From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=ugyh=4N=lists.ozlabs.org=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@kernel.org>
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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no
	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 7A7F8C35E0E
	for <linuxppc-dev@archiver.kernel.org>; Tue, 25 Feb 2020 21:22:48 +0000 (UTC)
Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.kernel.org (Postfix) with ESMTPS id 14E6720714
	for <linuxppc-dev@archiver.kernel.org>; Tue, 25 Feb 2020 21:22:46 +0000 (UTC)
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14E6720714
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 48RsN43vdSzDqS1
	for <linuxppc-dev@archiver.kernel.org>; Wed, 26 Feb 2020 08:22:44 +1100 (AEDT)
Authentication-Results: lists.ozlabs.org;
 spf=permerror (SPF Permanent Error: Unknown mechanism
 found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org
 (client-ip=63.228.1.57; helo=gate.crashing.org;
 envelope-from=segher@kernel.crashing.org; receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none)
 header.from=kernel.crashing.org
Received: from gate.crashing.org (gate.crashing.org [63.228.1.57])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 48RsKj0CdhzDqWS
 for <linuxppc-dev@lists.ozlabs.org>; Wed, 26 Feb 2020 08:20:38 +1100 (AEDT)
Received: from gate.crashing.org (localhost.localdomain [127.0.0.1])
 by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 01PLKXRT031687;
 Tue, 25 Feb 2020 15:20:33 -0600
Received: (from segher@localhost)
 by gate.crashing.org (8.14.1/8.14.1/Submit) id 01PLKWFM031686;
 Tue, 25 Feb 2020 15:20:32 -0600
X-Authentication-Warning: gate.crashing.org: segher set sender to
 segher@kernel.crashing.org using -f
Date: Tue, 25 Feb 2020 15:20:32 -0600
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v3 26/32] powerpc/64: system call zero volatile registers
 when returning
Message-ID: <20200225212032.GI22482@gate.crashing.org>
References: <20200225173541.1549955-1-npiggin@gmail.com>
 <20200225173541.1549955-27-npiggin@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200225173541.1549955-27-npiggin@gmail.com>
User-Agent: Mutt/1.4.2.3i
X-BeenThere: linuxppc-dev@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>
Cc: Michal Suchanek <msuchanek@suse.de>, linuxppc-dev@lists.ozlabs.org
Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Sender: "Linuxppc-dev"
 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

Hi!

On Wed, Feb 26, 2020 at 03:35:35AM +1000, Nicholas Piggin wrote:
> Kernel addresses and potentially other sensitive data could be leaked
> in volatile registers after a syscall.

>  	cmpdi	r3,0
>  	bne	.Lsyscall_restore_regs
> +	li	r0,0
> +	li	r4,0
> +	li	r5,0
> +	li	r6,0
> +	li	r7,0
> +	li	r8,0
> +	li	r9,0
> +	li	r10,0
> +	li	r11,0
> +	li	r12,0
> +	mtctr	r0
> +	mtspr	SPRN_XER,r0
>  .Lsyscall_restore_regs_cont:

What about LR?  Is that taken care of later?

This also deserves a big fat comment imo, it is very important after
all, and not so obvious.


Segher