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=-5.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 D5A67C43387 for ; Mon, 14 Jan 2019 16:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A318220873 for ; Mon, 14 Jan 2019 16:24:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="jDH92ecE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726849AbfANQYH (ORCPT ); Mon, 14 Jan 2019 11:24:07 -0500 Received: from mail.skyhub.de ([5.9.137.197]:49476 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbfANQYH (ORCPT ); Mon, 14 Jan 2019 11:24:07 -0500 Received: from zn.tnic (p200300EC2BC4CA0024FBBBED28F98094.dip0.t-ipconnect.de [IPv6:2003:ec:2bc4:ca00:24fb:bbed:28f9:8094]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id BBAC81EC0573; Mon, 14 Jan 2019 17:24:05 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1547483046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=ktyje5iriB+Gk+5OwpC3Vc8LFKZPk0n6IbU+QEixQPc=; b=jDH92ecEVOv+Rpa0gSgFcnO17mRrW3fwQg1cnU7/puCRO5s7OTyTCoaAYyjOHJTk7YWDxW xd9Jsbt09ctAaUXYd1Ipaz4oooIKBhNFV7wuCSCgtFRiK4x9FrYlugiKDVm3/vWqiL8ogy 4/HHw9ou9UTftldfIwex02v/BC9JkAY= Date: Mon, 14 Jan 2019 17:24:00 +0100 From: Borislav Petkov To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen Subject: Re: [PATCH 01/22] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() Message-ID: <20190114162400.GN2773@zn.tnic> References: <20190109114744.10936-1-bigeasy@linutronix.de> <20190109114744.10936-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190109114744.10936-2-bigeasy@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 09, 2019 at 12:47:23PM +0100, Sebastian Andrzej Siewior wrote: > This is a preparation for the removal of the ->initialized member in the > fpu struct. > __fpu__restore_sig() is deactivating the FPU via fpu__drop() and then > setting manually ->initialized followed by fpu__restore(). The result is > that it is possible to manipulate fpu->state and the state of registers > won't be saved/restored on a context switch which would overwrite > fpu->state. > > Don't access the fpu->state while the content is read from user space > and examined / sanitized. Use a temporary kmalloc() buffer for the > preparation of the FPU registers and once the state is considered okay, > load it. Should something go wrong, return with an error and without > altering the original FPU registers. > > The removal of "fpu__initialize()" is a nop because fpu->initialized is > already set for the user task. > > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/include/asm/fpu/signal.h | 2 +- > arch/x86/kernel/fpu/regset.c | 5 ++-- > arch/x86/kernel/fpu/signal.c | 41 ++++++++++++------------------- > 3 files changed, 19 insertions(+), 29 deletions(-) ... > @@ -315,40 +313,33 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) > * header. Validate and sanitize the copied state. > */ > struct user_i387_ia32_struct env; > + union fpregs_state *state; > int err = 0; > + void *tmp; > > - /* > - * Drop the current fpu which clears fpu->initialized. This ensures > - * that any context-switch during the copy of the new state, > - * avoids the intermediate state from getting restored/saved. > - * Thus avoiding the new restored state from getting corrupted. > - * We will be ready to restore/save the state only after > - * fpu->initialized is again set. > - */ > - fpu__drop(fpu); > + tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL); > + if (!tmp) > + return -ENOMEM; > + state = PTR_ALIGN(tmp, 64); > > if (using_compacted_format()) { > - err = copy_user_to_xstate(&fpu->state.xsave, buf_fx); > + err = copy_user_to_xstate(&state->xsave, buf_fx); > } else { > - err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); > + err = __copy_from_user(&state->xsave, buf_fx, state_size); > > if (!err && state_size > offsetof(struct xregs_state, header)) > - err = validate_xstate_header(&fpu->state.xsave.header); > + err = validate_xstate_header(&state->xsave.header); > } > > if (err || __copy_from_user(&env, buf, sizeof(env))) { > - fpstate_init(&fpu->state); > - trace_x86_fpu_init_state(fpu); > err = -1; > } else { > - sanitize_restored_xstate(tsk, &env, xfeatures, fx_only); > + sanitize_restored_xstate(state, &env, > + xfeatures, fx_only); Just let that one stick out - there are other lines in this file already longer than 80. Notwithstanding, I don't see anything wrong with this patch. Acked-by: Borislav Petkov -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.