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=-9.8 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=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 37C63C432C3 for ; Wed, 27 Nov 2019 21:35:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D78920665 for ; Wed, 27 Nov 2019 21:35:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574890516; bh=MdXxU8oNnNxUNykFVPJPxOfa36YJHrJlrvzu5GMEQSU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LfUobpL6jKKFf/PkKyEQsqBJYKuM5REJjAOoZs+Vo9g22MF53Ph7f3QCealnL4ab7 K+INdUATA99xyNg7fSbkZMQheWsz0Mqucq+nY/hOQ7vIZ38R6lQRFCdLoY0eyI3kCt JSnTkNnyHFdVVue/JuRYuaT3e4ovC3SCOB2JzDK8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729559AbfK0Utp (ORCPT ); Wed, 27 Nov 2019 15:49:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:35382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729044AbfK0Utm (ORCPT ); Wed, 27 Nov 2019 15:49:42 -0500 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 78CDD20678; Wed, 27 Nov 2019 20:49:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574887781; bh=MdXxU8oNnNxUNykFVPJPxOfa36YJHrJlrvzu5GMEQSU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OQxc6t1xowKwkynLpQQfZQbfNT2EDLFKGmLd/2mvgSVyDK1+1sW+gekbco5LcdIov svmuunugUN+rDCK8ybGTnN3I0/TpCNTt5BIW50xAXaD3JF4RvI6ZvIpSbdNmQh9UsP AbOQ+bXDchdOLroBDHLjGVDNP7j8128AnP4KAWj4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Felipe Rechia , Michael Ellerman , Sasha Levin Subject: [PATCH 4.14 090/211] powerpc/process: Fix flush_all_to_thread for SPE Date: Wed, 27 Nov 2019 21:30:23 +0100 Message-Id: <20191127203102.251927666@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191127203049.431810767@linuxfoundation.org> References: <20191127203049.431810767@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Felipe Rechia [ Upstream commit e901378578c62202594cba0f6c076f3df365ec91 ] Fix a bug introduced by the creation of flush_all_to_thread() for processors that have SPE (Signal Processing Engine) and use it to compute floating-point operations. >>From userspace perspective, the problem was seen in attempts of computing floating-point operations which should generate exceptions. For example: fork(); float x = 0.0 / 0.0; isnan(x); // forked process returns False (should be True) The operation above also should always cause the SPEFSCR FINV bit to be set. However, the SPE floating-point exceptions were turned off after a fork(). Kernel versions prior to the bug used flush_spe_to_thread(), which first saves SPEFSCR register values in tsk->thread and then calls giveup_spe(tsk). After commit 579e633e764e, the save_all() function was called first to giveup_spe(), and then the SPEFSCR register values were saved in tsk->thread. This would save the SPEFSCR register values after disabling SPE for that thread, causing the bug described above. Fixes 579e633e764e ("powerpc: create flush_all_to_thread()") Signed-off-by: Felipe Rechia Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/process.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 5e5da2073fdff..ba0d4f9a99bac 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -567,12 +567,11 @@ void flush_all_to_thread(struct task_struct *tsk) if (tsk->thread.regs) { preempt_disable(); BUG_ON(tsk != current); - save_all(tsk); - #ifdef CONFIG_SPE if (tsk->thread.regs->msr & MSR_SPE) tsk->thread.spefscr = mfspr(SPRN_SPEFSCR); #endif + save_all(tsk); preempt_enable(); } -- 2.20.1