From: Oleg Nesterov on
zap_pid_ns_processes() uses force_sig(SIGKILL) to ensure SIGKILL
will be delivered to sub-namespace inits as well. This is correct,
but we are going to change force_sig_info() semantics.
See http://bugzilla.kernel.org/show_bug.cgi?id=15395#c31

We can use send_sig_info(SEND_SIG_NOINFO) instead, since
614c517d7c00af1b26ded20646b329397d6f51a1 SEND_SIG_NOINFO means
"from user" and therefore send_signal() will get the correct
from_ancestor_ns = T flag.

Signed-off-by: Oleg Nesterov <oleg(a)redhat.com>
---

kernel/pid_namespace.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- mm/kernel/pid_namespace.c~NS_DONT_ABUSE_FORCE 2010-02-25 15:22:13.000000000 +0100
+++ mm/kernel/pid_namespace.c 2010-03-03 20:58:12.000000000 +0100
@@ -161,13 +161,12 @@ void zap_pid_ns_processes(struct pid_nam
rcu_read_lock();

/*
- * Use force_sig() since it clears SIGNAL_UNKILLABLE ensuring
- * any nested-container's init processes don't ignore the
- * signal
+ * Any nested-container's init processes won't ignore the
+ * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
*/
task = pid_task(find_vpid(nr), PIDTYPE_PID);
if (task)
- force_sig(SIGKILL, task);
+ send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);

rcu_read_unlock();


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