linux-kernel - [PATCH AUTOSEL 4.18 122/126] signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init

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Message-Id: <20181031230754.29029-122-sashal@kernel.org>
Date:   Wed, 31 Oct 2018 19:07:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.18 122/126] signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init

From: "Eric W. Biederman" <ebiederm@...ssion.com>

[ Upstream commit 3597dfe01d12f570bc739da67f857fd222a3ea66 ]

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")
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 41a5dd2df27d..1628b67992d6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1009,7 +1009,7 @@ 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 = group ? &t->signal->shared_pending : &t->pending;
-- 
2.17.1