From 9a5adbc45b1c7d43fe4b27936f2a6939660617a1 Mon Sep 17 00:00:00 2001 Message-Id: <9a5adbc45b1c7d43fe4b27936f2a6939660617a1.1528777685.git.jan.steffens@gmail.com> From: Serge Hallyn <serge.hallyn@canonical.com> Date: Fri, 31 May 2013 19:12:12 +0100 Subject: [PATCH 1/3] add sysctl to disallow unprivileged CLONE_NEWUSER by default Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com> [bwh: Remove unneeded binary sysctl bits] Signed-off-by: Daniel Micay <danielmicay@gmail.com> --- kernel/fork.c | 15 +++++++++++++++ kernel/sysctl.c | 12 ++++++++++++ kernel/user_namespace.c | 3 +++ 3 files changed, 30 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index a5d21c42acfc..675eb3f3a1d1 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -103,6 +103,11 @@ #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 @@ -1592,6 +1597,10 @@ 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. @@ -2386,6 +2395,12 @@ 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 6a78cf70761d..35a1d24282f4 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -105,6 +105,9 @@ 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; @@ -519,6 +522,15 @@ 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 246d4d4ce5c7..f64432b45cec 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -26,6 +26,9 @@ #include <linux/bsearch.h> #include <linux/sort.h> +/* sysctl */ +int unprivileged_userns_clone; + static struct kmem_cache *user_ns_cachep __read_mostly; static DEFINE_MUTEX(userns_state_mutex); -- 2.17.1