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- From d0c6bedb9c49fdd994f469309a4e2668134b4e5e 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 1/3] 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 6030a8235617..60b7fe5fa74a 100644
- --- a/include/linux/user_namespace.h
- +++ b/include/linux/user_namespace.h
- @@ -156,6 +156,8 @@ 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)
- @@ -189,6 +191,8 @@ 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 9ffb103fc927..f91ccd3c1456 100644
- --- a/init/Kconfig
- +++ b/init/Kconfig
- @@ -1226,6 +1226,22 @@ 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 10917c3e1f03..458360cf9bfb 100644
- --- a/kernel/fork.c
- +++ b/kernel/fork.c
- @@ -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 @@ __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.
- @@ -3411,6 +3419,12 @@ 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 157f7ce2942d..881fc4f5d61e 100644
- --- a/kernel/sysctl.c
- +++ b/kernel/sysctl.c
- @@ -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 @@ 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 eabe8bcc7042..ac9d1f702086 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 __ro_after_init;
- static DEFINE_MUTEX(userns_state_mutex);
-
- --
- 2.43.0
|
