From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EDD0FA372C for ; Fri, 8 Nov 2019 11:50:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF89121D7B for ; Fri, 8 Nov 2019 11:50:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573213803; bh=iy1DT5bUu1OBLH5vlxDMPqVN+I2GP5m989sEYk4zcWw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=u8tmjT26njKVEs14K9MV7hHSYx1iZFqVPhv55KpkcEgdD0b00joJkNoJ+SiReRG0C UI+t00fMidoW5s2ie8wVWXQaXqTwyfxaMvlvhpbTcU2lJCuZy+1arXfpEmGAt0fWes oi2Ms/gUqe+IxKyLv16l09Xwdd1FD/C+Y92M+K0o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390427AbfKHLuA (ORCPT ); Fri, 8 Nov 2019 06:50:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:36728 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391692AbfKHLry (ORCPT ); Fri, 8 Nov 2019 06:47:54 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C8AB521924; Fri, 8 Nov 2019 11:47:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573213674; bh=iy1DT5bUu1OBLH5vlxDMPqVN+I2GP5m989sEYk4zcWw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JktKvbldXm4wtg7rYtWKvrr3Cj42pfXAaGcT4/rnPdQgF7YHUwLXepPUvZiaie2t/ tN8SU85vATpTqfIs/MOiMpie9lueDHhaNP0taTnpTPM1QiXbOIi1ECMUUOJCp2zQoi jyH2adoodWKIihEgTSJ7/w98R6/Wu95gmoHL4wQI= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Eric W. Biederman" , Thomas Gleixner , Sasha Levin Subject: [PATCH AUTOSEL 4.4 25/44] signal: Always ignore SIGKILL and SIGSTOP sent to the global init Date: Fri, 8 Nov 2019 06:47:01 -0500 Message-Id: <20191108114721.15944-25-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191108114721.15944-1-sashal@kernel.org> References: <20191108114721.15944-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Eric W. Biederman" [ Upstream commit 86989c41b5ea08776c450cb759592532314a4ed6 ] If the first process started (aka /sbin/init) receives a SIGKILL it will panic the system if it is delivered. Making the system unusable and undebugable. It isn't much better if the first process started receives SIGSTOP. So always ignore SIGSTOP and SIGKILL sent to init. This is done in a separate clause in sig_task_ignored as force_sig_info can clear SIG_UNKILLABLE and this protection should work even then. Reviewed-by: Thomas Gleixner Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/signal.c b/kernel/signal.c index 072fd152ab01e..3095b2309876d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -71,6 +71,10 @@ static int sig_task_ignored(struct task_struct *t, int sig, bool force) handler = sig_handler(t, sig); + /* SIGKILL and SIGSTOP may not be sent to the global init */ + if (unlikely(is_global_init(t) && sig_kernel_only(sig))) + return true; + if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && handler == SIG_DFL && !(force && sig_kernel_only(sig))) return 1; -- 2.20.1