94 lines
2.7 KiB
Diff
94 lines
2.7 KiB
Diff
From: Serge Hallyn <serge.hallyn@canonical.com>
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Date: Fri, 31 May 2013 19:12:12 +0000 (+0100)
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Subject: add sysctl to disallow unprivileged CLONE_NEWUSER by default
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Origin: http://kernel.ubuntu.com/git?p=serge%2Fubuntu-saucy.git;a=commit;h=5c847404dcb2e3195ad0057877e1422ae90892b8
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add sysctl to disallow unprivileged CLONE_NEWUSER by default
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This is a short-term patch. Unprivileged use of CLONE_NEWUSER
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is certainly an intended feature of user namespaces. However
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for at least saucy we want to make sure that, if any security
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issues are found, we have a fail-safe.
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Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
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[bwh: Remove unneeded binary sysctl bits]
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---
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -86,6 +86,11 @@
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#define CREATE_TRACE_POINTS
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#include <trace/events/task.h>
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+#ifdef CONFIG_USER_NS
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+extern int unprivileged_userns_clone;
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+#else
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+#define unprivileged_userns_clone 0
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+#endif
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/*
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* Protected counters by write_lock_irq(&tasklist_lock)
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@@ -1149,6 +1154,10 @@ static struct task_struct *copy_process(
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if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
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return ERR_PTR(-EINVAL);
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+ if ((clone_flags & CLONE_NEWUSER) && !unprivileged_userns_clone)
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+ if (!capable(CAP_SYS_ADMIN))
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+ return ERR_PTR(-EPERM);
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+
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/*
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* Thread groups must share signals as well, and detached threads
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* can only be started up within the thread group.
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@@ -1843,6 +1852,12 @@ SYSCALL_DEFINE1(unshare, unsigned long,
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if (unshare_flags & CLONE_NEWNS)
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unshare_flags |= CLONE_FS;
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+ if ((unshare_flags & CLONE_NEWUSER) && !unprivileged_userns_clone) {
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+ err = -EPERM;
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+ if (!capable(CAP_SYS_ADMIN))
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+ goto bad_unshare_out;
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+ }
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+
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err = check_unshare_flags(unshare_flags);
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if (err)
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goto bad_unshare_out;
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--- a/kernel/sysctl.c
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+++ b/kernel/sysctl.c
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@@ -103,6 +103,9 @@ extern int core_uses_pid;
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extern char core_pattern[];
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extern unsigned int core_pipe_limit;
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#endif
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+#ifdef CONFIG_USER_NS
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+extern int unprivileged_userns_clone;
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+#endif
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extern int pid_max;
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extern int pid_max_min, pid_max_max;
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extern int percpu_pagelist_fraction;
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@@ -489,6 +492,15 @@ static struct ctl_table kern_table[] = {
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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+#endif
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+#ifdef CONFIG_USER_NS
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+ {
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+ .procname = "unprivileged_userns_clone",
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+ .data = &unprivileged_userns_clone,
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+ .maxlen = sizeof(int),
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+ .mode = 0644,
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+ .proc_handler = proc_dointvec,
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+ },
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#endif
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#ifdef CONFIG_PROC_SYSCTL
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{
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--- a/kernel/user_namespace.c
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+++ b/kernel/user_namespace.c
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@@ -23,6 +23,9 @@
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#include <linux/projid.h>
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#include <linux/fs_struct.h>
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+/* sysctl */
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+int unprivileged_userns_clone;
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+
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static struct kmem_cache *user_ns_cachep __read_mostly;
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static DEFINE_MUTEX(userns_state_mutex);
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