Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751935AbdHaPo3 (ORCPT ); Thu, 31 Aug 2017 11:44:29 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36382 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751794AbdHaPo0 (ORCPT ); Thu, 31 Aug 2017 11:44:26 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chunyan Zhang , Janet Liu , Ard Biesheuvel , Will Deacon Subject: [PATCH 3.18 17/24] arm64: flush FP/SIMD state correctly after execve() Date: Thu, 31 Aug 2017 17:43:53 +0200 Message-Id: <20170831154106.048843465@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170831154105.116844281@linuxfoundation.org> References: <20170831154105.116844281@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1682 Lines: 45 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ard Biesheuvel commit 674c242c9323d3c293fc4f9a3a3a619fe3063290 upstream. When a task calls execve(), its FP/SIMD state is flushed so that none of the original program state is observeable by the incoming program. However, since this flushing consists of setting the in-memory copy of the FP/SIMD state to all zeroes, the CPU field is set to CPU 0 as well, which indicates to the lazy FP/SIMD preserve/restore code that the FP/SIMD state does not need to be reread from memory if the task is scheduled again on CPU 0 without any other tasks having entered userland (or used the FP/SIMD in kernel mode) on the same CPU in the mean time. If this happens, the FP/SIMD state of the old program will still be present in the registers when the new program starts. So set the CPU field to the invalid value of NR_CPUS when performing the flush, by calling fpsimd_flush_task_state(). Reported-by: Chunyan Zhang Reported-by: Janet Liu Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/fpsimd.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -157,6 +157,7 @@ void fpsimd_thread_switch(struct task_st void fpsimd_flush_thread(void) { memset(¤t->thread.fpsimd_state, 0, sizeof(struct fpsimd_state)); + fpsimd_flush_task_state(current); set_thread_flag(TIF_FOREIGN_FPSTATE); }