From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836AbaBLIS0 (ORCPT ); Wed, 12 Feb 2014 03:18:26 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:50319 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752218AbaBLIOL (ORCPT ); Wed, 12 Feb 2014 03:14:11 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "halfdog" , "H. Peter Anvin" , "Borislav Petkov" , "Linus Torvalds" Date: Wed, 12 Feb 2014 08:10:12 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 26/79] x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround In-Reply-To: X-SA-Exim-Connect-IP: 91.84.160.45 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.55-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds commit 26bef1318adc1b3a530ecc807ef99346db2aa8b0 upstream. Before we do an EMMS in the AMD FXSAVE information leak workaround we need to clear any pending exceptions, otherwise we trap with a floating-point exception inside this code. Reported-by: halfdog Tested-by: Borislav Petkov Link: http://lkml.kernel.org/r/CA%2B55aFxQnY_PCG_n4=0w-VG=YLXL-yr7oMxyy0WU2gCBAf3ydg@mail.gmail.com Signed-off-by: H. Peter Anvin [bwh: Backported to 3.2: adjust filename, context] Signed-off-by: Ben Hutchings --- arch/x86/kernel/traps.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -582,12 +582,13 @@ void __math_state_restore(struct task_st /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is pending. Clear the x87 state here by setting it to fixed values. safe_address is a random variable that should be in L1 */ - alternative_input( - ASM_NOP8 ASM_NOP2, - "emms\n\t" /* clear stack tags */ - "fildl %P[addr]", /* set F?P to defined value */ - X86_FEATURE_FXSAVE_LEAK, - [addr] "m" (safe_address)); + if (unlikely(static_cpu_has(X86_FEATURE_FXSAVE_LEAK))) { + asm volatile( + "fnclex\n\t" + "emms\n\t" + "fildl %P[addr]" /* set F?P to defined value */ + : : [addr] "m" (safe_address)); + } /* * Paranoid restore. send a SIGSEGV if we fail to restore the state.