From patchwork Tue Jul 11 14:19:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 107389 Delivered-To: patch@linaro.org Received: by 10.140.101.44 with SMTP id t41csp4940207qge; Tue, 11 Jul 2017 07:21:36 -0700 (PDT) X-Received: by 10.99.127.23 with SMTP id a23mr147431pgd.47.1499782896594; Tue, 11 Jul 2017 07:21:36 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1499782896; cv=none; d=google.com; s=arc-20160816; b=afWKCAJ3FVCyrfwil6W8W7VxDKP1LJdm0Sc0bKrsjXRnYSRG2zspPJmEhVR2inuj1y JffL0mtW+ICA5fjJDb6THkhIL7Lk1cOOO3JMc1FzaDsmKGTctXwXeV3fJdvaw7kadFrr soKVgLfnkNFv/wkM89SKZXZsuaumzoFcqtI8CKKfAWNCENbdCtDhJlRwqEmypJEkA9HL mFf7CzssSVwTxsfQSMbkpVQwzXIUJelkVQR7qVDuNgAeDZiWHvvJCHWmgi2geLEWNxna qfZAJBvx9XZOoJfJtqpeNlLhrAw7qPVdlyQrPd67KS/e4Qw5WAg2aHwg9ILE6D7mQVfv dOTA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=Zfzrv8k11C88oq/PVVBt+HLhGeMBldIEGAlh0ks3jOk=; b=pNmFK8WxyPtsk7LFRKhpWHM2i+DFPfsqC41+gwZmWkKkTQxpjPqE3yAHCUlkH9fvUr MUDRlrkWyodgHcYrBbKF1P9+YH1h35O0gfra52Jc/CGh3xHIjJspGL74SxPDgzmMJgz/ +OmoAmBEFdcOivkSBbHxEqKeXeUHGGpGvb4p0PYIZsd7SGcMQPZCI+y/jUG7x8BIvqXK 1U2TnHis0pbFWVTuVOJYxGgB5utqnmoHK8HUOdOtnS4uQhumYK8ahWKbilaynHRZgHbv 7KZ72wfITBfhWWqO8RBfGnaSVWxC8bQaZQ1zr1OenT0kR3dFSe7qPi4NGwBFDHdq4MIN 0GUg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id i1si59970pfa.122.2017.07.11.07.21.36; Tue, 11 Jul 2017 07:21:36 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932997AbdGKOVL (ORCPT + 25 others); Tue, 11 Jul 2017 10:21:11 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:45526 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932653AbdGKOVI (ORCPT ); Tue, 11 Jul 2017 10:21:08 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 68A2215A2; Tue, 11 Jul 2017 07:21:02 -0700 (PDT) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 4C5803F3E1; Tue, 11 Jul 2017 07:21:00 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Cc: catalin.marinas@arm.com, james.morse@arm.com, labbott@redhat.com, linux@armlinux.org.uk, mark.rutland@arm.com, stable@vger.kernel.org, steve.capper@arm.com, will.deacon@arm.com, viro@zeniv.linux.org.uk, peterz@infradead.org, luto@amacapital.net Subject: [PATCH 1/2] arm64: mm: abort uaccess retries upon fatal signal Date: Tue, 11 Jul 2017 15:19:22 +0100 Message-Id: <1499782763-31418-2-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1499782763-31418-1-git-send-email-mark.rutland@arm.com> References: <1499782763-31418-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When there's a fatal signal pending, arm64's do_page_fault() implementation returns 0. 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. Signed-off-by: Mark Rutland Reviewed-by: Steve Capper Tested-by: Steve Capper Cc: Catalin Marinas Cc: James Morse Cc: Laura Abbott Cc: Will Deacon Cc: stable@vger.kernel.org --- arch/arm64/mm/fault.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) -- 1.9.1 diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 37b95df..3952d5e 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -397,8 +397,11 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, * signal first. We do not need to release the mmap_sem because it * would already be released in __lock_page_or_retry in mm/filemap.c. */ - if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) + if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { + if (!user_mode(regs)) + goto no_context; return 0; + } /* * Major/minor page fault accounting is only done on the initial