From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755482AbcE0QeI (ORCPT ); Fri, 27 May 2016 12:34:08 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:34904 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755124AbcE0QeH (ORCPT ); Fri, 27 May 2016 12:34:07 -0400 Subject: Re: [PATCH] arm64: kasan: instrument user memory access API To: Andrey Ryabinin , will.deacon@arm.com, catalin.marinas@arm.com References: <1464288231-11304-1-git-send-email-yang.shi@linaro.org> <57482930.6020608@virtuozzo.com> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org From: "Shi, Yang" Message-ID: Date: Fri, 27 May 2016 09:34:03 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <57482930.6020608@virtuozzo.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/27/2016 4:02 AM, Andrey Ryabinin wrote: > > > On 05/26/2016 09:43 PM, Yang Shi wrote: >> The upstream commit 1771c6e1a567ea0ba2cccc0a4ffe68a1419fd8ef >> ("x86/kasan: instrument user memory access API") added KASAN instrument to >> x86 user memory access API, so added such instrument to ARM64 too. >> >> Tested by test_kasan module. >> >> Signed-off-by: Yang Shi >> --- >> arch/arm64/include/asm/uaccess.h | 18 ++++++++++++++++-- >> 1 file changed, 16 insertions(+), 2 deletions(-) > > Please, cover __copy_from_user() and __copy_to_user() too. > Unlike x86, your patch doesn't instrument these two. I should elaborated this in my review. Yes, I did think about it, but unlike x86, __copy_to/from_user are implemented by asm code on ARM64. If I add kasan_check_read/write into them, I have to move the registers around to prepare the parameters for kasan calls, then restore them after the call, for example the below code for __copy_to_user: mov x9, x0 mov x10, x1 mov x11, x2 mov x0, x10 mov x1, x11 bl kasan_check_read mov x0, x9 mov x1, x10 So, I'm wondering if it is worth or not since __copy_to/from_user are just called at a couple of places, i.e. sctp, a couple of drivers, etc and not used too much. Actually, I think some of them could be replaced by __copy_to/from_user_inatomic. Any idea is appreciated. Thanks, Yang >