linux-kernel - [PATCH 2/3] protect the SIGNAL_UNKILLABLE tasks from !sig_kernel

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Date:   Fri, 3 Nov 2017 19:42:27 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     security@...nel.org, Robert O'Callahan <robert@...llahan.org>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kyle Huey <me@...ehuey.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] protect the SIGNAL_UNKILLABLE tasks from
 !sig_kernel_only() signals

Change sig_task_ignored() to drop the SIG_DFL && !sig_kernel_only()
signals even if force == T. This simplifies the next change and this
matches the same check in get_signal() which will drop these signals
anyway.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index b9aebe1..8fc0182 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -78,7 +78,7 @@ static int sig_task_ignored(struct task_struct *t, int sig, bool force)
 	handler = sig_handler(t, sig);
 
 	if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
-			handler == SIG_DFL && !force)
+	    handler == SIG_DFL && !(force && sig_kernel_only(sig)))
 		return 1;
 
 	return sig_handler_ignored(handler, sig);
-- 
2.5.0