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

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Date:   Mon,  3 Sep 2018 22:44:24 +0200
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-api@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 04/10] signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init

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@...ssion.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