From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> Subject: pidns: expose task pid_ns_for_children to userspace pid_ns_for_children set by a task is known only to the task itself, and it's impossible to identify it from outside. It's a big problem for checkpoint/restore software like CRIU, because it can't correctly handle tasks, that do setns(CLONE_NEWPID) in proccess of their work. This patch solves the problem, and it exposes pid_ns_for_children to ns directory in standard way with the name "pid_for_children": ~# ls /proc/5531/ns -l | grep pid lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] Link: http://lkml.kernel.org/r/149201123914.6007.2187327078064239572.stgit@localhost.localdomain Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> Cc: Andrei Vagin <avagin@xxxxxxxxxxxxx> Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Paul Moore <paul@xxxxxxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Serge Hallyn <serge@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/namespaces.c | 1 + include/linux/proc_ns.h | 1 + kernel/pid_namespace.c | 34 ++++++++++++++++++++++++++++++++++ 3 files changed, 36 insertions(+) diff -puN fs/proc/namespaces.c~pidns-expose-task-pid_ns_for_children-to-userspace fs/proc/namespaces.c --- a/fs/proc/namespaces.c~pidns-expose-task-pid_ns_for_children-to-userspace +++ a/fs/proc/namespaces.c @@ -23,6 +23,7 @@ static const struct proc_ns_operations * #endif #ifdef CONFIG_PID_NS &pidns_operations, + &pidns_for_children_operations, #endif #ifdef CONFIG_USER_NS &userns_operations, diff -puN include/linux/proc_ns.h~pidns-expose-task-pid_ns_for_children-to-userspace include/linux/proc_ns.h --- a/include/linux/proc_ns.h~pidns-expose-task-pid_ns_for_children-to-userspace +++ a/include/linux/proc_ns.h @@ -27,6 +27,7 @@ extern const struct proc_ns_operations n extern const struct proc_ns_operations utsns_operations; extern const struct proc_ns_operations ipcns_operations; extern const struct proc_ns_operations pidns_operations; +extern const struct proc_ns_operations pidns_for_children_operations; extern const struct proc_ns_operations userns_operations; extern const struct proc_ns_operations mntns_operations; extern const struct proc_ns_operations cgroupns_operations; diff -puN kernel/pid_namespace.c~pidns-expose-task-pid_ns_for_children-to-userspace kernel/pid_namespace.c --- a/kernel/pid_namespace.c~pidns-expose-task-pid_ns_for_children-to-userspace +++ a/kernel/pid_namespace.c @@ -374,6 +374,29 @@ static struct ns_common *pidns_get(struc return ns ? &ns->ns : NULL; } +static struct ns_common *pidns_for_children_get(struct task_struct *task) +{ + struct pid_namespace *ns = NULL; + + task_lock(task); + if (task->nsproxy) { + ns = task->nsproxy->pid_ns_for_children; + get_pid_ns(ns); + } + task_unlock(task); + + if (ns) { + read_lock(&tasklist_lock); + if (!ns->child_reaper) { + put_pid_ns(ns); + ns = NULL; + } + read_unlock(&tasklist_lock); + } + + return ns ? &ns->ns : NULL; +} + static void pidns_put(struct ns_common *ns) { put_pid_ns(to_pid_ns(ns)); @@ -440,6 +463,17 @@ const struct proc_ns_operations pidns_op .put = pidns_put, .install = pidns_install, .owner = pidns_owner, + .get_parent = pidns_get_parent, +}; + +const struct proc_ns_operations pidns_for_children_operations = { + .name = "pid_for_children", + .real_ns_name = "pid", + .type = CLONE_NEWPID, + .get = pidns_for_children_get, + .put = pidns_put, + .install = pidns_install, + .owner = pidns_owner, .get_parent = pidns_get_parent, }; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
