From patchwork Thu Jan 21 16:04:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Bogendoerfer X-Patchwork-Id: 12036879 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 92282C433E6 for ; Thu, 21 Jan 2021 16:08:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D93223A23 for ; Thu, 21 Jan 2021 16:08:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731633AbhAUQIN (ORCPT ); Thu, 21 Jan 2021 11:08:13 -0500 Received: from mx2.suse.de ([195.135.220.15]:52910 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731852AbhAUQFO (ORCPT ); Thu, 21 Jan 2021 11:05:14 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6DD20AB7A; Thu, 21 Jan 2021 16:04:22 +0000 (UTC) From: Thomas Bogendoerfer To: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Mark Rutland Subject: [PATCH] MIPS: mm: abort uaccess retries upon fatal signal Date: Thu, 21 Jan 2021 17:04:16 +0100 Message-Id: <20210121160416.111298-1-tsbogend@alpha.franken.de> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org When there's a fatal signal pending, MIPS's do_page_fault() implementation returns. The intent is that we'll return to the faulting userspace instruction, delivering the signal on the way. However, if we take a fatal signal during fixing up a uaccess, this results in a return to the faulting kernel instruction, which will be instantly retried, resulting in the same fault being taken forever. As the task never reaches userspace, the signal is not delivered, and the task is left unkillable. While the task is stuck in this state, it can inhibit the forward progress of the system. To avoid this, we must ensure that when a fatal signal is pending, we apply any necessary fixup for a faulting kernel instruction. Thus we will return to an error path, and it is up to that code to make forward progress towards delivering the fatal signal. [ Description taken from commit 746a272e4414 ("ARM: 8692/1: mm: abort uaccess retries upon fatal signal") ] Signed-off-by: Thomas Bogendoerfer Acked-by: Mark Rutland --- arch/mips/mm/fault.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c index 7c871b14e74a..e7abda9c013f 100644 --- a/arch/mips/mm/fault.c +++ b/arch/mips/mm/fault.c @@ -156,8 +156,11 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write, */ fault = handle_mm_fault(vma, address, flags, regs); - if (fault_signal_pending(fault, regs)) + if (fault_signal_pending(fault, regs)) { + if (!user_mode(regs)) + goto no_context; return; + } if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM)