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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 7A0CDC07E85 for ; Sun, 9 Dec 2018 22:13:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A67A2081F for ; Sun, 9 Dec 2018 22:13:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A67A2081F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728343AbeLIWNR (ORCPT ); Sun, 9 Dec 2018 17:13:17 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:37880 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728393AbeLIWNO (ORCPT ); Sun, 9 Dec 2018 17:13:14 -0500 Received: from pub.yeoldevic.com ([81.174.156.145] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gW73Q-0002ih-9f; Sun, 09 Dec 2018 21:56:00 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gW72Z-0003FO-FM; Sun, 09 Dec 2018 21:55:07 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Claudio Imbrenda" , "Martin Schwidefsky" Date: Sun, 09 Dec 2018 21:50:33 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 041/328] s390/kvm: fix deadlock when killed by oom In-Reply-To: X-SA-Exim-Connect-IP: 81.174.156.145 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Claudio Imbrenda commit 306d6c49ac9ded11114cb53b0925da52f2c2ada1 upstream. When the oom killer kills a userspace process in the page fault handler while in guest context, the fault handler fails to release the mm_sem if the FAULT_FLAG_RETRY_NOWAIT option is set. This leads to a deadlock when tearing down the mm when the process terminates. This bug can only happen when pfault is enabled, so only KVM clients are affected. The problem arises in the rare cases in which handle_mm_fault does not release the mm_sem. This patch fixes the issue by manually releasing the mm_sem when needed. Fixes: 24eb3a824c4f3 ("KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault") Signed-off-by: Claudio Imbrenda Signed-off-by: Martin Schwidefsky Signed-off-by: Ben Hutchings --- arch/s390/mm/fault.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -497,6 +497,8 @@ retry: /* No reason to continue if interrupted by SIGKILL. */ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { fault = VM_FAULT_SIGNAL; + if (flags & FAULT_FLAG_RETRY_NOWAIT) + goto out_up; goto out; } if (unlikely(fault & VM_FAULT_ERROR))