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diff -Nur a/include/linux/user_namespace.h b/include/linux/user_namespace.h
--- a/include/linux/user_namespace.h 2024-02-23 08:51:59.000000000 +0000
+++ b/include/linux/user_namespace.h 2024-02-24 11:24:37.945502209 +0000
@@ -156,6 +156,8 @@
#ifdef CONFIG_USER_NS
+extern int unprivileged_userns_clone;
+
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
{
if (ns)
@@ -189,6 +191,8 @@
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 -Nur a/init/Kconfig b/init/Kconfig
--- a/init/Kconfig 2024-02-23 08:51:59.000000000 +0000
+++ b/init/Kconfig 2024-02-24 11:24:37.945502209 +0000
@@ -1235,6 +1235,22 @@
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 -Nur a/kernel/fork.c b/kernel/fork.c
--- a/kernel/fork.c 2024-02-23 08:51:59.000000000 +0000
+++ b/kernel/fork.c 2024-02-24 11:24:37.946502209 +0000
@@ -100,6 +100,10 @@
#include <linux/user_events.h>
#include <linux/iommu.h>
+#ifdef CONFIG_USER_NS
+#include <linux/user_namespace.h>
+#endif
+
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
@@ -2265,6 +2269,10 @@
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.
@@ -3411,6 +3419,12 @@
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 -Nur a/kernel/sysctl.c b/kernel/sysctl.c
--- a/kernel/sysctl.c 2024-02-23 08:51:59.000000000 +0000
+++ b/kernel/sysctl.c 2024-02-24 11:24:37.946502209 +0000
@@ -80,6 +80,9 @@
#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 };
@@ -1623,6 +1626,15 @@
.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 -Nur a/kernel/user_namespace.c b/kernel/user_namespace.c
--- a/kernel/user_namespace.c 2024-02-23 08:51:59.000000000 +0000
+++ b/kernel/user_namespace.c 2024-02-24 11:40:48.120538387 +0000
@@ -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 __ro_after_init;
static DEFINE_MUTEX(userns_state_mutex);
|
