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=-6.8 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,URIBL_BLOCKED autolearn=unavailable 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 2F3F0C3A59B for ; Fri, 30 Aug 2019 19:46:58 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0535B22CE9 for ; Fri, 30 Aug 2019 19:46:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="b4voARKU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0535B22CE9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Subject:MIME-Version:Message-ID: In-Reply-To:Date:References:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=8CuhktNWDyKD9ne6RJNKwXxSpdbpyxQZ9jzi4JLe5IA=; b=b4voARKU95Y+hn 18NtvUBV64uokld+0ZMUPvpTSPdAx2oXZM2SY+EKtTA53eJoFf+vGFtCS0dtyZ4CQEXyKbZ/85PMC ricxCKFqrk3gcn6H4sMugzK806DHslcsGPOOFUmTCW6JEK2xAl/JVJciNrRQn6bEZUrY3UTpP4ABp zDRGDKI5Dk3s9b8iPdAIzwJxjHIGN/lNv4Y+OwjAVIiXrnJjYGVWjhHAQDea622NkWsmcMPflcuiF hRUe1jkaTR5G52cC+QX5n/3IvFIJucYCN7vdGzpznZvP/GF9z3Abc8sfcBi7U48PSroRRz2Slis8n 15lr1GaHmn3DLI5RPMtA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i3mrB-0004XG-41; Fri, 30 Aug 2019 19:46:49 +0000 Received: from out03.mta.xmission.com ([166.70.13.233]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i3mr8-0004Vb-Nf for linux-arm-kernel@lists.infradead.org; Fri, 30 Aug 2019 19:46:48 +0000 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1i3mqo-0002rY-QA; Fri, 30 Aug 2019 13:46:26 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1i3mqC-0002tz-B5; Fri, 30 Aug 2019 13:46:26 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Russell King - ARM Linux admin References: <1567171877-101949-1-git-send-email-jingxiangfeng@huawei.com> <20190830133522.GZ13294@shell.armlinux.org.uk> Date: Fri, 30 Aug 2019 14:45:36 -0500 In-Reply-To: <20190830133522.GZ13294@shell.armlinux.org.uk> (Russell King's message of "Fri, 30 Aug 2019 14:35:22 +0100") Message-ID: <87d0gmwi73.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1i3mqC-0002tz-B5; ; ; mid=<87d0gmwi73.fsf@x220.int.ebiederm.org>; ; ; hst=in02.mta.xmission.com; ; ; ip=68.227.160.95; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX18NMO9dKN/ZIv2eAbj5eODKvFQtgC+w5Xg= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH] arm: fix page faults in do_alignment X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190830_124646_802984_8B7C278C X-CRM114-Status: GOOD ( 14.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kstewart@linuxfoundation.org, gustavo@embeddedor.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Jing Xiangfeng , linux-mm@kvack.org, sakari.ailus@linux.intel.com, bhelgaas@google.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Russell King - ARM Linux admin writes: > On Fri, Aug 30, 2019 at 09:31:17PM +0800, Jing Xiangfeng wrote: >> The function do_alignment can handle misaligned address for user and >> kernel space. If it is a userspace access, do_alignment may fail on >> a low-memory situation, because page faults are disabled in >> probe_kernel_address. >> >> Fix this by using __copy_from_user stead of probe_kernel_address. >> >> Fixes: b255188 ("ARM: fix scheduling while atomic warning in alignment handling code") >> Signed-off-by: Jing Xiangfeng > > NAK. > > The "scheduling while atomic warning in alignment handling code" is > caused by fixing up the page fault while trying to handle the > mis-alignment fault generated from an instruction in atomic context. > > Your patch re-introduces that bug. And the patch that fixed scheduling while atomic apparently introduced a regression. Admittedly a regression that took 6 years to track down but still. So it looks like the code needs to do something like: diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c index 04b36436cbc0..5e2b8623851e 100644 --- a/arch/arm/mm/alignment.c +++ b/arch/arm/mm/alignment.c @@ -784,6 +784,9 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) instrptr = instruction_pointer(regs); + if (user_mode(regs)) + goto user; + if (thumb_mode(regs)) { u16 *ptr = (u16 *)(instrptr & ~1); fault = probe_kernel_address(ptr, tinstr); @@ -933,6 +936,34 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) return 1; user: + if (thumb_mode(regs)) { + u16 *ptr = (u16 *)(instrptr & ~1); + fault = get_user(tinstr, ptr); + tinstr = __mem_to_opcode_thumb16(tinstr); + if (!fault) { + if (cpu_architecture() >= CPU_ARCH_ARMv7 && + IS_T32(tinstr)) { + /* Thumb-2 32-bit */ + u16 tinst2 = 0; + fault = get_user(ptr + 1, tinst2); + tinst2 = __mem_to_opcode_thumb16(tinst2); + instr = __opcode_thumb32_compose(tinstr, tinst2); + thumb2_32b = 1; + } else { + isize = 2; + instr = thumb2arm(tinstr); + } + } + } else { + fault = get_user(instr, (u32*)instrptr); + instr = __mem_to_opcode_arm(instr); + } + + if (fault) { + type = TYPE_FAULT; + goto bad_or_fault; + } + ai_user += 1; if (ai_usermode & UM_WARN) Eric _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel