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 1AE34C677D4 for ; Mon, 8 Oct 2018 15:29:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBBC221557 for ; Mon, 8 Oct 2018 15:29:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="GXRzUECH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBBC221557 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 S1728999AbeJHWjk (ORCPT ); Mon, 8 Oct 2018 18:39:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:59126 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727303AbeJHWjj (ORCPT ); Mon, 8 Oct 2018 18:39:39 -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 BD75421533; Mon, 8 Oct 2018 15:27:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539012444; bh=PjjfhhsQjObJs/kvUaHpaPWUBPbkGDh42GW+jS5kgRg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GXRzUECHH931xf8tndBD2WC9AOj5SeKl2sBXCDHu1Jepqg3/veUdNBuq0qivIH7I0 4xWC48WcqFW6UwyPUGxtFe8NPLjKQpB5mflTwXP6t3bU/t1e2x/tOXLMnnb6k4krjf CE8G1PFS43aSyBkXcqduT0DYXy2ocWMff/zccWR4= 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 21/23] powerpc/tm: Fix userspace r13 corruption Date: Mon, 8 Oct 2018 11:27:01 -0400 Message-Id: <20181008152703.70891-21-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 cf13435b730a502e814c63c84d93db131e563f5f ] When we treclaim we store the userspace checkpointed r13 to a scratch SPR and then later save the scratch SPR to the user thread struct. Unfortunately, this doesn't work as accessing the user thread struct can take an SLB fault and the SLB fault handler will write the same scratch SPRG that now contains the userspace r13. To fix this, we store r13 to the kernel stack (which can't fault) before we access the user thread struct. Found by running P8 guest + powervm + disable_1tb_segments + TM. Seen as a random userspace segfault with r13 looking like a kernel address. Signed-off-by: Michael Neuling Reviewed-by: Breno Leitao Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/tm.S | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S index 3a2d04134da9..b0b99aadf504 100644 --- a/arch/powerpc/kernel/tm.S +++ b/arch/powerpc/kernel/tm.S @@ -166,13 +166,20 @@ _GLOBAL(tm_reclaim) std r1, PACATMSCRATCH(r13) ld r1, PACAR1(r13) - /* Store the PPR in r11 and reset to decent value */ std r11, GPR11(r1) /* Temporary stash */ + /* + * Store r13 away so we can free up the scratch SPR for the SLB fault + * handler (needed once we start accessing the thread_struct). + */ + GET_SCRATCH0(r11) + std r11, GPR13(r1) + /* Reset MSR RI so we can take SLB faults again */ li r11, MSR_RI mtmsrd r11, 1 + /* Store the PPR in r11 and reset to decent value */ mfspr r11, SPRN_PPR HMT_MEDIUM @@ -201,7 +208,7 @@ _GLOBAL(tm_reclaim) ld r4, GPR7(r1) /* user r7 */ ld r5, GPR11(r1) /* user r11 */ ld r6, GPR12(r1) /* user r12 */ - GET_SCRATCH0(8) /* user r13 */ + ld r8, GPR13(r1) /* user r13 */ std r3, GPR1(r7) std r4, GPR7(r7) std r5, GPR11(r7) -- 2.17.1