From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755183AbcARNTD (ORCPT ); Mon, 18 Jan 2016 08:19:03 -0500 Received: from mx2.suse.de ([195.135.220.15]:54161 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754902AbcARNS6 (ORCPT ); Mon, 18 Jan 2016 08:18:58 -0500 Date: Mon, 18 Jan 2016 14:18:53 +0100 Message-ID: From: Takashi Iwai To: Nicolas Boichat Cc: alsa-devel@alsa-project.org, Pierre-Louis Bossart , Jaroslav Kysela , linux-kernel@vger.kernel.org Subject: Re: [PATCH] ALSA: pcm: Fix snd_pcm_hw_params struct copy in compat mode In-Reply-To: References: <1453088958-6214-1-git-send-email-drinkcat@chromium.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.5 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 18 Jan 2016 14:00:19 +0100, Nicolas Boichat wrote: > > On Mon, Jan 18, 2016 at 2:37 PM, Takashi Iwai wrote: > > On Mon, 18 Jan 2016 04:49:18 +0100, > > Nicolas Boichat wrote: > >> > >> Running a kernel with KASan enabled, we spotted that the following > >> read in sound/soc/soc-pcm.c:soc_pcm_hw_params() is out of bounds: > >> > >> /* copy params for each codec */ > >> codec_params = *params; > >> > >> The problem comes from sound/core/pcm_compat.c, > >> snd_pcm_ioctl_hw_params_compat, where we're copying from a > >> struct snd_pcm_hw_params to a struct snd_pcm_hw_params32: > >> > >> /* only fifo_size is different, so just copy all */ > >> data = memdup_user(data32, sizeof(*data32)); > >> > >> It turns out that snd_pcm_hw_params is 4 bytes longer than > >> snd_pcm_hw_params32, that's why an out-of-bounds read happens. > >> > >> We separate kmalloc and memory copy operations to make sure > >> data has the correct length. > >> > >> Signed-off-by: Nicolas Boichat > > > > Thanks for reporting. This is indeed effectively a revert of the > > commit ef44a1ec6eee ('ALSA: sound/core: use memdup_user()'), which is > > obviously wrong. Sigh, it's a really danger of such a "cleanup" > > patch. > > Oh, well spotted! > > > Could you rephrase the changelog mentioning the affecting commit and > > resubmit? > > Sure. Looking at that commit, there is another suspicious memdup_user > in sound/seq/seq_compat.c (similar issue: struct snd_seq_port_info32 > is 4 bytes shorter than struct snd_seq_port_info). I'll revert that > one as well. Good catch. I'm looking forward to seeing newer patches! Takashi