From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964971AbaH0Syj (ORCPT ); Wed, 27 Aug 2014 14:54:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23220 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964948AbaH0Syd (ORCPT ); Wed, 27 Aug 2014 14:54:33 -0400 Date: Wed, 27 Aug 2014 20:52:02 +0200 From: Oleg Nesterov To: Al Viro , Andrew Morton , Fenghua Yu , Linus Torvalds , Suresh Siddha Cc: Bean Anderson , "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/4] x86, fpu: copy_process: sanitize fpu->last_cpu initialization Message-ID: <20140827185202.GA12515@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140827185138.GA12487@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Cosmetic, but imho memset(&dst->thread.fpu, 0) is not good simply because it hides the (important) usage of ->has_fpu/etc from grep. Change this code to initialize the members explicitly. And note that ->last_cpu = 0 looks simply wrong, this can confuse fpu_lazy_restore() if per_cpu(fpu_owner_task, 0) has already exited and copy_process() re-allocated the same task_struct. Fortunately this is not actually possible because child->fpu_counter == 0 and thus fpu_lazy_restore() will not be called, but still this is not clean/robust. Signed-off-by: Oleg Nesterov --- arch/x86/kernel/process.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 60076b4..36dfb1d 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -66,7 +66,9 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { *dst = *src; - memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu)); + dst->thread.fpu.has_fpu = 0; + dst->thread.fpu.last_cpu = ~0; + dst->thread.fpu.state = NULL; if (tsk_used_math(src)) { int err = fpu_alloc(&dst->thread.fpu); if (err) -- 1.5.5.1