From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: [PATCH 03/10] user namespaces: reset task's credentials on CLONE_NEWUSER Date: Fri, 22 Aug 2008 14:45:58 -0500 Message-ID: <20080822194558.GC10360@us.ibm.com> References: <20080822194513.GA10262@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20080822194513.GA10262-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Eric W. Biederman" , Linux Containers List-Id: containers.vger.kernel.org Currently, creating a new user namespace does not reset the task's uid or gid. Since generally that is done as root because it requires CAP_SYS_ADMIN, and since the first uid in the new namespace is 0, one usually doesn't notice. However, if one does capset cap_sys_admin=ep ns_exec su - hallyn ns_exec -U /bin/sh id then one will see hallyn's userid, and all preexisting groups. With this patch, cloning a new user namespace will set the task's uid and gid to 0, and reset the group_info to the empty set assigned to init. Signed-off-by: Serge E. Hallyn --- kernel/user_namespace.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 0045dd0..39aea7b 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -11,6 +11,9 @@ #include #include +/* defined in kernel/sys.c */ +extern struct group_info init_groups; + /* * Clone a new ns copying an original user ns, setting refcount to 1 * @old_ns: namespace to clone @@ -48,6 +51,17 @@ int create_new_userns(int flags, struct task_struct *tsk) put_user_ns(ns); task_switch_uid(tsk, ns->root_user); + tsk->uid = tsk->euid = tsk->suid = tsk->fsuid = 0; + tsk->gid = tsk->egid = tsk->sgid = tsk->fsgid = 0; + + /* this can't be safe for unshare, can it? it's safe + * for fork, though. I'm tempted to limit clone_newuser to + * fork only */ + task_lock(tsk); + put_group_info(tsk->group_info); + tsk->group_info = &init_groups; + get_group_info(tsk->group_info); + task_unlock(tsk); return 0; } -- 1.5.4.3