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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 CCB95C432C3 for ; Fri, 22 Nov 2019 10:41:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96A4020717 for ; Fri, 22 Nov 2019 10:41:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574419268; bh=mGPjGEXeFtYqntBkrRgeMklZjdB5TWfymVfeBoAC8P4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Vk5FJAkEyieZtW6iAxrLvPYAhIRiEuOomq8uVeSr0+ZQ7zx8CAGI9a7+kBqR/avQo FwOqHdAKwPP3Fa4tXw6X861Qa/SAEyC/+sb/OMZ5DjC0CaJr2z7iu8MLSr7egfi1XL aryzSDAlHo2Tj/qLY7m7DJfEwZznFNiRaGxIpLDU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728975AbfKVKlH (ORCPT ); Fri, 22 Nov 2019 05:41:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:45464 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727102AbfKVKlG (ORCPT ); Fri, 22 Nov 2019 05:41:06 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C33CC2071F; Fri, 22 Nov 2019 10:41:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574419265; bh=mGPjGEXeFtYqntBkrRgeMklZjdB5TWfymVfeBoAC8P4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SD1fsyDkDthRKmAV8spIYIlz8JbJyOKvGIp4QhoJNXnOgBPGOKtU5z7Etf4krDIYV iA7T7w8YFnCbqYo2/tYvehiVKoYX121bXsRuRxdunOG1kU3JBwPI2/S403djgRMqrE g1kDbSJHRWNRuKlGwUOQ0/7dZpfmb4SZhRLYCkRk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , "Eric W. Biederman" , Sasha Levin Subject: [PATCH 4.9 052/222] signal: Always ignore SIGKILL and SIGSTOP sent to the global init Date: Fri, 22 Nov 2019 11:26:32 +0100 Message-Id: <20191122100855.334236731@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191122100830.874290814@linuxfoundation.org> References: <20191122100830.874290814@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 2bb1f9dc86c7d..30914b3c76b21 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