From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kirill Tkhai Subject: [PATCH v2] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy Date: Thu, 27 Apr 2017 13:57:16 +0300 Message-ID: <149329053642.12846.16389129928422677700.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: agruenba-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, paul-r2n+y4ga6xFZroRs9YW3xA@public.gmane.org, ktkhai-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org, ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org, avagin-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org, gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org List-Id: linux-api@vger.kernel.org On implementing of nested pid namespaces support in CRIU (checkpoint-restore in userspace tool) we run into the situation, that it's impossible to create a task with specific NSpid effectively. After commit 49f4d8b93ccf "pidns: Capture the user namespace and filter ns_last_pid" it is impossible to set ns_last_pid on any pid namespace, except task's active pid_ns (before the commit it was possible to write to pid_ns_for_children). Thus, if a restored task in a container has more than one pid_ns levels, the restorer code must have a task helper for every pid namespace of the task's pid_ns hierarhy. This is a big problem, because of communication with a helper for every pid_ns in the hierarchy is not cheap. It's not performance-good as it implies many helpers wakeups to create a single task (independently, how you communicate with the helpers). This patch tries to decide the problem. It introduces a new pid_ns ioctl(NS_SET_LAST_PID_VEC), which allows to set a vector of last pids on pid_ns hierarchy. The vector is passed as array of pids in struct ns_ioc_pid_vec, written in reverse order. The first number corresponds to the opened namespace ns_last_pid, the second is to its parent, etc. So, if you have the pid namespaces hierarchy like: pid_ns1 (grand father) | v pid_ns2 (father) | v pid_ns3 (child) and the pid_ns3 is open, then the corresponding vector will be {last_ns_pid3, last_ns_pid2, last_ns_pid1}. This vector may be shorter and it may contain less levels. For example, {last_ns_pid3, last_ns_pid2} or even {last_ns_pid3}, in dependence of which levels you want to populate. v2: Kill pid_ns->child_reaper check as it's impossible to have such a pid namespace file open. Use generic namespaces ioctl() number. Pass pids as array, not as a string. Signed-off-by: Kirill Tkhai --- fs/nsfs.c | 5 +++++ include/linux/pid_namespace.h | 12 ++++++++++++ include/uapi/linux/nsfs.h | 7 +++++++ kernel/pid_namespace.c | 35 +++++++++++++++++++++++++++++++++++ 4 files changed, 59 insertions(+) diff --git a/fs/nsfs.c b/fs/nsfs.c index 323f492e0822..f669a1552003 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include @@ -186,6 +187,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, argp = (uid_t __user *) arg; uid = from_kuid_munged(current_user_ns(), user_ns->owner); return put_user(uid, argp); + case NS_SET_LAST_PID_VEC: + if (ns->ops->type != CLONE_NEWPID) + return -EINVAL; + return pidns_set_last_pid_vec(ns, (void *)arg); default: return -ENOTTY; } diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index c2a989dee876..c8dc4173a4e8 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -9,6 +9,7 @@ #include #include #include +#include struct pidmap { atomic_t nr_free; @@ -103,6 +104,17 @@ static inline int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) } #endif /* CONFIG_PID_NS */ +#if defined(CONFIG_PID_NS) && defined(CONFIG_CHECKPOINT_RESTORE) +extern long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec); +#else /* CONFIG_PID_NS && CONFIG_CHECKPOINT_RESTORE */ +static inline long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec) +{ + return -ENOTTY; +} +#endif /* CONFIG_PID_NS && CONFIG_CHECKPOINT_RESTORE */ + extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk); void pidhash_init(void); void pidmap_init(void); diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h index 1a3ca79f466b..59adf97d1d63 100644 --- a/include/uapi/linux/nsfs.h +++ b/include/uapi/linux/nsfs.h @@ -14,5 +14,12 @@ #define NS_GET_NSTYPE _IO(NSIO, 0x3) /* Get owner UID (in the caller's user namespace) for a user namespace */ #define NS_GET_OWNER_UID _IO(NSIO, 0x4) +/* Set a vector of ns_last_pid for a pid namespace stack */ +#define NS_SET_LAST_PID_VEC _IO(NSIO, 0x5) + +struct ns_ioc_pid_vec { + unsigned int nr; + pid_t pid[0]; +}; #endif /* __LINUX_NSFS_H */ diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index de461aa0bf9a..f68ee8793606 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -21,6 +21,7 @@ #include #include #include +#include struct pid_cache { int nr_ids; @@ -428,6 +429,40 @@ static struct ns_common *pidns_get_parent(struct ns_common *ns) return &get_pid_ns(pid_ns)->ns; } +#ifdef CONFIG_CHECKPOINT_RESTORE +long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec) +{ + struct pid_namespace *pid_ns = to_pid_ns(ns); + pid_t pid, __user *pid_ptr; + unsigned int nr; + + if (get_user(nr, &vec->nr)) + return -EFAULT; + if (nr > 32 || nr < 1) + return -EINVAL; + + pid_ptr = &vec->pid[0]; + do { + if (!ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + if (get_user(pid, pid_ptr)) + return -EFAULT; + if (pid < 0 || pid > pid_max) + return -EINVAL; + + /* Write directly: see the comment in pid_ns_ctl_handler() */ + pid_ns->last_pid = pid; + + pid_ns = pid_ns->parent; + pid_ptr++; + } while (--nr > 0 && pid_ns); + + return nr ? -EINVAL : 0; +} +#endif /* CONFIG_CHECKPOINT_RESTORE */ + static struct user_namespace *pidns_owner(struct ns_common *ns) { return to_pid_ns(ns)->user_ns;