a/kernel/fork.c
|
|
+++ b/kernel/fork.c
|
|
@@ -98,6 +98,10 @@
|
|
#include <linux/io_uring.h>
|
|
#include <linux/bpf.h>
|
|
|
|
+#ifdef CONFIG_USER_NS
|
|
+#include <linux/user_namespace.h>
|
|
+#endif
|
|
+
|
|
#include <asm/pgalloc.h>
|
|
#include <linux/uaccess.h>
|
|
#include <asm/mmu_context.h>
|
|
@@ -2008,6 +2012,10 @@ static __latent_entropy struct task_struct *copy_process(
|
|
if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
+ if ((clone_flags & CLONE_NEWUSER) && !unprivileged_userns_clone)
|
|
+ if (!capable(CAP_SYS_ADMIN))
|
|
+ return ERR_PTR(-EPERM);
|
|
+
|
|
/*
|
|
* Thread groups must share signals as well, and detached threads
|
|
* can only be started up within the thread group.
|
|
@@ -3166,6 +3174,12 @@ int ksys_unshare(unsigned long unshare_flags)
|
|
if (unshare_flags & CLONE_NEWNS)
|
|
unshare_flags |= CLONE_FS;
|
|
|
|
+ if ((unshare_flags & CLONE_NEWUSER) && !unprivileged_userns_clone) {
|
|
+ err = -EPERM;
|
|
+ if (!capable(CAP_SYS_ADMIN))
|
|
+ goto bad_unshare_out;
|
|
+ }
|
|
+
|
|
err = check_unshare_flags(unshare_flags);
|
|
if (err)
|
|
goto bad_unshare_out;
|
|
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
|
|
index c6d9dec11b749d..9a4514ad481b21 100644
|
|
--- a/kernel/sysctl.c
|
|
+++ b/kernel/sysctl.c
|
|
@@ -81,6 +81,9 @@
|
|
#ifdef CONFIG_RT_MUTEXES
|
|
#include <linux/rtmutex.h>
|
|
#endif
|
|
+#ifdef CONFIG_USER_NS
|
|
+#include <linux/user_namespace.h>
|
|
+#endif
|
|
|
|
/* shared constants to be used in various sysctls */
|
|
const int sysctl_vals[] = { 0, 1, 2, 3, 4, 100, 200, 1000, 3000, INT_MAX, 65535, -1 };
|
|
@@ -1659,6 +1662,15 @@ static struct ctl_table kern_table[] = {
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec,
|
|
},
|
|
+#ifdef CONFIG_USER_NS
|
|
+ {
|
|
+ .procname = "unprivileged_userns_clone",
|
|
+ .data = &unprivileged_userns_clone,
|
|
+ .maxlen = sizeof(int),
|
|
+ .mode = 0644,
|
|
+ .proc_handler = proc_dointvec,
|
|
+ },
|
|
+#endif
|
|
#ifdef CONFIG_PROC_SYSCTL
|
|
{
|
|
.procname = "tainted",
|
|
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
|
|
index 54211dbd516c57..16ca0c1516298d 100644
|
|
--- a/kernel/user_namespace.c
|
|
+++ b/kernel/user_namespace.c
|
|
@@ -22,6 +22,13 @@
|
|
#include <linux/bsearch.h>
|
|
#include <linux/sort.h>
|
|
|
|
+/* sysctl */
|
|
+#ifdef CONFIG_USER_NS_UNPRIVILEGED
|
|
+int unprivileged_userns_clone = 1;
|
|
+#else
|
|
+int unprivileged_userns_clone;
|
|
+#endif
|
|
+
|
|
static struct kmem_cache *user_ns_cachep __read_mostly;
|
|
static DEFINE_MUTEX(userns_state_mutex);
|
|
|