signals: zap_pid_ns_process() should use force_sig()
send_signal() assumes that signals with SEND_SIG_PRIV are generated from
within the same namespace. So any nested container-init processes become
immune to the SIGKILL generated by kill_proc_info() in
zap_pid_ns_processes().
Use force_sig() in zap_pid_ns_processes() instead - force_sig() clears the
SIGNAL_UNKILLABLE flag ensuring the signal is processed by
container-inits.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index fab8ea8..2d1001b 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -152,6 +152,7 @@
{
int nr;
int rc;
+ struct task_struct *task;
/*
* The last thread in the cgroup-init thread group is terminating.
@@ -169,7 +170,19 @@
read_lock(&tasklist_lock);
nr = next_pidmap(pid_ns, 1);
while (nr > 0) {
- kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
+ rcu_read_lock();
+
+ /*
+ * Use force_sig() since it clears SIGNAL_UNKILLABLE ensuring
+ * any nested-container's init processes don't ignore the
+ * signal
+ */
+ task = pid_task(find_vpid(nr), PIDTYPE_PID);
+ if (task)
+ force_sig(SIGKILL, task);
+
+ rcu_read_unlock();
+
nr = next_pidmap(pid_ns, nr);
}
read_unlock(&tasklist_lock);