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From dea1110505c920b0f7e0cdd8840448e48ef420fa Mon Sep 17 00:00:00 2001
Message-Id: <dea1110505c920b0f7e0cdd8840448e48ef420fa.1525295228.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 e5d9d405ae4e..c4be89c51f25 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
@@ -1591,6 +1596,10 @@ 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.
@@ -2385,6 +2394,12 @@ SYSCALL_DEFINE1(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 f98f28c12020..7256d339a32a 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;
@@ -515,6 +518,15 @@ 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);
--
2.17.0
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