From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753961AbbEDMwo (ORCPT ); Mon, 4 May 2015 08:52:44 -0400 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:51621 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753218AbbEDMpr (ORCPT ); Mon, 4 May 2015 08:45:47 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , Borislav Petkov , Andy Lutomirski , Borislav Petkov , Dave Hansen , Fenghua Yu , "H. Peter Anvin" , Linus Torvalds , Pekka Riikonen , Quentin Casasnovas , Suresh Siddha , Thomas Gleixner , Ingo Molnar , Jiri Slaby Subject: [PATCH 3.12 063/155] x86/fpu: Drop_fpu() should not assume that tsk equals current Date: Tue, 7 Apr 2015 14:50:32 +0200 Message-Id: X-Mailer: git-send-email 2.3.4 In-Reply-To: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> References: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit f4c3686386393c120710dd34df2a74183ab805fd upstream. drop_fpu() does clear_used_math() and usually this is correct because tsk == current. However switch_fpu_finish()->restore_fpu_checking() is called before __switch_to() updates the "current_task" variable. If it fails, we will wrongly clear the PF_USED_MATH flag of the previous task. So use clear_stopped_child_used_math() instead. Signed-off-by: Oleg Nesterov Signed-off-by: Borislav Petkov Reviewed-by: Rik van Riel Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Pekka Riikonen Cc: Quentin Casasnovas Cc: Suresh Siddha Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150309171041.GB11388@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Jiri Slaby --- arch/x86/include/asm/fpu-internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 5be9f879957f..18cd5ed4e1ba 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -368,7 +368,7 @@ static inline void drop_fpu(struct task_struct *tsk) preempt_disable(); tsk->fpu_counter = 0; __drop_fpu(tsk); - clear_used_math(); + clear_stopped_child_used_math(tsk); preempt_enable(); } -- 2.3.4