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=-9.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 2DAE6C677D4 for ; Mon, 8 Oct 2018 15:29:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC21521557 for ; Mon, 8 Oct 2018 15:29:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="pLpmvzG6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DC21521557 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1728845AbeJHWlQ (ORCPT ); Mon, 8 Oct 2018 18:41:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:59150 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728984AbeJHWjk (ORCPT ); Mon, 8 Oct 2018 18:39:40 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9181821531; Mon, 8 Oct 2018 15:27:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539012445; bh=4AQzGDkxcgVh8dZnzNqNA/W8U5dHcMTHcX3+R2DV1WA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pLpmvzG6httBvJiWlcqOn+2+FFJwPNnRSCp/msg/+VG6XiXuhIsJ5tz/FtgPsYtmC 4Ra8/r4Iyh5UK0P0aYqn62j5gmY55+LI2Zj+h0zFDcGahRd0gc4IOk9+QO4u/5GMkH pPqfrM7gr4YSFU8E8KN0h/a8yUfTVU++cyGQLvaE= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Michael Neuling , Michael Ellerman , Sasha Levin Subject: [PATCH AUTOSEL 4.9 22/23] powerpc/tm: Avoid possible userspace r1 corruption on reclaim Date: Mon, 8 Oct 2018 11:27:02 -0400 Message-Id: <20181008152703.70891-22-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181008152703.70891-1-sashal@kernel.org> References: <20181008152703.70891-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michael Neuling [ Upstream commit 96dc89d526ef77604376f06220e3d2931a0bfd58 ] Current we store the userspace r1 to PACATMSCRATCH before finally saving it to the thread struct. In theory an exception could be taken here (like a machine check or SLB miss) that could write PACATMSCRATCH and hence corrupt the userspace r1. The SLB fault currently doesn't touch PACATMSCRATCH, but others do. We've never actually seen this happen but it's theoretically possible. Either way, the code is fragile as it is. This patch saves r1 to the kernel stack (which can't fault) before we turn MSR[RI] back on. PACATMSCRATCH is still used but only with MSR[RI] off. We then copy r1 from the kernel stack to the thread struct once we have MSR[RI] back on. Suggested-by: Breno Leitao Signed-off-by: Michael Neuling Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/tm.S | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S index b0b99aadf504..f59b73810630 100644 --- a/arch/powerpc/kernel/tm.S +++ b/arch/powerpc/kernel/tm.S @@ -168,6 +168,13 @@ _GLOBAL(tm_reclaim) std r11, GPR11(r1) /* Temporary stash */ + /* + * Move the saved user r1 to the kernel stack in case PACATMSCRATCH is + * clobbered by an exception once we turn on MSR_RI below. + */ + ld r11, PACATMSCRATCH(r13) + std r11, GPR1(r1) + /* * Store r13 away so we can free up the scratch SPR for the SLB fault * handler (needed once we start accessing the thread_struct). @@ -204,7 +211,7 @@ _GLOBAL(tm_reclaim) SAVE_GPR(8, r7) /* user r8 */ SAVE_GPR(9, r7) /* user r9 */ SAVE_GPR(10, r7) /* user r10 */ - ld r3, PACATMSCRATCH(r13) /* user r1 */ + ld r3, GPR1(r1) /* user r1 */ ld r4, GPR7(r1) /* user r7 */ ld r5, GPR11(r1) /* user r11 */ ld r6, GPR12(r1) /* user r12 */ -- 2.17.1