Oops, Al is here by mistake. Sorry about that.
On Wed, Jan 02, 2019 at 12:59:39PM -0800, Andrei Vagin wrote: > Currently, exit_ptrace() adds all ptraced tasks in a dead list, than > zap_pid_ns_processes() waits all tasks in a current pid ns, and only > then tasks from the dead list are released. > > zap_pid_ns_processes() can stuck on waiting tasks from the dead list. In > this case, we will have one unkillable process with one or more dead > children. > > Cc: Oleg Nesterov <[email protected]> > Cc: "Eric W. Biederman" <[email protected]> > Cc: Andrew Morton <[email protected]> > Signed-off-by: Andrei Vagin <[email protected]> > --- > kernel/exit.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/kernel/exit.c b/kernel/exit.c > index 0e21e6d21f35..ccaa6f6549ba 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -664,9 +664,6 @@ static void forget_original_parent(struct task_struct > *father, > { > struct task_struct *p, *t, *reaper; > > - if (unlikely(!list_empty(&father->ptraced))) > - exit_ptrace(father, dead); > - > /* Can drop and reacquire tasklist_lock */ > reaper = find_child_reaper(father); > if (list_empty(&father->children)) > @@ -705,8 +702,18 @@ static void exit_notify(struct task_struct *tsk, int > group_dead) > LIST_HEAD(dead); > > write_lock_irq(&tasklist_lock); > - forget_original_parent(tsk, &dead); > + if (unlikely(!list_empty(&tsk->ptraced))) > + exit_ptrace(tsk, &dead); > + write_unlock_irq(&tasklist_lock); > + > + /* Ptraced tasks have to be released before zap_pid_ns_processes(). */ > + list_for_each_entry_safe(p, n, &dead, ptrace_entry) { > + list_del_init(&p->ptrace_entry); > + release_task(p); > + } > > + write_lock_irq(&tasklist_lock); > + forget_original_parent(tsk, &dead); > if (group_dead) > kill_orphaned_pgrp(tsk->group_leader, NULL); > > -- > 2.17.2 >
