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- From 164d2dd36ff81a5a4b4d6440317438cf6009cd59 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 1/4] ZEN: Add sysctl and CONFIG to disallow unprivileged
- CLONE_NEWUSER
- Our default behavior continues to match the vanilla kernel.
- ---
- init/Kconfig | 16 ++++++++++++++++
- kernel/fork.c | 15 +++++++++++++++
- kernel/sysctl.c | 12 ++++++++++++
- kernel/user_namespace.c | 7 +++++++
- 4 files changed, 50 insertions(+)
- diff --git a/init/Kconfig b/init/Kconfig
- index 74a5ac65644f..965a628556e8 100644
- --- a/init/Kconfig
- +++ b/init/Kconfig
- @@ -1102,6 +1102,22 @@ 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 48ed22774efa..ec61454a18d5 100644
- --- a/kernel/fork.c
- +++ b/kernel/fork.c
- @@ -106,6 +106,11 @@
-
- #define CREATE_TRACE_POINTS
- #include <trace/events/task.h>
- +#ifdef CONFIG_USER_NS
- +extern int unprivileged_userns_clone;
- +#else
- +#define unprivileged_userns_clone 0
- +#endif
-
- /*
- * Minimum number of threads to boot the kernel
- @@ -1848,6 +1853,10 @@ 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.
- @@ -2948,6 +2957,12 @@ 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 8a176d8727a3..9500597739a2 100644
- --- a/kernel/sysctl.c
- +++ b/kernel/sysctl.c
- @@ -110,6 +110,9 @@ extern int core_uses_pid;
- extern char core_pattern[];
- extern unsigned int core_pipe_limit;
- #endif
- +#ifdef CONFIG_USER_NS
- +extern int unprivileged_userns_clone;
- +#endif
- extern int pid_max;
- extern int pid_max_min, pid_max_max;
- extern int percpu_pagelist_fraction;
- @@ -534,6 +537,15 @@ static struct ctl_table kern_table[] = {
- .proc_handler = proc_dointvec,
- },
- #endif
- +#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 8eadadc478f9..c36ecd19562c 100644
- --- a/kernel/user_namespace.c
- +++ b/kernel/user_namespace.c
- @@ -21,6 +21,13 @@
- #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);
-
- --
- 2.27.0
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