From patchwork Mon Jun 1 17:53:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 225104 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,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 EC6B1C433E3 for ; Mon, 1 Jun 2020 18:04:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C6DDF20878 for ; Mon, 1 Jun 2020 18:04:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591034657; bh=2ZPjej86uWTbLn4JuUOXaDIYjHQwrcYDh8zvLp7nqxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OV+aCZdbtDrrrhcygfu/dEx32+lnDFMXNsUh42jT0Vz9QdD8y42U6MJpkeji2jgDg E4X/fWgynvWa2eIhbX/mxxWjK7L6NxhKe2rFCWXq11OplUfL+ONNY7BjCO3937Tdbi O9voSnocm0SWOWFLSjmn/5n6Ed4qWEHiPg0aWcYE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730170AbgFASEP (ORCPT ); Mon, 1 Jun 2020 14:04:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:48690 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730177AbgFASEO (ORCPT ); Mon, 1 Jun 2020 14:04:14 -0400 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 25952206E2; Mon, 1 Jun 2020 18:04:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591034653; bh=2ZPjej86uWTbLn4JuUOXaDIYjHQwrcYDh8zvLp7nqxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iQJiFqO4LeE3BH6+DNPsB119BwsPdohyHL8rqkrnlgNCp9wfe3hs7xfF5fqX+L8a8 ns8wn/nae5U6wKzJDSnSmHFUwP3mdHysmeg1Mw3VzzvEgEFts5zwvu1QHFJzdlTJsr XimWfBdmgNalP0bqeCcvxjDfdnuqF9wb/yIwZlEs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tomas Paukrt , Russell King , Sasha Levin Subject: [PATCH 4.19 49/95] ARM: uaccess: fix DACR mismatch with nested exceptions Date: Mon, 1 Jun 2020 19:53:49 +0200 Message-Id: <20200601174028.776470896@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200601174020.759151073@linuxfoundation.org> References: <20200601174020.759151073@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Russell King [ Upstream commit 71f8af1110101facfad68989ff91f88f8e2c3e22 ] Tomas Paukrt reports that his SAM9X60 based system (ARM926, ARMv5TJ) fails to fix up alignment faults, eventually resulting in a kernel oops. The problem occurs when using CONFIG_CPU_USE_DOMAINS with commit e6978e4bf181 ("ARM: save and reset the address limit when entering an exception"). This is because the address limit is set back to TASK_SIZE on exception entry, and, although it is restored on exception exit, the domain register is not. Hence, this sequence can occur: interrupt pt_regs->addr_limit = addr_limit // USER_DS addr_limit = USER_DS alignment exception __probe_kernel_read() old_fs = get_fs() // USER_DS set_fs(KERNEL_DS) addr_limit = KERNEL_DS dacr.kernel = DOMAIN_MANAGER interrupt pt_regs->addr_limit = addr_limit // KERNEL_DS addr_limit = USER_DS alignment exception __probe_kernel_read() old_fs = get_fs() // USER_DS set_fs(KERNEL_DS) addr_limit = KERNEL_DS dacr.kernel = DOMAIN_MANAGER ... set_fs(old_fs) addr_limit = USER_DS dacr.kernel = DOMAIN_CLIENT ... addr_limit = pt_regs->addr_limit // KERNEL_DS interrupt returns At this point, addr_limit is correctly restored to KERNEL_DS for __probe_kernel_read() to continue execution, but dacr.kernel is not, it has been reset by the set_fs(old_fs) to DOMAIN_CLIENT. This would not have happened prior to the mentioned commit, because addr_limit would remain KERNEL_DS, so get_fs() would have returned KERNEL_DS, and so would correctly nest. This commit fixes the problem by also saving the DACR on exception entry if either CONFIG_CPU_SW_DOMAIN_PAN or CONFIG_CPU_USE_DOMAINS are enabled, and resetting the DACR appropriately on exception entry to match addr_limit and PAN settings. Fixes: e6978e4bf181 ("ARM: save and reset the address limit when entering an exception") Reported-by: Tomas Paukrt Signed-off-by: Russell King Signed-off-by: Sasha Levin --- arch/arm/include/asm/uaccess-asm.h | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/arch/arm/include/asm/uaccess-asm.h b/arch/arm/include/asm/uaccess-asm.h index e46468b91eaa..907571fd05c6 100644 --- a/arch/arm/include/asm/uaccess-asm.h +++ b/arch/arm/include/asm/uaccess-asm.h @@ -67,15 +67,21 @@ #endif .endm -#ifdef CONFIG_CPU_SW_DOMAIN_PAN +#if defined(CONFIG_CPU_SW_DOMAIN_PAN) || defined(CONFIG_CPU_USE_DOMAINS) #define DACR(x...) x #else #define DACR(x...) #endif /* - * Save the address limit on entry to a privileged exception and - * if using PAN, save and disable usermode access. + * Save the address limit on entry to a privileged exception. + * + * If we are using the DACR for kernel access by the user accessors + * (CONFIG_CPU_USE_DOMAINS=y), always reset the DACR kernel domain + * back to client mode, whether or not \disable is set. + * + * If we are using SW PAN, set the DACR user domain to no access + * if \disable is set. */ .macro uaccess_entry, tsk, tmp0, tmp1, tmp2, disable ldr \tmp1, [\tsk, #TI_ADDR_LIMIT] @@ -84,8 +90,17 @@ DACR( mrc p15, 0, \tmp0, c3, c0, 0) DACR( str \tmp0, [sp, #SVC_DACR]) str \tmp1, [sp, #SVC_ADDR_LIMIT] - .if \disable - uaccess_disable \tmp0 + .if \disable && IS_ENABLED(CONFIG_CPU_SW_DOMAIN_PAN) + /* kernel=client, user=no access */ + mov \tmp2, #DACR_UACCESS_DISABLE + mcr p15, 0, \tmp2, c3, c0, 0 + instr_sync + .elseif IS_ENABLED(CONFIG_CPU_USE_DOMAINS) + /* kernel=client */ + bic \tmp2, \tmp0, #domain_mask(DOMAIN_KERNEL) + orr \tmp2, \tmp2, #domain_val(DOMAIN_KERNEL, DOMAIN_CLIENT) + mcr p15, 0, \tmp2, c3, c0, 0 + instr_sync .endif .endm