[PATCH 04/10] signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init

From: "Eric W. Biederman" <ebiederm@xmission.com>
To: linux-kernel@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-api@vger.kernel.org,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH 04/10] signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init
Date: Mon,  3 Sep 2018 22:44:24 +0200	[thread overview]
Message-ID: <20180903204430.25473-4-ebiederm@xmission.com> (raw)
In-Reply-To: <87musyl3fa.fsf@xmission.com>

Instead of playing whack-a-mole and changing SEND_SIG_PRIV to
SEND_SIG_FORCED throughout the kernel to ensure a pid namespace init
gets signals sent by the kernel, stop allowing a pid namespace init to
ignore SIGKILL or SIGSTOP sent by the kernel.  A pid namespace init is
only supposed to be able to ignore signals sent from itself and
children with SIG_DFL.

Fixes: 921cf9f63089 ("signals: protect cinit from unblocked SIG_DFL signals")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index b33264bb2064..8081ab79e97d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1039,7 +1039,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
 
 	result = TRACE_SIGNAL_IGNORED;
 	if (!prepare_signal(sig, t,
-			from_ancestor_ns || (info == SEND_SIG_FORCED)))
+			from_ancestor_ns || (info == SEND_SIG_PRIV) || (info == SEND_SIG_FORCED)))
 		goto ret;
 
 	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
-- 
2.17.1

