The patch titled
Subject: pidns: guarantee that the pidns init will be the last pidns process reaped
has been added to the -mm tree. Its filename is
pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2.patch
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------------------------------------------------------
From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Subject: pidns: guarantee that the pidns init will be the last pidns process reaped
Today we have a two-fold bug. Sometimes release_task on pid == 1 in a pid
namespace can run before other processes in a pid namespace have had
release task called. With the result that pid_ns_release_proc can be
called before the last proc_flush_task() is done using upid->ns->proc_mnt,
resulting in the use of a stale pointer. This same set of circumstances
can lead to waitpid(...) returning for a processes started with
clone(CLONE_NEWPID) before the every process in the pid namespace has
actually exited.
To fix this modify zap_pid_ns_processess wait until all other processes in
the pid namespace have exited, even EXIT_DEAD zombies.
The delay_group_leader and related tests ensure that the thread gruop
leader will be the last thread of a process group to be reaped, or to
become EXIT_DEAD and self reap. With the change to zap_pid_ns_processes
we get the guarantee that pid == 1 in a pid namespace will be the last
task that release_task is called on.
With pid == 1 being the last task to pass through release_task
pid_ns_release_proc can no longer be called too early nor can wait return
before all of the EXIT_DEAD tasks in a pid namespace have exited.
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Louis Rilling <louis.rilling@xxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 13 ++++++++++++-
kernel/pid_namespace.c | 11 +++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
diff -puN kernel/exit.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2 kernel/exit.c
--- a/kernel/exit.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2
+++ a/kernel/exit.c
@@ -64,15 +64,26 @@ static void exit_mm(struct task_struct *
static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
- detach_pid(p, PIDTYPE_PID);
if (group_dead) {
+ struct task_struct *parent;
+
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
list_del_rcu(&p->tasks);
list_del_init(&p->sibling);
__this_cpu_dec(process_counts);
+
+ /* If we are the last child process in a pid namespace
+ * to be reaped notify the child_reaper.
+ */
+ parent = p->real_parent;
+ if ((task_active_pid_ns(p)->child_reaper == parent) &&
+ list_empty(&parent->children) &&
+ (parent->flags & PF_EXITING))
+ wake_up_process(parent);
}
+ detach_pid(p, PIDTYPE_PID);
list_del_rcu(&p->thread_group);
}
diff -puN kernel/pid_namespace.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2 kernel/pid_namespace.c
--- a/kernel/pid_namespace.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2
+++ a/kernel/pid_namespace.c
@@ -189,6 +189,17 @@ void zap_pid_ns_processes(struct pid_nam
rc = sys_wait4(-1, NULL, __WALL, NULL);
} while (rc != -ECHILD);
+ read_lock(&tasklist_lock);
+ for (;;) {
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ if (list_empty(¤t->children))
+ break;
+ read_unlock(&tasklist_lock);
+ schedule();
+ read_lock(&tasklist_lock);
+ }
+ read_unlock(&tasklist_lock);
+
if (pid_ns->reboot)
current->signal->group_exit_code = pid_ns->reboot;
_
Subject: Subject: pidns: guarantee that the pidns init will be the last pidns process reaped
Patches currently in -mm which might be from ebiederm@xxxxxxxxxxxx are
origin.patch
linux-next.patch
cred-remove-task_is_dead-from-__task_cred-validation.patch
pidns-use-task_active_pid_ns-in-do_notify_parent.patch
pidns-make-killed-children-autoreap.patch
pidns-make-killed-children-autoreap-checkpatch-fixes.patch
pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2.patch
pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped-v2-fix.patch
syscalls-x86-add-__nr_kcmp-syscall-v8.patch
c-r-procfs-add-arg_start-end-env_start-end-and-exit_code-members-to-proc-pid-stat.patch
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